Note: Descriptions are shown in the official language in which they were submitted.
<br/> CA 02215886 2000-02-02<br/>(First Page)<br/> METHOD AND APPARATUS FOR CURRENCY DISCRIMINATION<br/> The present invention relates, in general, to currency identification. More<br/>specifically, the present invention relates to an apparatus and method for <br/>discriminating<br/>currency bills of different denominations.<br/>This application is divided from Canadian Patent Application 2,184,807, having<br/>an international filing date of March 8, 1995.<br/>Machines that are currently available for simultaneous scanning and counting <br/>of<br/>documents such as paper currency are relatively complex and costly, and <br/>relatively large<br/>in size. The complexity of such machines can also lead to excessive service <br/>and<br/>maintenance requirements. These drawbacks have inhibited more widespread use <br/>of<br/>such machines, particularly in banks and other financial institutions where <br/>space is<br/>limited in areas where the machines are most needed, such as teller areas.<br/> The above drawbacks are particularly difficult to overcome in machines which<br/>oiler much-needed features such as the ability to scan bills regardless of <br/>their orientation<br/>relative to the machine or to each other, and the ability to authenticate <br/>genuineness<br/>and/or denomination of the bills.<br/>A variety of techniques and apparatus have been used to satisfy the <br/>requirements<br/>of automated currency handling systems. At the lower end of<br/><br/> CA 02215886 2000-02-02<br/> I1<br/>sophistication in this area of technology are systems capable of handling only <br/>a<br/>specific type of currency, such as a specific dollar denomination, while <br/>rejecting all<br/>other currency types. At the upper end are complex systems which are capable <br/>of<br/>identifying and discriminating among and automatically counting multiple <br/>currency<br/>denominations.<br/> Currency discrimination systems typically employ either magnetic sensing or<br/>optical sensing for discriminating among different currency denominations. <br/>Magnetic<br/>sensing is based on detecting the presence or absence of magnetic ink in <br/>portions of<br/>the printed indicia on the currency by using magnetic sensors, usually ferrite <br/>core-<br/>based sensors, and using the detected magnetic signals, after undergoing <br/>analog or<br/>digital processing, as the basis for currency discrimination. A variety of <br/>currency<br/>characteristics can be measured using magnetic sensing. These include <br/>detection of<br/>patterns of changes in magnetic flux, patterns of vertical grid lines in the <br/>portrait area<br/>of bills, the presence of a security thread, total amount of magnetizable <br/>material of a<br/>bill, patterns from sensing the strength of magnetic fields along a bill, and <br/>other<br/>patterns and counts from scanning different portions of the bill such as the <br/>area in<br/>which the denomination is written out.<br/> The more commonly used optical sensing techniques, on the other hand, are<br/>based on detecting and analyzing variations in light reflectance or <br/>transmissivity<br/>characteristics occurring when a currency bill is illuminated and scanned by a <br/>strip of<br/>focused light. The subsequent currency discrimination is based on the <br/>comparison of<br/>sensed optical characteristics with prestored parameters for different <br/>currency<br/>denominations, while accounting for adequate tolerances reflecting differences <br/>among<br/>individual bills of a given denomination. A variety of currency <br/>characteristics can be<br/>measured using optical sensing. These include detection of a bill's density, <br/>color,<br/>length and thickness, the presence of a security thread and holes, and other <br/>patterns<br/>of reflectance and transmission. Color detection techniques may employ color <br/>filters,<br/>colored lamps, and/or dichroic beamsplitters.<br/> In addition to magnetic and optical sensing, other techniques of detecting<br/>characteristic infotination of currency include electrical conductivity <br/>sensing,<br/>capacitive sensing {such as for watermarks, security threads, thickness, and <br/>various<br/><br/> CA 02215886 2000-02-02<br/>12<br/>dielectric properties) and mechanical sensing (such as for size, limpness, and<br/>thickness).<br/> A major obstacle in implementing automated currency discrimination systems<br/>is obtaining an optimum compromise between the criteria used to adequately <br/>define<br/>the characteristic pattern for a particular currency denomination, the time <br/>required to<br/>analyze test data and compare it to predefined parameters in order to identify <br/>the<br/>currency bill under scrutiny, and the rate at which successive currency bills <br/>may be<br/>mechanically fed through and scanned. Even with the use of microprocessors for<br/>processing the test data resulting from the scanning of a bill, a finite <br/>amount of time<br/>is required for acquiring samples and for the process of comparing the test <br/>data to<br/>stored parameters to identify the denomination of the bill.<br/> Some of the currency scanning systems today scan for two or more<br/>characteristics of bills to discriminate among various denominations or to <br/>authenticate<br/>their genuineness. However, these systems do not efficiently utilize the <br/>information<br/>which is obtained. Rather, these systems generally conduct comparison based on <br/>the<br/>two or more characteristics independently of each other. As a result, the time<br/>required to make these comparisons is increased which in turn can reduce the.<br/>operating speed of the entire scanning system.<br/> Recent currency discriminating systems rely on comparisons between a<br/>scanned pattern obtained from a subject bill and sets of stored toaster <br/>patterns for the<br/>various denominations among which the system is designed to discriminate. As a<br/>result, the master patterns which are stored play an important role in a <br/>discrimination<br/>system's ability to discriminate among bills of various denominations as well <br/>as<br/>between genuine bills and counterfeit bills. These master patterns have been<br/>generated by scanning bills of various denominations known to be genuine and<br/>storing the resulting patterns. However, a pattern generated by scanning a <br/>genuine<br/>bill of a given denomination can vary depending upon a number of factors such <br/>as the<br/>condition of the bill, e.g., whether it is a crisp bill in new condition or a <br/>worn,<br/>flimsy bill, as well as year in which the bill was printed, e.g., before or <br/>after security<br/>threads were incorporated into bills of some denominations. Likewise, it has <br/>been<br/>found that bills which have experienced a high degree of usage may shrink, <br/>resulting<br/>in a reduction of the dimensions of such bills. Such shrinkage may likewise <br/>result in<br/><br/> CA 02215886 2000-02-02<br/>13<br/>variations in scanning patterns. As a result, if, for example, a $20 master <br/>pattern is<br/>generated by scanning a crisp, genuine $20 bill, the discrimination system may <br/>reject<br/>an unacceptable number of genuine but worn $20 bills. Likewise, if a $20 <br/>master<br/>pattern is generated using a very worn, genuine $20 bill, the discrimination <br/>system<br/>may reject an unacceptable number of genuine but crisp $20 bills.<br/> It has been found that scanning U.S. bills of different denominations along a<br/>central portion thereof provides scanning patterns sufficiently divergent to <br/>enable<br/>accurate discrimination between different denominations. Such a discrimination<br/>device is disclosed in U.S. Pat. No. 5,295,19b. However, currencies of other<br/>countries can differ from U.S. currency and from each other in a number of <br/>ways.<br/>For example, while all denominations of U.S. currencies are the same size, in <br/>many<br/>other countries currencies vary in size by denomination. Furthermore, there is <br/>a<br/>wide variety of bill sizes among different countries. In addition to size, the <br/>color of<br/>currency can vary by country and by denomination. Likewise, many other<br/>characteristics may vary between bills from different countries and of <br/>different<br/>denominations.<br/> As a result of the wide variety of currencies used throughout the world, a<br/>discrimination system designed to handle bills of one country generally can <br/>not<br/>handle bills from another country. Likewise, the method of discriminating <br/>bills of<br/>different denominations of one country may not be appropriate for use in<br/>discriminating bills of different denominations of another country. For <br/>example,<br/>scanning for a given characteristic pattern along a certain portion of bills <br/>of one<br/>country, such as optical reflectance about the central portion of U.S. bills, <br/>may not<br/>provide optimal discrimination properties for bills of another country, such <br/>as<br/> German marks.<br/> Furthermore, there is a distinct need for an identification system which is<br/>capable of accepting bills of a number of currency systems, that is, a system <br/>capable<br/>of accepting a number of bill-types. For example, a bank in Europe may need to<br/>process on a regular basis French, British, German, Dutch, etc. currency, each<br/>having a number of different denomination values.<br/> Some of the optical scanning systems available today employ two optical<br/>scanheads disposed on opposite sides of a bill transport path. One of the <br/>optical<br/><br/> CA 02215886 2000-02-02<br/>14<br/>scanheads scans one surface (e.g., green surface) of a currency bill to obtain <br/>a first<br/>set of reflectance data samples, while the other optical scanhead scans the <br/>opposite<br/>surface (e.g., black surface) of the currency bill to obtain a second set of <br/>reflectance<br/>data samples. These two sets of data samples are then processed and compared <br/>to<br/>stored characteristic patterns corresponding to the green surfaces of currency <br/>bills of<br/>different denominations. If degree of correlation between either set of data <br/>samples<br/>and any of the stored characteristic patterns is greater than a predetermined <br/>threshold,<br/>then the denomination of the bill is positively identified.<br/> A drawback of the foregoing technique for scanning both surfaces of a<br/>currency bill is that it is time-consuming to process and compare both sets of <br/>data<br/>samples for the scanned bill to the stored characteristic patterns. The set of <br/>data<br/>samples corresponding to the black surface of the scanned bill are processed <br/>and<br/>compared to the stored characteristic patterns even though no match should be <br/>found.<br/>As previously stated, the stored characteristic patterns correspond to the <br/>green<br/>surfaces of currency bills of different denominations.<br/> Another drawback of the foregoing scanning technique is that the set of data<br/>samples corresponding to the black surface of the scanned bill occasionally <br/>leads to<br/>false positive identification of a scanned bill. The reason for this false <br/>positive<br/>identification is that if a scanned bill is slightly shifted in the lateral <br/>direction relative<br/>to the bill transport path, the set of data samples corresponding to the black <br/>surface<br/>of the scanned bill may sufficiently correlate with one of the stored <br/>characteristic<br/>patterns to cause a false positive identification of the bill. The degree of <br/>correlation<br/>between the set of "black" data samples and the stored "green" characteristic <br/>patterns<br/>should, of course, not be greater than the predetermined threshold for <br/>positively<br/>identifying the denomination of the bill.<br/> Furthermore, in currency discriminating systems that rely on comparisons<br/>between a scanned pattern obtained from a subject bill and sets of stored <br/>master<br/>patterns, the ability of a system to accurately line up the scanned patterns <br/>to the<br/>master patterns to which they are being compared is important to the ability <br/>of a<br/>discrimination system to discriminate among bills of various denominations as <br/>well as<br/>between genuine bills and counterfeit bills without rejecting an unacceptable <br/>number<br/>of genuine bills. However, the ability of a system to line up scanned and <br/>master<br/><br/> CA 02215886 2000-02-02<br/>patterns is often hampered by the improper initiation of the scanning process <br/>which<br/>results in the generation of scanned patterns. If the generation of scanned <br/>patterns is<br/>initiated too early or too late, the resulting pattern will not correlate well <br/>with the<br/>master pattern associated with the identity of the currency; and as a result, <br/>a genuine<br/>5 bill may be rejected. There are a number of reasons why a discrimination <br/>system<br/>may initiate the generation of a scanned pattern too early or too late, for <br/>example,<br/>stray marks on a bill, the bleeding through of printed indicia from one bill <br/>in a stack<br/>onto an adjacent bill, the misdetection of the beginning of the area of the <br/>printed<br/>indicia which is desired to be scanned, and the reliance on the detection of <br/>the edge<br/>10 of a bill as the trigger for the scanning process coupled with the <br/>variance, from bill<br/>to bill, of the location of printed indicia relative to the edge of a bill. <br/>Therefore,<br/>there is a need to overcome the problems associated with correlating scanned <br/>and<br/>master patterns.<br/>In some currency discriminators bills are transported, one at a time, passed a<br/>15 discriminating unit. As the bills pass the discriminating unit, the <br/>denomination of<br/>each bill is determined and a running total of each particular currency <br/>denomination<br/>and/or of the total value of the bills that are processed is maintained. A <br/>number of<br/>discriminating techniques may be employed by the discriminating unit including<br/>optical or magnetic scanning of bills. A plurality of output bins are provided <br/>and the<br/>discriminator includes means for sorting bills into the plurality of bins. For <br/>example,<br/>a discriminator may be designed to recognize a number of different <br/>denominations of<br/>U.S. bills and comprise an equal number of output bins, one associated with <br/>each<br/>denomination. These discriminators also include a reject bin for receiving all <br/>bills<br/>which cannot be identified by the discriminating unit. These bills may later <br/>be<br/>examined by an operator and then either re-fed through the discriminator or <br/>set aside<br/>as unacceptable.<br/> Depending on the design of a discriminator, bills may be transported and<br/>scanned either along their long dimension or their narrow dimension. For a<br/>discriminator that transport bills in their narrow dimension, it is possible <br/>that a given<br/>bill may be oriented either face up or face down and either top edge first <br/>("forward"<br/>direction) or top edge last ("reverse" direction). For discriminators that <br/>transport<br/>bills in their long dimension, it is possible that a given bill may be <br/>oriented either<br/><br/> CA 02215886 2000-02-02<br/>16<br/>face up or face down and either left edge first ("forward" direction) or left <br/>edge last<br/>("reverse" direction). The manner in which a bill must be oriented as it <br/>passes a<br/>discriminating unit depends on the characteristics of the discriminator. Some<br/>discriminators are capable of identifying the denomination of a bill only if <br/>it is fed<br/>~ with a precise orientation, e.g., face up and top edge first. Other <br/>discriminators are<br/>capable of identifying bills provided they are "faced" (i.e., fed with a <br/>predetermined<br/>face orientation, that is all face up or all face down). For example, such a<br/>discriminator may be able to identify a bill fed face up regardless of whether <br/>the top<br/>edge is, fed first or last. Other discriminators are capable of identifying <br/>the<br/>denomination fed with any orientation. However, whether a given discriminator <br/>can<br/>discriminate between bills fed with different orientations depends on the<br/>discriminating method used. For example, a discriminator that discriminates <br/>bills<br/>based on patterns of transmitted light may be able to identify the <br/>denomination of a<br/>forward fed bill regardless of whether the bill is fed face up or face down, <br/>but the<br/>IS same discriminator would not be able to discriminate between a bill fed <br/>face up and a<br/>bill fed face down.<br/> Currently, discriminators are known which discriminate and/or sort by<br/>denomination when bills are properly faced. In such systems, all reverse-faced <br/>bills<br/>are not identified and are routed to a reject receptacle. Also discriminators <br/>are<br/>known which discriminate and/or sort between all bills facing up and all bills <br/>facing<br/>down. For example, in a multi-output pocket system, all face up bills, <br/>regardless of<br/>denomination, may be routed to a first pocket and all face down bills, <br/>regardless of<br/>denomination, may be routed to a second pocket. Furthermore, there is <br/>currently<br/>known discriminators designed to accept a stack of faced bills and flag the <br/>detection<br/>of a reverse-faced bill, thus allowing the reverse-faced bill to be removed <br/>from the<br/>stack. However, there remains a need for a discriminator that can detect and <br/>flag the<br/>presence of a bill oriented with an incorrect forward/reverse orientation and <br/>a<br/>discriminator that can sort between forward-oriented bills and reverse-<br/>oriented bills.<br/> Furthermore, for a number of reasons, a discriminating unit may be unable to<br/>determine the denomination of a bill. These reasons include a bill being <br/>excessively<br/>soiled, worn, or faded, a bill being torn or folded, a bill being oriented in <br/>a manner<br/>that the discriminating unit cannot handle, and the discriminating unit having <br/>poor<br/><br/> CA 02215886 2000-02-02<br/>17<br/>discriminating performance. Furthermore, the discriminating unit and/or a <br/>separate<br/>authenticating unit may determine that a bill is not genuine. In current<br/>discriminators, such unidentified or non-genuine bills are deposited in a <br/>reject<br/>receptacle.<br/>A characteristic of the above described discriminators is that the value of <br/>any<br/>rejected unidentified bills is not added to the running total of the aggregate <br/>value of<br/>the stack of bills nor do the counters keeping track of the number of each <br/>currency<br/>denomination reflect the rejected unidentified bills. While this is desirable <br/>with<br/>respect to bills which are positively identified as being fake, it may be <br/>undesirable<br/>with respect to bills which were not identified for other reasons even though <br/>they are<br/>genuine bills. While the bills in a reject receptacle may be re-fed through <br/>the<br/>discriminator, the operator must then add the totals from the first batch and <br/>the<br/>second batch together. Such a procedure can be inefficient in some situations. <br/>Also,<br/>if a bill was rejected the first time because it was, for example, excessively <br/>soiled or<br/>too worn, then it is likely that the bill will remain unidentified by the <br/>discriminating<br/>unit even if re-fed.<br/> A problem with the above described situations where the totals and/or counts<br/>do not reflect all the genuine bills in a stack is that an operator must then <br/>count all<br/>the unidentified genuine bills by. hand and add such bills to separately <br/>generated<br/>totals. As a result the chance for human error increases and operating <br/>efficiency<br/>decreases. Take for example a bank setting where a customer hands a teller a <br/>stack<br/>of currency to be deposited. The teller places the stack of bills in a <br/>discriminator,<br/>the display on the discriminator indicates that a total of $730 has been <br/>identified.<br/>However, fourteen genuine bills remain unidentified. As a result, the teller <br/>must<br/>count these fourteen bills by hand or re-fed through the discriminator and <br/>then add<br/>their total to the $730 total. An ermr could result from the teller <br/>miscounting the<br/>unidentified bills, the teller forgetting to add the two totals together, or <br/>the teller<br/>overlooking the unidentified bills entirely and only recording a deposit of <br/>$730.<br/>Moreover, even if the teller makes no mistakes, the efficiency of the teller <br/>is reduced<br/>by having to manually calculate additional totals. The decrease in efficiency <br/>is<br/>further aggravated where detailed records must be maintained about the <br/>specific<br/>number of each denomination processed during each transaction.<br/><br/> CA 02215886 2000-02-02<br/>18<br/> It is an object of the present invention to provide an improved method and<br/>apparatus for discriminating among currency bills comprising a plurality of <br/>currency<br/>denominations.<br/> It is another object of this invention to provide an improved method and<br/>apparatus of the above kind which is capable of efficiently discriminating <br/>among,<br/>authenticating, and counting bills of several currency denominations at a high <br/>speed and<br/>with a high degree of accuracy,<br/>Other features and advantages of the invention will become apparent upon<br/>reading the following detailed description in conjunction with the <br/>accompanying<br/>drawings.<br/>Briefly, in accordance with the present invention, a master pattern for a <br/>given<br/>denomination is generated by averaging a plurality of component patterns, <br/>typically<br/>three, each generated by scanning a genuine bill of the given denomination.<br/> According to one method, a master pattern for a given denomination is<br/>generated by averaging a plurality of component patterns, wherein the <br/>component<br/>patterns are generated by scanning one or more genuine bills of "standard" or<br/>average quality of the given denomination. A "standard" bill is a slightly <br/>used bill,<br/>as opposed to a crisp new bill or one which has been subject to a high degree <br/>of<br/>usage.<br/> According to another method, a master pattern for a given denomination is<br/>generated by averaging a plurality of component patterns, wherein some of the<br/>component patterns are generated by scanning one or more new bills of the <br/>given<br/>denomination and some of the component patterns are generated by scanning one <br/>or<br/>more old bills of the given denomination.<br/><br/> CA 02215886 2000-02-02<br/>19<br/> In accordance with a preferred embodiment of the present invention, the<br/>objectives enumerated above are achieved by scanning a document along one or <br/>more<br/>segments, generating one or more scanned patterns therefrom, and comparing the <br/>one<br/>or more scanned patterns to one or more master patterns associated with scans <br/>along<br/>corresponding segments of genuine documents. According to a preferred<br/>embodiment, bills are fed in and scanned across their narrow dimension. <br/>According<br/>to ahother preferred embodiment, bills are fed in and scanned across their <br/>wide<br/>dimension. A preferred embodiment of the present invention involves a <br/>technique<br/>based on the optical sensing of reflectance characteristics obtained by <br/>illuminating and<br/>scanning a document such as a currency bill along an appropriately selected <br/>segment<br/>or segments of a document. Light reflected from the bill as it is optically <br/>scanned is<br/>detected and used as an analog representation of the variation in the dark and <br/>light<br/>content of the printed pattern or indicia on the bill surface.<br/> A series of such detected reflectance signals are obtained by sampling and<br/>digitally processing, under microprocessor control, the reflected light at a <br/>plurality of<br/>predefined sample points as the bill is moved across the illuminated strip.<br/>Accordingly, a fixed number of reflectance samples is obtained across the <br/>note. The<br/>data samples obtained for a bill scan are subjected to digital processing, <br/>including a<br/>normalizing process to deaccentuate variations due to contrast fluctuations in <br/>the<br/>printed pattern or indicia existing on the surface of the bill being scanned. <br/>The<br/>normalized reflectance data represent a characteristic pattern that is fairly <br/>unique for<br/>a given bill identity and incorporates sufficient distinguishing features <br/>between<br/>characteristic patterns for different bill-types so as to accurately <br/>differentiate<br/>therebetween.<br/> By using the above approach, a series of master characteristic patterns are<br/>generated and stored using standard bills for each denomination of currency <br/>that is to<br/>be detected. The "standard" bills used to generate the master characteristic <br/>patterns<br/>are preferably bills that are slightly used bills. According to a preferred<br/>embodiment, two or four characteristic patterns are generated and stored <br/>within<br/><br/> CA 02215886 2000-02-02<br/>system memory for each detectable bill-type. The stored patterns correspond,<br/>respectively, to optical scans performed on one or both sides of a bill along<br/>"forward" and "reverse" directions relative to the pattern printed on the <br/>bill. For<br/>bills which produce significant pattern changes when shifted slightly to the <br/>left or<br/>5 right, such as the $10 bill in U.S. currency, it is preferred to store two <br/>patterns for<br/>each of the "forward" and "reverse" directions, each pair of patterns for the <br/>same<br/>direction represent two scan areas that are slightly displaced from each other <br/>along<br/>the lateral dimension of the bill. Preferably, the document identification <br/>system of<br/>this invention is adapted to identify different denominations of a plurality <br/>of currency<br/>10 systems. Accordingly, a master set of different characteristic patterns is <br/>stored<br/>within the system memory for subsequent correlation purposes.<br/>According to the correlation technique of this invention, the pattern <br/>generated<br/>by scanning a bill under test and processing the sampled data is compared with <br/>each<br/>of the prestored characteristic patterns within a preliminary set (to be <br/>described<br/>15 below) to generate, for each comparison, a correlation number representing <br/>the extent<br/>of similarity between corresponding ones of the plurality of data samples for <br/>the<br/>compared patterns. Bill identification is based on designating the scanned <br/>bill as<br/>belonging to the bill-type corresponding to the stored characteristic pattern <br/>for which<br/><br/> CA 02215886 1997-11-06<br/>21<br/>the correlation number resulting from pattern comparison is determined to be <br/>the<br/>highest. The possibility of a scanned bill having its identity <br/>mischaracterized<br/>following the comparison of characteristic patterns is significantly reduced <br/>by<br/>defining a bi-level threshold of correlation that must be satisfied for a <br/>"positive" call<br/>to be made.<br/> In essence, the present invention utilizes an optical sensing and correlation<br/>technique for positively identifying any of a plurality of different bill-<br/>types regardless<br/>of whether the bill is scanned along the "forward" or "reverse" directions. <br/>Likewise<br/>in a preferred embodiment of the present invention, the system is capable of<br/>identifying any of a plurality of different bill-types regardless of whether <br/>the bill is<br/>fed into the system with a "face up" or "face down" orientation. Face <br/>orientation can<br/>be accommodated by storing master patterns scanned from both sides of genuine<br/>documents, using a system having one or more scanheads on a single side of a<br/>document transport path, and comparing scanned patterns to master patterns <br/>retrieved<br/>from both sides of genuine documents. Alternatively, scanheads may be placed <br/>on<br/>both sides of a document transport path, scanned patterns retrieved from <br/>respective<br/>sides can be compared to master patterns from both sides or master patterns <br/>from<br/>corresponding sides where face orientation can be determined. Additionally, a <br/>cross<br/>check can be performed so that the identity determined by a match of patterns <br/>from<br/>one side of a document is consistent with the identity indicated by comparing <br/>patterns<br/>from the other side of the document. For both one-sided and two-sided scanhead<br/>systems, where the face orientation of a document can be determined before <br/>patterns<br/>are compared, scanned patterns from one side of a document can be compared <br/>only<br/>to master patterns retrieved from a corresponding side. Similar methods can be<br/>employed for accommodating documents fed in forward and reverse directions.<br/> In a preferred embodiment, the invention is particularly adapted to be<br/>implemented with a system programmed to track each identified currency <br/>identity so<br/>as to conveniently present aggregate totals for bills that have been <br/>identified at the<br/>end of a scan run. A preferred embodiment incorporates an abbreviated curved<br/>transport path for accepting currency bills that are to be counted and <br/>transporting the<br/>bills about their narrow dimension across a scanhead located downstream of the<br/>curved path and onto a conventional stacking station where sensed and counted <br/>bills<br/><br/> CA 02215886 2000-02-02<br/>22<br/>are collected. In a preferred embodiment, a scanhead of the present invention<br/>operates in conjunction with an optical encoder which is adapted to initiate <br/>the<br/>capture of a predefined number of reflectance data samples when a bill (and, <br/>thus,<br/>the indicia or pattern printed thereupon) moves across a coherent strip of <br/>light<br/>focused by the scanhead.<br/> In a preferred embodiment, a scanhead of the present invention uses a pair of<br/>light-emitting diodes ("LEDs") to focus a coherent light strip of predefined<br/>dimensions and having a normalized distribution of light intensity across the<br/>illuminated area. - The LEDs are angularly disposed and focus the desired <br/>strip of<br/>light onto the narrow dimension of a bill positioned flat across the scanning <br/>surface<br/>of the scanhead. A photodetector detects light reflected from the bill. The <br/>sampling<br/>of the photodetector output is controlled by the optical encoder to obtain the <br/>desired<br/>reflectance samples. In a preferred embodiment, initiation of sampling is <br/>based upon<br/>detection of the edge of a bill. In another preferred embodiment for bills <br/>having a<br/>borderline surrounding the remaining printed indicia, initiation of sampling <br/>is based<br/>upon detection of the borderline of a bill.<br/> Some of the above described techniques and apparatus as tailored to scanning<br/>U.S. currency are more fully disclosed in United States Patent No. 5,295,196, <br/>for a<br/>"Method and Apparatus for Currency Discrimination and Counting".<br/> In adapting the currency discriminating method and apparatus disclosed in<br/>United States Patent No. 5,295,196 to optimize the scanning of currencies from<br/>countries other than the United States, it is first noted that while it has <br/>been found<br/>that scanning along the central portion of the green side of U.S. bills <br/>provides good<br/>patterns to discriminate between the different U.S. denominations, foreign <br/>bills may<br/>require scanning along segments located in locations other than the center and <br/>the<br/>desirable areas to scan bills can vary from bill-type to bill-type. For <br/>example, it may<br/>be determined that it is desirable to scan German marks in the forward <br/>direction<br/>along a segment 1 inch (2.54 cm) to the left of center along the top face of a <br/>bill<br/>while it may be desirable to scan British pounds along a segment 1.5 inches <br/>(3.81<br/>cm) to the right of center. To provide a system capable of scanning along a <br/>plurality<br/>of laterally displaced segments, the present invention utilizes either a <br/>plurality of<br/><br/> CA 02215886 1997-11-06<br/>23<br/>laterally displaced stationary scanheads, one or more laterally moveable <br/>scanheads, or<br/>a linear array scanhead having a plurality of laterally displaced sensors. In <br/>a<br/>preferred embodiment, the scanheads or sensors are arranged in a symmetrical<br/>manner about the center of document to be scanned. Such a symmetrical<br/>S arrangement aids in providing a system which is capable of accepting bills <br/>fed in both<br/>the forward and reverse directions.<br/> Additionally, while all denominations of U.S. currency have the same size,<br/>currencies from other countries may vary in size from country to country as <br/>well as<br/>from denomination to denomination for currency from the same country. In a<br/>preferred embodiment of the present invention, variance in size is <br/>accommodated by<br/>incorporating means for determining the size of a document. These size <br/>determining<br/>means may include sensors separate from the scanheads or scanning sensors <br/>discussed<br/>above or alternatively, in some preferred embodiments of the present <br/>invention, may<br/>include the scanheads or scanning sensors discussed above which are used for <br/>the<br/>retrieval of scanned characteristic patterns. Based on the size information <br/>retrieved<br/>from a bill, selected scanheads may be activated, laterally moveable scanheads <br/>may<br/>be appropriately positioned and activated, and/or selected sensors in a linear <br/>array<br/>scanhead may be activated to permit scanning along appropriate segments of a <br/>bill<br/>based on its size. Alternatively, all scanheads or scanning sensors may be <br/>activated<br/>and the output of appropriately positioned scanheads or scanning sensors may <br/>be<br/>processed to generate scanned patterns based on the size of a bill. <br/>Furthermore,<br/>based on the size of a bill, a preliminary determination can be made as to <br/>which of a<br/>plurality of genuine bill-types a bill under test may potentially match. Based <br/>on such<br/>a preliminary determination, the comparison of generated scanned patterns can <br/>be<br/>limited to only master patterns associated with bill-types chosen from the <br/>preliminary<br/>set of potentially matching bills.<br/> Likewise, the transport mechanism which transports documents to be scanned<br/>past the above described scanheads may be designed to transport documents in a<br/>centered manner, left or right justified manner, in a non-controlled lateral <br/>positioned<br/>manner, in a non-skewed manner, or in a skewed manner. Sensors separate and<br/>distinct from the above described scanheads or the above described scanheads<br/>themselves may be used to determine the lateral positioning of transported <br/>bills<br/><br/> CA 02215886 1997-11-06<br/>24<br/>and/or their degree of skew. Based on a determination of the laterally <br/>positioning of<br/>a bill and/or its skew, appropriately positioned scanheads or scanning sensors <br/>may be<br/>activated or laterally moveable scanheads may be appropriately positioned and<br/>activated or the output from appropriately positioned scanheads or scanning <br/>sensors<br/>may be processed to generate scanned patterns based on the lateral positioning <br/>and/or<br/>skew of the bill.<br/> Additionally, while all denominations of U.S. currency have the same colors<br/>(a "green" side and a "black" side), currencies from other countries may vary <br/>in<br/>color from country to country as well as from denomination to denomination for<br/>currency from the same country. In a preferred embodiment of the present <br/>invention,<br/>variance in color is accommodated by incorporating means for determining the <br/>color<br/>of a document. These color determining means may include sensors separate from<br/>the scanheads or sensors discussed above or alternatively, in some preferred<br/>embodiments of the present invention, may include the appropriately modified<br/>scanheads or sensors discussed above which are used for the retrieval of <br/>scanned<br/>characteristic patterns. For example, colored filters may be placed in front <br/>of the<br/>above described scanheads or sensors. Based on the color information retrieved <br/>from<br/>a bill, selected scanheads may be activated, laterally moveable scanheads may <br/>be<br/>appropriately positioned and activated, and/or selected sensors in a linear <br/>array<br/>scanhead may be activated to permit scanning along appropriate segments of a <br/>bill<br/>based on its color. Alternatively, all scanheads or scanning sensors may be <br/>activated<br/>and the output of appropriately positioned scanheads or scanning sensors may <br/>be<br/>processed to generate scanned patterns based on the color of a bill. <br/>Furthermore,<br/>based on the color of a bill, a preliminary determination can be made as to <br/>which ~of<br/>a plurality of genuine bill-types a bill under test may potentially match. <br/>Based on<br/>such a preliminary determination, the comparison of generated scanned patterns <br/>can<br/>be limited to only master patterns associated with bill-types chosen from the<br/>preliminary set of potentially matching bills.<br/>In a preferred embodiment of the present invention, both color and size<br/>information may be utilized as described above.<br/><br/> CA 02215886 1997-11-06<br/> In a preferred embodiment of the present invention, scanheads are positioned<br/>on both sides of a document transport path so as to permit scanning of either <br/>or both<br/>sides of a document.<br/> According to a preferred embodiment, an apparatus for currency<br/>5 discrimination comprises first and second stationary scanheads, disposed on <br/>opposite<br/>sides of a bill transport path, for scanning respective first and second <br/>opposing<br/>surfaces of a bill traveling along the bill transport path and for producing <br/>respective<br/>output signals. The bill travels along the transport path in the direction of <br/>a<br/>predetermined dimension of the bill. A memory stores master characteristic <br/>patterns<br/>10 corresponding to associated predetermined surfaces (e.g., green surfaces) <br/>of a<br/>plurality of denominations of genuine bills. Sampling circuitry samples the <br/>output<br/>signals associated with the respective first and second opposing surfaces of <br/>the<br/>scanned bill. A signal processor is programmed to determine which one of the <br/>first<br/>and second opposing surfaces corresponds to the associated predetermined <br/>surfaces of<br/>15 the plurality of denominations of genuine bills. According to a preferred <br/>embodiment<br/>adapted for discriminating, for example, U.S. bills, the determination as to <br/>which<br/>surface of a bill corresponds to a predetermined surface is made by detecting <br/>the<br/>borderlines on each side of a bill and determining the relative times of <br/>detection of<br/>each borderline. The processor then correlates the output signal associated <br/>with the<br/>20 one of the first and second opposing surfaces corresponding to the <br/>associated<br/>predetermined surfaces with the master characteristic patterns. If the degree <br/>of<br/>correlation between the selected output signal and any of the stored <br/>characteristic<br/>patterns is greater than a predetermined threshold, then the denomination of <br/>the bill is<br/>positively identified.<br/>25 For each scanhead, initiation of sampling is based upon detection of the<br/>change in reflectance value that occurs when the outer border of the printed <br/>pattern<br/>on a bill is encountered relative to the reflectance value obtained at the <br/>edge of the<br/>bill where no printed pattern exists. According to a preferred embodiment of <br/>this<br/>invention, illuminated strips of at least two different dimensions are used <br/>for the<br/>scanning process. A narrow strip is used initially to detect the starting <br/>point of the<br/>printed pattern on a bill and is adapted to distinguish the thin borderline <br/>that typically<br/>marks the starting point of and encloses the printed pattern on a bill. For <br/>the rest of<br/><br/> CA 02215886 1997-11-06<br/>26<br/>the preselected dimension scanning following detection of the borderline of <br/>the<br/>printed pattern, a substantially wider strip of light is used to collect the <br/>predefined<br/>number of samples for a bill scan. The generation and storage of <br/>characteristic<br/>patterns using standard notes and the subsequent comparison and correlation<br/>procedure for classifying the scanned bill as belonging to one of several <br/>predefined<br/>currency denominations is based on the above-described sensing and correlation<br/>technique.<br/> Furthermore, in accordance with another feature of the present invention, the<br/>objectives enumerated above in connection with correlating patterns are <br/>achieved by<br/>repetitively comparing a scanned pattern with multiple sets of master patterns <br/>until a<br/>sufficient match is found, or alternatively, by repetitively comparing a set <br/>of original<br/>master patterns with multiple scanned patterns until a sufficient match is <br/>found. The<br/>multiple sets of master patterns comprise an original set of master patterns <br/>plus one<br/>or more sets of modified versions of the original master patterns. The <br/>multiple<br/>scanned patterns comprise an original scanned pattern plus one or more <br/>modified<br/>versions of the original scanned patterns. Each modified pattern comprises one <br/>or<br/>more replicated data values from a corresponding original pattern to which <br/>each<br/>modified pattern is to be compared. Alternatively, each modified master <br/>pattern<br/>comprises one or more data values which are set equal to zero.<br/> Briefly, in accordance with a preferred embodiment, an improved method of<br/>generating modified scanned or master patterns for use in a discrimination <br/>system<br/>capable of identifying one or more currency bills is provided. Each of the <br/>scanned<br/>and master patterns comprises a sequence of data values representing analog<br/>variations of characteristic information along a segment of a bill and each <br/>pattern has<br/>a leading end and a trailing end. Each of the data values has an associated <br/>sequence<br/>position. The modified scanned or master patterns are generated by designating<br/>either the scanned pattern or the master pattern for modification and <br/>inserting a<br/>predetermined number, R, of data values at either the trailing end of the <br/>sequence of<br/>data values of the designated pattern when the modification is performed in <br/>the<br/>forward direction or the leading end of the sequence of data values of the <br/>designated<br/>pattern when the modification is performed in the backward direction. This<br/>modification effectively removes R data values from the leading or trailing <br/>end of the<br/><br/> CA 02215886 1997-11-06<br/>27<br/>designated pattern. Either the last R data values of the designated pattern <br/>are set<br/>equal to the last R data values of the non-designated pattern when the <br/>modification is<br/>performed in the forward direction or the first R data values of the <br/>designated pattern<br/>are set equal to the first R data values of the non-designated pattern when <br/>the<br/>modification is performed in the backward direction. Alternatively, the <br/>modified<br/>master patterns are generated by inserting R data samples at the leading or <br/>trailing<br/>ends of the master patterns and by setting the first R or last R data samples <br/>of the<br/>modified master pattern equal to zero.<br/> According to a preferred method, a modified scanned pattern is generated by<br/>removing a predetermined number of leading or trailing data values of an <br/>original<br/>scanned pattern. Trailing or leading data values, respectively, are added to <br/>the<br/>modified scanned pattern with the added data values being copied from <br/>corresponding<br/>sequence positions of a corresponding master pattern. Alternatively, instead <br/>of<br/>explicitly removing leading or trailing data values, the leading or trailing <br/>data values<br/>may be effectively removed by adding data values to the opposite end of the <br/>scanned<br/>pattern and treating the modified scanned pattern as not including the <br/>"removed"<br/>leading or trailing data values. .<br/>According to another preferred method, a modified master pattern is generated<br/>in a similar manner except that added trailing or leading data values of the <br/>modified<br/>master pattern are set equal to data values copied from corresponding sequence<br/>positions of a scanned pattern.<br/> According to another preferred method, a modified master pattern is generated<br/>in a similar manner except that added trailing or leading data values of the <br/>modified<br/>master pattern are set equal to zero. .<br/> The above described modified patterns or pattern generation methods may be<br/>employed in currency identification systems to compensate for misalignment <br/>between<br/>scanned and master patterns.<br/> According to another preferred method, a scanned pattern comprising a<br/>number of data values is compared with one or more master patterns also <br/>comprising<br/>a number of data values. The scanned and master patterns represent analog<br/>variations in characteristic information retrieved from bills along <br/>corresponding<br/>segments. For example, the patterns may comprise 64 data values generated by<br/><br/> CA 02215886 1997-11-06<br/>28<br/>sampling the output of a photodetector as a bill is moved relative to a <br/>scanhead, the<br/>output of the photodetector representing analog variation in the reflectance <br/>of light<br/>along a given segment of the bill. If none of the master patterns sufficiently <br/>match<br/>the scanned pattern, the scanned pattern may be modified and the modified <br/>scanned<br/>pattern compared to the master patterns. For example, data values #1 and #2 <br/>may be<br/>removed from the scanned pattern sequence, scanned patterns #3 and #4 may be<br/>made the first and second values in the modified sequence with subsequent data<br/>values modified accordingly. As a result of such a process, the original data <br/>values<br/>#63 and #64 now become modified data values #61 and #62. As a result of the<br/>above steps an incomplete modified pattern of data values #1 - #62 is <br/>generated.<br/> According to a preferred embodiment, modified data values #63 and #64 are<br/>generated by replicating data values #63 and #64 of the master patterns to <br/>which the<br/>modified scanned pattern is to be compared. If the modified patterns do not<br/>sufficiently match any of the master patterns, the modification process may be<br/>reiterated except that new scanned modified values #61 - #64 are generated by<br/>replicating master pattern values #61 - #64. This process is repeated until a <br/>sufficient<br/>match is found or until a predetermined number of modification, iterations <br/>have<br/>occurred.<br/> According to another preferred embodiment, scanned patterns may be<br/>modified backwards instead of the forward modification described above.<br/> According to another preferred embodiment, master patterns may be modified<br/>instead of scanned patterns. According to this method, data values from <br/>scanned<br/>patterns are replicated into appropriate locations in modified master pattern<br/>sequences.<br/> According to another preferred embodiment, trailing or leading sequence<br/>positions of modified master patterns may be filled with zeros instead of <br/>replicated<br/>data values from a scanned pattern to which modified master patterns are to be<br/>compared.<br/> According to another preferred embodiment, modified master patterns with<br/>trailing or leading data values equal to zero are stored in a memory of an<br/>identification system along with corresponding unmodified master patterns, the <br/>master<br/>patterns and modified master patterns being stored before a bill under test is <br/>scanned<br/><br/> CA 02215886 1997-11-06<br/>29<br/>by the identification system. When a bill under test is scanned by the <br/>identification<br/>system it is compared to one or more of the master patterns. If the identity <br/>of the<br/>bill can not be determined based on this comparison, the scanned pattern is <br/>compared<br/>with one or more of the modified master patterns. This process can be <br/>repeated,<br/>with the scanned pattern being compared to multiply modified master patterns <br/>if<br/>necessary.<br/> According to another preferred embodiment, a currency evaluation device is<br/>provided that is able to discriminate among bills of different denominations <br/>from two<br/>or more currency systems. In a preferred embodiment, such a device is provided <br/>that<br/>is able to discriminate among both Canadian and German bills of different<br/>denominations. In a preferred embodiment, such a device utilizes three <br/>scanheads<br/>when scanning Canadian bills and a single scanhead when scanning German bills.<br/>The device is able to accept faced Canadian and German bills fed in either the<br/>forward or reverse directions. According to a preferred embodiment, the <br/>operator of<br/>the device pre-declares whether Canadian or German bills are to be <br/>discriminated.<br/>According to a preferred embodiment the measured length of the narrow <br/>dimension<br/>of German bills is utilized in discriminating German bills. To accommodate for<br/>possible lateral shifting of bills relative to the scanhead, multiple German <br/>master<br/>patterns associated with laterally displaced scans are stored for some <br/>denominations.<br/>To accommodate for possible lateral shifting of bills relative to the <br/>scanheads,<br/>multiple Canadian patterns associated with laterally displaced scans are <br/>generated and<br/>averaged in generated stored Canadian master patterns. To compensate for <br/>problems<br/>associated with triggering scanning relative to the edge of a bill, multiple <br/>patterns are<br/>stored for both Canadian and German bills associated with both leading and <br/>lagging<br/>printed indicia.<br/> In accordance with another preferred embodiment of the present invention, a<br/>correlation technique is utilized whereby a scanned pattern generated from the <br/>green<br/>side of a test bill is correlated against stored green-side master patterns. <br/>If as a result<br/>of the green-side correlation, the denomination of the test bill can not be <br/>called, a<br/>scanned pattern generated from the black side of the test bill is correlated <br/>against<br/>stored black-side master patterns. More particularly, if the green-side <br/>correlation<br/>results in an indication that the test bill is a $20, $50, or $100 bill but <br/>not with<br/><br/> CA 02215886 1997-11-06<br/>sufficiently high certainty so as to permit calling the denomination of the <br/>test bill,<br/>then the black-side scanned pattern is correlated against one or more black-<br/>side<br/>master patterns, provided the best call green-side correlation number is <br/>greater than a<br/>predetermined threshold.<br/>5 According to a preferred embodiment, documents, including currency bills,<br/>are discriminated by comparing a scanned pattern retrieved from a first side <br/>of a test<br/>document with one or more stored master patterns retrieved from a first side <br/>of one<br/>or more genuine documents and comparing a scanned pattern retrieved from a <br/>second<br/>side of a test document with one or more stored master patterns retrieved from <br/>a<br/>10 second side of one or more genuine documents.<br/> According to one embodiment a currency discriminator is provided that counts<br/>and discriminates bills as they pass a discriminating unit and that flags an <br/>unidentified<br/>bill or one having a predetermined characteristic, for example a bill having a<br/>specified orientation, by transferring the flagged bill to a location where it <br/>can be<br/>15 conveniently examined by an operator and then suspending the operation of <br/>the<br/>discriminator. The operator may then examine the bill and determine whether <br/>the<br/>bill is acceptable or not. Denomination selection elements such as keys are <br/>provided<br/>to enable the operator with the depression of a single button to indicate the<br/>denomination of an unidentified but acceptable bill, to cause the value of the <br/>bill to<br/>20 be reflected in any appropriate counters, and to cause the discriminator to <br/>resume<br/>operation. A continuation selection element is also provided to enable the <br/>operator to<br/>cause the discriminator to resume operation without adversely affecting any <br/>counters<br/>when an unidentified bill is determined to be unacceptable.<br/> According to one embodiment of the present invention, a discriminator is<br/>25 provided with a single output receptacle in which all bills are stacked <br/>after they pass<br/>by the discriminating unit. When an unidentified bill is detected, the <br/>discriminator<br/>halts operation with the unidentified bill positioned at a predetermined <br/>location within<br/>the stack such as at the top or back of the stack of bills in the output <br/>receptacle or at<br/>a predetermined position just prior to the stack. The bill may then be <br/>conveniently<br/>30 examined by the operator.<br/> According to another embodiment of the present invention, a discriminator is<br/>provided with an examining station where unidentified bills are transferred <br/>before the<br/><br/> CA 02215886 1997-11-06<br/>31<br/>discriminator halts operation. Upon determination that a bill is acceptable, <br/>the bill<br/>may then be transferred to the output receptacle in a single output receptacle<br/>discriminator or to an output receptacle associated with the denomination or <br/>other<br/>characteristic of the bill in a mufti-output receptacle discriminator. <br/>Additionally, a<br/>reject receptacle may be provided for receiving bills which are determined to <br/>be<br/>unacceptable.<br/> According to another embodiment of the present invention, a discriminator<br/>discriminates a stack of bills and flags bills having a given forward/reverse<br/>orientation. Accordingly, when a stack of bills predominately oriented in the <br/>forward<br/>or reverse direction is discriminated by the discriminator, any bills oriented <br/>in the<br/>opposite forward/reverse direction may be flagged. Any flagged bills may <br/>either be<br/>removed without replacement or re-oriented in the appropriate forward or <br/>reverse<br/>direction. As a result, a stack of bills may be generated in which all bills <br/>have the<br/>same forward/reverse orientation. Alternatively, in a mufti-output receptacle<br/>discriminator, instead of flagging bills based on their forward/reverse <br/>orientation,<br/>bills having a forward orientation may be routed to one output receptacle and <br/>those<br/>having a reverse orientation may be routed to another output receptacle.<br/>Likewise a discriminator may flag or sort bills based on their face <br/>orientation,<br/>that is face up or face down, or bills not belonging to a given denomination.<br/>Furthermore, the above criteria may be combined in various operating modes of <br/>the<br/>discriminator.<br/>In a preferred embodiment, the discriminator optically scans an area of a bill<br/>and generates a scanned pattern from optical reflectance samples. A scanned <br/>pattern<br/>is compared with a plurality of master patterns associated with genuine bills <br/>of<br/>different denominations. Furthermore, the discriminator may store master <br/>patterns<br/>associated with both forward and reverse scans and/or both top surface and <br/>bottom<br/>surface scans of genuine bills.<br/>In a preferred embodiment, a bill is scanned for first and second <br/>characteristic<br/>information, utilizing the first characteristic information to determine the<br/>denomination of a scanned bill, and using the second characteristic <br/>information to<br/>verify the genuineness of the bill. More particularly, a currency evaluation <br/>device,<br/>according to the present invention, comprises detection circuitry for <br/>detecting first<br/><br/>_ CA 02215886 1997-11-06<br/>32<br/>and second characteristic information from a scanned bill, a memory for <br/>storing sets<br/>of genuine first and second characteristic information for a plurality of <br/>denominations<br/>of genuine bills, and signal processing means for comparing the detected first <br/>and<br/>second characteristic information with the stored genuine first and second<br/>characteristic information. The signal processing means performs a first <br/>comparison<br/>whereby the detected first characteristic information is compared with the <br/>stored sets<br/>of genuine first characteristic information. This first comparison results in <br/>either an<br/>indication of the denomination of the scanned bill or an error. The results of <br/>the frst<br/>comparison are used to streamline a second comparison between detected and <br/>stored<br/>second characteristic information. The second comparison compares the detected<br/>second characteristic information with stored genuine second characteristic<br/>information corresponding to the denomination indicated by the first <br/>comparison. .<br/>The second comparison results in either an indication of the genuineness of <br/>the<br/>scanned bill or an error.<br/> According to a preferred embodiment of the present invention, a document to<br/>be authenticated is illuminated with ultraviolet light and the amount of <br/>ultraviolet<br/>light which is reflected off the document is measured. Based on the amount of<br/>ultraviolet light which is detected, the document is either authenticated or <br/>rejected.<br/>In the case of documents being authenticated relative to United States <br/>currency, a bill<br/>is rejected if a high level of reflected ultraviolet light is not detected.<br/> In another preferred embodiment, the above objectives are achieved by<br/>illuminating a document with ultraviolet light and measuring both the amount <br/>of<br/>reflected ultraviolet light and the amount of emitted visible light. Based on <br/>the<br/>amount of ultraviolet light detected and the amount of visible light detected, <br/>a<br/>document is either authenticated or rejected. In the case of documents being<br/>authenticated relative to United States currency, a bill is rejected if either <br/>a high level<br/>of reflected ultraviolet light is not detected or even a low level of visible <br/>light is<br/>detected.<br/> As explained above, it is known that some counterfeit United States bills<br/>fluoresce, or emit visible light, when illuminated by ultraviolet light. As <br/>genuine<br/>United States currency does not fluoresce, the emission of visible light has <br/>been<br/>employed as a means of detecting counterfeit United States currency. However, <br/>it<br/><br/> CA 02215886 1997-11-06<br/>33<br/>has been found that not all counterfeit United States bills fluoresce; and <br/>hence, such<br/>counterfeits will not be detected by the above described fluorescence test.<br/>It has been found that genuine United States currency reflects a high level of<br/>ultraviolet light when illuminated by an ultraviolet light source. It has also <br/>been<br/>found that some counterfeit United States bills do not reflect a high level of<br/>ultraviolet light. Such counterfeit bills may or may not also fluoresce under<br/>ultraviolet light. The present invention employs an authentication test <br/>wherein the<br/>amount of reflected ultraviolet light is measured and a bill is rejected if it <br/>does not<br/>reflect a high amount of ultraviolet light. By employing such a test, <br/>counterfeit<br/>United States bills which do not reflect a high level of ultraviolet light may <br/>be<br/>properly rejected.<br/> While not all counterfeit United States bills fail to reflect a high level of<br/>ultraviolet light and hence not all counterfeit United States bills will be <br/>detected using<br/>this test, the present invention provides an additional means for detecting <br/>counterfeit<br/>bills which might otherwise go undetected. Furthermore, the likelihood of a<br/>counterfeit United States bill going undetected may be further reduced by <br/>employing<br/>an alternative embodiment of the present invention wherein both the amount of<br/>reflected ultraviolet light and the amount of emitted visible light are <br/>measured. In<br/>such a system, a bill is rejected as counterfeit if either it fails to reflect <br/>a high level<br/>of ultraviolet light or it fluoresces.<br/> The above described embodiments may be adapted to authenticate currencies<br/>from other countries and other types of documents such as food stamps and <br/>checks.<br/>For instance some genuine documents may be designed to reflect ultraviolet <br/>light only<br/>in certain locations andlor in a predetermined pattern. An alternative <br/>embodiment of<br/>the present invention may be designed to accept documents which exhibit <br/>similar<br/>characteristics while rejecting those which do not. Likewise, an alternative<br/>embodiment of the present invention may be employed to authenticate documents<br/>based on both their characteristics with respect to reflected ultraviolet <br/>light and their<br/>characteristics with respect to fluorescent emissions, e.g., detecting the <br/>amount,<br/>location, and/or pattern of fluorescent emissions.<br/><br/> CA 02215886 1997-11-06<br/>34<br/> Brief Description Of The Drawings<br/> FIG. 1 is a perspective view of a currency scanning and counting machine<br/>embodying the present invention;<br/> FIG. 2a is a functional block diagram of the currency scanning and counting<br/>machine of FIG. 1 illustrating a scanhead arranged on each side of a transport <br/>path;<br/> FIG. 2b is a functional block diagram of the currency scanning and counting<br/>machine illustrating a scanhead arranged on a single side of a transport path;<br/> FIG. 2c is a functional block diagram of the currency scanning and counting<br/>machine similar to that of FIG. 2b but illustrating the feeding and scanning <br/>of bills<br/>along their wide direction;<br/> FIG. 2d is a functional block diagram of the currency scanning and counting<br/>machine similar to that of FIGs. 2a-2d illustrating the employment of a second<br/>characteristic detector;<br/> FIG. 3 is a diagrammatic perspective illustration of the successive areas<br/>scanned during the traversing movement of a single bill across an optical <br/>sensor<br/>according to a preferred embodiment of the present invention;<br/> FIGS. 4a and 4b are perspective views of a bill and a preferred area to be<br/>optically scanned on the bill;<br/> FIGs. Sa and Sb are diagrammatic side elevation views of the scan area to be<br/>optically scanned on a bill according to preferred embodiments of the present<br/>invention;<br/> FIG. 6a is a perspective view of a bill showing the preferred area of a first<br/>surface to be scanned by one of the two scanheads employed in the preferred<br/>embodiment of the present invention;<br/> FIG. 6b is another perspective view of the bill in FIG. 6a showing the<br/>preferred area of a second surface to be scanned by the other of the scanheads<br/>employed in the preferred embodiment of the present invention;<br/> FIG. 6c is a side elevation showing the first surface of a bill scanned by an<br/>upper scanhead and the second surface of the bill scanned by a lower scanhead;<br/> FIG. 6d is a side elevation showing the first surface of a bill scanned by a<br/>lower scanhead and the second surface of the bill scanned by an upper <br/>scanhead;<br/><br/>w CA 02215886 1997-11-06<br/> FIGS. 7a and 7b form a block diagram illustrating a preferred circuit<br/>arrangement for processing and correlating reflectance data according to the <br/>optical<br/>sensing and counting technique of this invention;<br/> FIGS. 8a and 8b comprise a flowchart illustrating the sequence of operations<br/>5 involved in implementing a discrimination and authentication system <br/>according to a<br/>preferred embodiment of the present invention;<br/> FIG. 9 is a flow chart illustrating the sequential procedure involved in<br/>detecting the presence of a bill adjacent the lower scanhead and the <br/>borderline on the<br/>side of the bill adjacent to the lower scanhead;<br/>10 FIG. 10 is a flow chart illustrating the sequential procedure involved in<br/>detecting the presence of a bill adjacent the upper scanhead and the <br/>borderline on the<br/>side of the bill adjacent to the upper scanhead;<br/>FIG. l la is a flow chart illustrating the sequential procedure involved in <br/>the<br/>analog-to-digital conversion routine associated with the lower scanhead;<br/>15 FIG. llb is a flow chart illustrating the sequential procedure involved in <br/>the<br/>analog fo-digital conversion routine associated with the upper scanhead;<br/> FIG. 12 is a flow chart illustrating the sequential procedure involved in<br/>determining which scanhead is scanning the green side of a U.S. currency bill;<br/> FIG. 13 is a flow chart illustrating the sequence of operations involved in<br/>20 determining the bill denomination from the correlation results;<br/> FIG. 14 is a flow chart illustrating the sequential procedure involved in<br/>decelerating and stopping the bill transport system in the event of an error;<br/>FIG. 15a is a graphical illustration of representative characteristic patterns<br/>generated by narrow dimension optical scanning of a $1 currency bill in the <br/>forward<br/>25 direction;<br/>FIG. lSb is a graphical illustration of representative characteristic patterns<br/>generated by narrow dimension optical scanning of a $2 currency bill in the <br/>reverse<br/>direction;<br/>FIG. 15c is a graphical illustration of representative characteristic patterns<br/>30 generated by narrow dimension optical scanning of a $100 currency bill in <br/>the<br/>forward direction;<br/><br/> CA 02215886 1997-11-06<br/>36<br/> FIG. 15d is a graph illustrating component patterns generated by scanning old<br/>and new $20 bills according a second method according to a preferred <br/>embodiment of<br/>the present invention;<br/> FIG. 15e is a graph illustrating an pattern for a $20 bill scanned in the<br/>forward direction derived by averaging the patterns of FIG. 15d according a <br/>second<br/>method according to a preferred embodiment of the present invention;<br/> FIGS. 16a-e are graphical illustrations of the effect produced on correlation<br/>pattern by using the progressive shifting technique, according to an <br/>embodiment of<br/>this invention;<br/> FIGS. 17a-17c are a flowchart illustrating a preferred embodiment of a<br/>modified pattern generation method according to the present invention;<br/>FIG. 18a is a flow chart illustrating the sequential procedure involved in the<br/>execution of multiple correlations of the scan data from a single bill;<br/>FIG. 18b is a flow chart illustrating a modified sequential procedure of that <br/>of<br/> FIG.l8a;<br/> FIG. 19a is a flow chart illustrating the sequence of operations involved in<br/>determining the bill denomination from the correlation results using data <br/>retrieved<br/>from the green side of U.S. bills according to one preferred embodiment of the<br/>present invention;<br/> FIGS. 19b and 19c are a flow chart illustrating the sequence of operations<br/>involved in determining the bill denomination from the correlation results <br/>using data<br/>retrieved from the black side of U.S. bills;<br/> FIG. 20a is an enlarged vertical section taken approximately through the<br/>center of the machine, but showing the various transport rolls in side <br/>elevation;<br/> FIG. 20b is a top plan view of the interior mechanism of the machine of FIG.<br/>1 for transporting bills across the optical scanheads, and also showing the <br/>stacking<br/>wheels at the front of the machine;<br/> FIG. 21a is an enlarged perspective view of the bill transport mechanism<br/>which receives bills from the stripping wheels in the machine of FIG. 1;<br/>FIG. 21b is a cross-sectional view of the bill transport mechanism depicted in<br/> FIG. 21 along line 21b;<br/><br/> CA 02215886 1997-11-06<br/>37<br/> FIG. 22 is a side elevation of the machine of FIG. 1, with the side panel of<br/>the housing removed;<br/> FIG. 23 is an enlarged bottom plan view of the lower support member in the<br/>machine of FIG. 1 and the passive transport rolls mounted on that member;<br/>FIG. 24 is a sectional view taken across the center of the bottom support<br/>member of FIG. 23 across the narrow dimension thereof;<br/> FIG. 25 is an end elevation of the upper support member which includes the<br/>upper scanhead in the machine of FIG. 1, and the sectional view of the lower <br/>support<br/>member mounted beneath the upper support member;<br/> FIG. 26 is a section taken through the centers of both the upper and lower<br/>support members, along the long dimension of the lower support member shown in<br/> FiG. 23;<br/> FIG. 27 is a top plan view of the upper support member which includes the<br/>upper scanhead;<br/> FIG. 28 is a bottom plan view of the upper support member which includes<br/>the upper scanhead;<br/>FIG. 29 is an illustration of the light distribution produced about one of the<br/>optical scanheads;<br/> FIGs. 30a and 30b are diagrammatic illustrations of the location of two<br/>auxiliary photo sensors relative to a bill passed thereover by the transport <br/>and<br/>scanning mechanism shown in FIGs. 20a-28;<br/> FIG. 31 is a flow chart illustrating the sequential procedure involved in a<br/>ramp-up routine for increasing the transport speed of the bill transport <br/>mechanism<br/>from zero to top speed;<br/> FIG. 32 is a flow chart illustrating the sequential procedure involved in a<br/>ramp-to-slow-speed routine for decreasing the transport speed of the bill <br/>transport<br/>mechanism from top speed to slow speed;<br/> FIG. 33 is a flow chart illustrating the sequential procedure involved in a<br/>ramp-to-zero-speed routine for decreasing the transport speed of the bill <br/>transport<br/>mechanism to zero;<br/><br/>_ CA 02215886 1997-11-06<br/>38<br/> FIG. 34 is a flow chart illustrating the sequential procedure involved in a<br/>pause-after-ramp routine for delaying the feedback loop while the bill <br/>transport<br/>mechanism changes speeds;<br/> FIG. 35 is a flow chart illustrating the sequential procedure involved in a<br/>feedback loop routine for monitoring and stabilizing the transport speed of <br/>the bill<br/>transport mechanism;<br/> FIG. 36 is a flow chart illustrating the sequential procedure involved in a<br/>doubles detection routine for detecting overlapped bills;<br/> FIG. 37 is a flow chart illustrating the sequential procedure involved in a<br/>routine for detecting sample data representing dark blemishes on a bill;<br/> FIG. 38 is a flow chart illustrating the sequential procedure involved in a<br/>routine for maintaining a desired readhead voltage level;<br/> FIG. 39 is a top view of a bill and size determining sensors according to a<br/>preferred embodiment of the present invention;<br/> FIG. 40 is a top view of a bill illustrating multiple areas to be optically<br/>scanned on a bill according to a preferred embodiment of the present <br/>invention;<br/> FIG. 41a is a graph illustrating a scanned pattern which is offset from a<br/>corresponding master pattern;<br/> FIG. 41b is a graph illustrating the same patterns of FIG. 41a after the<br/>scanned pattern is shifted relative to the master pattern;<br/> FIG. 42 is a side elevation of a multiple scanhead arrangement according to a<br/>preferred embodiment of the present invention;<br/> FIG. 43 is a side elevation of a multiple scanhead arrangement according to<br/>another preferred embodiment of the present invention;<br/> FIG. 44 is a side elevation of a multiple scanhead arrangement according to<br/>another preferred embodiment of the present invention;<br/> FIG. 45 is a side elevation of a multiple scanhead arrangement according to<br/>another preferred embodiment of the present invention; '<br/> FIG. 46 is a top view of a staggered scanhead arrangement according to a<br/>preferred embodiment of the present invention;<br/> FIG. 47a is a top view of a linear array scanhead according to a preferred<br/>embodiment of the present invention illustrating a bill being fed in a <br/>centered fashion;<br/><br/>-.,:, .<br/> CA 02215886 1997-11-06<br/>39<br/> FIG. 47b is a side view of a linear array scanhead according to a preferred<br/>embodiment of the present invention illustrating a bill being fed in a <br/>centered fashion;<br/> FIG. 48 is a top view of a linear array scanhead according to another<br/>preferred embodiment of the present invention illustrating a bill being fed in <br/>a non-<br/>centered fashion;<br/> FIG. 49 is a top view of a linear array scanhead according to another<br/>preferred embodiment of the present invention illustrating a bill being fed in <br/>a<br/>skewed fashion;<br/> FIGs. SOa and SOb are a flowchart of the operation of a currency<br/>discrimination system according to a preferred embodiment of the present <br/>invention;<br/> FIG. 51 is a top view of a triple scanhead arrangement utilized in a<br/>discriminating device able to discriminate both Canadian and Geiman bills <br/>according<br/>to a preferred embodiment of the present invention;<br/> FIG. 52 is a top view of Canadian bill illustrating the areas scanned by the<br/>triple scanhead arrangement of FIG. 51 according to a preferred embodiment of <br/>the<br/>present invention;<br/> FIG. 53 is a flowchart of the threshold tests utilized in calling the<br/>denomination of a Canadian bill according to a preferred embodiment of the <br/>present<br/>invention;<br/> FIG. 54a illustrates the general areas scanned in generating master 10 DM<br/> German patterns according to a preferred embodiment of the present invention;<br/> FIG. 54b illustrates the general areas scanned in generating master 20 DM,<br/>50 DM, and 100 DM German patterns according to a preferred embodiment of the<br/>present invention;<br/> FIG. 55 is a flowchart of the threshold tests utilized in calling the<br/>denomination of a German bill according to a preferred embodiment of the <br/>present<br/>invention;<br/>FIG. 56 is a functional block diagram illustrating a preferred embodiment of a <br/>.<br/>document authenticator and discriminator according to the present invention;<br/> FIG. 57 is a functional block diagram illustrating another preferred<br/>embodiment of a document authenticator and discriminator according to the <br/>present<br/>invention;<br/><br/> CA 02215886 1997-11-06<br/> FIG. 58 is a functional block diagram illustrating another preferred<br/>embodiment of a document authenticator and discriminator according to the <br/>present<br/>invention;<br/> FIG. 59 is an enlarged plan view of the control and display panes in the<br/>5 machine of FIG. 1;<br/> FIG. 60a is a side view of a preferred embodiment of a document<br/>authenticating system according to the present invention;<br/> FIG. 60b is a top view of the preferred embodiment of FIG. 60a along the<br/>direction 60b;<br/>10 FIG. 60c is a top view of the preferred embodiment of FIG. 60a along the<br/>direction 60c; and<br/>FIG. 61 is a functional block diagram illustrating a preferred embodiment of a<br/>document authenticating system according to the present invention.<br/>15 Detailed Description Of The Preferred Embodiments<br/> While the invention is susceptible to various modifications and alternative<br/>forms, specific embodiments thereof have been shown by way o~ example in the<br/>drawings and will herein be described in detail. It should be understood, <br/>however,<br/>that it is not intended to limit the invention to the particular forms <br/>disclosed, but on<br/>20 the contrary, the intention is to cover all modifications, equivalents, and <br/>alternatives<br/>falling within the spirit and scope of the invention as defined by the <br/>appended claims.<br/> According to a preferred embodiment of the present invention, a currency<br/>discrimination system adapted to U.S. currency is described in connection <br/>with, for<br/>example, FIGS. 1-38. Subsequently, modifications to such a discrimination <br/>system<br/>25 will be described in obtaining a currency discrimination system in <br/>accordance with<br/>other preferred embodiments of the present invention, such a currency <br/>discriminator<br/>systems having multiple scanheads per side. Furthermore, while the preferred<br/>embodiments below entail the scanning of currency bills, the system of the <br/>present<br/>invention is applicable to other documents as well. For example, the system of <br/>the<br/>30 present invention may be employed in conjunction with stock certificates, <br/>bonds, and<br/>postage and food stamps.<br/><br/> CA 02215886 1997-11-06<br/>41<br/> Referring now to FIGs. 1 and 2a, there is shown a preferred embodiment of a<br/>currency scanning and counting machine 10 according to the present invention. <br/>The<br/>machine 10 includes an input receptacle or bill accepting station 12 where <br/>stacks of<br/>currency bills that need to be identified and counted are positioned. Bills in <br/>the input<br/>receptacle are acted upon by a bill separating station 14 which functions to <br/>pick out<br/>or separate one bill at a time for being sequentially relayed by a bill <br/>transport<br/>mechanism 16 (FIG. 2a), according to a precisely predetermined transport path,<br/>between a pair of scanheads 18a, 18b where the currency denomination of the <br/>bill is<br/>scanned and identified. In the preferred embodiment, bills are scanned and <br/>identified<br/>at a rate in excess of 800 bills per minute. In the preferred embodiment <br/>depicted,<br/>each scanhead 18a, 18b is an optical scanhead that scans for characteristic<br/>information from a scanned bill 17 which is used to identify the denomination <br/>of the<br/>bill. The scanned bill 17 is then transported to an output receptacle or bill <br/>stacking<br/>station 20 where bills so processed are stacked for subsequent removal.<br/>Each optical scanhead 18a, 18b preferably comprises a pair of light sources 22<br/>directing light onto the bill transport path so as to illuminate a <br/>substantially<br/>rectangular light strip 24 upon a currency bill 17 positioned on the transport <br/>path<br/>adjacent the scanhead 18. Light reflected off the illuminated strip 24 is <br/>sensed by a<br/>photodetector 26 positioned between the two light sources. The analog output <br/>of the<br/>photodetector 26 is converted into a digital signal by means of an analog-to-<br/>digital<br/>(ADC) convertor unit 28 whose output is fed as a digital input to a central <br/>processing<br/>unit (CPU) 30.<br/> While scanheads 18a, 18b of FIG. 2a are optical scanheads, it should be<br/>understood that it may be designed to detect a variety of characteristic <br/>information<br/>from currency bills. Additionally, the scanhead may employ a variety of <br/>detection<br/>means such as magnetic, optical, electrical conductivity, and capacitive <br/>sensors. Use<br/>of such sensors is discussed in more detail below (see e.g., FIG. 2d).<br/> Referring again to FIG. 2a, the bill transport path is defined in such a way<br/>that the transport mechanism 16 moves currency bills with the narrow dimension <br/>of<br/>the bills being parallel to the transport path and the scan direction. <br/>Alternatively, the<br/>system 10 may be designed to scan bills along their long dimension or along a<br/>skewed dimension. As a bill 17 traverses the scanheads 18a, 18b, the coherent <br/>light<br/><br/> CA 02215886 1997-11-06<br/>42<br/>strip 24 effectively scans the bill across the narrow dimension of the bill. <br/>In the<br/>preferred embodiment depicted, the transport path is so arranged that a <br/>currency bill<br/>17 is scanned across a central section of the bill along its narrow dimension, <br/>as<br/>shown in FIG. 2a. Each scanhead functions to detect light reflected from the <br/>bill as<br/>it moves across the illuminated light strip 24 and to provide an analog <br/>representation<br/>of the variation in reflected light, which, in turn, represents the variation <br/>in the dark<br/>and light content of the printed pattern or indicia on the surface of the <br/>bill. This<br/>variation in light reflected from the narrow dimension scanning of the bills <br/>serves as<br/>a measure for distinguishing, with a high degree of confidence, among a <br/>plurality of<br/>currency denominations which the system is programmed to handle.<br/> A series of such detected reflectance signals are obtained across the narrow<br/>dimension of the bill, or across a selected segment thereof, and the resulting <br/>analog<br/>signals are digitized under control of the CPU 30 to yield a fined number of <br/>digital<br/>reflectance data samples. The data samples are then subjected to a normalizing<br/>routine for processing the sampled data for improved correlation and for <br/>smoothing<br/>out variations due to "contrast" fluctuations in the printed pattern existing <br/>on the bill<br/>surface. The normalized reflectance data represents a characteristic pattern <br/>that is<br/>unique for a given bill denomination and provides sufficient distinguishing <br/>features<br/>among characteristic patterns for different currency denominations.<br/> In order to ensure strict correspondence between reflectance samples obtained<br/>by narrow dimension scanning of successive bills, the reflectance sampling <br/>process is<br/>preferably controlled through the CPU 30 by means of an optical encoder 32 <br/>which is<br/>linked to the bill transport mechanism 16 and precisely tracks the physical <br/>movement<br/>of the bill 17 between the scanheads 18a, 18b. More specifically, the optical <br/>encoder<br/>32 is linked to the rotary motion of the drive motor which generates the <br/>movement<br/>imparted to the bill along the transport path. In addition, the mechanics of <br/>the feed<br/>mechanism ensure that positive contact is maintained between the bill and the<br/>transport path, particularly when the bill is being scanned by the scanheads. <br/>Under<br/>these conditions, the optical encoder 32 is capable of precisely tracking the <br/>movement<br/>of the bill 17 relative to the light strips 24 generated by the scanheads 18a, <br/>18b by<br/>monitoring the rotary motion of the drive motor.<br/><br/> CA 02215886 1997-11-06<br/>43<br/> The outputs of the photodetectors 26 are monitored by the CPU 30 to initially<br/>detect the presence of the bill adjacent the scanheads and, subsequently, to <br/>detect the<br/>starting point of the printed pattern on the bill, as represented by the thin <br/>borderline<br/>17a which typically encloses the printed indicia on currency bills. Once the<br/>borderline 17a has been detected, the optical encoder 32 is used to control <br/>the timing<br/>and number of reflectance samples that are obtained from the outputs of the<br/>photodetectors 26 as the bill 17 moves across the scanheads.<br/> FIG. Zb illustrates a preferred embodiment of a currency scanning and<br/>counting machine 10 similar to that of FIG. 2a but having a scanhead on only a<br/>single side of the transport path.<br/> FIG. 2c illustrates a preferred embodiment of a currency scanning and<br/>counting machine 10 similar to that of FIG. 2b but illustrating feeding and <br/>scanning<br/>of bills along their wide direction.<br/> As illustrated in FIGs. 2b-2c, the transport mechanism 16 moves currency<br/>bills with a preselected one of their two dimensions (narrow or wide) being <br/>parallel<br/>to the transport path and the scan direction. FIGs. 2b and 4a illustrate bills <br/>oriented<br/>with their narrow dimension "W" parallel to the direction of movement and <br/>scanning<br/>while FIGS. 2c and 4b illustrate bills oriented with their wide dimension "L" <br/>parallel<br/>to the direction of movement and scanning.<br/> Referring now to FIG. 2d, there is shown a functional block diagram<br/>illustrating a preferred embodiment of a currency discriminating and <br/>authenticating<br/>system according to the present invention. The operation of the system of FIG. <br/>2d is<br/>the same as that of FIG. 2a except as modified below. The system 10 includes a <br/>bill<br/>accepting station 12 where stacks of currency bills that need to be <br/>identified,<br/>authenticated, and counted are positioned. Accepted bills are acted upon by a <br/>bill<br/>separating station 14 which functions to pick out or separate one bill at a <br/>time for<br/>being sequentially relayed by a bill transport mechanism 16, according to a <br/>precisely<br/>predetermined transport path, across two scanheads 18 and 39 where the <br/>currency<br/>denomination of the bill is identified and the genuineness of the bill is <br/>authenticated.<br/>In the preferred embodiment depicted, scanhead 18 is an optical scanhead that <br/>scans<br/>for a first type of characteristic information from a scanned bill 17 which is <br/>used to<br/>identify the bill's denomination. A second scanhead 39 scans for a second type <br/>of<br/><br/> CA 02215886 2000-02-02<br/>44<br/>characteristic information from the scanned bill 17. While in the illustrated <br/>preferred<br/>embodiment scanheads 18 and 39 are separate and distinct, it is understood <br/>that these<br/>may be incorporated into a single scanhead. For example, where the first<br/>characteristic sensed is intensity of reflected light and the second <br/>characteristic sensed<br/>is color, a single optical scanhead having a plurality of detectors, one or <br/>more<br/>without filters and one or more with colored filters, may be employed (U.S. <br/>Pat. No.<br/>4,992, 860 ). The scanned bill is then transported to a bill stacking station <br/>20<br/>where bills so processed are stacked for subsequent removal.<br/> The optical scanhead 18 of the preferred embodiment depicted in FIG. 2d<br/>comprises at least one light source 22 directing a beam of coherent light <br/>downwardly<br/>onto the bill transport path so as to illuminate a substantially rectangular <br/>light strip 24<br/>upon a currency bill 17 positioned on the transport path below the scanhead <br/>18.<br/>Light reflected off the illuminated strip 24 is sensed by a photodetector 26 <br/>positioned<br/>IS directly above the strip. The analog output of photodetector 26 is <br/>converted into a<br/>digital signal by means of an analog-to-digital (ADC) convertor unit 28 whose <br/>output<br/>is fed as a digital input to a central processing unit (CPU) 30.<br/> The second scanhead 39 comprises at least one detector 41 for sensing a<br/>second type of characteristic information from a bill. The analog output of <br/>the<br/>detector 41 is converted into a digital signal by means of a second analog to <br/>digital<br/>converter 43 whose output is also fed as a digital input to the central <br/>processing unit<br/>(CPU) 30. "<br/> While scanhead 18 in the preferred embodiment of FIG. 2d is an optical<br/>scanhead, it should be understood that the first and second scanheads 18 and <br/>39 may<br/>be designed to detect a variety of characteristic information from currency <br/>bills.<br/> Additionally these scanheads may employ a variety of detection means such as<br/>magnetic or optical sensors. For example, a variety of currency <br/>characteristics can<br/>be -measured using magnetic sensing. These include detection of patterns of <br/>changes<br/>in magnetic flux (U.S. Pat. No. 3,280,974), patterns of vertical grid lines in <br/>the<br/>portrait area of bills (U.S. Pat. No. 3,870,629), the presence of a security <br/>thread<br/>(U.S. Pat. No. 5,151,607), total amount of magnetizable material of a bill <br/>(U.S. Pat.<br/>No. 4,617,458), patterns from sensing the strength of magnetic fields along a <br/>bill<br/><br/> CA 02215886 1997-11-06<br/>(U.S. Pat. No. 4,593,184), and other patterns and counts from scanning <br/>different<br/>portions of the bill such as the area in which the denomination is written out <br/>(U.S.<br/> Pat. No. 4,356,473).<br/> With regards to optical sensing, a variety of currency characteristics can be<br/>5 measured such as detection of density (U.S. Pat. No. 4,381,447), color (U.S. <br/>Pat.<br/> Nos. 4,490,846; 3,496,370; 3,480,785), length and thickness (U.S. Pat. No.<br/>4,255,651), the presence of a security thread (U.S. Pat. No. 5,151,607) and <br/>holes<br/>(U.S. Pat. No. 4,381,447), and other patterns of reflectance and transmission <br/>(U.S.<br/>Pat. No. 3,496,370; 3,679,314; 3,870,629; 4,179,685). Color detection <br/>techniques<br/>10 may employ color filters, colored lamps, and/or dichroic beamsplitters <br/>(U.S. Pat.<br/> Nos. 4,841,358; 4,658,289; 4,716,456; 4,825,246, 4,992,860 and EP 325,364).<br/> In addition to magnetic and optical sensing, other techniques of detecting<br/>characteristic information of currency include electrical conductivity <br/>sensing,<br/>capacitive sensing (U.S. Pat. No. 5,122,754 [watermark, security thread]; <br/>3,764,899<br/>IS [thickness]; 3,815,021 [dielectric properties]; 5,151,607 [security <br/>thread]), and<br/>mechanical sensing (U.S. Pat. No. 4,381,447 [limpness]; 4,255,651 <br/>[thickness]).<br/> According to one preferred embodiment, the detection of the borderline 17a<br/>constitutes an important step and realizes improved discrimination efficiency <br/>in<br/>systems designed to accommodate U.S. currency since the borderline 17a serves <br/>as<br/>20 an absolute reference point for initiation of sampling. If the edge of a <br/>bill were to be<br/>used as a reference point, relative displacement of sampling points can occur <br/>because<br/>of the random manner in which the distance from the edge to the borderline I7a<br/>varies from bill to bill due to the relatively large range of tolerances <br/>permitted during<br/>printing and cutting of currency bills. As a result, it becomes difficult to <br/>establish<br/>25 direct correspondence between sample points in successive bill scans and <br/>the<br/>discrimination efficiency is adversely affected. Accordingly, the modified <br/>pattern<br/>generation method of the present invention (to be discussed below) is <br/>especially<br/>important in discrimination systems designed to accommodate bills other than <br/>U.S.<br/>currency because many non-U.S. bills lack a borderline around the printed <br/>indicia on<br/>30 their bills. Likewise, the modified pattern generation method of the <br/>present invention<br/>is especially important in discrimination systems designed to accommodate <br/>bills other<br/>than U.S. currency because the printed indicia of many non-U.S. bills lack <br/>sharply<br/><br/> CA 02215886 1997-11-06<br/>4b<br/>defined edges which in turns inhibits using the edge of the printed indicia of <br/>a bill as<br/>a trigger for the initiation of the scanning process and instead promotes <br/>reliance on<br/>using the edge of the bill itself as the trigger for the initiation of the <br/>scanning<br/>process.<br/>The use of the optical encoder 32 for controlling the sampling process <br/>relative<br/>to the physical movement of a bill 17 across the scanheads 18a, 18b is also<br/>advantageous in that the encoder 32 can be used to provide a predetermined <br/>delay<br/>following detection of the borderline 17a prior to initiation of samples. The <br/>encoder<br/>delay can be adjusted in such a way that the bill 17 is scanned only across <br/>those<br/>segments which contain the most distinguishable printed indicia relative to <br/>the<br/>different currency denominations.<br/> In the case of U.S. currency, for instance, it has been determined that the<br/>central, approximately two-inch (approximately 5 cm) portion of currency <br/>bills, as<br/>scanned across the central section of the narrow dimension of the bill, <br/>provides<br/>sufficient data for distinguishing among the various U.S. currency <br/>denominations.<br/>Accordingly, the optical encoder can be used to control the scanning process <br/>so that<br/>reflectance samples are taken for a set period of time and only after a <br/>certain period<br/>of time has elapsed after the borderline 17a is detected, thereby restricting <br/>the<br/>scanning to the desired central portion of the narrow dimension of the bill.<br/> FIGs. 3-Sb illustrate the scanning process in more detail. Referring to FIG.<br/>4a, as a bill 17 is advanced in a direction parallel to the narrow edges of <br/>the bill,<br/>scanning via a slit in the scanhead 18a or 18b is effected along a segment S <br/>of the<br/>central portion of the bill 17. This segment S begins a fixed distance D <br/>inboard of<br/>the borderline 17a. As the bill 17 traverses the scanhead, a strip s of the <br/>segment S<br/>is always illuminated, and the photodetector 26 produces a continuous output <br/>signal<br/>which is proportional to the intensity of the light reflected from the <br/>illuminated strip s<br/>at any given instant. This output is sampled at intervals controlled by the <br/>encoder, so<br/>that the sampling intervals are precisely synchronized with the movement of <br/>the bill<br/>across the scanhead. FIG. 4b is similar to FIG. 4a but illustrating scanning <br/>along the<br/>wide dimension of the bill 17.<br/>As illustrated in FIGs. 3, Sa, and Sb, it is preferred that the sampling <br/>intervals<br/>be selected so that the strips s that are illuminated for successive samples <br/>overlap one<br/><br/> CA 02215886 1997-11-06<br/>47<br/>another. The odd-numbered and even-numbered sample strips have been separated <br/>in<br/>FIGS. 3, Sa, and Sb to more clearly illustrate this overlap. For example, the <br/>first<br/>and second strips sl and s2 overlap each other; the second and third strips s2 <br/>and s3<br/>overlap each other, and so on. Each adjacent pair of strips overlap each <br/>other. In<br/>the illustrative example, this is accomplished by sampling strips that are <br/>0.050 inch<br/>(0.127 cm) wide at 0.029 inch (0.074 cm) intervals, along a segment S that is <br/>1.83<br/>inch {4.65 cm) long (64 samples).<br/> FIGS. 6a and 6b illustrate two opposing surfaces of U.S. bills. The printed<br/>pattern on the black and green surfaces of the bill are each enclosed by <br/>respective<br/>thin borderlines Bi and B2. As a bill is advanced in a direction parallel to <br/>the narrow<br/>edges of the bill, scanning via the wide slit of one of the scanheads is <br/>effected along<br/>a segment SA of the central portion of the black surface of the bill (FIG. <br/>6a). As<br/>previously stated, the orientation of the bill along the transport path <br/>determines<br/>whether the upper or lower scanhead scans the black surface of the bill. This<br/>segment SA begins a fixed distance D1 inboard of the borderline B,, which is <br/>located<br/>a distance W i from the edge of the bill. The scanning along segment SA is as<br/>describe in connection with FIGs. 3, 4a, and Sa.<br/> Similarly, the other of the two scanheads scans a segment SB of the central<br/>portion of the green surface of the bill (FIG. 6b). The orientation of the <br/>bill along<br/>the transport path determines whether the upper or lower scanhead scans the <br/>green<br/>surface of the bill. This segment SB begins a fixed distance DZ inboard of the <br/>border<br/>line B2, which is located a distance WZ from the edge of the bill. For U.S. <br/>currency,<br/>the distance W2 on the green surface is greater than the distance Wl on the <br/>black<br/>surface. It is this feature of U.S. currency which permits one to determine <br/>the<br/>orientation of the bill relative to the upper and lower scanheads 18, thereby<br/>permitting one to select only the data samples corresponding to the green <br/>surface for<br/>correlation to the master characteristic patterns in the EPROM 34. The <br/>scanning<br/>along segment SB is as describe in connection with FIGs. 3, 4a, and Sa.<br/> FIGs. 6c and 6d are side elevations of FIG. 2a according to a preferred<br/>embodiment of the present invention. FIG. 6c shows the first surface of a bill<br/>scanned by an upper scanhead and the second surface of the bill scanned by a <br/>lower<br/>scanhead while FIG. 6d shows the first surface of a bill scanned by a lower <br/>scanhead<br/><br/> CA 02215886 1997-11-06<br/>48<br/>and the second surface of the bill scanned by an upper scanhead. FIGs. 6c and <br/>6d<br/>illustrate the pair of optical scanheads 18a, 18b are disposed on opposite <br/>sides of the<br/>transport path to permit optical scanning of both opposing surfaces of a bill. <br/>With<br/>respect to United States currency, these opposing surfaces correspond to the <br/>black<br/>and Green surfaces of a bill. One of the optical scanheads 18 (the "upper" <br/>scanhead<br/>18a in FIGS. 6c-6d) is positioned above the transport path and illuminates a <br/>light strip<br/>upon a first surface of the bill, while the other of the optical scanheads 18 <br/>(the<br/>"lower" scanhead 18b in FIGs. 6c-6d) is positioned below the transport path <br/>and<br/>illuminates a light strip upon the second surface of the bill. The surface of <br/>the bill<br/>scanned by each scanhead 18 is determined by the orientation of the bill <br/>relative to<br/>the scanheads 18. The upper scanhead 18a is located slightly upstream relative <br/>to the<br/>lower scanhead 18b.<br/> The photodetector of the upper scanhead 18a produces a first analog output<br/>corresponding to the first surface of the bill, while the photodetector of the <br/>lower<br/>scanhead 18b produces a second analog output corresponding to the second <br/>surface of<br/>the bill. The first and second analog outputs are converted into respective <br/>first and<br/>second digital outputs by means of respective analog-to-digital (ADC) <br/>convertor units<br/>28 whose outputs are fed as digital inputs to a central processing unit (CPU) <br/>30. As<br/>described in detail below, the CPU 30 uses the sequence of operations <br/>illustrated in<br/>FiG. 12 to determine which of the first and second digital outputs corresponds <br/>to the<br/>green surface of the bill, and then selects the "green" digital output for <br/>subsequent<br/>correlation to a series of master characteristic patterns stored in EPROM 34. <br/>As<br/>explained below, the master characteristic patterns are preferably generated <br/>by<br/>performing scans on the green surfaces, not black surfaces, of bills of <br/>different<br/>denominations. According to a preferred embodiment, the analog output<br/>corresponding to the black surface of the bill is not used for subsequent <br/>correlation.<br/> The optical sensing and correlation technique is based upon using the above<br/>process to generate a series of stored intensity signal patterns using genuine <br/>bills for<br/>each denomination of currency that is to be detected. According to a preferred<br/>embodiment, two or four sets of master intensity signal samples are generated <br/>and<br/>stored within the system memory, preferably in the form of an EPROM 34 (see <br/>FIG.<br/>2a), for each detectable currency denomination. According to one preferred<br/><br/> CA 02215886 1997-11-06<br/>49<br/>embodiment these are sets of master green-surface intensity signal samples. In <br/>the<br/>case of U.S. currency, the sets of master intensity signal samples for each <br/>bill are<br/>generated from optical scans, performed on the green surface of the bill and <br/>taken<br/>along both the "forward" and "reverse" directions relative to the pattern <br/>printed on<br/>the bill. Alternatively, the optical scanning may be performed on the black <br/>side of<br/>U.S. currency bills or on either surface of foreign bills. Additionally, the <br/>optical<br/>scanning may be performed on both sides of a bill.<br/> In adapting this technique to U.S. currency, for example, sets of stored<br/>intensity signal samples are generated and stored for seven different <br/>denominations of<br/>U.S. currency, i.e., $1, $2, $5, $10, $20, $50 and $100. For bills which <br/>produce<br/>significant pattern changes when shifted slightly to the left or right, such <br/>as the $2,<br/>the $10 and/or the $100 bills in U.S. currency, it is preferred to store two <br/>green-side<br/>patterns for each of the "forward" and "reverse" directions, each pair of <br/>patterns for<br/>the same direction represent two scan areas that are slightly displaced from <br/>each<br/>other along the long dimension of the bill. Accordingly, a set of 16 [or 18] <br/>different<br/>green-side master characteristic patterns are stored within the EPROM for <br/>subsequent<br/>correlation purposes (four master patterns for the $10 bill [or four master <br/>patterns for<br/>the $10 bill and the $2 bill and/or the $100 bill] and two master patterns for <br/>each of<br/>the other denominations). The generation of the master patterns is discussed <br/>in more<br/>below. Once the master patterns have been stored, the pattern generated by <br/>scanning<br/>a bill under test is compared by the CPU 30 with each of the 16 [or 18] master<br/>patterns of stored intensity signal samples to generate, for each comparison, <br/>a<br/>correlation number representing the extent of correlation, i.e., similarity <br/>between<br/>corresponding ones of the plurality of data samples, for the sets of data <br/>being<br/>compared.<br/> According to a preferred embodiment, in addition to the above set of 18<br/>original green-side master patterns, five more sets of green-side master <br/>patterns are<br/>stored in memory. These sets are explained more fully in conjunction with <br/>FIGs.<br/>18a and 18b below.<br/> The CPU 30 is programmed to identify the denomination of the scanned bill<br/>as corresponding to the set of stored intensity signal samples for which the <br/>correlation<br/>number resulting from pattern comparison is found to be the highest. In order <br/>to<br/><br/> CA 02215886 1997-11-06<br/>preclude the possibility of mischaracterizing the denomination of a scanned <br/>bill, as<br/>well as to reduce the possibility of spurious notes being identified as <br/>belonging to a<br/>valid denomination, a bi-level threshold of correlation is used as the basis <br/>for making<br/>a "positive" call. If a "positive" call can not be made for a scanned bill, an <br/>error<br/>5 signal is generated.<br/> According to a preferred embodiment, master patterns are also stored for<br/>selected denominations corresponding to scans along the black side of U.S. <br/>bills.<br/>More particularly, according to a preferred embodiment, multiple black-side <br/>master<br/>patterns are stored for $20, $50 and $100 bills. For each of these <br/>denominations,<br/>10 three master patterns are stored for scans in the forward and reverse <br/>directions for a<br/>total of six patterns for each denomination. For a given scan direction, black-<br/>side<br/>master patterns are generated by scanning a corresponding denominated bill <br/>along a<br/>segment located about the center of the narrow dimension of the bill, a <br/>segment<br/>slightly displaced (0.2 inches) to the left of center, and a segment slightly <br/>displaced<br/>15 (0.2 inches) to the right of center. When the scanned pattern generated <br/>from the<br/>green side of a test bill fails to sufficiently correlate with one of the <br/>green-side master<br/>patterns, the scanned pattern generated from the black side of a_ test bill is <br/>then<br/>compared to black-side master patterns in some situations as described in more <br/>detail<br/>below in conjunction with FIGS. 19a-19c.<br/>20 Using the above sensing and correlation approach, the CPU 30 is programmed<br/>to count the number of bills belonging to a particular currency denomination <br/>as part<br/>of a given set of bills that have been scanned for a given scan batch, and to<br/>determine the aggregate total of the currency amount represented by the bills <br/>scanned<br/>during a scan batch. The CPU 30 is also linked to an output unit 36 (FIGs. 2a <br/>and<br/>25 FIG. 2b) which is adapted to provide a display of the number of bills <br/>counted, the<br/>breakdown of the bills in terms of currency denomination, and the aggregate <br/>total of<br/>the currency value represented by counted bills. The output unit 36 can also <br/>be<br/>adapted to provide a print-out of the displayed information in a desired <br/>format.<br/> Referring again to the preferred embodiment depicted in FIG. 2d, as a result<br/>30 of the first comparison described above based on the reflected light <br/>intensity<br/>information retrieved by scanhead 18, the CPU 30 will have either determined <br/>the<br/>denomination of the scanned bill 17 or determined that the first scanned <br/>signal<br/><br/> CA 02215886 1997-11-06<br/>51<br/>samples fail to su~ciently correlate with any of the sets of stored intensity <br/>signal<br/>samples in which case an error is generated. Provided that an error has not <br/>been<br/>generated as a result of this first comparison based on reflected light <br/>intensity<br/>characteristics, a second comparison is performed. This second comparison is<br/>performed based on a second type of characteristic information, such as <br/>alternate<br/>reflected light properties, similar reflected light properties at alternate <br/>locations of a<br/>bill, light transmissivity properties, various magnetic properties of a bill, <br/>the presence<br/>of a security thread embedded within a bill, the color of a bill, the <br/>thickness or other<br/>dimension of a bill, etc. The second type of characteristic information is <br/>retrieved<br/>from a scanned bill by the second scanhead 39. The scanning and processing by<br/>scanhead 39 may be controlled in a manner similar to that described above with<br/>regard to scanhead 18.<br/>In addition to the sets of stored first characteristic information, in this <br/>example<br/>stored intensity signal samples, the EPROM 34 stores sets of stored second<br/>characteristic information for genuine bills of the different denominations <br/>which the<br/>system 10 is capable of handling. Based on the denomination indicated by the <br/>first<br/>comparison, the CPU 30 retrieves the set or sets of stored second <br/>characteristic data<br/>for a genuine bill of the denomination so indicated and compares the retrieved<br/>information with the scanned second characteristic information. If sufficient<br/>correlation exists between the retrieved information and the scanned <br/>information, the<br/> CPU 30 verifies the genuineness of the scanned bill 17. Otherwise, the CPU<br/>generates an error. While the preferred embodiment illustrated in FIG. 2d <br/>depicts a<br/>single CPU 30 for making comparisons of first and second characteristic <br/>information<br/>and a single EPROM 34 for storing first and second characteristic information, <br/>it is<br/>understood that two or more CPUs and/or EPROMs could be used, including one<br/>CPU for making first characteristic information comparisons and a second CPU <br/>for<br/>making second characteristic information comparisons. Using the above sensing <br/>and<br/>correlation approach, the CPU 30 is programmed to count the number of bills<br/>belonging to a particular currency denomination whose genuineness has been <br/>verified<br/>as pan of a given set of bills that have been scanned for a given scan batch, <br/>and to<br/>determine the aggregate total of the currency amount represented by the bills <br/>scanned<br/>during a scan batch.<br/><br/> CA 02215886 1997-11-06<br/>__<br/>52<br/> Referring now to FIGs. 7a and 7b, there is shown a representation, in block<br/>diagram form, of a preferred circuit arrangement for processing and <br/>correlating<br/>reflectance data according to the system of this invention. The CPU 30 accepts <br/>and<br/>processes a variety of input signals including those from the optical encoder <br/>32, the<br/>sensor 26 and the erasable programmable read only memory (EPROM) 60. The<br/> EPROM 60 has stored within it the correlation program on the basis of which<br/>patterns are generated and test patterns compared with stored master programs <br/>in<br/>order to identify the denomination of test currency. A crystal 40 serves as <br/>the time<br/>base for the CPU 30, which is also provided with an external reference voltage <br/>VHF<br/>42 on the basis of which peak detection of sensed reflectance data is <br/>performed.<br/> According to one embodiment, the CPU 30 also accepts a timer reset signal<br/>from a reset unit 44 which, as shown in FIG. 7b, accepts the output voltage <br/>from the<br/>photodetector 26 and compares it, by means of a threshold detector 44a, <br/>relative to a<br/>pre-set voltage threshold, typically S.0 volts, to provide a reset signal <br/>which goes<br/>i5 "high" when a reflectance value corresponding to the presence of paper is <br/>sensed.<br/>More specifically, reflectance sampling is based on the premise that no <br/>portion of the<br/>illuminated light strip (24 in FIG. 2a) is reflected to the photodetector in <br/>the absence<br/>of a bill positioned below the scanhead. Under these conditions, the output of <br/>the<br/>photodetector represents a "dark" or "zero" level reading. The photodetector <br/>output<br/>changes to a "white" reading, typically set to have a value of about 5.0 <br/>volts, when<br/>the edge of a bill first becomes positioned below the scanhead and falls under <br/>the<br/>light strip 24. When this occurs, the reset unit 44 provides a "high" signal <br/>to the<br/> CPU 30 and marks the initiation of the scanning procedure.<br/> The machine-direction dimension, that is, the dimension parallel to the<br/>direction of bill movement, of the illuminated strip of light produced by the <br/>light<br/>sources within the scanhead is set to be relatively small for the initial <br/>stage of the<br/>scan when the thin borderline is being detected, according to a preferred<br/>embodiment. The use of the narrow slit increases the sensitivity with which <br/>the<br/>reflected light is detected and allows minute variations in the "gray" level <br/>reflected<br/>off the bill surface to be sensed. This is important in ensuring that the thin<br/>borderline of the pattern, i:e., the starting point of the printed pattern on <br/>the bill, is<br/>accurately detected. Once the borderline has been detected, subsequent <br/>reflectance<br/><br/> CA 02215886 1997-11-06<br/>53<br/>sampling is performed on the basis of a relatively wider light strip in order <br/>to<br/>completely scan across the narrow dimension of the bill and obtain the desired<br/>number of samples, at a rapid rate. The use of a wider slit for the actual <br/>sampling<br/>also smooths out the output characteristics of the photodetector and realizes <br/>the<br/>relatively large magnitude of analog voltage which is essential for accurate<br/>representation and processing of the detected reflectance values.<br/> The CPU 30 processes the output of the sensor 26 through a peak detector 50<br/>which essentially functions to sample the sensor output voltage and hold the <br/>highest,<br/>i.e., peak, voltage value encountered after the detector has been enabled. For <br/>U.S.<br/>currency, the peak detector is also adapted to define a scaled voltage on the <br/>basis of<br/>which the printed borderline on the currency bills is detected. The output of <br/>the peak<br/>detector 50 is fed to a voltage divider 54 which lowers the peak voltage down <br/>to a<br/>scaled voltage VS representing a predefined percentage of this peak value. The<br/>voltage VS is based upon the percentage drop in output voltage of the peak <br/>detector as<br/>it reflects the transition from the "high" reflectance value resulting from <br/>the scanning<br/>of the unprinted edge portions of a currency bill to the relatively lower <br/>"gray"<br/>reflectance value resulting when the thin borderline is encountered. <br/>Preferably, the<br/>scaled voltage VS is set to be about 70 - 80 percent of the peak voltage.<br/>The scaled voltage VS is supplied to a line detector 56 which is also provided<br/>with the incoming instantaneous output of the sensor 26. The line detector 56<br/>compares the two voltages at its input side and generates a signal LpE.I. <br/>which<br/>normally stays "low" and goes "high" when the edge of the bill is scanned. The<br/>signal I,DET goes "low" when the incoming sensor output reaches the pre-<br/>defined<br/>percentage of the peak output up to that point, as represented by the voltage <br/>VS.<br/>Thus, when the signal L~E.t. goes "low", it is an indication that the <br/>borderline of the<br/>bill pattern has been detected. At this point, the CPU 30 initiates the actual<br/>reflectance sampling under control of the encoder 32 and the desired fixed <br/>number of<br/>reflectance samples are obtained as the currency bill moves across the <br/>illuminated<br/>light strip and is scanned along the central section of its narrow dimension.<br/> When master characteristic patterns are being generated, the reflectance<br/>samples resulting from the scanning of one or more genuine bills for each<br/>denomination are loaded into corresponding designated sections within a system<br/><br/> CA 02215886 1997-11-06<br/>54<br/>memory 60, which is preferably an EPROM. During currency discrimination, the<br/>reflectance values resulting from the scanning of a test bill are sequentially <br/>compared,<br/>under control of the correlation program stored within the EPROM 60, with the<br/>corresponding master characteristic patterns stored within the EPROM 60. A <br/>pattern<br/>averaging procedure for scanning bills and generating characteristic patterns <br/>is<br/>described below in connection with FIGs. 15a-15e.<br/>In addition to the optical scanheads, the bill-scanning system (e.g., FIGs. 2a-<br/>2d) preferably includes a magnetic scanhead. A variety of currency <br/>characteristics<br/>can be measured using magnetic scanning. These include detection of patterns <br/>of<br/>changes in magnetic flux (U.S. Pat. No. 3,280,974), patterns of vertical grid <br/>lines in<br/>the portrait area of bills (U.S. Pat. No. 3,870,629), the presence of a <br/>security thread<br/>(U.S. Pat. No. 5,151,607), total amount of magnetizable material of a bill <br/>(U.S. Pat.<br/>No. 4,617,458), patterns from sensing the strength of magnetic fields along a <br/>bill<br/>(U.S. Pat. No. 4,593,184), and other patterns and counts from scanning <br/>different<br/>portions of the bill such as the area in which the denomination is written out <br/>(U.S.<br/> Pat. No. 4,356,473).<br/>The interrelation between the use of the first and second . type of <br/>characteristic<br/>information can be seen by considering FIGs. 8a and 8b which comprise a <br/>flowchart<br/>illustrating the sequence of operations involved in implementing a <br/>discrimination and<br/>authentication system according to a preferred embodiment of the present <br/>invention.<br/>Upon the initiation of the sequence of operations (step 1748), reflected light <br/>intensity<br/>information is retrieved from a bill being scanned (step 1750). Similarly, <br/>second<br/>characteristic information is also retrieved from the bill being scanned (step <br/>1752).<br/>Denomination error and second characteristic error flags are cleared (steps <br/>1753 and<br/>1754).<br/> Next the scanned intensity information is compared to each set of stored<br/>intensity information corresponding to genuine bills of all denominations the <br/>system is<br/>programmed to accommodate (step 1758). For each denomination, a correlation<br/>number is calculated. The system then, based on the correlation numbers <br/>calculated,<br/>determines either the denomination of the scanned bill or generates a <br/>denomination<br/>error by setting the denomination error flag steps 1760 and 1762). In the case <br/>where<br/>the denomination error flag is set (step 1762), the process is ended (step <br/>1772).<br/><br/> CA 02215886 1997-11-06<br/>__T_3 _ _ ~___,._._ _ _<br/>Alternatively, if based on this first comparison, the system is able to <br/>determine the<br/>denomination of the scanned bill, the system proceeds to compare the scanned <br/>second<br/>characteristic information with the stored second characteristic information<br/>corresponding to the denomination determined by the first comparison (step <br/>1764).<br/>5 For example, if as a result of the first comparison the scanned bill is<br/>determined to be a $20 bill, the scanned second characteristic information is<br/>compared to the stored second characteristic information corresponding to a <br/>genuine<br/>$20 bill. In this manner, the system need not make comparisons with stored <br/>second<br/>characteristic information for the other denominations the system is <br/>programmed to<br/>10 accommodate. If based on this second comparison (step 1764) it is <br/>determined that<br/>the scanned second characteristic information does not sufficiently match that <br/>of the<br/>stored second characteristic information (step 1766), then a second <br/>characteristic<br/>error is generated by setting the second characteristic error flag (step 1768) <br/>and the<br/>process is ended (step 1772). If the second comparison results in a sufficient <br/>match<br/>15 between the scanned and stored second characteristic information (step <br/>1766), then<br/>the denomination of the scanned bill is indicated (step 1770) and the process <br/>is ended<br/>(step 1772).<br/>An example of an interrelationship between authentication based on a first and<br/>second characteristic can be seen by considering Table 1. The denomination<br/>20 determined by optical scanning of a bill is preferably used to facilitate <br/>authentication<br/>of the bill by magnetic scanning, using the relationship set forth in Table 1.<br/> Table 1<br/> Sensitivity 1 2 3 4 5<br/> Denomination <br/>$1 200 250 300 375 450<br/>$2 100 125 150 225 300<br/>$5 200 250 300 350 400<br/>$10 100 125 150 200 250<br/>$20 120 150 180 270 360<br/><br/> CA 02215886 1997-11-06<br/>56<br/>$50 200 250 300 375 450<br/>$100 100 125 150 250 350<br/> Table 1 depicts relative total magnetic content thresholds for various<br/>denominations of genuine bills. Columns 1-5 represent varying degrees of <br/>sensitivity<br/>selectable by a user of a device employing the present invention. The values <br/>in Table<br/>1 are set based on the scanning of genuine bills of varying denominations for <br/>total<br/>magnetic content and setting required thresholds based on the degree of <br/>sensitivity<br/>selected. The information in Table 1 is based on the total magnetic content of <br/>a<br/>genuine $1 being 1000. The following discussion is based on a sensitivity <br/>setting of<br/>4. In this example it is assumed that magnetic content represents the second<br/>characteristic tested. If the comparison of first characteristic information, <br/>such as<br/>reflected light intensity, from a scanned billed and stored information <br/>corresponding<br/>to genuine bills results in an indication that the scanned bill is a $10 <br/>denomination,<br/>then the total magnetic content of the scanned bill is compared to the total <br/>magnetic<br/>content threshold of a genuine $10 bill, i.e., 200. If the magnetic content of <br/>the<br/>scanned bill is less than 200, the bill is rejected. Otherwise it is accepted <br/>as a $10<br/>bill.<br/>In order to avoid problems associated with re-feeding bills, counting bills by<br/>hand, and adding together separate totals, according to a preferred embodiment <br/>of the<br/>present invention a number of selection elements associated with individual<br/>denominations are provided. In FIG. 1, these selection elements are in the <br/>form of<br/>keys or buttons of a keypad. Other types of selection elements such as <br/>switches or<br/>displayed keys in a touch-screen environment may be employed. The operation of<br/>the selection elements and several of the operating modes of the discriminator <br/>10 are<br/>described below in conjunction with FIGS. 56 and 59.<br/> Referring now to FIGs. 9-l lb, there are shown flow charts illustrating the<br/>sequence of operations involved in implementing the above-described optical <br/>sensing<br/>and correlation technique. FIGS. 9 and 10, in particular, illustrate the <br/>sequences<br/>involved in detecting the presence of a bill adjacent the scanheads and the <br/>borderlines<br/>on each side of the bill. Turning to FIG. 9, at step 70, the lower scanhead <br/>fine line<br/><br/> CA 02215886 1997-11-06<br/>57<br/>interrupt is initiated upon the detection of the fine line by the lower <br/>scanhead. An<br/>encoder counter is maintained that is incremented for each encoder pulse. The<br/>encoder counter scrolls from 0 - 65,535 and then starts at 0 again. At step 71 <br/>the<br/>value of the encoder counter is stored in memory upon the detection of the <br/>fine line<br/>by the lower scanhead. At step 72 the Lower scanhead fine line interrupt is <br/>disabled<br/>so that it will not be triggered again during the interrupt period. At step <br/>73, it is<br/>determined whether the magnetic sampling has been completed for the previous <br/>bill.<br/>If it has not, the magnetic total for the previous bill is stored in memory at <br/>step 74<br/>and the magnetic sampling done flag is set at step 75 so that magnetic <br/>sampling of<br/>the present bill may thereafter be performed. Steps 74 and 75 are skipped if <br/>it is<br/>determined at step 73 that the magnetic sampling has been completed for the <br/>previous<br/>bill. At step 76, a lower scanhead bit in the trigger flag is set. ~ This bit <br/>is used to<br/>indicate that the lower scanhead has detected the fine line. The magnetic <br/>sampler is<br/>initialized at step 77 and the magnetic sampling interrupt is enabled at step <br/>78. A<br/>density sampler is initialized at step 79 and a density sampling interrupt is <br/>enabled at<br/>step 80. The lower read data sampler is initialized at step 81 and a lower <br/>scanhead<br/>data sampling interrupt is enabled at step 82. At step 83, the lower scanhead <br/>fine<br/>line interrupt flag is reset and at step 84 the program returns from the <br/>interrupt.<br/> Turning to FIG. 10, at step 85, the upper scanhead fine line interrupt is<br/>initiated upon the detection of the fine line by the upper scanhead. At step <br/>86 the<br/>value of the encoder counter is stored in memory upon the detection of the <br/>fine line<br/>by the upper scanhead. This information in connection with the encoder counter<br/>value associated with the detection of the fine line by the lower scanhead may <br/>then be<br/>used to determine the face orientation of a bill, that is whether a bill is <br/>fed green side<br/>up or green side down in the case of U.S. bills as is described in more detail <br/>below<br/>in connection with FIG. 12. At step 87 the upper scanhead fine line interrupt <br/>is<br/>disabled so that it will not be triggered again during the interrupt period. <br/>At step 88,<br/>the upper scanhead bit in the trigger flag is set. This bit is used to <br/>indicate that the<br/>upper scanhead has detected the fine line. By checking the lower and upper <br/>scanhead<br/>bits in the trigger flag it can be determined whether each side has detected a<br/>respective fine line. Next, the upper scanhead data sampler is initialized at <br/>step 89<br/>and the upper scanhead data sampling interrupt is enabled at step 90. At step <br/>91, the<br/><br/> CA 02215886 1997-11-06<br/>58<br/>upper scanhead fine line interrupt flag is reset and at step 92 the program <br/>returns<br/>from the interrupt.<br/> Referring now to FIGS. l la and 1 ib there are shown, respectively, the<br/>digitizing routines associated with the lower and upper scanheads. FIG. l la <br/>is a flow<br/>chart illustrating the sequential procedure involved in the analog-to-digital <br/>conversion<br/>routine associated with the lower scanhead. The routine is started at step <br/>93a. Next,<br/>the sample pointer is decremented at step 94a so as to maintain an indication <br/>of the<br/>number of samples remaining to be obtained. The sample pointer provides an<br/>indication of the sample being obtained and digitized at a given time. At step <br/>95a,<br/>the digital data corresponding to the output of the photodetector associated <br/>with the<br/>lower scanhead for the current sample is read. The data is converted to its <br/>final form<br/>at step 96a and stored within a pre-defined memory segment as X~N-L at step <br/>97a.<br/> Next, at step 98a, a check is made to see if the desired fixed number of<br/>samples "N" has been taken. If the answer is found to be negative, step 99a is<br/>accessed where the interrupt authorizing the digitization of the succeeding <br/>sample is<br/>enabled and the program returns from interrupt at step 100a for completing the <br/>rest<br/>of the digitizing process. However, if the answer at step 98a is.found to be <br/>positive,<br/>i.e., the desired number of samples have already been obtained, a flag, namely <br/>the<br/>lower scanhead done flag bit, indicating the same is set at step lOla and the <br/>program<br/>returns from interrupt at step 102a.<br/>FIG. l lb is a flow chart illustrating the sequential procedure involved in <br/>the<br/>analog-to-digital conversion routine associated with the upper scanhead. The <br/>routine<br/>is started at step 93b. Next, the sample pointer is decremented at step 94b so <br/>as to<br/>maintain an indication of the number of samples remaining to be obtained. The<br/>sample pointer provides an indication of the sample being obtained and <br/>digitized at a<br/>given time. At step 95b, the digital data corresponding to the output of the<br/>photodetector associated with the upper scanhead for the current sample is <br/>read. The<br/>data is converted to its final form at step 96b and stored within a pre-<br/>defined memory<br/>segment as X,N-a at step 97b.<br/> Next, at step 98b, a check is made to see if the desired fixed number of<br/>samples "N" has been taken. If the answer is found to be negative, step 99b is<br/>accessed where the interrupt authorizing the digitization of the succeeding <br/>sample is<br/><br/> CA 02215886 1997-11-06<br/>59<br/>enabled and the program returns from interrupt at step 100b for completing the <br/>rest<br/>of the digitizing process. However, if the answer at step 98b is found to be <br/>positive,<br/>i.e., the desired number of samples have already been obtained, a flag, namely <br/>the<br/>upper scanhead done flag bit, indicating the same is set at step lOlb and the <br/>program<br/>returns from interrupt at step 102b.<br/> The CPU 30 is programmed with the sequence of operations in FIG. 12 to<br/>correlate at least initially only the test pattern corresponding to the green <br/>surface of a<br/>scanned bill. As shown in FIGS. 6c-6d, the upper scanhead 18a is located <br/>slightly<br/>upstream adjacent the bill transport path relative to the lower scanhead i8b. <br/>The<br/>distance between the scanheads 18a, 18b in a direction parallel to the <br/>transport path<br/>corresponds to a predetermined number of encoder counts. It should be <br/>understood<br/>that the encoder 32 produces a repetitive tracking signal synchronized with<br/>incremental movements of the bill transport mechanism, and this repetitive <br/>tracking<br/>signal has a repetitive sequence of counts (e.g., 65,535 counts) associated <br/>therewith.<br/>As a bill is scanned by the upper and lower scanheads 18a, 18b, the CPU 30<br/>monitors the output of the upper scanhead 18a to detect the borderline of a <br/>first bill<br/>surface facing the upper scanhead 18a. Once this borderline of .the first <br/>surface . is<br/>detected, the CPU 30 retrieves and stores a first encoder count in memory.<br/>Similarly, the CPU 30 monitors the output of the lower scanhead 18b to detect <br/>the<br/>borderline of a second bill surface facing the lower scanhead 18b. Once the<br/>borderline of the second surface is detected, the CPU 30 retrieves and stores <br/>a second<br/>encoder count in memory.<br/> Referring to FIG. 12, the CPU 30 is programmed to calculate the difference<br/>between the first and second encoder counts (step lOSa). If this difference is <br/>greater<br/>than the predetermined number of encoder counts corresponding to the distance<br/>between the scanheads 18a, 18b plus some safety factor number "X", e.g., 20 <br/>(step<br/>106), the bill is oriented with its black surface facing the upper scanhead <br/>18a and its<br/>green surface facing the lower scanhead 18b. This can best be understood by<br/>reference to FIG. 6c which shows a bill with the foregoing orientation. In <br/>this<br/>situation, once the borderline Bi of the black surface passes beneath the <br/>upper<br/>scanhead 18a and the first encoder count is stored, the borderline BZ still <br/>must travel<br/>for a distance greater than the distance between the upper and lower scanheads <br/>18a,<br/><br/> CA 02215886 1997-11-06<br/>18b in order to pass over the lower scanhead i8b. As a result, the difference<br/>between the second encoder count associated with the borderline B, and the <br/>first<br/>encoder count associated with the borderline B, will be greater than the<br/>predetermined number of encoder counts corresponding to the distance between <br/>the<br/>5 scanheads 18a, 18b. With the bill oriented with its green surface facing the <br/>lower<br/>scanhead, the CPU 30 sets a flag to indicate that the test pattern produced by <br/>the<br/>lower scanhead i8b should be correlated (step 107). Next, this test pattern is<br/>correlated with the green-side master characteristic patterns stored in memory <br/>(step<br/>109) .<br/>10 If at step 106 the difference between the first and second encoder counts <br/>is<br/>less than the predetermined number of encoder counts corresponding to the <br/>distance<br/>between the scanheads 18a, 18b, the CPU 30 is programmed to determine whether<br/>the difference between the first and second encoder counts is less than the<br/>predetermined number minus some safety number "X", e.g., 20 (step 108). If the<br/>15 answer is negative, the orientation of the bill relative to the scanheads <br/>18a, 18b is<br/>uncertain so the CPU 30 is programmed to correlate the test patterns produced <br/>by<br/>both the upper and lower scanheads 18a, 18b with the green-side master <br/>characteristic<br/>patterns stored in memory (steps 109, 110, and 111).<br/>if the answer is affirmative, the bill is oriented with its green surface <br/>facing<br/>20 the upper scanhead 18a and its black surface facing the lower scanhead 18b. <br/>This<br/>can best be understood by reference to FiG. 6d, which shows a bill with the<br/>foregoing orientation. In this situation, once the borderline BZ of the green <br/>surface<br/>passes beneath the upper scanhead 18a and the first encoder count is stored, <br/>the<br/>borderline B1 must travel for a distance less than the distance between the <br/>upper and<br/>25 lower scanheads 18a, 18b in order to pass over the lower scanhead 18b. As a <br/>result,<br/>the difference between the second encoder count associated with the borderline <br/>Bl and<br/>the first encoder count associated with the borderline BZ should be less than <br/>the<br/>predetermined number of encoder counts corresponding to the distance between <br/>the<br/>scanheads 18a, 18b. To be on the safe side, it is required that the difference <br/>between<br/>30 first and second encoder counts be less than the predetermined number minus <br/>the<br/>safety number "X". Therefore, the CPU 30 is programmed to correlate the test<br/><br/> CA 02215886 1997-11-06<br/>61<br/>pattern produced by the upper scanhead 18a with the green-side master <br/>characteristic<br/>patterns stored in memory (step 111).<br/> After correlating the test pattern associated with either the upper scanhead<br/>18a, the lower scanhead 18b, or both scanheads I8a, 18b, the CPU 30 is<br/>programmed to perform the bi-level threshold check (step 112).<br/>A simple correlation procedure is utilized for processing digitized <br/>reflectance<br/>values into a form which is conveniently and accurately compared to <br/>corresponding<br/>values pre-stored in an identical format. More specifically, as a first step, <br/>the mean<br/>value X for the set of digitized reflectance samples (comparing "n" samples) <br/>obtained<br/>for a bill scan run is first obtained as below:<br/>n (1)<br/> X<br/>i=0<br/> Subsequently, a normalizing factor Sigma ("o") is determined as being<br/>equivalent to the sum of the square of the difference between each sample and <br/>the<br/>mean, as normalized by the total number n of samples. More specifically, the<br/>normalizing factor is calculated as below:<br/>~ lXl-XI r<br/>i=0 n<br/> In the final step, each reflectance sample is normalized by obtaining the<br/>difference between the sample and the above-calculated mean value and dividing <br/>it by<br/>the square root of the normalizing factor o as defined by the following <br/>equation:<br/> X~ -X (3)<br/> Xn c (Q)t/Z<br/><br/> CA 02215886 1997-11-06<br/>62<br/>The result of using the above correlation equations is that, subsequent to the<br/>normalizing process, a relationship of correlation exists between a test <br/>pattern and a<br/>master pattern such that the aggregate sum of the products of corresponding <br/>samples<br/>in a test pattern and any master pattern, when divided by the total number of<br/>samples, equals unity if the patterns are identical. Otherwise, a value less <br/>than unity<br/>is obtained. Accordingly, the correlation number or factor resulting from the<br/>comparison of normalized samples within a test pattern to those of a stored <br/>master<br/>pattern provides a clear indication of the degree of similarity or correlation <br/>between<br/>the two patterns.<br/> According to a preferred embodiment of this invention, the fixed number of<br/>reflectance samples which are digitized and normalized for a bill scan is <br/>selected to<br/>be 64. It has experimentally been found that the use of higher binary orders <br/>of<br/>samples (such as 128, 256, etc.) does not provide a correspondingly increased<br/>discrimination efficiency relative to the increased processing time involved <br/>in<br/>i5 implementing the above-described correlation procedure. It has also been <br/>found that<br/>the use of a binary order of samples lower than 64, such as 32, produces a <br/>substantial<br/>drop in discrimination efficiency.<br/> The correlation factor can be represented conveniently in binary terms for<br/>ease of correlation. In a preferred embodiment, for instance, the factor of <br/>unity<br/>which results when a hundred percent correlation exists is represented in <br/>terms of the<br/>binary number 2'°, which is equal to a decimal value of 1024. Using the <br/>above<br/>procedure, the normalized samples within a test pattern are compared to the <br/>master<br/>characteristic patterns stored within the system memory in order to determine <br/>the<br/>particular stored pattern to which the test pattern corresponds most closely <br/>by<br/>identifying the comparison which yields a correlation number closest to 1024.<br/> A bi-level threshold of correlation is required to be satisfied before a<br/>particular call is made, for at least certain denominations of bills. More <br/>specifically,<br/>the correlation procedure is adapted to identify the two highest correlation <br/>numbers<br/>resulting from the comparison of the test pattern to one of the stored <br/>patterns. At<br/>that point, a minimum threshold of correlation is required to be satisfied by <br/>these two<br/>correlation numbers. It has experimentally been found that a correlation <br/>number of<br/>about 850 serves as a good cut-off threshold above which positive calls may be <br/>made<br/><br/> CA 02215886 1997-11-06<br/>63<br/>with a high degree of confidence and below which the designation of a test <br/>pattern as<br/>corresponding to any of the stored patterns is uncertain. As a second <br/>threshold level,<br/>a minimum separation is prescribed between the two highest correlation numbers<br/>before making a call. This ensures that a positive call is made only when a <br/>test<br/>pattern does not correspond, within a given range of correlation, to more than <br/>one<br/>stored master pattern. Preferably, the minimum separation between correlation<br/>numbers is set to be 150 when the highest correlation number is between 800 <br/>and<br/>850. When the highest correlation number is below 800, no call is made.<br/> The procedure involved in comparing test patterns to master patterns is<br/>discussed below in connection with FIG. 18a.<br/> Next a routine designated as "CORRES" is initiated. The procedure involved<br/>in executing the routine CORRES is illustrated at FIG. 13 which shows the <br/>routine as<br/>starting at step 114. Step 115 determines whether the bill has been identified <br/>as a $2<br/>bill, and, if the answer is negative, step 116 determines whether the best <br/>correlation<br/>number ("call #1 ") is greater than 799. if the answer is negative, the <br/>correlation<br/>number is too low to identify the denomination of the bill with certainty, and <br/>thus<br/>step 117 generates a "no call" code. A "no call previous bill" flag is then <br/>set at step<br/>118, and the routine returns to the main program at step 119.<br/> An affirmative answer at step 116 advances the system to step 120, which<br/>determines whether the sample data passes an ink stain test (described below). <br/>If the<br/>answer is negative, a "no call" code is generated at step 117. if the answer <br/>is<br/>affirmative, the system advances to step 121 which determines whether the best<br/>correlation number is greater than 849. An affirmative answer at step 121 <br/>indicates<br/>that the correlation number is sufficiently high that the denomination of the <br/>scanned<br/>bill can be identified with certainty without any further checking. <br/>Consequently, a<br/>"denomination" code identifying the denomination represented by the stored <br/>pattern<br/>resulting in the highest correlation number is generated at step 122, and the <br/>system<br/>returns to the main program at step 119.<br/>A negative answer at step 121 indicates that the correlation number is between<br/>800 and 850. It has been found that correlation numbers within this range are<br/>sufficient to identify all bills except the $2 bill. Accordingly, a negative <br/>response at<br/>step 121 advances the system to step 123 which determines whether the <br/>difference<br/><br/> CA 02215886 1997-11-06<br/>64<br/>between the two highest correlation numbers ("call #1" and "call #2") is <br/>greater than<br/>149. If the answer is affirmative, the denomination identified by the highest<br/>correlation number is acceptable, and thus the "denomination" code is <br/>generated at<br/>step 122. If the difference between the two highest correlation numbers is <br/>less than<br/>150, step 123 produces a negative response which advances the system to step <br/>117 to<br/>generate a "no call" code.<br/>Returning to step 115, an affirmative response at this step indicates that the<br/>initial call is a $2 bill. This affirmative response initiates a series of <br/>steps 124-127<br/>which are identical to steps 116, 120, 121 and i23 described above, except <br/>that the<br/>numbers 799 and 849 used in steps 116 and 121 are changed to 849 and 899,<br/>respectively, in steps 124 and 126. The result is either the generation of a <br/>"no call"<br/>code at step 117 or the generation of a $2 "denomination" code at step 122.<br/> One problem encountered in currency recognition and counting systems is the<br/>difficulty involved in interrupting (for a variety of reasons) and resuming <br/>the<br/>scanning and counting procedure as a stack of bills is being scanned. If a <br/>particular<br/>currency recognition unit (CRU) has to be halted in operation due to a "major"<br/>system error, such as a bill being jammed along the transport path, there is <br/>generally<br/>no concern about the outstanding transitional status of the overall <br/>recognition and<br/>counting process. However, where the CRU has to be halted due to a "minor" <br/>error,<br/>such as the identification of a scanned bill as being a counterfeit (based on <br/>a variety<br/>of monitored parameters) or a "no call" (a bill which is not identifiable as <br/>belonging<br/>to a specific currency denomination based on the plurality of stored master <br/>patterns<br/>andlor other criteria), it is desirable that the transitional status of the <br/>overall<br/>recognition and counting process be retained so that the CRU may be restarted<br/>without any effective disruptions of the recognition/counting process.<br/>More specifically, once a scanned bill has been identified as a "no call" bill<br/>(B1) based on some set of predefined criteria, it is desirable that this bill <br/>B1 be<br/>transported directly to the system stacker and the CRU brought to a halt with <br/>bill B1<br/>being the last bill deposited in the output receptacle, while at the same time <br/>ensuring<br/>that the following bills are maintained in positions along the bill transport <br/>path<br/>whereby CRU operation can be conveniently resumed without any disruption of <br/>the<br/>recognitionlcounting process.<br/><br/> CA 02215886 1997-11-06<br/> Since the bill processing speeds at which currency recognition systems must<br/>operate are substantially high (speeds of the order of 800 to 1500 bills per <br/>minute), it<br/>is practically impossible to totally halt the system following a "no call" <br/>without the<br/>following bill BZ already overlapping the optical scanhead and being partially<br/>5 scanned. As a result, it is virtually impossible for the CRU system to <br/>retain the<br/>transitional status of the recognition/counting process (particularly with <br/>respect to bill<br/> BZ) in order that the process may be resumed once the bad bill B1 has been<br/>transported to the stacker, conveniently removed therefrom, and the system <br/>restarted.<br/>The basic problem is that if the CRU is halted with bill BZ only partially <br/>scanned, it<br/>10 is difficult to reference the data reflectance samples extracted therefrom <br/>in such a<br/>way that the scanning may be later continued (when the CRU is restarted) from<br/>exactly the same point where the sample extraction process was interrupted <br/>when the<br/> CRU was stopped.<br/> Even if an attempt were made at immediately halting the CRU system<br/>15 following a "no call," any subsequent scanning of bills would be totally <br/>unreliable<br/>because of mechanical backlash effects and the resultant disruption of the <br/>optical<br/>encoder routine used for bill scanning. Consequently, when the CRU is <br/>restarted, the<br/>call for the following bill is also likely to be bad and the overall <br/>recognition/counting<br/>process is totally disrupted as a result of an endless loop of "no calls. "<br/>20 The above problems are solved by the use of a currency detecting and<br/>counting technique whereby a scanned bill identified as a "no call" is <br/>transported<br/>directly to the top of the system stacker and the CRU is halted without <br/>adversely<br/>affecting the data collection and processing steps for a succeeding bill. <br/>Accordingly,<br/>when the CRU is restarted, the overall bill recognition and counting procedure <br/>can be<br/>25 resumed without any disruption as if the CRU had never been halted at all.<br/> According to a preferred technique, if the bill is identified as a "no call"<br/>based on any of a variety of conventionally defined bill criteria, the CRU is <br/>subjected<br/>to a controlled deceleration process whereby the speed at which bills are <br/>moved<br/>across the scanhead is reduced from the normal operating speed. During this<br/>30 deceleration process the "no call" bill (Bl) is transported to the top of <br/>the stacker and,<br/>at the same time, the following bill B2 is subjected to the standard scanning<br/>procedure in order to identify the denomination.<br/><br/> CA 02215886 1997-11-06<br/>66<br/>The rate of deceleration is such that optical scanning of bill BZ is completed<br/>by the time the CRU operating speed is reduced to a .predefined operating <br/>speed.<br/>While the exact operating speed at the end of the scanning of bill B2 is not <br/>critical,<br/>the objective is to permit complete scanning of bill B~ without subjecting it <br/>to<br/>backlash effects that would result if the ramping were too fast, while at the <br/>same time<br/>ensuring that bill Bt has in fact been transported to the stacker.<br/> It has been experimentally determined that at nominal operating speeds of the<br/>order of 1000 bills per minute, the deceleration is preferably such that the <br/>CRU<br/>operating speed is reduced to about one-fifth of its normal operating speed at <br/>the end<br/>of the deceleration phase, i.e., by the time optical scanning of bill BZ has <br/>been<br/>completed. It has been determined that at these speed levels, positive calls <br/>can be<br/>made as to the denomination of bill B2 based on reflectance samples gathered <br/>during<br/>the deceleration phase with a relatively high degree of certainty (i.e., with <br/>a<br/>correlation number exceeding about 850).<br/>Once the optical scanning of bill B., has been completed, the speed is reduced<br/>to an even slower speed until the bill B2 has passed bill-edge sensors S 1 and <br/>S2<br/>described below, and the bill B, is then brought to a complete stop. At the <br/>same<br/>time, the results of the processing of scanned data corresponding to bill BZ <br/>are stored<br/>in system memory. The ultimate result of this stopping procedure is that the <br/>CRU is<br/>brought to a complete halt following the point where the scanning of bill BZ <br/>has been<br/>reliably completed, and the scan procedure is not subjected to the disruptive <br/>effects<br/>(backlash, etc.) which would result if a complete halt were attempted <br/>immediately<br/>after bill Bi is identified as a "no cali."<br/> The reduced operating speed of the machine at the end of the deceleration<br/>phase is such that the CRU can be brought to a total halt before the next <br/>following<br/>bill B3 has been transported over the optical scanhead. Thus, when the CRU is <br/>in<br/>fact halted, bill Bi is positioned at the top of the system stacker, bill BZ <br/>is maintained<br/>in transit between the optical scanhead and the stacker after it has been <br/>subjected to '<br/>scanning, and the following bill B3 is stopped short of the optical scanhead.<br/> When the CRU is restarted, presumably after corrective action has been taken<br/>in response to the "minor" error which led to the CRU being stopped (such as <br/>the<br/>removal of the "no call" bill from the output receptacle), the overall <br/>scanning<br/><br/> CA 02215886 1997-11-06<br/>67<br/>operation can be resumed in an uninterrupted fashion by using the stored call <br/>results<br/>for bill BZ as the basis for updating the system count appropriately, moving <br/>bill B2<br/>from its earlier transitional position along the transport path into the <br/>starker, and<br/>moving bill B3 along the transport path into the optical scanhead area where <br/>it can be<br/>subjected to normal scanning and processing. A routine for executing the<br/>deceleration/stopping procedure described above is illustrated by the flow <br/>chart in<br/>FIG. 14. This routine is initiated at step 170 with the CRU in its normal <br/>operating<br/>mode. At step 171, a test bill B, is scanned and the data reflectance samples<br/>resulting therefrom are processed. Next, at step 172, a determination is made <br/>as to<br/>whether or not test bill B, is a "no call" using predefined criteria in <br/>combination with<br/>the overall bill recognition procedure, such as the routine of FIG. 13. if the <br/>answer<br/>at step 172 is negative, i.e., the test bill B, can be identified, step 173 is <br/>accessed<br/>where normal bill processing is continued in accordance with the procedures<br/>described above. If, however, the test bill B, is found to be a "no call" at <br/>step 172,<br/>step 174 is accessed where CRU deceleration is initiated, e.g., the transport <br/>drive<br/>motor speed is reduced to about one-fifth its normal speed.<br/>Subsequently, the "no call" bill B1 is guided to the starker while, at the <br/>same<br/>time, the following test bill BZ is brought under the optical scanhead and <br/>subjected to<br/>the scanning and processing steps. The call resulting from the scanning and<br/>processing of bill BZ is stored in system memory at this point. Step 175 <br/>determines<br/>whether the scanning of bill B2 is complete. When the answer is negative, step <br/>176<br/>determines whether a preselected "bill timeout" period has expired so that the <br/>system<br/>does not wait for the scanning of a bill that is not present. An affirmative <br/>answer at<br/>step 176 results in the transport drive motor being stopped at step 179 while <br/>a<br/>negative answer at step 176 causes steps 175 and 176 to be reiterated until <br/>one of<br/>them produces an affirmative response.<br/> After the scanning of bill B2 is complete and before stopping the transport<br/>drive motor, step 178 determines whether either of the sensors S 1 or S2 <br/>(described<br/>below) is covered by a bill. A negative answer at step 178 indicates that the <br/>bill has<br/>cleared both sensors S1 and S2, and thus the transport drive motor is stopped <br/>at step<br/>179. This signifies the end of the decelerationlstopping process. At this <br/>point in<br/><br/>CA 02215886 1997-11-06<br/>time, bill BZ remains in transit while the following bill B3 is stopped on the <br/>transport<br/>path just short of the optical scanhead.<br/>Following step 179, corrective action responsive to the identification of a <br/>"no<br/>call" bill is conveniently undertaken; the top-most bill in the slacker is <br/>easily<br/>removed therefrom and the CRU is then in condition for resuming the scanning<br/>process. Accordingly, the CRU can be restarted and the stored results <br/>corresponding<br/>to bill B~, are used to appropriately update the system count. Next, the <br/>identified bill<br/>B~ is guided along the transport path to the slacker, and the CRU continues <br/>with its<br/>normal processing routine. While the above deceleration process has been <br/>described<br/>in a context of a "no call" error, other minor errors (e.g., suspect bills, <br/>stranger bills<br/>in stranger mode, etc.) are handled in the same manner.<br/> In currency discrimination systems in which discrimination is based on the<br/>comparison of a pattern obtained from scanning a subject bill to stored master<br/>patterns corresponding to various denominations, the patterns which are <br/>designated as<br/>master patterns significantly influence the performance characteristics of a<br/>discrimination system. For example, in the system described in United States <br/>Patent<br/> No. 5,295,196, the correlation procedure and the accuracy with. which a<br/>denomination is identified directly relates to the degree of correspondence <br/>between<br/>reflectance samples on the test pattern and corresponding samples on the <br/>stored<br/>master patterns. In other systems, master patterns have been produced by <br/>scanning a<br/>genuine bill for a given denomination and storing the resulting pattern as the <br/>master<br/>pattern for that denomination. However, due to variations among genuine bills, <br/>this<br/>method is likely to result in poor .performance of the discrimination system <br/>by<br/>rejecting an unacceptable number of genuine bills. It has been found that the <br/>relative<br/>crispness,. age, shrinkage, usage, and other characteristics of a genuine bill <br/>can effect<br/>the resulting pattern generated by scanning. These factors are often <br/>interrelated. For<br/>example, it has been found that currency bills which have experienced a high <br/>degree<br/>of usage exhibit a reduction in both the narrow and wide dimensions of the <br/>bills.<br/>This shrinkage of "used" bills which, in turn, causes corresponding reductions <br/>in<br/>their narrow dimensions, can possibly produce a drop in the degree of <br/>correlation<br/>between such used bills of a given denomination and the corresponding master<br/>patterns.<br/><br/> CA 02215886 1997-11-06<br/>69<br/>As a result, a discrimination system which generates a master pattern based on<br/>a single scan of a genuine bill is not likely to perform satisfactorily. For <br/>example, if<br/>the $20 master pattern is generated by scanning a crisp, genuine $20 bill, the<br/>discrimination system may reject an unacceptable number of genuine but worn <br/>$20<br/>bills. Likewise, if the $20 master pattern is generated using a very worn, <br/>genuine<br/>$20 bill, the discrimination system may reject an unacceptable number of <br/>genuine but<br/>crisp $20 bills.<br/> According to a preferred embodiment of the present invention, a master<br/>pattern for a given denomination is generated by averaging a plurality of <br/>component<br/>patterns. Each component pattern is generated by scanning a genuine bill of <br/>the<br/>given denomination.<br/> According to a first method, master patterns are generated by scanning a<br/>standard bill a plurality of times, typically three (3) times, and obtaining <br/>the average<br/>of corresponding data samples before storing the average as representing a <br/>master<br/>pattern. In other words, a master pattern for a given denomination is <br/>generated by<br/>averaging a plurality of component patterns, wherein all of the component <br/>patterns<br/>are generated by scanning a single genuine bill of "standard" quality of the <br/>given<br/>denomination. The "standard" bill is a slightly used bill, as opposed to a <br/>crisp new<br/>bill or one which has been subject to a high degree of usage. Rather, the <br/>standard<br/>bill is a bill of good to average quality. Component patterns generated <br/>according to<br/>this first methods are illustrated in FIGs. 15a-15c. More specifically, FIGs. <br/>15a-15c<br/>show three test patterns generated, respectively, for the forward scanning of <br/>a $1 bill<br/>along its green side, the reverse scanning of a $2 bill on its green side, and <br/>the<br/>forward scanning of a $100~bill on its green side. It should be noted that, <br/>for<br/>purposes of clarity the test patterns in FIGS. 15a-15c were generated by using <br/>128<br/>reflectance samples per bill scan, as opposed to the preferred use of only 64 <br/>samples.<br/>The marked difference existing among corresponding samples for these three <br/>test<br/>patterns is indicative of the high degree of confidence with which currency<br/>denominations may be called using the foregoing optical sensing and <br/>correlation<br/>procedure.<br/> According to a second method, a master pattern for a given denomination is<br/>generated by scanning two or more standard bills of standard quality and <br/>obtaining a<br/><br/> CA 02215886 1997-11-06<br/>plurality of component patterns. These component patterns are then averaged in<br/>deriving a master pattern. For example, it has been found that some genuine $5 <br/>bills<br/>have dark stairs on the Lincoln Memorial while other genuine $5 bills have <br/>light<br/>stairs. To compensate for this variation, standard bills for which component <br/>patterns<br/>are derived may be chosen with at least one standard bill scanned having dark <br/>stairs<br/>and with at least one standard bill having light stairs.<br/> It has been found that an alternate method can lead to improved performance<br/>in a discrimination systems, especially with regards to certain denominations. <br/>For<br/>example, it has been found that the printed indicia on a $10 bill has changed <br/>slightly<br/>with 1990 series bills incorporating security threads. More specifically, 1990 <br/>series<br/>$10 bills have a borderline-to-borderline dimension which is slightly greater <br/>than<br/>previous series $10 bills. Likewise it has been found that the scanned pattern <br/>of an<br/>old, semi-shrunken $5 bill can differ significantly from the scanned pattern <br/>of a new<br/>$5 bill.<br/> According to a third method, a master pattern for a given denomination is<br/>generated by averaging a plurality of component patterns, wherein some of the<br/>component patterns are generated by scanning one or more new bills of the <br/>given<br/>denomination and some of the component patterns are generated by scanning one <br/>or<br/>more old bills of the given denomination. New bills are bills of good quality <br/>which<br/>have been printed in recent years and have a security thread incorporated <br/>therein (for<br/>those denominations in which security threads are placed). New bills are <br/>preferably<br/>relatively crisp. A new $10 bill is preferably a 1990 series or later bill of <br/>very high<br/>quality, meaning that the bill is in near mint condition. Old bills are bills <br/>exhibiting<br/>some shrinkage and often some discoloration. Shrinkage may result from a bill<br/>having been subjected to a relatively high degree of use. A new bill utilized <br/>in this<br/>third method is of higher quality than a standard bill of the previous <br/>methods, while<br/>an old bill in this third method is of lower quality than a standard bill.<br/>The third method can be understood by considering Table 2 which summarizes<br/>the manner in which component patterns are generated for a variety of<br/>denominations.<br/><br/> CA 02215886 1997-11-06<br/>71<br/> Table 2. Component Scans by Denomination<br/> Denomination Scan DirectionCPl CP2 CP3<br/>$1 Forward -0.2 std 0.0 std +0.2 std<br/>$1 Reverse -0.2 std 0.0 std +0.2 std<br/> S2, left Forward -0.2 std -0.15 std -0.1 std<br/> S2, left Reverse -0.2 std -0.15 std -0.1 std<br/>$2, right Forward 0.0 std +0.1 std +0.2 std<br/>$2, right Reverse 0.0 std +0.1 std +0.2 std<br/>$5 Forward -0.2 old 0.0 new +0.2 old<br/>(It str) (dk str) (lt str)<br/>$5 Reverse -0.2 old 0.0 new +0.2 old<br/>(lt str) (dk str) (lt str)<br/>$10, left Forward -0.2 old -0.1 new 0.0 old<br/>$10, left Reverse D.0 oid +0. i new +0.2 old<br/>$10, right Forward +0.1 old +0.2 new +0.3 old<br/>$I0, right Reverse -0.2 old -0.15 new -0.1 old<br/>$20 Forward -0.2 old 0.0 new +0.2 old<br/>$20 Reverse -0.2 old 0.0 new +0.2 old<br/>$50 Forward -0.2 std 0.0 std +0.2 std<br/>$50 Reverse -0.2 std 0.0 std +0.2 std<br/>$100 Forward -0.2 std 0.0 std +0.2 std<br/>$100 Reverse -0.2 std 0.0 std +0.2 std<br/> Table 2 summarizes the position of the scanhead relative to the center of the<br/>green surface of United States currency as well as the type of bill to be <br/>scanned for .<br/>generating component patterns for various denominations. The three component<br/>patterns ("CP") for a given denomination and for a given scan direction are <br/>averaged<br/>to yield a corresponding master pattern. The eighteen (18) rows correspond to <br/>the<br/>preferred method of storing eighteen (18) master patterns. The scanhead <br/>position is<br/><br/> CA 02215886 1997-11-06<br/>72<br/>indicated relative to the center of the borderlined area of the bill. Thus a <br/>position of<br/>"0.0" indicates that the scanhead is centered over the center of the <br/>borderlined area<br/>of the bill. Displacements to the left of center are indicated by negative <br/>numbers,<br/>while displacements to the right are indicated by positive numbers. Thus a <br/>position<br/>of "-0.2" indicates a displacement of 2/lOths of an inch to Lhe left of the <br/>center of a<br/>bill, while a position of " +0. I " indicates a displacement of 1/ lOths of an <br/>inch to the<br/>right of the center of a bill.<br/> Accordingly, Table 2 indicates that component patterns for a $20 bill scanned<br/>in the forward direction are obtained by scanning an old $20 bill 2110ths of a <br/>inch to<br/>the right and to the left of the center of the bill and by scanning a new $20 <br/>bill<br/>directly down the center of the bill. FIG. 15d is a graph illustrating these <br/>three<br/>patterns. These three patterns are then averaged to obtain the master pattern <br/>for a<br/>$20 bill scanned in the forward direction. FIG. lSe is a graph illustrating an <br/>pattern<br/>for a $20 bill scanned in the forward direction derived by averaging the <br/>patterns of<br/> FIG. 15d. This pattern becomes the corresponding $20 master pattern after<br/>undergoing normalization. In generating the master patterns, one may use a <br/>scanning<br/>device in which a bill to be scanned is held stationary and a scanhead is <br/>moved over<br/>the bill. Such a device permits the scanhead to be moved laterally, left and <br/>right,<br/>over a bill to be scanned and thus permits the scanhead to be positioned over <br/>the area<br/>of the bill which one wishes to scan, for example, 2/lOths of inch to the left <br/>of the<br/>center of the borderlined area.<br/> As discussed above, for $10 bills two patterns are obtained in each scan<br/>direction with one pattern being scanned slightly to the left of the center <br/>and one<br/>pattern being scanned slightly to the right of the center. For $5 bills, it <br/>has been<br/>found that some $5 bills are printed with darker stairs ("dk str") on the <br/>picture of the<br/>Lincoln Memorial while others are printed with lighter stairs ("lt str"). The <br/>effect of<br/>this variance is averaged out by using an old bill having light stairs and a <br/>new bill<br/>having dark stairs.<br/> As can be seen from Tabie 2, for some bills, the third method of using old<br/>and new bills is not used; rather, a standard ("std") bill is used for <br/>generating all<br/>three component patterns as with the first method. Thus, the master pattern <br/>for a $1<br/>bill scanned in the forward direction is obtained by averaging three component<br/><br/> CA 02215886 1997-11-06<br/>73<br/>patterns generated by scanning a standard bill three times, once 2/lOths of an <br/>inch to<br/>the left, once down the center, and once 2110ths of an inch to the right.<br/> As illustrated by Table 2; a discrimination system may employ a combination<br/>of the developed methods of this invention wherein, for example, some master<br/>patterns are generated according the first method and some master patterns are<br/>generated according to the third method. Likewise, a discrimination system may<br/>combine the scanning of new, standard, and old bills to generate component <br/>patterns<br/>to be averaged in obtaining a master pattern. Additionally, a discrimination <br/>system<br/>may generate master patterns by scanning bills of various qualities and/or <br/>having<br/>various characteristics and then averaging the resultant patterns. <br/>Alternatively, a<br/>discrimination system may scan multiple bills of a given quality for a given<br/>denomination, e.g., three new $50 bills, while scanning one or more bills of a<br/>different quality for a different denomination, e.g., three old and worn $1 <br/>bills, to<br/>generate component. patterns to be averaged in obtaining master patterns.<br/> The optical sensing and correlation technique described above permits<br/>identification of pre-programmed currency denominations with a high degree of<br/>accuracy and is based upon a relatively low processing time for digitizing <br/>sampled<br/>reflectance values and comparing them to the master characteristic patterns. <br/>The<br/>approach is used to scan currency bills, normalize the scanned data and <br/>generate -<br/>master patterns in such a way that bill scans during operation have a direct<br/>correspondence between compared sample points in portions of the bills which<br/>possess the most distinguishable printed indicia. A relatively low number of<br/>reflectance samples is required in order to be able to adequately distinguish <br/>among<br/>several currency denominations.<br/>An advantage with this approach is that it is not required that currency bills <br/>be<br/>scanned along their wide dimensions. Further, the reduction in the number of<br/>samples reduces the processing time to such an extent that additional <br/>comparisons can<br/>be made during the time available between the scanning of successive bills. <br/>More<br/>specifically, as described above, it becomes possible to compare a test <br/>pattern with<br/>multiple stored master characteristic patterns so that the system is made <br/>capable of<br/>identifying currency which is scanned in the "forward" or "reverse" directions <br/>along<br/>the green surface of the bill.<br/><br/> CA 02215886 1997-11-06<br/> Another advantage accruing from the reduction in processing time realized by<br/>the preferred sensing and correlation scheme is that the response time <br/>involved in<br/>either stopping the transport of a bill that has been identified as <br/>"spurious", i.e., not<br/>corresponding to any of the stored master characteristic patterns, or <br/>diverting such a<br/>bill to a separate stacker bin, is correspondingly shortened. Accordingly, the <br/>system<br/>can conveniently be programmed to set a flag when a scanned pattern does not<br/>correspond to any of the master patterns. The identification of such a <br/>condition can<br/>be used to stop the bill transport drive motor for the mechanism. Since the <br/>optical<br/>encoder is tied to the rotational movement of the drive motor, synchronism can <br/>be<br/>maintained between pre- and post-stop conditions.<br/> The correlation procedure and the accuracy with which a denomination is<br/>identified directly relates to the degree of correspondence between <br/>reflectance<br/>samples on the test pattern and corresponding samples on the stored master <br/>patterns.<br/>Thus, shrinkage of "used" bills which, in turn, causes corresponding <br/>reductions in<br/>both their narrow and wide dimensions, can possibly produce a drop in the <br/>degree of<br/>correlation between such used bills of a given denomination and the <br/>corresponding<br/>master patterns. Currency bills which have experienced a high degree of usage<br/>exhibit such a reduction in both the narrow and wide dimensions of the bills. <br/>While<br/>the illustrated sensing and correlation technique remains relatively <br/>independent of any<br/>changes in the non-preselected dimension of bills, reduction along the <br/>preselected<br/>dimension can affect correlation factors by realizing a relative displacement <br/>of<br/>reflectance samples obtained as the "shrunk" bills are transported across the<br/>scanhead. Thus, if the bills are transported and scanned along their wide <br/>dimension,<br/>the sensing and correlation technique will remain relatively independent of <br/>any<br/>changes in the narrow dimension of bills and reduction along the wide <br/>dimension can<br/>affect correlation factors. Similarly, if the bills are transported and <br/>scanned along<br/>their narrow dimension, the sensing and correlation technique will remain <br/>relatively<br/>independent of any changes in the wide dimension of bills and reduction along <br/>the<br/>narrow dimension can affect correlation factors.<br/> In order to accommodate or nullify the effect of such bill shrinking, the<br/>above-described correlation technique can be modified by use of a progressive<br/>shifting approach whereby a test pattern which does not correspond to any of <br/>the<br/><br/> CA 02215886 1997-11-06<br/>_-.~_. __--......._.._..__:..._...r~ ....- _ __.<br/>master patterns is partitioned into predefined sections, and samples in <br/>successive<br/>sections are progressively shifted and compared again to the stored patterns <br/>in order<br/>to identify the denomination. It has experimentally been determined that such<br/>progressive shifting effectively counteracts any sample displacement resulting <br/>from<br/>shrinkage of a bill along the preselected dimension.<br/>The progressive shifting effect is best illustrated by the correlation <br/>patterns<br/>shown in FIGs. 16a-e. For purposes of clarity, the illustrated patterns were<br/>generated using 128 samples for each bill scan as compared to the preferred <br/>use of 64<br/>samples. FIG. 16a shows the correlation between a test pattern (represented by <br/>a<br/>heavy line) and a corresponding master pattern (represented by a thin line). <br/>It is<br/>clear from FIG. 16a that the degree of correlation between the two patterns is<br/>relatively low and exhibits a correlation factor of 606.<br/> The manner in which the correlation between these patterns is increased by<br/>employing progressive shifting is best illustrated by considering the <br/>correlation at the<br/>reference points designated as A-E along the axis defining the number of <br/>samples.<br/>The effect on correlation produced by "single" progressive shifting is shown <br/>in FIG.<br/>16b which shows "single" shifting of the test pattern of FIG. 16a. This is <br/>effected by<br/>dividing the test pattern into two equal segments each comprising 64 samples. <br/>The<br/>first segment is retained without any shift, whereas the second segment is <br/>shifted by a<br/>factor of one data sample. Under these conditions, it is found that the <br/>correlation<br/>factor at the reference points located in the shifted section, particularly at <br/>point E, is<br/>improved.<br/> FIG. 16c shows the effect produced by "double" progressive shifting whereby<br/>sections of the test pattern are shifted in three stages. This is, <br/>accomplished by<br/>dividing the overall pattern into three approximately equal sized sections. <br/>Section<br/>one is not shifted, section two is shifted by one data sample (as in FIG. <br/>16b), and<br/>section three is shifted by a factor,of two data samples. With "double" <br/>shifting, it<br/>can be seen that the correlation factor at point E is further increased.<br/> On a similar basis, FIG. 16d shows the effect on correlation produced by<br/>"triple" progressive shifting where the overall pattern is first divided into <br/>four (4)<br/>approximately equal sized sections. Subsequently, section one is retained <br/>without any<br/>shift, section two is shifted by one data sample, section three is shifted by <br/>two data<br/><br/> CA 02215886 1997-11-06<br/>76<br/>samples, and section four is shifted by three data samples. Under these <br/>conditions,<br/>the correlation factor at point E is seen to have increased again.<br/> FIG. 16e shows the effect on correlation produced by "quadruple" shifting,<br/>where the pattern is first divided into five (5) approximately equal sized <br/>sections.<br/>The first four (4) sections are shifted in accordance with the "triple" <br/>shifting<br/>approach of FIG. 16d, whereas the fifth section is shifted by a factor of four <br/>(4) data<br/>samples. From FIG. 16e it is clear that the correlation at point E is <br/>increased almost<br/>to the point of superimposition of the compared data samples.<br/> In an alternative progressive shifting approach, the degree of shrinkage of a<br/>scanned bill is determined by comparing the length of the scanned bill, as <br/>measured<br/>by the scanhead, with the length of an "unshrunk" bill. This "unshrunk" length <br/>is<br/>pre-stored in the system memory. The type of progressive shifting, e.g., <br/>"single",<br/>"double", "triple", etc., applied to the test pattern is then directly based <br/>upon the<br/>measured degree of shrinkage. The greater the degree of shrinkage, the greater <br/>the<br/>number of sections into which the test pattern is divided. An advantage of <br/>this<br/>approach is that only one correlation factor is calculated, as opposed to <br/>potentially<br/>calculating several correlation factors for different types of progressive <br/>shifting.<br/> In yet another progressive shifting approach, instead of applying progressive<br/>shifting to the test pattern, progressive shifting is applied to each of the <br/>master<br/>patterns. The master patterns in the system memory are partitioned into <br/>predefined<br/>sections, and samples in successive sections are progressively shifted and <br/>compared<br/>again to the scanned test pattern in order to identify the denomination. To <br/>reduce the<br/>amount of processing time, the degree of progressive shifting which should be<br/>applied to the master patterns may be determined by first measuring the degree <br/>of<br/>shrinkage of the scanned bill. By first measuring the degree of shrinkage, <br/>only one<br/>type of progressive shifting is applied to the stored master patterns.<br/>Instead of rearranging the scanned test pattern or the stored master patterns,<br/>the system memory may contain pre-stored patterns corresponding to various <br/>types of<br/>progressive shifting. The scanned test pattern is then compared to all of <br/>these stored<br/>patterns in the system memory. However, to reduce the time required for <br/>processing<br/>the data, this approach may be modified to first measure the degree of <br/>shrinkage and<br/><br/> CA 02215886 1997-11-06<br/>77<br/>to then select only those stored patterns from the system memory which <br/>correspond<br/>to the measure degree of shrinkage for comparison with the scanned test <br/>pattern.<br/> The advantage of using the progressive shifting approach, as opposed to<br/>merely shifting by a set amount of data samples across the overall test <br/>pattern, is that<br/>S the improvement in correlation achieved in the initial sections of the <br/>pattern as a<br/>result of shifting is not neutralized or offset by any subsequent shifts in <br/>the test<br/>pattern. It is apparent from the above figures that the degree of correlation <br/>for<br/>sample points failing within the progressively shifted sections increases<br/>correspondingly.<br/>More importantly, the progressive shifting realizes substantial increases in <br/>the<br/>overall correlation factor resulting from pattern comparison. For instance, <br/>the<br/>original correlation factor of 606 (FIG. 16a) is increased to 681 by the <br/>"single"<br/>shifting shown in FIG. 16b. The "double" shifting shown in FIG. 16c increases <br/>the<br/>correlation number to 793, the "triple" shifting of FIG. l6d increases the <br/>correlation<br/>number to 906, and, finally, the "quadruple" shifting shown in FIG. 16e <br/>increases<br/>the overall correlation number to 960. Using the above approach, it has been<br/>determined that used currency bills which exhibit a high degree .of shrinkage <br/>and<br/>which cannot be accurately identified as belonging to the correct currency<br/>denomination when the correlation is performed without any shifting, can be<br/>identified with a high degree of certainty by using progressive shifting <br/>approach,<br/>preferably by adopting "triple" or "quadruple" shifting.<br/> In currency discrimination systems in which discrimination is based on the<br/>comparison of a pattern obtained from scanning a subject bill to stored master<br/>patterns corresponding to various denominations, the patterns which are <br/>compared to<br/>each other significantly influence the performance characteristics of a <br/>discrimination<br/>system. For example, in the system described in United States Patent No.<br/>5,295,196, the correlation procedure and the accuracy with which a <br/>denomination is<br/>identified directly relates to the degree of correspondence between <br/>reflectance<br/>samples on the test pattern and corresponding samples on the stored master <br/>patterns.<br/>In accordance with method described above, the identity of a bill under test <br/>is<br/>determined by comparing a scanned pattern generated by scanning the bill under <br/>test<br/>with one or more master patterns associated with genuine bills. If the scanned<br/><br/> CA 02215886 1997-11-06<br/>7g<br/>pattern sufficiently correlates to one of the master pattern, the identity of <br/>the bill may<br/>be called. The process of identifying a bill under test may be subjected,to a <br/>bi-level<br/>threshold test as described above.<br/> However, the degree of correlation between a scanned and a master pattern<br/>may be negatively impacted if the two patterns are not properly aligned with <br/>each<br/>other. Such misalignment between patterns may in turn negatively impact upon <br/>the<br/>performance of a currency identification system. Misalignment between patterns <br/>may<br/>result from a number of factors. For example, if a system is designed so that <br/>the<br/>scanning process is initiated in response to the detection of the thin <br/>borderline<br/>surrounding U. S . currency or the detection of some other printed indicia <br/>such as the<br/>edge of printed indicia on a bill, stray marks may cause initiation of the <br/>scanning<br/>process at an improper time. This is especially true for stray marks in the <br/>area<br/>between the edge of a bill and the edge of the printed indicia on the bill. <br/>Such stray<br/>marks may cause the scanning process to be initiated too soon, resulting in a <br/>scanned<br/>pattern which leads a corresponding master pattern. Alternatively, where the<br/>detection of the edge of a bill is used to trigger the scanning process, <br/>misalignment<br/>between patterns may result from variances between the location of printed <br/>indicia on<br/>a bill relative to the edges of a bill. Such variances may result from <br/>tolerances<br/>permitted during the printing and/or cutting processes in the manufacture of <br/>currency.<br/>For example, it has been found that location of the leading edge of printed <br/>indicia on<br/> Canadian currency relative to the edge of Canadian currency may vary up to<br/>approximately 0.2 inches (approximately 0.5 cm).<br/> According to a preferred embodiment of the present invention, the problems<br/>associated with misaligned patterns are overcome by employing an improved <br/>method<br/>of generating multiple scanned and/or master patterns and comparing the <br/>multiple<br/>scanned and master patterns with each other. Briefly, a preferred embodiment <br/>of the<br/>improved pattern generation method involves removing data samples from one end <br/>of<br/>a pattern to be modified and adding data values on the opposite end equal to <br/>the data<br/>values contained in the corresponding sequence positions of the pattern to <br/>which the<br/>modified pattern is to be compared. This process may be repeated, up to a<br/>predetermined number of times, until a sufficiently high correlation is <br/>obtained<br/>between the two patterns so as to permit the identity of a bill under test to <br/>be called.<br/><br/> CA 02215886 1997-11-06<br/>79<br/> A preferred embodiment of the present invention can be further understood by<br/>considering Table 3. Table 3 contains data samples generated by scanning the<br/>narrow dimension of Canadian $2 bills along a segment positioned about the <br/>center of<br/>the bill on the side opposite the portrait side. Mare specifically, the second <br/>column<br/>of Table 3 represents a scanned pattern generated by scanning a test Canadian <br/>$2 bill.<br/>The scanned pattern comprises 64 data samples arranged in a sequence. Each <br/>data<br/>sample has a sequence position, 1-64, associated therewith. The fifth column<br/>represents a master pattern associated with a Canadian $2 bill. The master <br/>pattern<br/>likewise comprises a sequence of 64 data samples. The third and fourth columns<br/>represent the scanned pattern after it has been modified in the forward <br/>direction one<br/>and two times, respectively. In the embodiment depicted in Table 3, one data <br/>sample<br/>is removed from the beginning of the preceding pattern during each <br/>modification.<br/> Table 3<br/> Sequence Scanned Scanned PatternScanned PatternMaster I<br/> Position Pattern Modified Once Modified TwicePattern<br/>1 93 50 -21 161<br/>2 50 -21 50 100<br/>3 -21 50 93 171<br/>4 50 93 65 191<br/>5 93 65 22 252<br/>6 65 22 79 403<br/>7 22 79 136 312<br/>8 79 136 193 434<br/>9 136 193 278 90<br/>10 193 278 164 0<br/>11 278 164 136 20<br/> I 12 164 136 278 444<br/><br/> CA 02215886 1997-11-06<br/> Sequence Seanned Scanned PatternScanned PatternMaster<br/> Position Pattern Modified Once Modified TwicePattern<br/>52 -490 -518 -4.47 -1090<br/>53 -518 -447 -646 -767<br/>54 -447 -646 -348 -575<br/>55 -646 -348 -92 -514<br/>56 -348 -92 -63 -545<br/>57 -92 -63 -205 -40<br/>58 -63 -205 605 1665<br/>59 -205 605 1756 1705<br/>60 605 1756 1401 1685<br/>61 1756 1401 1671 2160<br/>62 1401 1671 2154 2271<br/>63 1671 2154 *2240 2240<br/>64 2154 *2210 *2210 2210<br/>The modified pattern represented in the third column is generated by adding an<br/>additional data value to the end of the original scanned pattern sequence <br/>which<br/>effectively removes the first data sample of the original pattern, e.g., 93, <br/>from the<br/>modified pattern. The added data value in the last sequence position, 64, is <br/>set equal<br/>5 to the data value contained in the 64th sequence position of the master <br/>pattern, e.g.,<br/>2210. This copying of the 64th data sample is indicated by an asterisk in the <br/>third<br/>column. The second modified pattern represented in the fourth column is <br/>generated<br/>by adding two additional data values to the end of the original scanned <br/>pattern which<br/>effectively removes the first two data samples of the original scanned, e.g., <br/>93 and<br/>10 50, from the second modified pattern. The last two sequence positions, 63 <br/>and 64,<br/>are filled with the data value contained in the 63rd and 64th sequence <br/>positions of the<br/>master pattern, e.g., 2240 and 2210, respectively. The copying of the 63rd and <br/>64th<br/>data samples is indicated by asterisks in the fourth column.<br/> In the example of Table 3, the printed area of the bill under test from which<br/>15 the scanned pattern was generated was farther away from the leading edge of <br/>the bill<br/><br/> CA 02215886 1997-11-06<br/>81<br/>than was the printed area of the bill from which the master pattern was <br/>generated.<br/> As a result, the scanned pattern trailed the master pattern. The preferred<br/>embodiment of the pattern generation method described in conjunction with <br/>Table 3<br/>compensates for the variance of the distance between the edge of the bill and <br/>the edge<br/>of the printed indicia by modifying the scanned pattern in the forward <br/>direction. As<br/>a result of the modification method employed, the correlation between the <br/>original<br/>and modified versions of the scanned pattern and the master pattern increased <br/>from<br/>705 for the original, unmodified scanned pattern to 855 for the first modified <br/>pattern<br/>and to 988 for the second modified pattern. Accordingly, the bill under test <br/>which<br/>would otherwise have been rejected may now be properly called as a genuine $2<br/>Canadian bill through the employment of the pattern generation method <br/>discussed<br/>above.<br/>Another preferred embodiment of the present invention can be understood<br/>with reference to the flowchart of FIGs. 17a-17c. The process of FIGs. 17a-i7c<br/>involves a method of identifying a bill under test by comparing a scanned <br/>pattern<br/>retrieved from a bill under test with one or more master patterns associated <br/>with one<br/>or more genuine bills. After the process begins at step 128a, the scanned <br/>pattern is<br/>compared with one or more master patterns associated with genuine bills (step <br/>128b).<br/>At step 129 it is determined whether the bill under test can be identified <br/>based on the<br/>comparison at step 128b. This may be accomplished by evaluating the <br/>correlation<br/>between the scanned pattern and each of the master patterns. If the bill can <br/>be<br/>identified, the process is ended at step 130. Otherwise, one or more of the <br/>master<br/>patterns are designated for further processing at step 131. For example, all <br/>of the<br/>master patterns may be designated for further processing. Alternatively, less <br/>than all<br/>of the master patterns may be designated based on a preliminary assessment <br/>about the<br/>identity of the bill under test. For example, only the master patterns which <br/>had the<br/>four highest correlation values with respect to the scanned pattern at step <br/>128b might<br/>be chosen for further processing. In any case, the number of master patterns<br/>designated for further processing is M1.<br/> At step 132, either the scanned pattern is designated for modification or the<br/>M1 master patterns designated at step 131 are designated for modification. In <br/>a<br/>preferred embodiment of the present invention, the scanned pattern is <br/>designated for<br/><br/> CA 02215886 1997-11-06<br/>82<br/>modification and the master patterns remain unmodified. At step 133, it is <br/>designated<br/>whether forward modification or reverse modification is to be performed. This<br/>determination may be made, for example, by analyzing the beginning or ending <br/>data<br/>samples of the scanned pattern to determine whether the scanned pattern trails <br/>or<br/>leads the master patterns.<br/>At step 134, the iteration counter, I, is set equal to one. The iteration <br/>counter<br/>is used to keep track of how many times the working patterns have been <br/>modified.<br/>Then at step 135, the number of incremental data samples, R, to be removed <br/>during<br/>each iteration is set. For example, in a preferred embodiment of the present<br/>invention, only one additional data sample is removed from each working <br/>pattern<br/>during each iteration in which case R is set equal to one.<br/> At step 136, it is determined whether the scanned pattern has been designated<br/>for modification. If it has, then the scanned pattern is replicated M1 times <br/>and the<br/>M1 replicated patterns, one for each of the Ml master patterns, are designated <br/>as<br/>working patterns at step 137. If the scanned pattern has not been designated <br/>for<br/>modification, then the M1 master patterns have been so designated, and the M1<br/>master patterns are replicated and designated as working patterns at step 138.<br/>Regardless of which pattern or patterns were designated for modification, at <br/>step 139,<br/>it is determined whether forward or reverse modification is to be performed on <br/>the<br/>working patterns.<br/> If forward modification is to be performed, the first R x I data samples from<br/>each working pattern are removed at step 140. The first R x I data samples may<br/>either be explicitly removed from the working patterns or be removed as a <br/>result of<br/>adding additional data samples (step 141) to the end of the pattern and <br/>designating the<br/>beginning of the modified pattern to be the R x I + 1 sequence position of the<br/>original pattern. As a result of the modification, the data sample which was <br/>in the<br/>64th sequence position in the original working pattern will be in the 64 - (R <br/>x I)<br/>sequence position. The added data values in the last R x I sequence positions <br/>of a<br/>working pattern are copied from the data samples in the last R x I sequence <br/>positions<br/>of a corresponding non-designated pattern at step 141. After the above <br/>described<br/>modification, the working patterns are compared with either respective ones of <br/>the<br/>non-designated patterns (scanned pattern modified/Ml master patterns not <br/>designated<br/><br/> CA 02215886 1997-11-06<br/>83<br/>for modification) or the non-designated pattern (lbT1 master patterns <br/>designated for<br/>modification/scanned pattern not designated for modification) at step 142.<br/>Alternatively, if reverse modification is to be performed, the last R x I data<br/>samples from each working pattern are removed at step 143. The last R x I data<br/>S samples may either be explicitly removed from the working patterns or be <br/>removed<br/>as a result of adding additional data samples (step 144) to the beginning of <br/>the pattern<br/>and designating the beginning of the modified pattern to start with the added <br/>data<br/>samples. As a result of the modification, the data sample which was in the 1st<br/>sequence position in the original working pattern will be in the (R x I) + 1 <br/>sequence<br/>position. The added data samples in first R x I sequence positions of a <br/>working<br/>pattern are copied from the data samples in the first R x I sequence positions <br/>of a<br/>corresponding non-designated pattern at step 144. After the above described<br/>modification, the working patterns are compared with either respective ones of <br/>the<br/>non-designated patterns (scanned pattern modified/M l master patterns not <br/>designated<br/>for modification) or the non-designated pattern {M1 master patterns designated <br/>for<br/>modification/scanned pattern not designated for modification) at step 142.<br/>For example, if the scanned pattern is designated for forward modification and<br/>four master patterns are designated for further processing, four working <br/>patterns are<br/>generated from the scanned pattern at step 137, one for each of the four <br/>master<br/>patterns: If R is set to two at step 135, during the first iteration the last <br/>two data<br/>samples from each of the Ml master patterns are copied and added to the end of <br/>the<br/>M1 working patterns so as to become the last two sequence positions of the Nil<br/>working patterns, one working pattern being associated with each of the M1 <br/>master<br/>patterns. As a result, after the first iteration, four different working <br/>patterns are<br/>generated with each working pattern corresponding to a modified version of the<br/>scanned pattern but with each having data values in its last two sequence <br/>positions<br/>copied from the last two sequence positions of a respective one of the M1 <br/>master<br/>patterns. After a second iteration, the last four sequence positions of each <br/>of the M1<br/>master patterns are copied and added to the end of the Ml working patterns so <br/>as to<br/>become the last four sequence positions of a respective one of the M1 working<br/>patterns.<br/><br/> CA 02215886 1997-11-06<br/>$4<br/> As another example, if four master patterns are designated for further<br/>processing and the four designated master patterns are designated for forward<br/>modification, four working patterns are generated at step 138, one from each <br/>of the<br/>four designated master patterns. If R is set to two at step 135, during the <br/>first<br/>iteration the last two data samples of the scanned pattern are copied and <br/>added to the<br/>end of the M1 working patterns so as to become the last two sequence positions <br/>of<br/>the M1 working patterns, one working pattern being associated with each of the <br/>M1<br/>master patterns. As a result, after the first iteration, four different <br/>working patterns<br/>are generated with each working pattern corresponding to a modified version of <br/>a<br/>corresponding master pattern but with each having data values in its last two<br/>sequence position copied from the last two sequence positions of the scanned <br/>pattern.<br/>After a second iteration, the last four sequence positions of the scanned <br/>pattern are<br/>copied and added to the end of the M1 working patterns so as to become the <br/>last four<br/>sequence positions of the M1 working patterns.<br/>1~ After the comparison at step 142, it is determined whether the bill under <br/>test<br/>can be identified at step 145. If the bill can be identified the process is <br/>ended at step<br/>146. Otherwise, the iteration counter, I, is incremented by one. (step 147) <br/>and the<br/>incremented iteration counter is compared to a maximum iteration number, T <br/>(step<br/>148). If the iteration counter, I, is greater than the maximum iteration <br/>number, T,<br/>then a no call is issued (step 149a), meaning that a match sufficient to <br/>identify the<br/>bill under test was not obtained, and the process is ended (step 149b). <br/>Otherwise, if<br/>the iteration is not greater than the maximum iteration number, the <br/>modification<br/>process is repeated beginning with step 136.<br/> The flowchart of FIGs. 17a-17c is intended to illustrate one preferred<br/>embodiment of the present invention. However, it is recognized that there are<br/>numerous ways in which the steps of the flowchart of FIGS. 17a-17c may be<br/>rearranged or altered and yet still result in the comparison of the same <br/>patterns as<br/>would be compared if the steps of FIGs. 17a-17c were followed exactly. For<br/>example, instead of generating multiple working patterns, a single working <br/>pattern<br/>may be generated and the leading or trailing sequence positions successively <br/>altered<br/>before comparisons to corresponding non-designated patterns. Likewise, instead <br/>of<br/>generating multiple modified patterns directly from unmodified patterns, <br/>multiple<br/><br/> CA 02215886 1997-11-06<br/>$5<br/>modified patterns may be generated from the preceding modified patterns. For<br/>example, instead of generating a twice forward modified scanned pattern by <br/>removing<br/>the first two data samples from the original scanned pattern and copying the <br/>last 2R<br/>sequence positions of a corresponding master pattern and adding these data <br/>values to<br/>the end of the original scanned pattern, the first data sample of the single <br/>forward<br/>modified scanned pattern may be removed and one data sample added to the end <br/>of<br/>the single modified scanned pattern and then the data samples in the last two<br/>sequence positions may be set equal to the data samples in the last 2R <br/>sequence<br/>positions of a corresponding master pattern.<br/> In an alternate preferred embodiment of the present invention, instead of<br/>copying data values from a scanned pattern into corresponding sequence <br/>positions of<br/>modified master patterns, leading or trailing sequence positions of modified <br/>master<br/>patterns are filled with zeros.<br/> In an alternate preferred embodiment of the present invention, modified<br/>master patterns are stored, for example in EPROM 60 of FIG. 7a, before a bill <br/>under<br/>test is scanned. In such an embodiment, a scanned pattern retrieved from a <br/>bill<br/>under test is compared to the modified master patterns stored in memory. <br/>Modified<br/>master patterns are generated by modifying a corresponding master pattern in <br/>either<br/>the forward or backward direction, or both, and filling in any trailing or <br/>leading<br/>sequence positions with zeros. An advantage of such a preferred embodiment is <br/>that<br/>no modification needs to be performed during the normal operation of an<br/>identification device incorporating such an embodiment.<br/> An example of a procedure involved in comparing test patterns to master<br/>patterns is illustrated at FIG. 18a which shows the routine as starting at <br/>step 150a.<br/>At step 151a, the best and second best correlation results {referred to in <br/>FIG. 18a as<br/>the "#1 and #2 answers") are initialized to zero and, at step 152a, the test <br/>pattern is<br/>compared with each of the sixteen or eighteen original master patterns stored <br/>in the<br/>memory. At step 153a, the calls corresponding to the two highest correlation<br/>numbers obtained up to that point are determined and saved. At step 154a, a <br/>post-<br/>processing flag is set. At step 155a the test pattern is compared with each of <br/>a<br/>second set of 16 or 18 master patterns stored in the memory. This second set <br/>of<br/>master patterns is the same as the 16 or 18 original master patterns except <br/>that the<br/><br/> CA 02215886 1997-11-06<br/>86<br/>last sample is dropped and a zero is inserted in front of the first sample. If <br/>any of<br/>the resulting correlation numbers is higher than the two highest numbers <br/>previously<br/>saved, the #1 and #2 answers are updated at step 156.<br/> Steps 155a and 156a are repeated at steps 157a and 158a, using a third set of<br/>master patterns formed by dropping the last two samples from each of the 16 <br/>original<br/>master patterns and inserting two zeros in front of the first sample. At steps <br/>159a<br/>and 160a the same steps are repeated again, but using only $50 and $100 master<br/>patterns formed by dropping the last three samples from the original master <br/>patterns<br/>and adding three zeros in front of the first sample. Steps l6la and 162a <br/>repeat the<br/>procedure once again, using only $1, $5, $10 and $20 master patterns formed by<br/>dropping the 33rd sample whereby original samples 34-64 become samples 33-63 <br/>and<br/>inserting a 0 as the new last sample. Finally, steps 163a and 164a repeat the <br/>same<br/>procedure, using master patterns for $10 and $50 bills printed in 1950, which <br/>differ<br/>significantly from bills of the same denominations printed in later years. <br/>This routine<br/>then returns to the main program at step 165a. The above multiple sets of <br/>master<br/>patterns may be pre-stored in EPROM 60.<br/> A modified procedure involved in comparing test patterns to green-side master<br/>patterns is illustrated at FIG. 18b which shows the routine as starting at <br/>step 150b.<br/>At step 151b, the best and second best correlation results (referred to in <br/>FIG. 18b as<br/>the "#1 and #2 answers") are initialized to zero and, at step I52b, the test <br/>pattern is<br/>compared with each of the eighteen original green-side master patterns stored <br/>in the<br/>memory. At step 153b, the calls corresponding to the two highest correlation<br/>numbers obtained up to that point are determined and saved. At step 154b, a <br/>post-<br/>processing flag is set. At step 155b the test pattern is compared with each of <br/>a<br/>second set of 18 green-side master patterns stored in the memory. This second <br/>set of<br/>master patterns is the same as the 18 original green-side master patterns <br/>except that<br/>the last sample is dropped and a zero is inserted in front of the first <br/>sample. If any<br/>of the resulting correlation numbers is higher than the two highest numbers<br/>previously saved, the #1 and #2 answers are updated at step 156b.<br/> Steps 155b and 156b are repeated at steps 157b and 158b, using a third set of<br/>green-side master patterns formed by dropping the last two samples from each <br/>of the<br/>18 original master patterns and inserting two zeros in front of the first <br/>sample. At<br/><br/> CA 02215886 1997-11-06<br/>87<br/>steps 159b and 160b the same steps are repeated again, but using only $50 and <br/>$100<br/>master patterns (two patterns for the $50 and four patterns for the $100) <br/>formed by<br/>dropping the last three samples from the original master patterns and adding <br/>three<br/>zeros in front of the first sample. Steps 161b and 162b repeat the procedure <br/>once<br/>again, using only $1, $5, $10, $20 and $50 master patterns (four patterns for <br/>the $10<br/>and two patterns for the other denominations) formed by dropping the 33rd <br/>sample<br/>whereby original samples 34-64 become samples 33-63 and inserting a 0 as the <br/>new<br/>last sample. Finally, steps 163b and 164b repeat the same procedure, using <br/>master<br/>patterns for $10 and $50 bills printed in 1950 (two patterns scanned along a <br/>center<br/>segment for each denomination), which differ significantly from bills of the <br/>same<br/>denominations printed in later years. This routine then returns to the main <br/>program<br/>at step 165b. The above multiple sets of master patterns may be pre-stored in<br/> EPROM 60.<br/> In a preferred embodiment where conditional black-side correlation is to be<br/>performed a modified version of the routine designated as "CORRES" is <br/>initiated.<br/>The procedure involved in executing the modified version of CORRES is <br/>illustrated<br/>at FIG. 19a which shows the routine as starting at step 180. Step 181 <br/>determines<br/>whether the bill has been identified as a $2 bill, and, if the answer is <br/>negative, step<br/>182 determines whether the best correlation number ("call #1 ") is greater <br/>than 799.<br/> If the answer is negative, the correlation number is too low to identify the<br/>denomination of the bill with certainty, and at step 183b a black side <br/>correlation<br/>routine is called (described in more detail below in conjunction with FIGS. <br/>19b-19c).<br/> An affirmative answer at step 182 advances the system to step 186, which<br/>determines whether the sample data passes an ink stain test (described below). <br/>If the<br/>answer is negative, a "no call" bit is set in a correlation result flag at <br/>step 183a. A<br/>"no call previous bill" flag is then set at step 184, and the routine returns <br/>to the main<br/>program at step 185. If the answer at step 186 is affirmative, the system <br/>advances to<br/>step 187 which determines whether the best correlation number is greater than <br/>849.<br/>An affirmative answer at step 187 indicates that the correlation number is <br/>sufficiently<br/>high that the denomination of the scanned bill can be identified with <br/>certainty without<br/>any further checking. Consequently, a "good call" bit is set in the <br/>correlation result<br/>flag at step 188. A separate register associated with the best correlation <br/>number (#1)<br/><br/> CA 02215886 1997-11-06<br/>88<br/>may then be used to identify the denomination represented by the stored <br/>pattern<br/>resulting in the highest correlation number. The system returns to the main <br/>program<br/>at step 185.<br/>A negative answer at step 187 indicates that the correlation number is between<br/>800 and 850. It has been found that correlation numbers within this range are<br/>sufficient to identify all bills except the $2 bill. Accordingly, a negative <br/>response at<br/>step 187 advances the system to step 189 which determines whether the <br/>difference<br/>between the two highest correlation numbers ("call #1" and "call #2") is <br/>greater than<br/>149. If the answer is affirmative, the denomination identified by the highest<br/>correlation number is acceptable, and thus the "good call" bit is set in the <br/>correlation<br/>result flag at step 188. If the difference between the two highest correlation <br/>numbers<br/>is less than 150, step 189 produces a negative response which advances the <br/>system to<br/>step i83b where the black side correlation routine is called.<br/>Returning to step i 81, an affirmative response at this step indicates that <br/>the<br/>initial call is a $2 bill. This affirmative response initiates a series of <br/>steps 190-193<br/>which are similar to steps 182, 186, 187 and 189 described above, except that <br/>the<br/>numbers 799 and 849 used in steps 182 and 187 are changed to, 849 and 899,<br/>respectively, in steps 190 and 192. The result is either the setting of a "no <br/>call" bit<br/>in a correlation result flag at step 183a, the setting of the "good call" bit <br/>in the<br/>correlation result flag at step 188, or the calling of the black side <br/>correlation routine<br/>at step 183b.<br/> Turning now to FIGs. 19b and 19c there is shown a flowchart illustrating the<br/>steps of the black side correlation routine called at step 183b of FIG. 19a. <br/>After the<br/>black side correlation routine is initiated at step 600, it is determined at <br/>step 602<br/>whether the lower read head was the read head that scanned the black side of <br/>the test<br/>bill. If it was, the lower read head data is normalized at step 604. <br/>Otherwise, it is<br/>determined at step 606 whether the upper read head was the read head that <br/>scanned<br/>the black side of the test bill. If it was, the upper read head data is <br/>normalized at<br/>step 608. If it cannot be determined which read head scanned the black side of <br/>the<br/>bill, then the patterns generated from both sides of the test bill were <br/>correlated<br/>against the green-side master patterns (see e.g.; step 110 of FIG. 12). Under <br/>such a<br/>circumstance, the no call bit in the correlation result flag is set at step <br/>610, the no<br/><br/> CA 02215886 1997-11-06<br/>89<br/>call previous bill flag is set at step 611, and the program returns to the <br/>calling point<br/>at step 612.<br/> After the lower read head data is normalized at step 604, or the upper read<br/>head data is normalized at step 608, it is determined whether the best green-<br/>side<br/>correlation number is greater than 700 at step 6I4. A negative response at <br/>step 614<br/>results in the no call bit in the correlation result flag being set at step <br/>610, the no call<br/>previous bill flag being set at step 611, and the program returning to the <br/>calling point<br/>at step 612. An affirmative response at step 614 results in a determination <br/>being<br/>made as to whether the best call from the green side correlation corresponds <br/>to a<br/>$20, $50, or $100 bill at step 616. A negative response at step 616 results in <br/>the no<br/>call bit in the correlation result flag being set at step 610, the no call <br/>previous bill<br/>flag being set at step 611, and thee program returning to the calling point at <br/>step 612.<br/>If it determined at step 616 that the best call from the green side <br/>correlation<br/>corresponds to a $20, $50, or $100 bill, the scanned pattern from the black <br/>side is<br/>correlated against the black-side master patterns associated with the specific<br/>denomination and scan direction associated the best call from the green side.<br/>According to a preferred embodiment, multiple black-side master patterns are <br/>stored<br/>for $20, $50 and $100 bills. For each of these denominations, three master <br/>patterns<br/>are stored for scans in the forward and three master patterns are stored for <br/>scans in<br/>the reverse direction for a total of six patterns for each denomination. For a <br/>given<br/>scan direction, black-side master patterns are generated by scanning a <br/>corresponding<br/>denominated bill along a segment located about the center of the narrow <br/>dimension of<br/>the bill, a segment slightly displaced (0.2 inches) to the left of center, and <br/>a segment<br/>slightly displaced (0.2 inches) to the right of center.<br/> For example, at step 618, it is determined whether the best call from the<br/>green side is associated with a forward scan of a $20 bill and, if it is, the <br/>normalized<br/>data from the black side of the test bill is correlated against the black-side <br/>master<br/>patterns associated with a forward scan of a $20 bill at step 620. Next it is<br/>determined whether the black-side correlation number is greater than 900 at <br/>step 622.<br/>If it is, the good call bit in the correlation result flag is set at step 648 <br/>and the<br/>program returns to the calling point at step 646. If the black-side <br/>correlation number<br/>is not greater than 900, then the no call bit in the correlation result flag <br/>is set at step<br/><br/> CA 02215886 1997-11-06<br/>642, the no call previous bill flag is set at step 644, and the program <br/>returns to the<br/>calling point at step 646. If it is determined that the best call from the <br/>green side is<br/>not associated with a forward scan of $20 bill at step 618, the program <br/>branches<br/>accordingly at steps 624 - 640 so that the normalized data from the black side <br/>of the<br/>5 test bill is correlated against the appropriate black-side master patterns.<br/> Referring now to FIGs. 20a-22, the mechanical portions of the preferred<br/>currency discrimination and counting machine include a rigid frame formed by a <br/>pair<br/>of side plates 201 and 202, a pair of top plates 203a and 203b, and a lower <br/>front<br/>plate 204. The input receptacle for receiving a stack of bills to be processed <br/>is<br/>10 formed by downwardly sloping and converging walls 205 and 206 formed by a <br/>pair<br/>of removable covers 207 and 208 which snap onto the frame. The rear wall 206<br/>supports a removable hopper 209 which includes a pair of vertically disposed <br/>side<br/>walls 210a and 210b which complete the receptacle for the stack of currency <br/>bills to<br/>be processed.<br/>15 From the input receptacle, the currency bills are moved in seriatim from <br/>the<br/>bottom of the stack along a curved guideway 211 which receives bills moving<br/>downwardly and rearwardly and changes the direction of travel to a forward<br/>direction. The curvature of the guideway 211 corresponds substantially to the <br/>curved<br/>periphery of the drive roll 223 so as to form a narrow passageway for the <br/>bills along<br/>20 the rear side of the drive roil. The exit end of the guideway 211 directs <br/>the bills<br/>onto a linear path where the bills are scanned and stacked. The bills are <br/>transported<br/>and stacked with the narrow dimension of the bills maintained parallel to the<br/>transport path and the direction of movement at all times.<br/>Stacking of the bills is effected at the forward end of the linear path, where<br/>25 the bills are fed into a pair of driven stacking wheels 212 and 213. These <br/>wheels<br/>project upwardly through a pair of openings in a slacker plate 214 to receive <br/>the bills<br/>as they are advanced across the downwardly sloping upper surface of the plate. <br/>The<br/>slacker wheels 212 and 213 are supported for rotational movement about a shaft <br/>215<br/>journalled on the rigid frame and driven by a motor 216. The flexible blades <br/>of the<br/>30 slacker wheels deliver the bills into an output receptacle 217 at the <br/>forward end of<br/>the slacker plate 214. During operation, a currency bill which is delivered to <br/>the<br/>slacker plate 214 is picked up by the flexible blades and becomes lodged <br/>between a<br/><br/> CA 02215886 1997-11-06<br/>91<br/>pair of adjacent blades which, in combination, define a curved enclosure which<br/>decelerates a bill entering therein and serves as a means for supporting and<br/>transferring the bill into the output receptacle 217 as the slacker wheels <br/>2I2, 213<br/>rotate. The mechanical configuration of the slacker wheels, as well as the <br/>manner in<br/>which they cooperate with the slacker plate, is conventional and, accordingly, <br/>is not<br/>described in detail herein.<br/> Returning now to the input region of the machine as shown in FIGs. 20a-22,<br/>bills that are stacked on the bottom wall 205 of the input receptacle are <br/>stripped, one<br/>at a time, from the bottom of the stack. The bills are stripped by a pair of <br/>stripping<br/>wheels 220 mounted on a drive shaft 221 which, in turn, is supported across <br/>the side<br/>walls 201, 202. The stripping wheels 220 project through a pair of slots <br/>formed in<br/>the cover 207. Part of the periphery of each wheel 220 is provided with a <br/>raised<br/>high-friction, serrated surface 222 which engages the bottom bill of the input <br/>stack as<br/>the wheels 220 rotate, to initiate feeding movement of the bottom bill from <br/>the stack.<br/>The serrated surfaces 222 project radially beyond the rest of the wheel <br/>peripheries so<br/>that the wheels "jog" the bill stack during each revolution so as to agitate <br/>and loosen<br/>the bottom currency bill within the stack, thereby facilitating the stripping <br/>of the<br/>bottom bill from the stack.<br/>The stripping wheels 220 feed each stripped bill B (FIG. 21a) onto a drive <br/>roll<br/>223 mounted on a driven shaft 224 supported across the side walls 201 and 202. <br/>As<br/>can be seen most clearly in FIGs. 21a and 21b, the drive roll 223 includes a <br/>central<br/>smooth friction surface 225 formed of a material such as rubber or hard <br/>plastic. This<br/>smooth friction surface 225 is sandwiched between a pair of grooved surfaces <br/>226<br/>and 227 having serrated portions 228 and 229 formed from a high-friction <br/>material.<br/>The serrated surfaces 228, 229 engage each bill after it is fed onto the drive<br/>roll 223 by the stripping wheels 220, to frictionally advance the bill into <br/>the narrow<br/>arcuate passageway formed by the curved guideway 211 adjacent the rear side of <br/>the<br/>drive roll 223. The rotational movement of the drive roll 223 and the <br/>stripping<br/>wheels 220 is synchronized so that the serrated surfaces on the drive roll and <br/>the<br/>stripping wheels maintain a constant relationship to each other. Moreover, the <br/>drive<br/>roll 223 is dimensioned so that the circumference of the outermost portions of <br/>the<br/>grooved surfaces is greater than the width W of a bill, so that the bills <br/>advanced by<br/><br/> CA 02215886 1997-11-06<br/>92<br/>the drive roll 223 are spaced apart from each other, for the reasons discussed <br/>above.<br/>That is, each bill fed to the drive roll 223 is advanced by that roll only <br/>when the<br/>serrated surfaces 22$, 229 come into engagement with the bill, so that the<br/>circumference of the drive roll 223 determines the spacing between the leading <br/>edges<br/>of successive bills.<br/>To avoid the simultaneous removal of multiple bills from the stack in the <br/>input<br/>receptacle, particularly when small stacks of bills are loaded into the <br/>machine, the<br/>stripping wheels 220 are always stopped with the raised, serrated portions 222<br/>positioned below the bottom wall 205 of the input receptacle. This is <br/>accomplished<br/>by continuously monitoring the angular position of the serrated portions of <br/>the<br/>stripping wheels 220 via the encoder 32, and then controlling the stopping <br/>time of the<br/>drive motor so that the motor always stops the stripping wheels in a position <br/>where<br/>the serrated portions 222 are located beneath the bottom wall 205 of the input<br/>receptacle. Thus, each time a new stack of bills is loaded into the machine, <br/>those<br/>bills will rest on the smooth portions of the stripping wheels. This has been <br/>found to<br/>significantly reduce the simultaneous feeding of double or triple bills, <br/>particularly<br/>when small stacks of bills are involved.<br/> In order to ensure firm engagement between the drive roll 223 and the<br/>currency bill being fed, an idler roll 230 urges each incoming bill against <br/>the smooth<br/>central surface 225 of the drive roll 223. The idler roll 230 is journalled on <br/>a pair of<br/>atins 231 which are pivotally mounted on a support shaft 232. Also mounted on <br/>the<br/>shaft 232, on opposite sides of the idler roll 230, are a pair of grooved <br/>guide wheels<br/>233 and 234. The grooves in these two wheels 233, 234 are registered with the<br/>central ribs in the two grooved surfaces 226, 227 of the drive roll 223. The <br/>wheels<br/>233, 234 are locked to the shaft 232, which in turn is locked against movement <br/>in the<br/>direction of the bill movement (clockwise as view in FIG. 20a) by a one-way <br/>spring<br/>clutch 235. Each time a bill is fed into the nip between the guide wheels 233, <br/>234<br/>and the drive roll 223, the clutch 235 is energized to turn the shaft 232 just <br/>a few<br/>degrees in a direction opposite the direction of bill movement. These repeated<br/>incremental movements distribute the wear uniformly around the circumferences <br/>of<br/>the guide wheels 233, 234. Although the idler roll 230 and the guide wheels <br/>233,<br/>234 are mounted behind the guideway 211, the guideway is aperiured to allow <br/>the<br/><br/>CA 02215886 1997-11-06<br/>93<br/>roll 230 and the wheels 233, 234 to engage the bills on the front side of the<br/>guideway.<br/> Beneath the idler roll 230, a spring-loaded pressure roll 236 (FIGs. 20a and<br/>Zlb) presses the bills into firm engagement with the smooth friction surface <br/>225 of<br/>the drive roll as the bills curve downwardly along the guideway 211. This <br/>pressure<br/>roll 236 is journalled on a pair of arms 237 pivoted on a stationary shaft <br/>238. A<br/>spring 239 attached to the lower ends of the arms 237 urges the roll 236 <br/>against the<br/>drive roll 233, through an aperture in the curved guideway 211.<br/> At the lower end of the curved guideway 211, the bill being transported by<br/>the drive roll 223 engages a flat guide plate 240 which carries a lower scan <br/>head 18.<br/>Currency bills are positively driven along the flat plate 240 by means of a <br/>transport<br/>roll arrangement which includes the drive roll 223 at one end of the plate and <br/>a<br/>smaller driven roll 24i at the other end of the plate. Both the driver roll <br/>223 and the<br/>smaller roll 241 include pairs of smooth raised cylindrical surfaces 242 and <br/>243<br/>which hold the bill flat against the plate 240. A pair of O rings 244 and 245 <br/>fit into<br/>grooves formed in both the roll 241 and the roll 223 to engage the bill <br/>continuously<br/>between the two rolls 223 and 241 to transport the bill while helping to hold <br/>the bill<br/>flat against the guide plate 240.<br/> The flat guide plate 240 is provided with openings through which the raised<br/>surfaces 242 and 243 of both the drive roll 223 and the smaller driven roll <br/>241 are<br/>subjected to counter-rotating contact with corresponding pairs of passive <br/>transport<br/>rolls 250 and 251 having high-friction rubber surfaces. The passive rolls 250, <br/>251<br/>are mounted on the underside of the flat plate 240 in such a manner as to be<br/>freewheeling about their axes 254 and 255 and biased into counter-rotating <br/>contact<br/>with the corresponding upper rolls 223 and 241. The passive rolls 250 and 251 <br/>are<br/>biased into contact with the driven rolls 223 and 241 by means of a pair of H-<br/>shaped<br/>leaf springs 252 and 253 (see FIGs. 23 and 24). Each of the four rolls 250, <br/>251 is<br/>cradled between a pair of parallel arms of one of the H-shaped leaf springs <br/>252 and<br/>253. The central portion of each leaf spring is fastened to the plate 240, <br/>which is<br/>fastened rigidly to the machine frame, so that the relatively stiff arms of <br/>the H-<br/>shaped springs exert a constant biasing pressure against the rolls and push <br/>them<br/>against the upper rolls 223 and 241.<br/><br/> CA 02215886 1997-11-06<br/>94<br/> The points of contact between the driven and passive transport rolls are<br/>preferably coplanar with the flat upper surface of the plate 240 so that <br/>currency bills<br/>can be positively driven along the top surface of the plate in a flat manner. <br/>The<br/>distance between the axes of the two driven transport rolls, and the <br/>corresponding<br/>counter-rotating passive rolls, is selected to be just short of the length of <br/>the narrow<br/>dimension of the currency bills. Accordingly, the bills are firmly gripped <br/>under<br/>uniform pressure between the upper and lower transport rolls within the <br/>scanhead<br/>area, thereby minimizing the possibility of bill skew and enhancing the <br/>reliability of<br/>the overall scanning and recognition process.<br/> The positive guiding arrangement described above is advantageous in that<br/>uniform guiding pressure is maintained on the bills as they are transported <br/>through<br/>the optical scanhead area, and twisting or skewing of the bills is <br/>substantially<br/>reduced. This positive action is supplemented by the use of the H-springs 252, <br/>253<br/>for uniformly biasing the passive rollers into contact with the active rollers <br/>so that<br/>bill twisting or skew resulting from differential pressure applied to the <br/>bills along the<br/>transport path is avoided. The O-rings 244, 245 function as simple, yet <br/>extremely<br/>effective means for ensuring that the central portions of the bills are held <br/>flat. .<br/> The location of a magnetic head 256 and a magnetic head adjustment screw<br/>257 are illustrated in FIG. 23. The adjustment screw 257 adjusts the proximity <br/>of<br/>the magnetic head 256 relative to a passing bill and thereby adjusts the <br/>strength of the<br/>magnetic field in the vicinity of the bill.<br/> FIG. 22 shows the mechanical arrangement for driving the various means for<br/>transporting currency bills through the machine. A motor 260 drives a shaft <br/>261<br/>carrying a pair of pulleys 262 and 263. The pulley 262 drives the roll 241 <br/>through a<br/>belt 264 and pulley 265, and the pulley 263 drives the roll 223 through a belt <br/>266<br/>and pulley 267. Both pulleys 265 and 267 are larger than pulleys 262 and 263 <br/>in<br/>order to achieve the desired speed reduction from the typically high speed at <br/>which<br/>the motor 260 operates.<br/> The shaft 221 of the stripping wheels 220 is driven by means of a pulley 268<br/>provided thereon and linked to a corresponding pulley 269 on the shaft 224 <br/>through a<br/>belt 270. The pulleys 268 and 269 are of the same diameter so that the shafts <br/>221<br/>and 224 rotate in unison.<br/><br/> CA 02215886 1997-11-06<br/> As shown in FIG. 20b, the optical encoder 32 is mounted on the shaft of the<br/>roller 241 for precisely tracking the position of each bill as it is <br/>transported through<br/>the machine, as discussed in detail above in connection with the optical <br/>sensing and<br/>correlation technique.<br/>5 The upper and lower scanhead assemblies are shown most clearly in FIGS. 25-<br/>28. It can be seen that the housing for each scanhead is formed as an integral <br/>part of<br/>a unitary molded plastic support member 280 or 281 that also forms the <br/>housings for<br/>the light sources and photodetectors of the photosensors PS1 and PS2. The <br/>lower<br/>member 281 also forms the flat guide plate 240 that receives the bills from <br/>the drive<br/>10 roll 223 and supports the bills as they are driven past the scanheads 18a <br/>and 18b.<br/> The two support members 280 and 281 are mounted facing each other so that<br/>the lenses 282 and 283 of the two scanheads 18a, 18b define a narrow gap <br/>through<br/>which each bill is transported. Similar, but slightly larger, gaps are formed <br/>by the<br/>opposed lenses of the light sources and photodetectors of the photosensors PSl <br/>and<br/>15 PS2. The upper support member 280 includes a tapered entry guide 280a which<br/>guides an incoming bill into the gaps between the various pairs of opposed <br/>lenses.<br/> The lower support member 281 is attached rigidly to the,machine frame. The<br/>upper support member 280, however, is mounted for limited vertical movement <br/>when<br/>it is lifted manually by a handle 284, to facilitate the clearing of any paper <br/>jams that<br/>20 occur beneath the member 280. To allow for such vertical movement, the <br/>member<br/>280 is slidably mounted on a pair of posts 285 and 286 on the machine frame, <br/>with a<br/>pair of springs 287 and 288 biasing the member 280 to its lowermost position.<br/> Each of the two optical scanheads 18a and 18b housed in the support members<br/>280, 281 includes a pair of light sources acting in combination to uniformly<br/>25 illuminate light strips of the desired dimension on opposite sides of a <br/>bill as it is<br/>transported across the plate 240. Thus, the upper scanhead 18a includes a pair <br/>of<br/>LEDs 22a, directing light downwardly through an optical mask on top of the <br/>lens 282<br/>onto a bill traversing the flat guide plate 240 beneath the scanhead. The LEDs <br/>22a<br/>are angularly disposed relative to the vertical axis of the scanhead so that <br/>their<br/>30 respective light beams combine to illuminate the desired light strip <br/>defined by an<br/>aperture in the mask. The scanhead 18a also includes a photodetector 26a <br/>mounted<br/>directly over the center of the illuminated strip for sensing the light <br/>reflected off the<br/><br/> CA 02215886 1997-11-06<br/>96<br/>strip. The photodetector 26a is linked to the CPU 30 through the ADC 28 for<br/>processing the sensed data as described above.<br/> When the photodetector 26a is positioned on an axis passing through the<br/>center of the illuminated strip, the illumination by the LED's as a function <br/>of the<br/>distance from the central point "0" along the X axis, should optimally <br/>approximate a<br/>step function as illustrated by the curve A in FIG. 29. With the use of a <br/>single light<br/>source angularly displaced relative to a vertical axis through the center of <br/>the<br/>illuminated strip, the variation in illumination by an LED typically <br/>approximates a<br/> Gaussian function, as illustrated by the curve B in FIG. 29.<br/> The two LEDs 22a are angularly disposed relative to the vertical axis by<br/>angles « and ~3, respectively. The angles a and (3 are selected to be such <br/>that the<br/>resultant strip illumination by the LED's is as close as possible to the <br/>optimum<br/>distribution curve A in FIG. 29. The LED illumination distribution realized by <br/>this<br/>arrangement is illustrated by the curve designated as "C" in FIG. 29 which<br/>effectively merges the individual Gaussian distributions of each light source <br/>to yield a<br/>composite distribution which su~ciently approximates the optimum curve A.<br/> In the particular embodiment of the scanheads 18a and 18b illustrated in the<br/>drawings, each scanhead includes two pairs of LEDs and two photodetectors for<br/>illuminating, and detecting light reflected from, strips of two different <br/>sizes. Thus,<br/>each mask also includes two slits which are formed to allow light from the <br/>LEDs to<br/>pass through and illuminate light strips of the desired dimensions. More <br/>specifically,<br/>one slit illuminates a relatively wide strip used for obtaining the <br/>reflectance samples<br/>which correspond to the characteristic pattern for a test bill. In a preferred<br/>embodiment, the wide slit has a length of about 0.500" and a width of about <br/>0.050" .<br/>The second slit forms a relatively narrow illuminated strip used for detecting <br/>the thin<br/>borderline surrounding the printed indicia on currency bills, as described <br/>above in<br/>detail. In a preferred embodiment, the narrow slit 283 has a length of about <br/>0.300"<br/>and a width of about 0.010".<br/> In order to prevent dust from fouling the operation of the scanheads, each<br/>scanhead includes three resilient seals or gaskets 290, 291, and 292. The two <br/>side<br/>seals 290 and 291 seal the outer ends of the LEDs 22, while the center seal <br/>292 seals<br/>the outer end of the photodetector 26. Thus, dust cannot collect on either the <br/>light<br/><br/> CA 02215886 1997-11-06<br/>97<br/>sources or the photodetectors, and cannot accumulate and block the slits <br/>through<br/>which light is transmitted from the sources to the bill, and from the bill to <br/>the<br/>photodetectors.<br/>Doubling or overlapping of bills in the illustrative transport system is <br/>detected<br/>by two photosensors PS 1 and PS2 which are located on a common transverse axis<br/>that is perpendicular to the direction of bill flow (see e.g., FiGs. 30a and <br/>30b). The<br/>photosensors PS 1 and PS2 include photodetectors 293 and 294 mounted within <br/>the<br/>lower support member 281 in immediate opposition to corresponding light <br/>sources<br/>295 and 296 mounted in the upper support member 280. The photodetectors 293,<br/>294 detect beams of light directed downwardly onto the bill transport path <br/>from the<br/>Light sources 295, 296 and generate analog outputs which correspond to the <br/>sensed<br/>light passing through the bill. Each such output is convened into a digital <br/>signal by a<br/>conventional ADC convertor unit (not shown) whose output is fed as a digital <br/>input to<br/>and processed by the system CPU.<br/> The presence of a bill adjacent the photosensors PSl and PS2 causes a change<br/>in the intensity of the detected light, and the corresponding changes in the <br/>analog<br/>outputs of the photodetectors 293 and 294 serve as a convenient means for <br/>density-<br/>based measurements for detecting the presence of "doubles" (two or more <br/>overlaid or<br/>overlapped bills) during the currency scanning process. For instance, the<br/>photosensors may be used to collect a predefined number of density <br/>measurements on<br/>a test bill, and the average density value for a bill may be compared to <br/>predetermined<br/>density thresholds (based, for instance, on standardized density readings for <br/>master<br/>bills) to determine the presence of overlaid bills or doubles.<br/> In order to prevent the accumulation of dirt on the light sources 295 and 296<br/>and/or the photodetectors 293, 294 of the photosensors PS1 and PS2, both the <br/>light<br/>sources and the photodetectors are enclosed by lenses mounted so close to the <br/>bill<br/>path that they are continually wiped by the bills. This provides a self <br/>cleaning action<br/>which reduces maintenance problems and improves the reliability of the outputs <br/>from<br/>the photosensors over long periods of operation.<br/> The CPU 30, under control of software stored in the EPROM 34, monitors<br/>and controls the speed at which the bill transport mechanism 16 transports <br/>bills from<br/>the bill separating station 14 to the bill stacking unit. Flowcharts of the <br/>speed control<br/><br/> CA 02215886 1997-11-06<br/>98<br/>routines stored in the EPROM 34 are depicted in FIGS. 31-35. To execute more <br/>than<br/>the first step in any given routine, the currency discriminating system 10 <br/>must be<br/>operating in a mode requiring the execution of the routine.<br/> Referring first to FIG. 31, when a user places a stack of bills in the bill<br/>accepting station 12 for counting, the transport speed of the bill transport <br/>mechanism<br/>16 must accelerate or "ramp up" from zero to top speed. Therefore, in response <br/>to<br/>receiving the stack of bills in the bill accepting station 12, the CPU 30 sets <br/>a ramp-up<br/>bit in a motor flag stored in the memory unit 38. Setting the ramp-up bit <br/>causes the<br/>CPU 30 to proceed beyond step 300b of the ramp-up routine. If the ramp-up bit <br/>is<br/>set, the CPU 30 utilizes a ramp-up counter and a fixed parameter "ramp-up <br/>step" to<br/>incrementally increase the transport speed of the bill transport mechanism 16 <br/>until the<br/>bill transport mechanism 16 reaches its top speed. The "ramp-up step" is equal <br/>to<br/>the incremental increase in the transport speed of the bill transport <br/>mechanism i6,<br/>and the ramp-up counter determines the amount of time between incremental<br/>increases in the bill transport speed. The greater the value of the "ramp-up <br/>step", the<br/>greater the increase in the transport speed of the bill transport mechanism 16 <br/>at each<br/>increment. The greater the maximum value of the ramp-up counter, the greater <br/>the<br/>amount of time between increments. Thus, the greater the value of the "ramp-up<br/>step" and the lesser the maximum value of the ramp-up counter, the lesser the <br/>time it<br/>takes the bill transport mechanism 16 to reach its top speed.<br/> The ramp-up routine in FIG. 31 employs a variable parameter "new speed", a<br/>fixed parameter "full speed", and the variable parameter "transport speed". <br/>The "full<br/>speed" represents the top speed of the bill transport mechanism 16, while the <br/>"new<br/>speed" and "transport speed" represent the desired current speed of the bill <br/>transport<br/>mechanism 16. To account for operating offsets of the bill transport mechanism <br/>16,<br/>the "transport speed" of the bill transport mechanism 16 actually differs from <br/>the<br/>"new speed" by a "speed offset value" . Outputting the "transport speed" to <br/>the bill<br/>transport mechanism 16 causes the bill transport mechanism 16 to operate at <br/>the<br/>transport speed.<br/> To incrementally increase the speed of the bill transport mechanism 16, the<br/>CPU 30 first decrements the ramp-up counter from its maximum value (step 301). <br/>If<br/>the maximum value of the ramp-up counter is greater than one at step 302, the <br/>CPU<br/><br/> CA 02215886 1997-11-06 _<br/>99<br/>30 exits the speed control software in FIGs. 31-35 and repeats steps 300b, <br/>301, and<br/>302 during subsequent iterations of the ramp-up routine until the ramp-up <br/>counter is<br/>equal to zero. When the ramp-up counter is equal to zero, the CPU 30 resets <br/>the<br/>ramp-up counter to its maximum value (step 303). Next, the CPU 30 increases <br/>the<br/>"new speed" by the "ramp-up step" (step 304). If the "new speed" is not yet <br/>equal to<br/>the "full speed" at step 305, the "transport speed" is set equal to the "new <br/>speed"<br/>plus the "speed offset value" (step 306). The "transport speed" is output to <br/>the bill<br/>transport mechanism 16 at step 307 of the routine in FIG. 31 to change the <br/>speed of<br/>the bill transport mechanism 16 to the "transport speed". During subsequent<br/>iterations of the ramp-up routine, the CPU 30 repeats steps 300b-306 until the <br/>"new<br/>speed" is greater than or equal to the "full speed".<br/>Once the "new speed" is greater than or equal to the "full speed" at step 305,<br/>the ramp-up bit in the motor flag is cleared (step 308), a pause-after-ramp <br/>bit in the<br/>motor flag is set (step 309), a pause-after-ramp counter is set to its maximum <br/>value<br/>(step 310), and the parameter "new speed" is set equal to the "full speed" <br/>(step 311).<br/>Finally, the "transport speed" is set equal to the "new speed" plus the "speed <br/>offset<br/>value" (step 306). Since the "new speed" is equal to the "full speed", <br/>outputting the<br/>"transport speed" to the bill transport mechanism 16 causes the bill transport<br/>mechanism 16 to operate at its top speed. The ramp-up routine in FIG. 31 <br/>smoothly<br/>increases the speed of the bill transport mechanism without causing jerking or <br/>motor<br/>spikes. Motor spikes could cause false triggering of the optical scanhead 18 <br/>such that<br/>the scanhead 18 scans non-existent bills.<br/> During normal counting, the bill transport mechanism 16 transports bills from<br/>the bill separating station 14 to the bill stacking unit at its top speed. In <br/>response to<br/>the optical scanhead 18 detecting a stranger, suspect or no call bill, <br/>however, the<br/>CPU 30 sets a ramp-to-slow-speed bit in the motor flag. Setting the ramp-to-<br/>slow-<br/>speed bit causes the CPU 30 to proceed beyond step 312 of the ramp-to-slow-<br/>speed<br/>routine in FIG. 32 on the next iteration of the software in FIGs. 31-35. Using <br/>the<br/>ramp-to-slow-speed routine in FIG. 32, the CPU 30 causes the bill transport<br/>mechanism 16 to controllably decelerate or "ramp down" from its top speed to a <br/>slow<br/>speed. As the ramp-to-slow speed routine in FIG. 32 is similar to the ramp-up<br/>routine in FIG. 31, it is not described in detail herein.<br/><br/> CA 02215886 1997-11-06<br/>100<br/>It suffices to state that if the ramp-to-slow-speed bit is set in the motor <br/>flag,<br/>the CPU 30 decrements a ramp-down counter (step 313) and determines whether or<br/>not the ramp-down counter is equal to zero (step 314). If the ramp-down <br/>counter is<br/>not equal to zero, the CPU 30 exits the speed control software in FIGs. 31-35 <br/>and<br/>repeats steps 312, 313, and 314 of the ramp-to-slow-speed routine in FIG. 32 <br/>during<br/>subsequent iterations of the speed control software until the ramp-down <br/>counter is<br/>equal to zero. Once the ramp-down counter is equal to zero, the CPU 30 resets <br/>the<br/>ramp-down counter to its maximum value (step 315) and subtracts a "ramp-down<br/>step" from the variable parameter "new speed" (step 316). The "new speed" is <br/>equal<br/>to the fixed parameter "full speed" prior to initiating the ramp-to-slow-speed <br/>routine<br/>in FIG. 32.<br/> After subtracting the "ramp-down step" from the "new speed", the "new<br/>speed" is compared to a fixed parameter "slow speed" (step 317). If the "new <br/>speed"<br/>is greater than the "slow speed", the "transport speed" is set equal to the <br/>"new<br/>speed" plus the "speed offset value" (step 318) and this "transport speed" is <br/>output to<br/>the bill transport mechanism lb (step 307 of FIG. 31). During subsequent <br/>iterations<br/>of the ramp-to-slow-speed routine, the CPU 30 continues to decrement the "new<br/>speed" by the "ramp-down step" until the "new speed" is less than or equal to <br/>the<br/>"slow speed". Once the "new speed" is less than or equal to the "slow speed" <br/>at step<br/>317, the CPU 30 clears the ramp-to-slow-speed bit in the motor flag (step <br/>319), sets<br/>the pause-after-ramp bit in the motor flag (step 320), sets the pause-after-<br/>ramp<br/>counter (step 321), and sets the "new speed" equal to the "slow speed" (step <br/>322).<br/>Finally, the "transport speed" is set equal to the "new speed" plus the "speed <br/>offset<br/>value" (step 318). Since the "new speed" is equal to the "slow speed", <br/>outputting the<br/>"transport speed" to the bill transport mechanism 16 causes the bill transport<br/>mechanism 16 to operate at its slow speed. The ramp-to-slow-speed routine in <br/>FIG.<br/>32 smoothly decreases the speed of the bill transport mechanism 16 without <br/>causing<br/>jerking or motor spikes.<br/> FIG. 33 depicts a ramp-to-zero-speed routine in which the CPU 30 ramps<br/>down the transport speed of the bill transport mechanism 16 to zero either <br/>from its<br/>top speed or its slow speed. In response to completion of counting of a stack <br/>of<br/>bills, the CPU 30 enters this routine to ramp down the transport speed of the <br/>bill<br/><br/> CA 02215886 1997-11-06<br/>101<br/>transport mechanism 16 from its top speed to zero. Similarly, in response to <br/>the<br/>optical scanhead 18 detecting a stranger, suspect, or no call bill and the <br/>ramp-to-<br/>slow-speed routine in FIG. 32 causing the transport speed to be equal to a <br/>slow<br/>speed, the CPU 30 enters the ramp-to-zero-speed routine to ramp down the <br/>transport<br/>speed from the slow speed to zero.<br/> With the ramp-to-zero-speed bit set at step 323, the CPU 30 determines<br/>whether or not an initial-braking bit is set in the motor flag (step 324). <br/>Prior to<br/>ramping down the transport speed of the bill transport mechanism 16, the <br/>initial-<br/>braking bit is clear. Therefore, flow proceeds to the left branch of the ramp-<br/>to-zero-<br/>speed routine in FIG. 33. In this left branch, the CPU 30 sets the initial-<br/>braking bit<br/>in the motor flag (step 325), resets the ramp-down counter to its maximum <br/>value<br/>(step 326), and subtracts an "initial-braking step" from the variable <br/>parameter "new<br/>speed" (step 327). Next, the CPU 30 determines whether or not the "new speed" <br/>is<br/>greater than zero (step 328). If the "new speed" is greater than zero at step <br/>328, the<br/>variable parameter "transport speed" is set equal to the "new speed" plus the <br/>"speed<br/>offset value" (step 329) and this "transport speed" is output to the bill <br/>transport<br/>mechanism 16 at step 307 in FIG. 31.<br/> During the next iteration of the ramp-to-zero-speed routine in FIG. 33, the<br/>CPU 30 enters the right branch of the routine at step 324 because the initial-<br/>braking<br/>bit was set during the previous iteration of the ramp-to-zero-speed routine. <br/>With the<br/>initial-braking bit set, the CPU 30 decrements the ramp-down counter from its<br/>maximum value (step 330) and determines whether or not the ramp-down counter <br/>is<br/>equal to zero (step 331). If the ramp-down counter is not equal to zero, the <br/>CPU 30<br/>immediately exits the speed control software in FIGs. 31-35 and repeats steps <br/>323,<br/>324, 330, and 331 of the ramp-to-slow-speed routine during subsequent <br/>iterations of<br/>the speed control software until the ramp-down counter is equal to zero. Once <br/>the<br/>ramp-down counter is equal to zero, the CPU 30 resets the ramp-down counter to <br/>its<br/>maximum value (step 332) and subtracts a "ramp-down step" from the variable<br/>parameter "new speed" (step 333). This "ramp-down step" is smaller than the<br/>"initial-braking step" so that the "initial-braking step" causes a larger <br/>decremental<br/>change in the transport speed of the bill transport mechanism 16 than that <br/>caused by<br/>the "ramp-down step" .<br/><br/> CA 02215886 1997-11-06<br/>102<br/> Next, the CPU 30 determines whether or not the "new speed" is greater than<br/>zero (step 328). If the "new speed" is greater than zero, the "transport <br/>speed" is set<br/>equal to the "new speed" plus the "speed offset value" (step 329) and this <br/>"transport<br/>speed" is outputted to the bill transport mechanism 16 (step 307 in FIG. 31). <br/>During<br/>subsequent iterations of the speed control software, the CPU 30 continues to<br/>decrement the "new speed" by the "ramp-down step" at step 333 until the "new<br/>speed" is less than or equal to zero at step 328. Once the "new speed" is less <br/>than or<br/>equal to the zero at step 328, the CPU 30 clears the ramp-to-zero-speed bit <br/>and the<br/>initial-braking bit in the motor flag (step 334), sets a motor-at-rest bit in <br/>the motor<br/>flag (step 335), and sets the "new speed" equal to zero (step 336). Finally, <br/>the<br/>"transport speed" is set equal to the "new speed" plus the "speed offset <br/>value" (step<br/>329). Since the "new speed" is equal to zero, outputting the "transport speed" <br/>to the<br/>bill transport mechanism 16 at step 307 in FIG. 31 halts the bill transport <br/>mechanism<br/>16.<br/> Using the feedback loop routine in FIG. 35, the CPU 30 monitors and<br/>stabilizes the transport speed of the bill transport mechanism 16 when the <br/>bill<br/>transport mechanism 16 is operating at its top speed or at slow speed. To <br/>measure<br/>the transport speed of the bill transport mechanism 16, the CPU 30 monitors <br/>the<br/>optical encoder 32. While monitoring the optical encoder 32, it is important <br/>to<br/>synchronize the feedback loop routine with any transport speed changes of the <br/>bill<br/>transport mechanism 16. To account for the time lag between execution of the <br/>ramp-<br/>up or ramp-to-slow-speed routines in FIGs. 31-32 and the actual change in the<br/>transport speed of the bill transport mechanism 16, the CPU 30 enters a pause-<br/>after-<br/>ramp routine in FIG. 34 prior to entering the feedback loop routine in FIG. 35 <br/>if the<br/>bill transport mechanism 16 completed ramping up to its top speed or ramping <br/>down<br/>to slow speed during the previous iteration of the speed control software in <br/>FIGs. 31-<br/>35.<br/> The pause-after-ramp routine in FIG. 34 allows the bill transport mechanism<br/>16 to "catch up" to the CPU 30 so that the CPU 30 does not enter the feedback <br/>loop<br/>routine in FIG. 35 prior to the bill transport mechanism 16 changing speeds. <br/>As<br/>stated previously, the CPU 30 sets a pause-after-ramp bit during step 309 of <br/>the<br/>ramp-up routine in FIG. 3I or step 320 of the ramp-to-slow-speed routine in <br/>FIG.<br/><br/> CA 02215886 1997-11-06<br/>103<br/>32. With the pause-after-ramp bit set, flow proceeds from step 337 of the <br/>pause-<br/>after-ramp routine to step 338, where the CPU 30 decrements a pause-after-ramp<br/>counter from its maximum value. If the pause-after-ramp counter is not equal <br/>to zero<br/>at step 339, the CPU 30 exits the pause-after-ramp routine in FIG. 34 and <br/>repeats<br/>steps 337, 338, and 339 of the pause-after-ramp routine during subsequent <br/>iterations<br/>of the speed control software until the pause-after-ramp counter is equal to <br/>zero.<br/>Once the pause-after-ramp counter decrements to zero, the CPU 30 clears the <br/>pause-<br/>after-ramp bit in the motor flag (step 340) and sets the feedback loop counter <br/>to its<br/>maximum value (step 341). The maximum value of the pause-after-ramp counter is<br/>selected to delay the CPU 30 by an amount of time sufficient to permit the <br/>bill<br/>transport mechanism 16 to adjust to a new transport speed prior to the CPU 30<br/>monitoring the new transport speed with the feedback loop routine in FIG. 35.<br/>Referring now to the feedback loop routine in FIG. 35, if the motor-at-rest <br/>bit<br/>in the motor flag is not set at step 342, the CPU 30 decrements a feedback <br/>loop<br/>counter from its maximum value (step 343). If the feedback loop counter is not <br/>equal<br/>to zero at step 344, the CPU 3fl immediately exits the feedback loop routine <br/>in FIG.<br/>35 and repeats steps 342, 343, and 344 of the feedback loop routine during<br/>subsequent iterations of the speed control software in FIGs. 31-36 until the <br/>feedback<br/>loop counter is equal to zero. Once the feedback loop counter is decremented <br/>to<br/>zero, the CPU 30 resets the feedback loop counter to its maximum value (step <br/>345),<br/>stores the present count of the optical encoder 32 (step 346), and calculates <br/>a variable<br/>parameter "actual difference" between the present count and a previous count <br/>of the<br/>optical encoder 32 (step 347). The "actual difference" between the present and<br/>previous encoder counts represents the transport speed of the bill transport<br/>mechanism 16. The larger the "actual difference" between the present and <br/>previous<br/>encoder counts, the greater the transport speed of the bill transport <br/>mechanism. The<br/> CPU 30 subtracts the "actual difference" from a fixed parameter "requested<br/>difference" to obtain a variable parameter "speed difference" (step 348).<br/>If the "speed difference" is greater than zero at step 349, the bill transport<br/>speed of the bill transport mechanism 16 is too slow. To counteract slower <br/>than ideal<br/>bill transport speeds, the CPU 30 multiplies the "speed difference" by a "gain<br/>constant" (step 354) and sets the variable parameter "transport speed" equal <br/>to the<br/><br/> CA 02215886 1997-11-06<br/>104<br/>multiplied difference from step 354 plus the "speed offset value" plus a fixed<br/>parameter "target speed" (step 355). The "target speed" is a value that, when <br/>added<br/>to the "speed offset value", produces the ideal transport speed. The <br/>calculated<br/>"transport speed" is greater than this ideal transport speed by the amount of <br/>the<br/>multiplied difference. If the calculated "transport speed" is nonetheless less <br/>than or<br/>equal to a fixed parameter "maximum allowable speed" at step 356, the <br/>calculated<br/>"transport speed" is output to the bill transport mechanism 16 at step 307 so <br/>that the<br/>bill transport mechanism 16 operates at the calculated "transport speed". If,<br/>however, the calculated "transport speed" is greater than the "maximum <br/>allowable<br/>IO speed" at step 356, the parameter "transport speed" is set equal to the <br/>"maximum<br/>allowable speed" (step 357) and is output to the bill transport mechanism 16 <br/>(step<br/>307).<br/> If the "speed difference" is less than or equal to zero at step 349, the bill<br/>transport speed of the bill transport mechanism 16 is too fast or is ideal. To<br/>counteract faster than ideal bill transport speeds, the CPU 30 multiplies the <br/>"speed<br/>difference" by a "gain constant" (step 350) and sets the variable parameter <br/>"transport<br/>speed" equal to the multiplied difference from step 350 plus the "speed offset <br/>value"<br/>plus a fixed parameter "target speed" (step 351). The calculated "transport <br/>speed" is<br/>less than this ideal transport speed by the amount of the multiplied <br/>difference. If the<br/>calculated "transport speed" is nonetheless greater than or equal to a fixed <br/>parameter<br/>"minimum allowable speed" at step 352, the calculated "transport speed" is <br/>output to<br/>the bill transport mechanism 16 at step 307 so that the bill transport <br/>mechanism 16<br/>operates at the calculated "transport speed" . If, however, the calculated <br/>"transport<br/>speed" is less than the "minimum allowable speed" at step 352, the parameter<br/>"transport speed" is set equal to the "minimum allowable speed" (step 353) and <br/>is<br/>output to the bill transport mechanism 16 (step 307).<br/> It should be apparent that the smaller the value of the "gain constant", the<br/>smaller the variations of the bill transport speed between successive <br/>iterations of the<br/>feedback control routine in FIG. 35 and, accordingly, the less quickly the <br/>bill<br/>transport speed is adjusted toward the ideal transport speed. Despite these <br/>slower<br/>adjustments in the bill transport speed, it is generally preferred to use a <br/>relatively<br/><br/> CA 02215886 1997-11-06<br/>105<br/>small "gain constant" to prevent abrupt fluctuations in the bill transport <br/>speed and to<br/>prevent overshooting the ideal bill transport speed.<br/>A routine for using the outputs of the two photosensors PS 1 and PS2 to detect<br/>any doubling or overlapping of bills is illustrated in FIG. 36 by sensing the <br/>optical<br/>density of each bill as it is scanned. This routine starts at step 40i and <br/>retrieves the<br/>denomination determined for the previously scanned bill at step 402. This <br/>previously<br/>determined denomination is used for detecting doubles in the event that the <br/>newly<br/>scanned bill is a "no call", as described below. Step 403 determines whether <br/>the<br/>current bill is a "no call," and if the answer is negative, the denomination <br/>determined<br/>for the new bill is retrieved at step 404.<br/>If the answer at step 403 is affirmative, the system jumps to step 405, so <br/>that<br/>the previous denomination retrieved at step 402 is used in subsequent steps. <br/>To<br/>permit variations in the sensitivity of the density measurement, a "density <br/>setting" is<br/>retrieved from memory at step 405. The operator makes this choice manually,<br/>according to whether the bills being scanned are new bills, requiring a high <br/>degree of<br/>sensitivity, or used bills, requiring a lower level of sensitivity. If the <br/>"density<br/>setting" has been turned off, this condition is sensed at step 406, and the <br/>system .<br/>returns to the main program at step 413. If the "density setting" is not <br/>turned off, a<br/>denominational density comparison value is retrieved from memory at step 407.<br/> The memory preferably contains five different density values (for five<br/>different density settings, i.e., degrees of sensitivity) for each <br/>denomination. Thus,<br/>for a currency set containing seven different denominations, the memory <br/>contains 35<br/>different values. The denomination retrieved at step 404 (or step 402 in the <br/>event of<br/>a "no call"), and the density setting retrieved st step 405, determine which <br/>of the 35<br/>stored values is retrieved at step 407 for use in the comparison steps <br/>described below.<br/>At step 408, the density comparison value retrieved at step 407 is compared to<br/>the average density represented by the output of the photosensor PS 1. The <br/>result of<br/>this comparison is evaluated at step 409 to determine whether the output of <br/>sensor S 1<br/>identifies a doubling of bills for the particular denomination of bill <br/>determined at step<br/>402 or 404. If the answer is negative, the system returns to the main program <br/>at step<br/>413. If the answer is affirmative, step 410 then compares the retrieved <br/>density<br/>comparison value to the average density represented by the output of the <br/>second<br/><br/> CA 02215886 1997-11-06<br/>106<br/>sensor PS2. The result of this comparison is evaluated at step 411 to <br/>determine<br/>whether the output of the photosensor PS2 identifies a doubling of bills. <br/>Affirmative<br/>answers at both step 409 and step 411 result in the setting of a "doubles <br/>error" flag at<br/>step 412, and the system then returns to the main program at step 413. The<br/>"doubles error" flag can, of course, be used to stop the bill transport motor.<br/>FIG. 37 illustrates a routine that enables the system to detect bills which <br/>have<br/>been badly defaced by dark marks such as ink blotches, felt-tip pen marks and <br/>the<br/>like. Such severe defacing of a bill can result in such distorted scan data <br/>that the<br/>data can be interpreted to indicate the wrong denomination for the bill.<br/>Consequently, it is desirable to detect such severely defaced bills and then <br/>stop the<br/>bill transport mechanism so that the bill in question can be examined by the <br/>operator.<br/> The routine of FIG. 37 retrieves each successive data sample at step 450b and<br/>then advances to step 451 to determine whether that sample is too dark. As<br/>described above, the output voltage from the photodetector 26 decreases as the<br/>darkness of the scanned area increases. Thus, the lower the output voltage <br/>from the<br/>photodetector, the darker the scanned area. For the evaluation carried out at <br/>step<br/>451, a preselected threshold level for the photodetector output voltage, such <br/>as a<br/>threshold level of about 1 volt, is used to designate a sample that is "too <br/>dark. "<br/> An affirmative answer at step 451 advances the system to step 452 where a<br/>"bad sample" count is incremented by one. A single sample that is too dark is <br/>not<br/>enough to designate the bill as seriously defaced. Thus, the "bad sample" <br/>count is<br/>used to determine when a preselected number of consecutive samples, e.g., ten<br/>consecutive samples, are determined to be too dark. .From step 452, the system<br/>advances to step 453 to determine whether ten consecutive bad samples have <br/>been<br/>received. If the answer is affirmative, the system advances to step 454 where <br/>an<br/>error flag is set. This represents a "no call" condition, which causes the <br/>bill<br/>transport system to be stopped in the same manner discussed above.<br/> When a negative response is obtained at step 451, the system advances to step<br/>455 where the "bad sample" count is reset to zero, so that this count always<br/>represents the number of consecutive bad samples received. From step 455 the<br/>system advances to step 456 which deternines when all the samples for a given <br/>bill<br/>have been checked. As long as step 456 yields a negative answer, the system<br/><br/> CA 02215886 1997-11-06<br/>107<br/>continues to retrieve successive samples at step 450b. When an affirmative <br/>answer is<br/>produced at step 456, the system returns to the main program at step 457.<br/> A routine for automatically monitoring and making any necessary corrections<br/>in various line voltages is illustrated in FIG. 38. This routine is useful in<br/>automatically compensating for voltage drifts due to temperature changes, <br/>aging of<br/>components and the like. The routine starts at step 550 and reads the output <br/>of a line<br/>sensor which is monitoring a selected voltage at step SSOb. Step 551 <br/>determines<br/>whether the reading is below 0.60, and if the answer is affirmative, step 552<br/>determines whether the reading is above 0.40. If step 552 also produces an<br/>affirmative response, the voltage is within the required range and thus the <br/>system<br/>returns to the main program step 553. If step 551 produces a negative <br/>response, an<br/>incremental correction is made at step 554 to reduce the voltage in an attempt <br/>to<br/>return it to the desired range. Similarly, if a negative response is obtained <br/>at step<br/>552, an incremental correction is made at step 555 to increase the voltage <br/>toward the<br/>desired range.<br/> Now that a currency scanner has been described in connection with scanning<br/>U.S. currency, an additional currency discrimination system of the present <br/>invention<br/>will be described.<br/>First of all, because currencies come in a variety of sizes, sensors are added<br/>to determine the size of a bill to be scanned. These sensors are placed <br/>upstream of<br/>the scanheads to be described below. A preferred embodiment of size <br/>determining<br/>sensors is illustrated in FIG. 39. Two leading/trailing edge sensors 1062 <br/>detect the<br/>leading and trailing edges of a bill 1064 as it passing along the transport <br/>path. These<br/>sensors in conjunction with the encoder 32 (FIG. 2a-2b) may be used to <br/>determine<br/>the dimension of the bill along a direction parallel to the scan direction <br/>which in FIG.<br/>39 is the narrow dimension (or width) of the bill 1064. Additionally, two side <br/>edge<br/>sensors 1066 are used to detect the dimension of a bill 1064 transverse to the <br/>scan<br/>direction which in FIG. 39 is the wide dimension (or length) of the bill 1064. <br/>While<br/>the sensors 1062 and 1066 of FIG. 39 are optical sensors, other means of<br/>determining the size of a bill may be employed.<br/>Once the size of a bill is determined, the potential identity of the bill is <br/>limited<br/>to those bills having the same size. Accordingly, the area to be scanned can <br/>be<br/><br/> CA 02215886 1997-11-06<br/>108<br/>tailored to the area or areas best suited for identifying the denomination and <br/>country<br/>of origin of a bill having the measured dimensions.<br/>Secondly, while the printed indicia on U.S. currency is enclosed within a thin<br/>borderline, the sensing of which may serve as a trigger to begin scanning <br/>using a<br/>wider slit, most currencies of other currency systems such as those from other<br/>countries do not have such a borderline. Thus the system described above may <br/>be<br/>modified to begin scanning relative to the edge of a bill for currencies <br/>lacking such a<br/>borderline. Referring to FIG. 40, two leading edge detectors 1068 are shown. <br/>The<br/>detection of the leading edge 1069 of a bill 1070 by leading edge sensors 1068<br/>triggers scanning in an area a given distance away from the leading edge of <br/>the bill<br/>1070, e.g., D1 or DZ, which may vary depending upon the preliminary indication <br/>of<br/>the identity of a bill based on the dimensions of a bill. Alternatively, the <br/>leading<br/>edge 1069 of a bill may be detected by one or more of the scanheads (to be <br/>described<br/>below) in a similar manner as that described with respect to FIGS. 7a and 7b.<br/>Alternatively, the beginning of scanning may be triggered by positional <br/>information<br/>provided by the encoder 32 of FIG. 2a-2b, for example, in conjunction with the<br/>signals provided by sensors 1062 of FIG. 39, thus eliminating the need for <br/>leading<br/>edge sensors 1068.<br/> However, when the initiation of scanning is triggered by the detection of the<br/>leading edge of a bill, the chance that a scanned pattern will be offset <br/>relative to a<br/>corresponding master pattern increases. Offsets can result from the existence <br/>of<br/>manufacturing tolerances which permit the location of printed indicia of a <br/>document<br/>to vary relative to the edges of the document. For example, the printed <br/>indicia on<br/>U.S. bills may vary relative to the leading edge of a bill by as much as 50 <br/>mils<br/>which is 0.05 inches (1.27 mm). Thus when scanning is triggered relative to <br/>the<br/>edge of a bill (rather than the detection of a certain part of the printed <br/>indicia itself,<br/>such as the printed borderline of U.S. bills), a scanned pattern can be offset <br/>from a<br/>corresponding master pattern by one or more samples. Such offsets can lead to<br/>erroneous rejections of genuine bills due to poor correlation between scanned <br/>and<br/>master patterns. To compensate, overall scanned patterns and master patterns <br/>can be<br/>shifted relative to each other as illustrated in FIGS. 41a and 41b. More <br/>particularly,<br/>FIG. 41a illustrates a scanned pattern which is offset from a corresponding <br/>master<br/><br/> CA 02215886 1997-11-06<br/>i09<br/>pattern. FIG. 41b illustrates the same patterns after the scanned pattern is <br/>shifted<br/>relative to the master pattern, thereby increasing the correlation between the <br/>two<br/>patterns. Alternatively, instead of shifting either scanned patterns or master <br/>patterns,<br/>master patterns may be stored in memory corresponding to different offset <br/>amounts.<br/>Thirdly, while it has been determined that the scanning of the central area on<br/>the green side of a U.S. bill (see segment S of FIG. 4) provides sufficiently <br/>distinct<br/>patterns to enable discrimination among the plurality of U.S. denominations, <br/>the<br/>central area may not be suitable for bills originating in other countries. For <br/>example,<br/>for bills originating from Country 1, it may be determined that segment Sl <br/>(FIG. 40)<br/>provides a more preferable area to be scanned, while segment Sz (FIG. 40) is <br/>more<br/>preferable for bills originating from Country 2. Alternatively, in order to <br/>sufficiently<br/>discriminate among a given set of bills, it may be necessary to scan bills <br/>which are<br/>potentially from such set along more than one segment, e.g., scanning a single <br/>bill<br/>along both St and S2. To accommodate scanning in areas other than the central<br/>portion of a bill, multiple scanheads may be positioned next to each other. A<br/>preferred embodiment of such a multiple scanhead system is depicted in FIG. <br/>42.<br/>Multiple scanheads 1072a-c and 1072d-f are positioned next to each other along <br/>a<br/>direction lateral to the direction of bill movement. Such a system permits a <br/>bill 1074<br/>to be scanned along different segments. Multiple scanheads 1072a-f are <br/>arranged on<br/>each side of the transport path, thus permitting both sides of a bill 1074 to <br/>be<br/>scanned.<br/>Two-sided scanning may be used to permit bills to be fed into a currency<br/>discrimination system according to the present invention with either side face <br/>up. An<br/>example of a two-sided scanhead arrangement is described above in connection <br/>with<br/>FIGS. 2a, 6c, and 6d. Master patterns generated by scanning genuine bills may <br/>be<br/>stored for segments on one or both sides. In the case where master patterns <br/>are<br/>stored from the scanning of only one side of a genuine bill, the patterns <br/>retrieved by<br/>scanning both sides of a bill under test may be compared to a master set of <br/>single-<br/>sided master patterns. In such a case, a pattern retrieved from one side of a <br/>bill<br/>under test should match one of the stored master patterns, while a pattern <br/>retrieved<br/>from the other side of the bill under test should not match one of the master <br/>patterns.<br/>Alternatively, master patterns may be stored for both sides of genuine bills. <br/>In such<br/><br/> CA 02215886 1997-11-06<br/>110<br/>a two-sided system, a pattern retrieved by scanning one side of a bill under <br/>test<br/>should match with one of the master patterns of one side (Match 1) and a <br/>pattern<br/>retrieved from scanning the opposite side of a bill under test should match <br/>the master<br/>pattern associated with the opposite side of a genuine bill identified by <br/>Match 1.<br/>Alternatively, in situations where the face orientation of a bill (i.e., <br/>whether a<br/>bill is "face up" or "face down") may be determined prior to or during <br/>characteristic<br/>pattern scanning, the number of comparisons may be reduced by limiting <br/>comparisons<br/>to patterns corresponding to the same side of a bill. That is, for example, <br/>when it is<br/>known that a bill is "face up", scanned patterns associated with scanheads <br/>above the<br/>transport path need only be compared to master patterns generated by scanning <br/>the<br/>"face" of genuine bills. By "face" of a bill it is meant a side which is <br/>designated as<br/>the front surface of the bill. For example, the front or "face" of a U.S. bill <br/>may be<br/>designated as the "black" surface while the back of a U.S. bill may be <br/>designated as<br/>the "green" surface. The face orientation may be determinable in some <br/>situations by<br/>sensing the color of the surfaces of a bill. An alternative method of <br/>determining the<br/>face orientation of U.S. bills by detecting the borderline on each side of a <br/>bill is<br/>described above in connection with FIGs. 6c, 6d, and 12. The implementation of<br/>color sensing is discussed in more detailed below.<br/> According to the embodiment of FIG. 42, the bill transport mechanism<br/>operates in such a fashion that the central area C of a bill 1074 is <br/>transported<br/>between central scanheads 1072b and 1072e. Scanheads 1072a and 1072c and<br/>likewise scanheads 1072d and 1072f are displaced the same distance from <br/>central<br/>scanheads 1072b and 1072e, respectively. By symmetrically arranging the <br/>scanheads<br/>about the central region of a bill, a bill may be scanned in either direction, <br/>e.g., top<br/>edge first (forward direction) or bottom edge first (reverse direction). As <br/>described<br/>above with respect to FIGs. 1-7b, master patterns are stored from the scanning <br/>of<br/>genuine bills in both the forward and reverse directions. While a symmetrical<br/>arrangement is preferred, it is not essential provided appropriate master <br/>patterns are<br/>stored for a non-symmetrical system.<br/> While FIG. 42 illustrates a system having three scanheads per side, any<br/>number of scanheads per side may be utilized. Likewise, it is not necessary <br/>that<br/>there be a scanhead positioned over the central region of a bill. For example, <br/>FIG.<br/><br/> CA 02215886 1997-11-06<br/>ill<br/>43 illustrates another preferred embodiment of the present invention capable <br/>of<br/>scanning the segments S, and SZ of FIG. 40. Scanheads 1076a, 1076d, 1076e, and<br/>1076h scan a bill 1078 along segment S, while scanheads 1076b, 1076c, 1076f, <br/>and<br/>10768 scan segment S~.<br/> FiG. 44 depicts another preferred embodiment of a scanning system according<br/>to the present invention having laterally moveable scanheads 1080a-b. Similar<br/>scanheads may be positioned on the opposite side of the transport path. <br/>Moveable<br/>scanheads 1080a-b may provide more flexibility that may be desirable in <br/>certain<br/>scanning situations. Upon the determination of the dimensions of a bill as <br/>described<br/>in connection with FIG. 39, a preliminary determination of the identity of a <br/>bill may<br/>be made. Based on this preliminary determination, the moveable scanheads 1080a-<br/>b<br/>may be positioned over the area of the bill which is most appropriate for <br/>retrieving<br/>discrimination information. For example, if based on the size of a scanned <br/>bill, it is<br/>preliminarily determined that the bill is a Japanese 5000 Yen bill-type, and <br/>if it has<br/>been determined that a suitable characteristic pattern for a 5000 Yen bill-<br/>type is<br/>obtained by scanning a segment 2.0 cm to the left of center of the bill fed in <br/>the<br/>forward direction, scanheads 1080a and 1080b may be appropriately positioned <br/>for<br/>scanning such a segment, e.g., scanhead 1080a positioned 2.0 cm left of center <br/>and<br/>scanhead 1080b positioned 2.0 cm right of center. Such positioning permits <br/>proper<br/>discrimination regardless of the whether the scanned bill is being fed in the <br/>forward<br/>or reverse direction. Likewise scanheads on the opposite side of the transport <br/>path<br/>(not shown) could be appropriately positioned. Alternatively, a single <br/>moveable<br/>scanhead may be used on one or both sides of the transport path. In such a <br/>system,<br/>size and color information (to be described in more detail below)'may be used <br/>to<br/>properly position a single laterally moveable scanhead, especially where the<br/>orientation of a bill may be determined before scanning.<br/> FIG. 44 depicts a system in which the transport mechanism is designed to<br/>deliver a bill 1082 to be scanned centered within the area in which scanheads <br/>i080a-b<br/>are located. Accordingly, scanheads 1080a-b are designed to move relative to <br/>the<br/>center of the transport path with scanhead 1080a being moveable within the <br/>range R,<br/>and scanhead 1080b being moveable within range R2.<br/><br/> CA 02215886 1997-11-06<br/>il2<br/> FIG. 45 depicts another preferred embodiment of a scanning system according<br/>to the present invention wherein bills to be scanned are transported in a left <br/>justified<br/>manner along the transport path, that is wherein the left edge L of a bill <br/>1084 is<br/>positioned in the same lateral location relative to the transport path. Based <br/>on the<br/>dimensions of the bill, the position of the center of the bill may be <br/>determined and<br/>the scanheads 1086a-b may in turn be positioned accordingly. As depicted in <br/>FIG.<br/>45, scanhead 1086a has a range of motion R3 and scanhead 1086b has a range of<br/>motion R4. The ranges of motion of scanheads 1086a-b may be influenced by the<br/>range of dimensions of bills which the discrimination system is designed to<br/>accommodate. Similar scanheads may be positioned on the opposite side of the<br/>transport path.<br/> Alternatively, the transport mechanism may be designed such that scanned<br/>bills are not necessarily centered or justified along the lateral dimension of <br/>the<br/>transport path. Rather the design of the transport mechanism may permit the <br/>position<br/>of bills to vary left and right within the lateral dimension of the transport <br/>path. In<br/>such a case, the edge sensors 1066 of FIG. 39 may be used to locate the edges <br/>and<br/>center of a bill, and thus provide positional information in a moveable <br/>scanhead<br/>system and selection criteria in a stationary scanhead system.<br/> In addition to the stationary scanhead and moveable scanhead systems<br/>described above, a hybrid system having both stationary and moveable scanheads <br/>may<br/>be used. Likewise, it should be noted that the laterally displaced scanheads <br/>described<br/>above need not lie along the same lateral axis. That is, the scanheads may be, <br/>for<br/>example, staggered upstream and downstream from each other. FIG. 46 is a top<br/>view of a staggered scanhead arrangement according to a preferred embodiment <br/>of<br/>the present invention. As illustrated in FIG. 46, a bill 1130 is transported <br/>in a<br/>centered manner along the transport path 1132 so that the center 1134 of the <br/>bill 1130<br/>is aligned with the center 1136 of the transport path 1132. Scanheads 1140a-h <br/>are<br/>arranged in a staggered manner so as to permit scanning of the entire width of <br/>the<br/>transport path 1132. The areas illuminated by each scanhead are illustrated by <br/>strips<br/>1142a, 1142b, 1142e, and 1142f for scanheads 1140a, 1140b, 1140e, and 1140f,<br/>respectively. Based on size determination sensors, scanheads 1140a and 1140h <br/>may<br/>either not be activated or their output ignored.<br/><br/> CA 02215886 1997-11-06<br/>113<br/> In general, if prior to scanning a document, preliminary information about a<br/>document can be obtained, such as its size or color, appropriately positioned<br/>stationary scanheads may be activated or laterally moveable scanheads may be<br/>appropriately positioned provided the preliminary information provides some<br/>indication as to the potential identity of the document. Alternatively, <br/>especially in<br/>systems having scanheads positioned over a significant portion of the <br/>transport path,<br/>many or all of the scanheads of a system may be activated to scan a document. <br/>Then<br/>subsequently, afrer some preliminary determination as to a document's identity <br/>has<br/>been made, only the output or derivations thereof of appropriately located <br/>scanheads<br/>may be used to generate scanned patterns. Derivations of output signals <br/>include, for<br/>example, data samples stored in memory generated by sampling output signals.<br/> Under such an alternative embodiment, information enabling a preliminary<br/>determination as to a document's identity may be obtained by analyzing <br/>information<br/>either from sensors separate from the scanheads or from one or more of the<br/>scanheads themselves. An advantage of such preliminary determinations is that <br/>the<br/>number of scanned patterns which have to be generated or compared to a set of<br/>master patterns is reduced. Likewise the number of master patterns to which <br/>scanned<br/>patterns must be compared may also be reduced.<br/> While the scanheads 1140a-h of FIG. 46 are arranged in a non-overlapping<br/>manner, they may alternatively be arranged in an overlapping manner. By <br/>providing<br/>additional lateral positions, an overlapping scanhead arrangement may provide <br/>greater<br/>selectivity in the segments to be scanned. This increase in scanable segments <br/>may be<br/>beneficial in compensating for currency manufacturing tolerances which result <br/>in<br/>positional variances of the printed indicia on bills relative to their edges.<br/>Additionally, in a preferred embodiment, scanheads positioned above the <br/>transport<br/>path are positioned upstream relative to their corresponding scanheads <br/>positioned<br/>below the transport path.<br/> FIGS. 47a and 47b illustrate another preferred embodiment of the present in<br/>invention wherein a plurality of analog sensors 1150 such as photodetectors <br/>are<br/>laterally displaced from each other and are arranged in a linear array within <br/>a single<br/>scanhead 1152. FIG. 47a is a top view while FIG. 47b is a side elevation view <br/>of<br/>such a linear array embodiment. The output of individual sensors 1150 are <br/>connected<br/><br/> CA 02215886 1997-11-06<br/>114<br/>to analog-to-digital converters (not shown) through the use of graded index <br/>fihers,<br/>such as a "lens array" manufactured by MSG America, Inc., part number<br/> SLA20A1675702A3, and subsequently to a CPU (not shown) in a manner similar to<br/>that depicted in FIGs. 1 and 6a. As depicted in FIGS. 47a and 47b, a bill 1154 <br/>is<br/>transported past the linear array scanhead 1152 in a centered fashion. A <br/>preferred<br/>length for the linear array scanhead is about 6-7 inches (15 cm - 17 cm).<br/>In a manner similar to that described above, based on the determination of the<br/>size of a bill, appropriate sensors may be activated and their output used to <br/>generate<br/>scanned patterns. Alternatively many or all of the sensors may be activated <br/>with only<br/>the output or derivations thereof of appropriately located sensors being used <br/>to<br/>generate scanned patterns. Derivations of output signals include, for example, <br/>data<br/>samples stored in memory generated by sampling output signals. As a result, a<br/>discriminating system incorporating a linear array scanhead according the <br/>present<br/>invention would be capable of accommodating a wide variety of bill-types.<br/>Additionally, a linear array scanhead provides a great deal of flexibility in <br/>how<br/>information may be read and processed with respect to various bills. In <br/>addition to<br/>the ability to generate scanned patterns along segments in a direction <br/>parallel to the<br/>direction of bill movement, by appropriately processing scanned samples, <br/>scanned<br/>patterns may be "generated" or approximated in a direction perpendicular to <br/>the<br/>direction of bill movement. For example, if the linear array scanhead 1152<br/>comprises one hundred and sixty (160) sensors 1150 over a length of 7 inches <br/>(17.78<br/>cm) instead of taking samples for 64 encoder pulses from say 30 sensors, <br/>samples<br/>may be taken for 5 encoder pulses from all 160 cells (or all those positioned <br/>over the<br/>bill 1154). Alternatively, 160 scanned patterns {or selected -ones thereof) of <br/>5 data<br/>samples each may be used for pattern comparisons. Accordingly, it can be seen <br/>that<br/>the data acquisition time is significantly . reduced from 64 encoder pulses to <br/>only 5<br/>encoder pulses. The time saved in acquiring data can be used to permit more <br/>time to<br/>be spent processing data and/or to reduce the total scanning time per bill <br/>thus<br/>enabling increased throughput of the identification system. Additionally, the <br/>linear<br/>array scanhead permits a great deal of flexibility in tailoring the areas to <br/>be scanned.<br/>For example, it has been found that the leading edge of Canadian bills contain<br/>valuable graphic information. Accordingly, when it is determined that a test <br/>bill may<br/><br/> CA 02215886 1997-11-06<br/>115<br/>be a Canadian bill (or when the identification system is set to a Canadian <br/>currency<br/>setting), the scanning area can be limited to the leading edge area of bills, <br/>for<br/>example, by activating many laterally displaced sensors for a relatively few <br/>number<br/>of encoder pulses.<br/> S FIG. 48 is a top view of another preferred embodiment of a linear array<br/>scanhead 1170 having a plurality of analog sensors 1172 such as photodetectors<br/>wherein a bill 1174 is transported past the scanhead 1170 in a non-centered <br/>manner.<br/>As discussed above, positional information from size determining sensors may <br/>be<br/>used to select appropriate sensors. Alternatively, the linear array scanhead <br/>itself may<br/>be employed to determine the size of a bill, thus eliminating the need for <br/>separate<br/>size determining sensors. For example, all sensors may be activated, data <br/>samples<br/>derived from sensors located on the ends of the linear array scanhead may be<br/>preliminarily processed to determine the lateral position and the length of a <br/>bill. The<br/>width of a bill may be determined either by employing separate <br/>leading/trailing edge<br/>sensors or pre-processing data samples derived from initial and ending cycle <br/>encoder<br/>pulses. Once size information is obtained about a bill under test, only the <br/>data<br/>samples retrieved from appropriate areas of a bill need be further processed.<br/> FIG. 49 is a top view of another preferred embodiment of a linear scanhead<br/>1180 according to the present invention illustrating the ability to compensate <br/>for<br/>skewing of bills. Scanhead 1180 has a plurality of analog sensors 1182 and a <br/>bill<br/>1184 is transported past scanhead 1180 in a skewed manner. Once the skew of a<br/>bill has been determined, for example through the use of leading edge sensors,<br/>readings from sensors 1182 along the scanhead 1180 may be appropriately <br/>delayed.<br/>For example, suppose it is determined that a bill is being fed past scanhead 1 <br/>i80 so<br/>that the left front corner of the bill reaches the scanhead five encoder <br/>pulses before<br/>the right front corner of the bill. In such a case, sensor readings along the <br/>right edge<br/>of the bill can be delayed for 5 encoder pulses to compensate for the skew. <br/>Where<br/>scanned patterns are to be generated over only a few encoder pulses, the bill <br/>may be<br/>treated as being fed in a non-skewed manner since the amount of lateral <br/>deviation<br/>between a scan along a skewed angle and a scan along a non-skewed angle is <br/>minimal<br/>for a scan of only a few encoder pulses. However, where it is desired to <br/>obtain a<br/>scan over a large number of encoder pulses, a single scanned pattern may be<br/><br/> CA 02215886 1997-11-06<br/>116<br/>generated from the outputs of more than one sensor. For example, a scanned <br/>pattern<br/>may be generated by taking data samples from sensor 1186a for a given number <br/>of<br/>encoder pulses, then taking data samples from sensor 1186b for a next given <br/>number<br/>of encoder pulses, and then taking data samples from sensor 118bc for a next <br/>given<br/>number of encoder pulses. The number of given encoder pulses for which data<br/>samples may be taken from the same sensor is influenced by the degree of skew, <br/>the<br/>greater the degree of skew of the bill, the fewer the number of data samples <br/>which<br/>may be obtained before switching to the next sensor. Alternatively, master <br/>patterns<br/>may be generated and stored for various degrees of skew, thus permitting a <br/>single<br/>sensor to generate a scanned pattern from a bill under test.<br/> With regards to FIGs. 47-49, while only a single linear array scanhead is<br/>shown, another linear array scanhead may be positioned on the opposite side of <br/>the<br/>transport path to permit scanning of either or both sides of a bill. Likewise, <br/>the<br/>benefits of using a linear array scanhead may also be obtainable using a <br/>multiple<br/>scanhead arrangement which is configured appropriately, for example such as<br/>depicted in FIG. 46 or a linear arrangement of multiple scanheads.<br/>In addition to size and scanned characteristic patterns, color may also be <br/>used<br/>to discriminate bills. For example, while all U.S. bills are printed in the <br/>same<br/>colors, e.g., a green side and a black side, bills from other countries often <br/>vary in<br/>color with the denomination of the bill. For example, a German 50 deutsche <br/>mark<br/>bill-type is brown in color while a German 100 deutsche mark bill-type is blue <br/>in<br/>color. Alternatively, color detection may be used to determine the face <br/>orientation of<br/>a bill, such as where the color of each side of a bill varies. For example, <br/>color<br/>detection may be used to determine the face orientation of U.S. bills by <br/>detecting<br/>whether or not the "green" side of a U.S. bill is facing upwards. Separate <br/>color<br/>sensors may be added upstream of the scanheads described above. According to <br/>such<br/>an embodiment, color information may be used in addition to size information <br/>to<br/>preliminarily identify a bill. Likewise, color information may be used to <br/>determine '<br/>the face orientation of a bill which determination may be used to select upper <br/>or<br/>lower scanheads for scanning a bill accordingly or compare scanned patterns <br/>retrieved<br/>from upper scanheads with a set of master patterns generated by scanning a<br/>corresponding face while the scanned patterns retrieved from the lower <br/>scanheads are<br/><br/> CA 02215886 2000-02-02<br/>117<br/>compared with a set of master patterns generated by scanning an opposing face.<br/>Alternatively, color sensing may be incorporated into the scanheads described <br/>above.<br/>Such color sensing may be achieved by, for example, incorporating color <br/>filters,<br/>colored light sources, and/or dichroic beamsplitters into the currency <br/>discrimination<br/>system of the present invention. Various color information acquisition<br/>techniques are described in U.S. Patent Nos. :4,841,358; 4,658,289; 4,716,456;<br/>4,825,246; and 4,992,860.<br/> The operation of a currency discriminator according to a preferred<br/>embodiment of the present invention may be further understood by referring to <br/>the<br/>flowchart of FIGs. ~50a and 50b. In the process beginning at step 1100, a bill <br/>is fed<br/>along a transport path (step 1102) past sensors which measure the length and <br/>width of<br/>the bill (step 1104). These size determining sensors may be, for example, <br/>those<br/>illustrated in FIG. 39. Next at step 1106, it is determined whether the <br/>measured<br/>dimensions of the bill match the dimensions of at least one bill stored in <br/>memory,<br/>such as EPROM 60 of FIG. 7a. If no match is fouad, an appropriate error is<br/>generated at step 1108. If a match is found, the color of the bill is scanned <br/>for at<br/>step 1110. At step 1112, it is determined whether the color of the bill <br/>matches a<br/>color associated with a genuine bill having the dimensions measured at step <br/>1104.<br/>An error is generated at step 1114 if no such match is found. However, if a <br/>match is<br/>found, a preliminary set of potentially matching bills is generated' ~at step <br/>1116.<br/>Often, only one possible identity will exist for a bill having a given color <br/>and<br/>dimensions. However, the preliminary set of step 1116 is not limited to the<br/>identification of a single bill-type, that is, a specific denomination of a <br/>specific<br/>currency system; but rather, the preliminary set may comprise a number of <br/>potential<br/>bill-types. For example, all U.S. bills have the same size and color. <br/>Therefore, the<br/>preliminary set generated by scanning a U.S. $5 bill would include U.S. bills <br/>of all<br/>denominations.<br/> Based on the preliminary set (step 1116), selected scanheads in a stationary<br/>scanhead system may be activated (step 1118). For example, if the preliminary<br/>identification indicates that a bill being scanned has the color and <br/>dimensions of a<br/><br/> CA 02215886 1997-11-06<br/>118<br/>German 100 deutsche mark, the scanheads over regions associated with the <br/>scanning<br/>of an appropriate segment for a German 100 deutsche mark may be activated. <br/>Then<br/>upon detection of the leading edge of the bill by sensors 1068 of FIG. 40, the<br/>appropriate segment may be scanned. Alternatively, all scanheads may be active <br/>with<br/>only the scanning information from selected scanheads being processed.<br/>Alternatively, based on the preliminary identification of a bill (step 1116), <br/>moveable<br/>scanheads may be appropriately positioned (step 1118).<br/>Subsequently, the bill is scanned for a characteristic pattern (step 1120). At<br/>step 1122, the scanned patterns produced by the scanheads are compared with <br/>the<br/>stored master patterns associated with genuine bills as dictated by the <br/>preliminary set.<br/>By only making comparisons with master patterns of bills within the <br/>preliminary set,<br/>processing time may be reduced. Thus for example, if the preliminary set <br/>indicated<br/>that the scanned bill could only possibly he a German 100 deutsche mark, then <br/>only<br/>the master pattern or patterns associated with a German 100 deutsche mark need <br/>be<br/>compared to the scanned patterns. If no match is found, an appropriate error <br/>is<br/>generated (step 1124). If a scanned pattern does match an appropriate master <br/>pattern,<br/>the identity of the bill is accordingly indicated (step 1126) and the process <br/>is ended<br/>(step 1128).<br/> While some of the preferred embodiments discussed above entailed a system<br/>capable of identifying a plurality of bill-types, the system may be adapted to <br/>identify<br/>a bill under test as either belonging to a specific bill-type or not. For <br/>example, the<br/>system may be adapted to store master information associated with only a <br/>single bill-<br/>type such as a United Kingdom 5 pound bill. Such a system would identify bills<br/>under test which were United Kingdom 5 pound bills and would reject all other <br/>bill-<br/>types.<br/> The scanheads of the present invention may be incorporated into a document<br/>identification system capable of identifying a variety of documents. For <br/>example, the<br/>system may be designed to accommodate a number of currencies from different<br/>countries. Such a system may be designed to permit operation in a number of<br/>modes. For example, the system may be designed to permit an operator to select <br/>one<br/>or more of a plurality of bill-types which the system is designed to <br/>accommodate.<br/>Such a selection may be used to limit the number of master patterns with which<br/><br/> CA 02215886 1997-11-06<br/>119<br/>scanned patterns are to be compared. Likewise, the operator may be permitted <br/>to<br/>select the manner in which bills will be fed, such as all bills face up, all <br/>bills top<br/>edge first, random face orientation, and/or random top edge orientation.<br/> Additionally, the system may be designed to permit output information to be<br/>displayed in a variety of formats to a variety of peripherals, such as a <br/>monitor, LCD<br/>display, or printer. For example, the system may be designed to count the <br/>number of<br/>each specific bill-types identified and to tabulate the total amount of <br/>currency counted<br/>for each of a plurality of currency systems. For example, a stack of bills <br/>could be<br/>placed in the bill accepting station 12 of FIG. 2a-2b, and the output unit 36 <br/>of FIG.<br/>2a-2b may indicate that a total of 370 British pounds and 650 German marks <br/>were<br/>counted. Alternatively, the output from scanning the same batch of bills may <br/>prow ide<br/>more detailed information about the specific denominations counted, for <br/>example one<br/>100 pound bill, five 50 pound bills, and one 20 pound bill and thirteen 50 <br/>deutsche<br/>mark bills. Such a device would be useful in a bank teller environment. A bank<br/>customer could hand the teller the above stack of bills. The teller could then <br/>place<br/>the stack of bills in the device. The device quickly scans the bills and <br/>indicates that a<br/>total of 370 British pounds and 650 German marks were counted. The teller <br/>could<br/>then issue the customer a receipt. At some point after the above transaction, <br/>the<br/>teller could separate the bills either by hand and/or by using an automatic <br/>sorter<br/>device located, for example, in a back room. The above transaction could then <br/>be<br/>performed rapidly without the customer being detained while the bills are <br/>being<br/>sorted.<br/> In a document identification system capable of identifying a variety of bills<br/>from a number of countries, a manual selection device, such as a switch or a<br/>scrolling selection display, may be provided so that the operator may <br/>designate what<br/>type of currency is to be discriminated. For example, in a system designed to<br/>accommodate both Canadian and German currency, the operator could turn a dial <br/>to<br/>the Canadian bill setting or scroll through a displayed menu and designate <br/>Canadian<br/>bills. By pre-declaring what type of currency is to be discriminated, scanned <br/>patterns<br/>need only be compared to master patterns corresponding to the indicated type <br/>of<br/>currency, e.g., Canadian bills. By reducing the number of master patterns <br/>which<br/>have to be compared to scanned patterns, the processing time can be reduced.<br/><br/> CA 02215886 1997-11-06<br/>120<br/> Alternatively, a system may be designed to compare scanned patterns to all<br/>stored master patterns. In such a system, the operator need not pre-declare <br/>what type<br/>of currency is to be scanned. This reduces the demands on the operator of the<br/>device. Furthermore, such a system would permit the inputting of a mixture of <br/>bills<br/>from a number of countries. The system would scan each bill and automatically<br/>determine the issuing country and the denomination.<br/> In addition to the manual and automatic bill-type discriminating systems, an<br/>alternate system employs a semi-automatic bill-type discriminating method. <br/>Such a<br/>system would work in a manner similar to the stranger mode described above. In<br/>such a system, a stack of bills is placed in the input hopper. The first bill <br/>is scanned<br/>and the generated scanned pattern is compared with the master patterns <br/>associated<br/>with bills from a number of different countries. The discriminator identifies <br/>the<br/>country-type and the denomination of the bill. Then the discriminator compares <br/>all<br/>subsequent bills in the stack to the master patterns associated with bills <br/>only from the<br/>same country as the first bill. For example, if a stack of U.S. bills were <br/>placed in<br/>the input hopper and the first bill was a $5 bill, the first bill would be <br/>scanned. The<br/>scanned pattern would be compared to master patterns associated with bills <br/>from a<br/>number of countries, e.g., U.S., Canadian, and German bills. Upon determining <br/>that<br/>the first bill is a U.S. $5 bill, scanned patterns from the remaining bills in <br/>the stack<br/>are compared only to master patterns associated with U.S. bills, e.g., $i, $2, <br/>$5,<br/>$10, $20, $50, and $100 bills. When a bill fails to sufficiently match one of <br/>the<br/>compared patterns, the bill may be flagged as described above such as by <br/>stopping<br/>the transport mechanism with the flagged bill being the last bill deposited in <br/>the<br/>output receptacle.<br/> A currency discriminating device designed to accommodate both Canadian and<br/> German currency bills will now be described. According to this preferred<br/>embodiment, a currency discriminating device similar to that described above <br/>in<br/>connection with scanning U.S. currency (see, e.g., FIGs. 1-38 and accompanying <br/>'<br/>description) is modified so as to be able to accept both Canadian and German<br/>currency bills. According to a preferred embodiment when Canadian bills are <br/>being<br/>discriminated, no magnetic sampling or authentication is performed.<br/><br/> CA 02215886 1997-11-06<br/>12i<br/>Canadian bills have one side with a portrait (the portrait side) and a reverse<br/>side with a picture (the picture side). Likewise, German bills also have one <br/>side with<br/>a portrait (the portrait side) and a reverse side with a picture (the picture <br/>side). In a<br/>preferred embodiment, the discriminator is designed to accept either stacks of<br/>Canadian bills or stacks of German bills, the bills in the stacks being faced <br/>so that the<br/>picture side of all the bills will be scanned by a triple scanhead arrangement <br/>to be<br/>described in connection with FIG. 51. In a preferred embodiment, this triple<br/>scanhead replaces the single scanhead arrangement housed in the unitary molded<br/>plastic support member 280 (see, e.g., FIGs. 25 and 26).<br/> FIG. 51 is a top view of a triple scanhead arrangement 1200. The triple<br/>scanhead arrangement 1200 comprises a center scanhead 1202, a left scanhead <br/>1204,<br/>and a right scanhead 1206 housed in a unitary molded plastic support member <br/>1208.<br/>A bill 1210 passes under the arrangement 1200 in the direction shown. O-rings <br/>are<br/>positioned near each scanhead, preferably two O-rings per scanhead, one on <br/>each side<br/>of a respective scanhead, to engage the bill continuously while transporting <br/>the bill<br/>between rolls 223 and 241 (FIG. 20a) and to help hold the bill flat against <br/>the guide<br/>plate 240 (FIG. 20a). The left 1204 and right 1206 scanhead are placed <br/>slightly<br/>upstream of the center scanhead 1202 by a distance D3. In a preferred <br/>embodiment,<br/>D3 is 0.083 inches (0.21 cm). The center scanhead 1202 is centered over the <br/>center<br/>C of the transport path 1216. The center h~ of the left scanhead 1204 and the <br/>center<br/>R~ of the right scanhead 1206 are displaced laterally from center C of the <br/>transport<br/>path in a symmetrical fashion by a distance D4. In a preferred embodiment D4 <br/>is<br/>1.625 inches (4.128 cm).<br/> The scanheads 1202, 1204, and 1206 are each similar to the s~canheads<br/>describe above connection with FIGs. 1-38, except only a wide slit having a <br/>length of<br/>about 0.500" and a width of about 0.050" is utilized. The wide slit of each <br/>scanhead<br/>is used both to detect the leading edge of a bill and to scan a bill after the <br/>leading<br/>edge has been detected.<br/> Two photosensors 1212 and 1214 are located along the lateral axis of the left<br/>and right scanheads 1204 and 1206, one on either side of the center scanhead <br/>1202.<br/> Photosensors 1212 and 1214 are same as the photosensors PS 1 and PS2 describe<br/>above (see, e.g., FIGs. 26 and 30). Photosensors 1212 and 1214 are used to <br/>detect<br/><br/> CA 02215886 1997-11-06<br/>122<br/>doubles and also to measure the dimension of bills in the direction of bill <br/>movement<br/>which in the preferred embodiment depicted in FIG. 5I is the narrow dimension <br/>of<br/>bills. Photosensors 1212 and 1214 are used to measure the narrow dimension of <br/>a<br/>bill by indicating when the leading and trailing edges of a bill passes by the<br/>photosensors 1212 and 1214. This information in combination with the encoder<br/>information permits the narrow dimension of a bill to be measured.<br/> All Canadian bills are 6" (15.24 cm) in their long dimension and 2.75" (6.985<br/>cm) in their narrow dimension. German bills vary in size according to <br/>denomination.<br/>In a preferred embodiment of the currency discriminating system, the <br/>discriminating<br/>device is designed to accept and discriminate $2, $5, $10, $20, $50, and $100<br/> Canadian bills and 10 DM, 20 DM, 50 DM, and 100 DM German bills. These<br/>German bills vary in size from 13.0 cm (5.12") in the long dimension by 6.0 cm<br/>(2.36") in the narrow dimension for 10 DM bills to 16.0 cm (6.30") in the long<br/>dimension by 8.0 cm (3.15") in the narrow dimension for 100 DM bills. The <br/>input<br/>hopper of the discriminating device is made sufficiently wide to accommodate <br/>all the<br/>above listed Canadian and German bills, e.g., 6.3" (16.0 cm) wide.<br/>FIG. 52 is a top view of a Canadian bill illustrating the areas scanned by the<br/>triple scanhead arrangement of FIG. 51. In generating scanned patterns from a<br/>Canadian bill 1300 traveling along a transport path 1301, segments SLI, SC,, <br/>and SRl<br/>are scanned by the left 1204, center 1202, and right 1206 scanheads, <br/>respectively, on<br/>the picture side of the bill 1300. These segments are similar to segment S in <br/>FIG. 4.<br/>Each segment begins a predetermined distance DS inboard. of the leading edge <br/>of the<br/>bill. In a preferred embodiment DS is 0.5" (1.27 cm). Segments SLI, SC1, and <br/>SRl<br/>each comprise 64 samples as shown in FIGs. 3 and 5. In a preferred embodiment<br/>Canadian bills are scanned at a rate of 1000 bills per minute. The lateral <br/>location of<br/>segments SL,, SC,, and SRl is fixed relative to the transport path 1301 but <br/>may vary<br/>left to right relative to bill 1300 since the lateral position of bill 1300 <br/>may vary left to<br/>right within the transport path 1301.<br/> A set of eighteen (18) master Canadian patterns are stored for each type of<br/>Canadian bill that the system is designed to discriminate, three (3) for each <br/>scanhead<br/>in both the forward and reverse directions. For example, three patterns are <br/>generated<br/>by scanning a given genuine Canadian bill in the forward direction with the <br/>center<br/><br/> CA 02215886 1997-11-06<br/>123<br/>scanhead. One pattern is generated by scanning down the center of the bill <br/>along<br/>segment SC,, a second is generated by scanning along a segment SCE initiated <br/>1.5<br/>samples before the beginning of SCI, and a third is generated by scanning <br/>along a<br/>segment SC3 initiated 1.5 samples after the beginning of SC,. The second and <br/>third<br/>patterns are generated to compensate for the problems associated with <br/>triggering off<br/>the edge of a bill as discussed above.<br/>To compensate for possible lateral displacement of bills to be scanned along a<br/>direction transverse to the direction of bill movement, the exact lateral <br/>location along<br/>which each of the above master patterns is generated is chosen after <br/>considering the<br/>correlation results achieved when a bill is displaced .slightly to the left or <br/>to the right<br/>of the center of each scanhead, i.e., lines Lc, Sc, and Rc. For example, in<br/>generating a master pattern associated with segment SCI, a scan of a genuine <br/>bill may<br/>be taken down the center of a bill, a second scan may be taken along a segment<br/>0.15" to the right of center (+0.15"), and a third scan may be taken along a <br/>segment<br/>0.15" to the left of center (-0.15"). Based on the correlation result <br/>achieved, the<br/>actual scan location may be adjusted slightly to the right or left so the <br/>effect of the<br/>lateral displacement of a bill on the correlation results is minimized. Thus, <br/>for<br/>example, the master pattern associated with a forward scan of a Canadian $2 <br/>bill<br/>using the center scanhead 1202 may be taken along a line 0.05" to the right of <br/>the<br/>center of the bill.<br/> Furthermore, the above stored master patterns are generated either by<br/>scanning both a relatively new crisp genuine bill and an older yellowed <br/>genuine bill<br/>and averaging the patterns generated from each or, alternatively, by scanning <br/>an<br/>average looking bill.<br/> Master patterns are stored for nine (9) types of Canadian bills, namely, the<br/>newer series $2, $5, $10, $20, $50, and $100 bills and the older series $20, <br/>$50, and<br/>$100 bills. Accordingly, a total of 162 Canadian master patterns are stored (9 <br/>types<br/>x 18 per type). '<br/>FIG. 53 is a flowchart of the threshold test utilized in calling the <br/>denomination<br/>of a Canadian bill. When Canadian bills are being discriminated the flowchart <br/>of<br/>FIG. 53 replaces the flowchart of FIG. 13. The correlation results associated <br/>with<br/>correlating a scanned pattern to a master pattern of a given type of Canadian <br/>bill in a<br/><br/> CA 02215886 1997-11-06<br/>124<br/>given scan direction and a given offset in the direction of bill movement from <br/>each of<br/>the three scanheads are summed. The highest of the resulting 54 summations is<br/>designated the #1 correlation and the second highest is preliminarily <br/>designated the #2<br/>correlation. The #1 and #2 correlations each have a given bill type associated <br/>with<br/>them. If the bill type associated with the #2 correlation is merely a <br/>different series<br/>from, but the same denomination as, the bill type associated with the #1<br/>denomination, the preliminarily designated #2 correlation is substituted with <br/>the next<br/>highest correlation where the bill denomination is different from the <br/>denomination of<br/>the bill type associated with the #1 correlation.<br/> The threshold test of FIG. 53 begins at step 1302. Step 1304 checks the<br/>denomination associated with the #1 correlation. If the denomination <br/>associated with<br/>the #1 correlation is not a $50 or $100, the #1 correlation is compared to a <br/>threshold<br/>of 1900 at step 1306. If the #1 correlation is less than or equal to 1900, the<br/>correlation number is too low to identify the denomination of the bill with <br/>certainty.<br/>Therefore, step 1308 sets a "no call" bit in a correlation result flag and the <br/>system<br/>returns to the main program at step 1310. If, however, the #1 correlation is <br/>greater<br/>than 1900 at step 1306, the system advances to step 1312 which determines <br/>whether<br/>the #1 correlation is greater than 2000. If the #1 correlation is greater than <br/>2000, the<br/>correlation number is sufficiently high that the denomination of the scanned <br/>bill can<br/>be identified with certainty without any further checking. Consequently, a <br/>"good<br/>call" bit is set in the correlation result flag at step 1314 and the system <br/>returns to the<br/>main program at step 1310.<br/> If the #1 correlation is not greater than 2000 at step 1312, step 1316 checks<br/>the denomination associated with the #2 correlation. If the denomination <br/>associated<br/>with the #2 correlation is not a $50 or $100, the #2 correlation is compared <br/>to a<br/>threshold of 1900 at step 1318. If the #2 correlation is less than or equal to <br/>1900,<br/>the denomination identified by the #1 correlation is acceptable, and thus the <br/>"good<br/>call" bit is set in the correlation result flag at step 1314 and the system <br/>returns to the<br/>main program at step 1310. If, however, the #2 correlation is greater than <br/>1900 at<br/>step 1318, the denomination of the scanned bill cannot be identified with <br/>certainty<br/>because the #1 and #2 correlations are both above 1900 and, yet, are <br/>associated with<br/><br/> CA 02215886 1997-11-06<br/>125<br/>different denominations. Accordingly, the "no call" bit is set in the <br/>correlation result<br/>flag at step 1308.<br/>If the denomination associated with the #2 correlation is a $50 or $100 at <br/>step<br/>1316, the #2 correlation is compared to a threshold of 1500 at step 1320. If <br/>the #2<br/>correlation is less than or equal to 1500, the denomination identified by the <br/>#I<br/>correlation is acceptable, and thus the "good call" bit is set in the <br/>correlation result<br/>flag at step 1314 and the system returns to the main program at step 1310. If,<br/>however, the #2 correlation is greater than 1500 at step 1320, the <br/>denomination of<br/>the scanned bill cannot be identified with certainty. As a result, the "no <br/>call" bit is<br/>set in the correlation result flag at step 1308.<br/>If the denomination associated with the #1 correlation is a $50 or $100 at <br/>step<br/>1304, the #1 correlation is compared to a threshold of 15th at step 1322. If <br/>the #i<br/>correlation is less than or equal to 1500, the denomination of the scanned <br/>bill cannot<br/>be identified with certainty and, therefore, the "no call" bit is set in the <br/>correlation<br/>result flag at step 1308. If, however, the #1 correlation at step 1322 is <br/>greater than<br/>1500, the system advances to step 1312 which determines whether the #1 <br/>correlation<br/>is greater than 2000. If the #1 correlation is greater than 2000,.the <br/>correlation<br/>number is su~ciently high that the denomination of the scanned bill can be <br/>identified<br/>with certainty without any further checking. Consequently, a "good call" bit <br/>is set in<br/>the correlation result flag at step 1314 and the system returns to the main <br/>program at<br/>step 1310.<br/> If the #1 correlation is not greater than 2000 at step 1312, step 1316 checks<br/>the denomination associated with the #2 correlation. If the denomination <br/>associated<br/>with the #2 correlation is not a $50 or $100, the #2 correlation is compared <br/>to a<br/>threshold of 1900 at step 1318. If the #2 correlation is less than or equal to <br/>1900,<br/>the denomination identified by the #1 correlation is acceptable, and thus the <br/>"good<br/>call" bit is set in the correlation result flag at step 1314 and the system <br/>returns to the<br/>main program at step 1310. If, however, the #2 correlation is greater than <br/>1900 at<br/>step 1318, the denomination of the scanned bill cannot be identified with <br/>certainty.<br/>Accordingly, the "no call" bit is set in the correlation result flag at step <br/>1308.<br/>If the denomination associated with the #2 correlation is a $50 or $100 at <br/>step<br/>1316, the #2 correlation is compared to a threshold of 1500 at step 1320. If <br/>the #2<br/><br/> CA 02215886 1997-11-06<br/>126<br/>correlation is less than or equal to 1500, the denomination identified by the <br/>#1<br/>correlation is acceptable, and thus the "goad call" bit is set in the <br/>correlation result<br/>flag at step 1314 and the system returns to the main program at step 1310. If,<br/>however, the #2 correlation is greater than 1500 at step 1320, the <br/>denomination of<br/>the scanned bill cannot be identified with certainty. As a result, the "no <br/>call" bit is<br/>set in the correlation result flag at step 1308 and the system returns to the <br/>main<br/>program at step 1310.<br/> Now the use of the triple scanhead arrangement 1200 in scanning and<br/>discriminating German currency will be described. When scanning German bills,<br/>only the output of the center scanhead 1202 is utilized to generate scanned <br/>patterns.<br/>A segment similar to segment S of FIG. 4 is scanned over the center of the <br/>transport<br/>path at a predetermined distance D6 inboard after the leading edge of a bill <br/>is<br/>detected. In a preferred embodiment D6 is 0.25" (0.635 cm). The scanned <br/>segment<br/>comprises 64 samples as shown in FIGs. 3 and 5. In a preferred embodiment<br/>German bills are scanned at a rate of 1000 bills per minute. The lateral <br/>location of<br/>the scanned segment is fixed relative to the transport path 1216 but may vary <br/>left to<br/>right relative to bill 1210 since the lateral position of bill 1210 may vary <br/>left to right<br/>within the transport path 1216.<br/> FIG. 54a illustrates the general areas scanned in generating master 10 DM<br/>German patterns. Due to the short length of 10 DM bills in their long <br/>dimension<br/>relative to the width of the transport path, thirty (30) 10 DM master patterns <br/>are<br/>stored. A first set of five patterns are generated by scanning a genuine 10 DM <br/>bill<br/>1400 in the forward direction along laterally displaced segments all beginning <br/>a<br/>predetermined distance D6 inboard of the leading edge of the bill 1400. Each <br/>of<br/>these five laterally displaced segments is centered about a respective one of <br/>lines Ll-<br/>L5. One such segment S 101 centered about line L, is illustrated in FIG. 54a. <br/>Line L,<br/>is disposed down the center C of the bill 1400. In a preferred embodiment <br/>lines Lz-<br/>LS are disposed in a symmetrical fashion about the center C of the bill 1400. <br/>In a<br/>preferred embodiment lines L2 and L3 are laterally displaced from L, by a <br/>distance D,<br/>where D, is 0.24" (0.61 cm) and lines L4 and LS are laterally displaced from <br/>Ll by a<br/>distance D$ where D8 is 0.48" (1.22 cm).<br/><br/> CA 02215886 1997-11-06<br/>127<br/> A second set of five patterns are generated by scanning a genuine i0 DM bill<br/>1400 in the forward direction along laterally displaced segments along lines <br/>L,-LS all<br/>beginning at a second predetermined distance inboard of the leading edge of <br/>the bill<br/>1400, the second predetermined distance being less than the predetermined <br/>distance<br/>D6. One such segment S 10, centered about line L, is illustrated in FIG. 54a. <br/>In a<br/>preferred embodiment the second predetermined distance is such that scanning <br/>begins<br/>one sample earlier than D6, that is about 30 mils before the initiation of the <br/>patterns<br/>in the first set of five patterns.<br/> A third set of five patterns are generated by scanning a genuine i0 DM bill<br/>1400 in the forward direction along laterally displaced segments along lines <br/>Ll-LS all<br/>beginning at a third predetermined distance inboard of the leading edge of the <br/>bill<br/>1400, the third predetermined distance being greater than the predetermined <br/>distance<br/>D6. One such segment S 103 centered about line Ll is illustrated in FIG. 54a. <br/>In a<br/>preferred embodiment the third predetermined distance is such that scanning <br/>begins<br/>one sample later than D6, that is about 30 mils after the initiation of the <br/>patterns in<br/>the first set of five patterns.<br/> The above three sets of five patterns yield fifteen patterns in the forward<br/>direction. Fifteen additional IO DM master patterns taken in tile manner <br/>described<br/>above but in the reverse direction are also stored.<br/> FIG. 54b illustrates the general areas scanned in generating master 20 DM, 50<br/> DM, and 100 DM German patterns. Due to the lengths of 20 DM, 50 DM, and 100<br/>DM bills in their long dimension being shorter than the width of the transport <br/>path,<br/>eighteen (18) 20 DM master patterns, eighteen (18) 50 DM master patterns, and<br/>eighteen (18) 100 DM master patterns are stored. The 50 DM master patterns and<br/>the 100 DM master patterns are taken in the same manner as the 20 DM master<br/>patterns except that the 50 DM master patterns and 100 DM master patterns are<br/>generated from respective genuine 50 DM bills and 100 DM bills while the 20 DM<br/>master patterns are generated from genuine 20 DM bills. Therefore, only the<br/>generation of the 20 DM master patterns will be described in detail.<br/>A first set of three patterns are generated by scanning a genuine 20 DM bill<br/>1402 in the forward direction along laterally displaced segments all beginning <br/>a<br/>predetermined distance D6 inboard of the leading edge of the bill 1402. Each <br/>of<br/><br/> CA 02215886 1997-11-06<br/>128<br/>these three laterally displaced segments is centered about a respective one of <br/>lines L6-<br/>Lg. One such segment S201 centered about line L6 is illustrated in FIG. 54b. <br/>Line<br/>L6 is disposed down the center C of the bill 1402. In a preferred embodiment <br/>lines<br/>L,-L8 are disposed in a symmetrical fashion about the center C of the bill <br/>1402. In a<br/>preferred embodiment lines L, and L8 are laterally displaced from L,6 by a <br/>distance D9<br/>where D9 is 0.30" (0.76 cm) for the 20 DM bill. The value of D9 is 0.20" (0.51 <br/>cm)<br/>for the 50 DM bill and 0.10" (0.25 cm) for the 100 DM bill.<br/> A second set of three patterns are generated by scanning a genuine 20 DM bill<br/>1402 in the forward direction along laterally displaced segments along lines <br/>L6-L$ all<br/>beginning at a second predetermined distance inboard of the leading edge of <br/>the bill<br/>1402, the second predetermined distance being less than the predetermined <br/>distance<br/>D6. One such segment 5202 centered about line L6 is illustrated~in FIG. 54b. <br/>In a<br/>preferred embodiment the second predetermined distance is such that scanning <br/>begins<br/>one sample earlier than D6, that is about 30 mils before the initiation of the <br/>patterns<br/>in the first set of three patterns.<br/> A third set of three patterns are generated by scanning a genuine 20 DM bill<br/>1402 in the forward direction along laterally displaced segments along lines <br/>L6-L8 all<br/>beginning at a third predetermined distance inboard of the leading edge of the <br/>bill .<br/>1402, the third predetermined distance being greater than the predetermined <br/>distance<br/>Db. One such segment 5203 centered about line L6 is illustrated in FIG. 54b. <br/>In a<br/>preferred embodiment the third predetermined distance is such that scanning <br/>begins<br/>one sample later than D6, that is about 30 mils after the initiation of the <br/>patterns in<br/>the first set of three patterns.<br/> The above three sets of three patterns yield nine patterns in the forward<br/>direction. Nine additional 20 DM master patterns taken in the manner described<br/>above but in the reverse direction are also stored. Furthermore, the above <br/>stored<br/>master patterns are generated either by scanning both a relatively new crisp <br/>genuine<br/>bill and an older yellowed genuine bill and averaging the patterns generated <br/>from<br/>each or, alternatively, by scanning an average looking bill.<br/> This yields a total of 84 German master patterns (30 for 10 DM bills, 18 for<br/>20 DM bills, 18 for 50 DM bills, and 18 for 100 DM bills). To reduce the <br/>number<br/>of master patterns that must compared to a given scanned pattern, the narrow<br/><br/> CA 02215886 1997-11-06<br/>129<br/>dimension of a scanned bill is measured using photosensors 1212 and 1214. <br/>After a<br/>given bill has been scanned by the center scanhead 1202, the generated scanned<br/>pattern is correlated only against certain ones of above described 84 master <br/>patterns<br/>based on the size of the narrow dimension of the bill as determined by the<br/>photosensors 1212 and 1214. The narrow dimension of each bill is measured<br/>independently by photosensors 1212 and 1214 and then averaged to indicate the<br/>length of the narrow dimension of a bill. In particular, a first number of <br/>encoder<br/>pulses occur between the detection of the leading and trailing edges of a bill <br/>by the<br/>photosensor 1212. Likewise, a second number of encoder pulses occur between <br/>the<br/>detection of the leading and trailing edges of the bill by the photosensor <br/>1214. These<br/>first and second numbers of encoder pulses are averaged to indicate the length <br/>of the<br/>narrow dimension of the bill in terms of encoder poises.<br/> The photosensors 1212 and 1214 can also determine the degree of skew of a<br/>bill as it passes by the triple scanhead arrangement 1200. By counting the <br/>number of<br/>encoder pulses between the time when photosensors 1212 and 1214 detect the <br/>leading<br/>edge of a bill, the degree of skew can be determined in terms of encoder <br/>pulses. If<br/>no or little skew is measured, a generated scanned pattern is only compared to <br/>master<br/>patterns associated with genuine bills having the same narrow dimension <br/>length. If a<br/>relatively large degree of skew is detected, a scanned pattern will be <br/>compared with<br/>master patterns associated with genuine bills having the next smaller <br/>denominational<br/>amount than would be indicated by the measured narrow dimension length.<br/> Table 4 indicates which denominational set of master patterns are chosen for<br/>comparison to the scanned pattern based on the measured narrow dimension <br/>length in<br/>terms of encoder pulses and the measured degree of skew in terms of encoder <br/>pulses:<br/> TABLE d<br/> Narrow Dimension Degree of Skew in Selected Set of Master<br/> Length in Encoder Encoder Pulses Patterns<br/> Pulses <br/>< 1515 Not applicable 10 DM<br/>>_ 1515 and < 1550 >_ 175 10 DM<br/>>_ 1515 and < 1550 < 175 20 DM<br/>>_ 1550 and < 1585 >_ 300 10 DM<br/><br/> CA 02215886 1997-11-06 - -<br/>130<br/>>_ 150 < 1585 < 300 20 DM<br/>and <br/>>_ 1585and< 1620 >_ 200 20 DM<br/>>_ 1585and< i620 < 200 50 DM<br/>>_ 1620and< 1655 >_ 300 20 DM<br/>_> 1620and< 1655 < 300 50 DM<br/>>_ 1655and< 1690 >_ 150 50 DM<br/>>_ 1655 < 1690 < 150 100 DM<br/>and <br/>>_ I690and< 1725 >_ 300 50 DM<br/>_> 1690and< 1725 < 300 100 DM<br/>>_ 1725 Not i00 DM<br/>applicable <br/>FIG. 55 is a flowchart of the threshold test utilized in calling the <br/>denomination<br/>of a German bill. It should be understood that this threshold test compares <br/>the<br/>scanned bill pattern only to the set of master patterns selected in accordance <br/>with<br/> Table 4. Therefore, the selection made in accordance with Table 4 provides a<br/>preliminary indication as to the denomination of the scanned bill. The <br/>threshold test<br/>in FIG. 55, in effect, serves to confirm or overturn the preliminary <br/>indication given<br/>by Table 4.<br/> The threshold test of FIG. 55 begins at step 1324. Step 1326 checks the<br/>narrow dimension length of the scanned bill in terms of encoder pulses. If the<br/>narrow dimension length is less than 1515 at step 1326, the preliminary <br/>indication is<br/>that the denomination bf the scanned bill is a 10 DM bill. In order to confirm <br/>this<br/>preliminary indication, the #1 correlation is compared to 550 at step 1328. If <br/>the #1<br/>correlation is greater than 550, the correlation number is sufficiently high <br/>to identify<br/>the denomination of the bill as a 10 DM bill. Accordingly, a "good call" bit <br/>is set in<br/>a correlation result flag at step 1330, and the system returns to the main <br/>program at<br/>step 1332. If, however, the #1 correlation is less than or equal to 550 at <br/>step 1328, .<br/>the preliminary indication that the scanned bill is a 10 DM bill is <br/>effectively<br/>overturned. The system advances to step 1334 which sets a "no call" bit in the<br/>correlation result flag.<br/><br/> CA 02215886 1997-11-06<br/>131<br/>r''<br/> If step 1326 determines that the narrow dimension length is greater than or<br/>equal to 1515, a correlation threshold of 800 is required to confirm the <br/>preliminary<br/>denominational indication provided by Table 4. Therefore, if the #1 <br/>correlation is<br/>greater than 800 at step 1336, the preliminary indication provided by Table 4 <br/>is<br/>confirmed. To confirm the preliminary indication, the "good call" bit is set <br/>in the<br/>correlation result flag. If, however, the #1 correlation is less than or equal <br/>to 800 at<br/>step 1336, the preliminary indication is rejected and the "no call" bit in the<br/>correlation result flag is set at step 1334. The system then returns to the <br/>main<br/>program at step 1332.<br/> According to a preferred embodiment, the operator of the above described<br/>currency discriminating device designed to accommodate both Canadian and <br/>German<br/>currency bills pre-declares whether Canadian or German bills are to be <br/>discriminated.<br/>By depressing an appropriate key on the keypad 62 (FIG. 59), the display 63 <br/>will<br/>scroll through five different modes: a count mode, a Canadian stranger mode, a<br/>1~ Canadian mixed mode, a German stranger mode, and a German mixed mode. In <br/>the<br/>count mode, the device acts like a simply bill counter (counting the number of <br/>bills in<br/>a stack but not discriminating them by denomination). Canadian stranger mode <br/>is<br/>similar to the stranger mode described below in connection with FIG. 59 but <br/>bills are<br/>scanned as described above in connection with FIG. 52 and scanned patterns are<br/>correlated against Canadian master patterns. Likewise, Canadian mixed mode is<br/>similar to the mixed mode described below in connection with FIG. 59 but bills <br/>are<br/>scanned as described above in connection with FIG. 52 and scanned patterns are<br/>correlated against Canadian master patterns. Likewise German stranger and <br/>German<br/>mixed mode are similar to the stranger and mixed modes described below in<br/>connection with FIG. 59 but bills are scanned as described above in connection <br/>with<br/>the scanning of German bills and scanned patterns are correlated against <br/>German<br/>master patterns.<br/> FIG. 56 is a functional block diagram illustrating another preferred<br/>embodiment of a currency discriminator system 1662 according to the present<br/>invention. The discriminator system 1662 comprises an input receptacle 1664 <br/>for<br/>receiving a stack of currency bills. A transport mechanism (as represented by <br/>arrows<br/>A and B) transports the bills in the input receptacle passed an authenticating <br/>and<br/><br/> CA 02215886 2000-02-02<br/>132<br/>discriminating unit 1666 to an output receptacle 1668 where the bills are re-<br/>stacked<br/>such that each bill is stacked on top of or behind the previous bill so that <br/>the most<br/>recent bill is the top-most or rear-most bill. The authenticating and <br/>discriminating<br/>unit scans and determines the denomination of each passing bill. Any variety <br/>of<br/>S discriminating techniques may be used. For example, the discriminating <br/>method<br/>disclosed in U.S. Pat. No. 5,295,196 may be<br/>employed to optically scan each bill. Depending on the characteristics of the<br/>discriminating unit employed, the discriminator may be able to recognize bills <br/>only if<br/>fed face up or face down, regardless of whether fed face up or face down, only <br/>if fed<br/>in a forward orientation or reverse orientation, regardless of whether fed in <br/>a forward<br/>or reverse orientation, or some combination thereof. Additionally, the <br/>discriminating<br/>unit may be able to scan only one side or both sides of a bill. In addition to<br/>determining the denomination of each scanned bill, the authenticating and<br/>discriminating unit 1666 may additionally include various authenticating tests <br/>such as<br/>an ultraviolet authentication test as disclosed in U.S. Patent No. 5,640,463 <br/>issued June<br/>17, 1997 for a "Method and Apparatus for Authenticating Documents Including<br/> Currency."<br/> Signals from the authenticating and discriminating unit 1666 are sent to a<br/>signal processor such as a central processor unit ("CPU") 1670. The CPU 1670<br/>records of results of the authenticating and discriminating tests in a memory <br/>1672.<br/> When the authenticating and discriminating unit 1666 is able to confirm the<br/>genuineness and denomination of a bill, the value of the bill is added to a <br/>total value<br/>counter in memory 1672 that keeps track of the total value of the stack of <br/>bills that<br/>were inserted in the input receptacle 1664 and scanned by the authenticating <br/>and<br/>discriminating unit 1666. Additionally, depending on the mode of operation of <br/>the<br/>discriminator system 1662, counters associated with one or more denominations <br/>are<br/>maintained in the memory 1672. For example, a $1 counter may be maintained to<br/>record how many $1 bills were scanned by the authenticating and discriminating <br/>unit<br/>1666. Likewise, a $5 counter may be maintained to record how many $5 bills <br/>were<br/>scanned, and so on. In an operating mode where individual denomination <br/>counters<br/>are maintained, the total value of the scanned bills may be determined without<br/>maintaining a separate total value counter. The total value of the scanned <br/>bills andlor<br/><br/> CA 02215886 1997-11-06<br/>133<br/>the number of each individual denomination may be displayed on a display 1674 <br/>such<br/>as a monitor or LCD display.<br/> As discussed above, a discriminating unit such as the authenticating and<br/>discriminating unit 1666 may not be able to identify the denomination of one <br/>or more<br/>bills in the stack of bills loaded into the input receptacle 1664. For <br/>example, if a bill<br/>is excessively worn or soiled or if the bill is torn a discriminating unit may <br/>not be<br/>able to identify the bill. Furthermore, some known discrimination methods do <br/>not<br/>have a high discrimination efficiency and thus are unable to identify bills <br/>which vary<br/>even somewhat from an "ideal" bill condition or which are even somewhat <br/>displaced<br/>by the transport mechanism relative to the scanning mechanism used to <br/>discriminate<br/>bills. Accordingly, such poorer performing discriminating units may yield a<br/>relatively large number of bills which are not identified. Alternatively, some<br/>discriminating units may be capable of identifying bills only when they are <br/>fed in a<br/>predetermined manner. For example, some discriminators may require a bill to <br/>be<br/>faced in a predetermined manner. Accordingly, when a bill is fed face down <br/>passed<br/>a discriminating unit which can only identify bills fed face up, the <br/>discriminating unit<br/>can not identify the bill. Likewise, other discriminators require a specif c <br/>edge of a<br/>bill to be fed first, for example, the top edge of a bill. Accordingly, bills <br/>which are<br/>not fed in the forward direction, that is, those that are fed in the reverse <br/>direction,<br/>are not identified by such a discriminating unit.<br/> According to a preferred embodiment, the discriminator system 1662 is<br/>designed so that when the authenticating and discriminating unit is unable to <br/>identify<br/>a bill, the transport mechanism is stopped so that the unidentified bill is <br/>the last bill<br/>transported to the output receptacle. After the transport mechanism stops, the<br/>unidentified bill is then, for example, positioned at the top of or at the <br/>rear of the<br/>stack of bills in the output receptacle 1668. The output receptacle 1668 is <br/>preferably<br/>positioned within the discriminator system 1662 so that the operator may <br/>conveniently<br/>see the flagged bill and/or remove it for closer inspection. Accordingly, the <br/>operator<br/>is able to easily see the bill which has not been identified by the <br/>authenticating and<br/>discriminating unit 1666. The operator may then either visually inspect the <br/>flagged<br/>bill while it is resting on the top of or at the rear of the stack, or <br/>alternatively, the<br/>operator may chose to remove the bill from the output receptacle in order to <br/>examine<br/><br/> CA 02215886 1997-11-06<br/>134<br/>the flagged bill more closely. The discriminator system 1662 may be designed <br/>to<br/>continue operation automatically when a flagged bill is removed from the <br/>output<br/>receptacle or, according to a preferred embodiment of the present invention, <br/>may be<br/>designed to require a selection element to be depressed. Upon examination of a<br/>S flagged bill by the operator, it may be found that the flagged bill is <br/>genuine even<br/>though is was not identified by the discriminating unit. However, because the <br/>bill<br/>was not identified, the total value and/or denomination counters in the memory <br/>1672<br/>will not reflect its value. According to one embodiment, such an unidentified <br/>bill is<br/>removed from the output stack and either re-fed through the discriminator or <br/>set<br/>aside. In the latter case, any genuine set aside bills are counted by hand.<br/>In prior discriminators, unidentified discriminators were routed to a separate<br/>reject receptacle. In such systems, an unidentified genuine bill would have to <br/>be<br/>removed from a reject receptacle and re-fed through the discriminator or the <br/>stack of<br/>rejected bills would have to be counted by hand and the results separately <br/>recorded.<br/>Furthermore, because re-fed bills have gone unidentified once, they are more <br/>likely<br/>to go unidentified again and ultimately may have to be counted by hand. <br/>However,<br/>as discussed above, such procedures may increase the chance for human error or <br/>at<br/>least lower the efficiency of the discriminator and the operator.<br/>In order to avoid problems associated with re-feeding bills, counting bills by<br/>hand, and adding together separate totals, according to a preferred embodiment <br/>of the<br/>present invention a number of selection elements associated with individual<br/>denominations are provided. In FIG. 56, these selection elements are in the <br/>form of<br/>keys or buttons of a keypad 1676 or 62. ~ Other types of selection elements <br/>such as<br/>switches or displayed keys in a touch-screen environment may be employed. The<br/>operation of the selection elements will be described in more detail in <br/>connection with<br/>FIG. 59 but briefly when an operator determines that a flagged bill is <br/>acceptable, the<br/>operator may simply depress the selection element associated with the <br/>denomination<br/>of the flagged bill and the corresponding denomination counter and/or the <br/>total value<br/>counter are appropriately incremented and the discriminator system 1662 or i0<br/>resumes operating again. As discussed above, a bill may be flagged for any <br/>number<br/>of reasons including the bill being a no call or suspect bill. In non-<br/>automatic restart<br/>discriminators, where an operator has removed a genuine flagged bill from the <br/>output<br/><br/> CA 02215886 1997-11-06<br/>135<br/>receptacle for closer examination, the bill is first replaced into the output <br/>receptacle<br/>before a corresponding selection element is chosen. When an operator <br/>determines<br/>that a flagged bill is not acceptable, the operator may remove the <br/>unacceptable<br/>flagged bill from the output receptacle without replacement and depress a<br/>continuation key on the keypad 1676 or 62. When the continuation key is <br/>selected<br/>the denomination counters and the total value counter are not affected and the<br/>discriminator system 1662 or 10 will resume operating again. In automatic <br/>restart<br/>discriminators, the removal of a bill from the output receptacle is treated as <br/>an<br/>indication that the bill is unacceptable and the discriminator automatically <br/>resumes<br/>operation without affecting the denomination counters and/or total value <br/>counters.<br/>An advantage of the above described procedure . is that appropriate counters <br/>are<br/>incremented and the discriminator is restarted with the touch of a single key, <br/>greatly<br/>simplifying the operation of the discriminator system 1662 or 10 while <br/>reducing the<br/>opportunities for human error.<br/> IS Turning now to FIG. 57, there is shown a functional block diagram<br/>illustrating another preferred embodiment of a document aurhenticator and<br/>discriminator according to the present invention. The discriminator system <br/>1680<br/>comprises an input receptacle 1682 for receiving a stack of currency bills. A<br/>transport mechanism (as represented by arrow C) transports the bills in the <br/>input<br/>receptacle, one at a time, passed an authenticating and discriminating unit <br/>1684.<br/>Based on the results of the authenticating and discriminating unit 1684, a <br/>bill is either<br/>transported to one of a plurality of output receptacles 1686 (arrow D), to a <br/>reject<br/>receptacle 1688 {arrow E), or to an operator inspection station 1690 (arrow <br/>F).<br/>When is bill is determined to be genuine and its denomination has been <br/>identified, the<br/>2~ bill is transported to an output receptacle associated with its <br/>denomination. For<br/>example, the discriminator system 1680 may comprise seven output receptacles <br/>1686,<br/>one associated with each of seven U.S. denominations, i.e., $1, $2, $5, $10, <br/>$20,<br/>$50, and $100. The transport mechanism directs (arrow D) the identified bill <br/>to the<br/>corresponding output receptacle. Alternatively, where the authenticating and<br/>discriminating unit determines that a bill is a fake, the bill is immediately <br/>routed<br/>(arrow E) to the reject receptacle 1688. Finally, if a bill is not determined <br/>to be fake<br/>but for some reason the authenticating and discriminating unit 1684 is not <br/>able to<br/><br/> CA 02215886 1997-11-06<br/>136<br/>identify the denomination of the bill, the flagged bill is routed (arrow F) to <br/>an<br/>inspection station and the discriminator system 1680 stops operating. The <br/>inspection<br/>station is preferably positioned within the discriminator system 1680 so that <br/>the<br/>operator may conveniently see the flagged bill andlor remove it for closer <br/>inspection.<br/>If the operator determines that the bill is acceptable, the operator returns <br/>the bill to<br/>the inspection station if it was removed and selects a selection element (not <br/>shown)<br/>corresponding to the denomination of the flagged bill. Appropriate counters <br/>(not<br/>shown) are incremented, the discriminator system 1680 resumes operation, and <br/>the<br/>flagged bill is routed (arrow G) to the output receptacle associated with the <br/>chosen<br/>selection element. On the other hand, if the operator determines that the <br/>flagged bill<br/>is unacceptable, the operator returns the bill to the inspection station if it <br/>was<br/>removed and selects a continuation element (not shown). The discriminator <br/>system<br/>1680 resumes operation, and the flagged bill is routed (arrow H) to the reject<br/>receptacle 1688 without incrementing the counters associated with the various<br/>denomination and/or the total value counters. Alternatively, the discriminator <br/>system<br/>1680 may permit the operator to place any unacceptable unidentified bills <br/>aside or<br/>into the reject receptacle by hand. While transport paths D and G and paths E <br/>and H<br/>are illustrated as separate paths, paths D and G and paths E and ~ H, <br/>respectively, may<br/>be the same path so that all bills proceeding to either one of the output <br/>receptacles<br/>1686 or the reject receptacle 1688, respectively, are routed through the <br/>inspection<br/>station 1690.<br/>. Turning now to FIG. 58, there is shown a functional block diagram<br/>illustrating another preferred embodiment of a document authenticator and<br/>discriminator according to the present invention. The discriminator system <br/>1692<br/>comprises an input receptacle 1694 for receiving a stack of currency bills. A<br/>transport mechanism (as represented by arrow I) transports the bills in the <br/>input<br/>receptacle, one at a time, passed an authenticating and discriminating unit <br/>1696.<br/>Based on the results of the authenticating and discriminating unit 1684, a <br/>bill is either<br/>transported to a single output receptacle 1698 (arrow n or to an operator <br/>inspection<br/>station 1699 (arrow K). When is bill is determined to be genuine and its<br/>denomination has been identified, the bill is transported to the single output<br/>receptacle. Alternatively, where the authenticating and discriminating unit <br/>determines<br/><br/> CA 02215886 1997-11-06<br/>137<br/>that a bill is a fake or for some reason the authenticating and discriminating <br/>unit 1684<br/>is not able to identify the denomination of the bill, the flagged bill is <br/>routed (arrow<br/>K) to an inspection station and the discriminator system 1692 stops operating. <br/>The<br/>inspection station is preferably positioned within the discriminator system <br/>1692 so<br/>that the operator may conveniently see the flagged bill and/or remove it for <br/>closer<br/>inspection. Where a bill has been positively determined to be a fake by the<br/>authenticating and discriminating unit 1696, an appropriate indication, for <br/>example,<br/>via a message in a display or the illumination of a light, can be given to the <br/>operator<br/>as to the lack of genuineness of the bill. The operator may then remove the <br/>bill<br/>without replacement from the inspection station 1699 and select a continuation<br/>element. Where a bill has not been positively identified as a fake nor has had <br/>its<br/>denomination identified and where the operator determines that the bill is <br/>acceptable,<br/>the operator returns the bill to the inspection station if it was removed and <br/>selects a<br/>selection element (not shown) corresponding to the denomination of the flagged <br/>bill.<br/>Appropriate counters (not shown) are incremented, the discriminator system <br/>1680<br/>resumes operation, and the flagged bill is routed {arrow L) to the single <br/>output<br/>receptacle 1698. On the other hand, if the operator determines that the <br/>flagged bill is<br/>unacceptable, the operator removes the bill without replacement form the <br/>inspection<br/>station and selects a continuation element {not shown). The discriminator <br/>system<br/>1692 resumes operation without incrementing the counters associated with the <br/>various<br/>denomination and/or the total value counters. While transport paths J and L <br/>are<br/>illustrated as separate paths, they may be the same path so that all bills <br/>proceeding to<br/>the single output receptacle 1698 are routed through the inspection station <br/>1699.<br/> The operation of the selection elements will now be described in more detail<br/>in conjunction with FIG. 59 which is a front view of a control panel 61 of a<br/>preferred embodiment of the present invention. The control panel 61 comprises <br/>a<br/>keypad 62 and a display section 63. The keypad 62 comprises a plurality of <br/>keys<br/>including seven denomination selection elements 64a-64g, each associated with <br/>one of<br/>seven U.S. currency denominations, i.e., $1, $2, $5, $10, $20, $50, and $100. <br/>The<br/>$1 denomination selection key 64a also serves as a mode selection key. The <br/>keypad<br/>62 also comprises a "Continuation" selection element 65. Various information <br/>such<br/>as instructions, mode selection information, authentication and discrimination<br/><br/> CA 02215886 1997-11-06<br/>138<br/>information, individual denomination counter values, and total batch counter <br/>value<br/>are communicated to the operator via an LCD 66 in the display section 63. A<br/>discriminator according to a preferred embodiment of the present invention has <br/>a<br/>number of operating modes including a mixed mode, a stranger mode, a sort <br/>mode, a<br/>face mode, and a forward/reverse orientation mode. The operation of a <br/>discriminator<br/>having the denomination selection elements 64a-64g and the continuation <br/>element 65<br/>will now be discussed in connection with several operating modes.<br/>(A) Mixed Mode<br/> Mixed mode is designed to accept a stack of bills of mixed denomination,<br/>total the aggregate value of all the bills in the stack and display the <br/>aggregate value in<br/>the display b3. Information regarding the number of bills of each individual<br/>denomination in a stack may also be stored in denomination counters. When an<br/>otherwise acceptable bill remains unidentified after passing through the <br/>authenticating<br/>and discriminating unit, operation of the discriminator may be resumed and the<br/>corresponding denomination counter and/or the aggregate value counter may be<br/>appropriately incremented by selecting the denomination selection key 64a-64g<br/>associated with the denomination of the unidentified bill. For example, if the<br/>discriminator system 62 of FIG. 56 or 10 of FIG. 1 stops operation with an <br/>otherwise<br/>acceptable $5 bill being the last bill deposited in the output receptacle, the <br/>operator<br/>may simply select key 64b. When key 64b is depressed, the operation of the<br/>discriminator is resumed and the $5 denomination counter is incremented and/or <br/>the<br/>aggregate value counter is incremented by $5. Furthermore, in the <br/>discriminator<br/>systems 1680 of FIG. 57 and 1692 of FIG. 58, the flagged bill may be routed <br/>from<br/>the inspection station to an appropriate output receptacle. Otherwise, if the <br/>operator<br/>determines the flagged bill is unacceptable, the bill may be removed from the <br/>output<br/>receptacle of FIGS. 1 or 56 or the inspection station of FIGs. 8 and 9 (or in <br/>the<br/>system 1680 of FIG. 57, the flagged bill may be routed to the reject <br/>receptacle<br/>1688). The continuation key 65 is depressed after the unacceptable bill is <br/>removed,<br/>and the discriminator resumes operation without affecting the total value <br/>counter<br/>and/or the individual denomination counters.<br/><br/> CA 02215886 1997-11-06<br/>139<br/>(B) Stranger Mode<br/> Stranger mode is designed to accommodate a stack of bills all having the same<br/>denomination, such as a stack of $10 bills. In such a mode, when a stack of <br/>bills is<br/>processed by the discriminator the denomination of the first bill in the stack <br/>is<br/>determined and subsequent bills are flagged if they are not of the same <br/>denomination.<br/>Alternatively, the discriminator may be designed to permit the operator to <br/>designate<br/>the denomination against which bills will be evaluated with those of a <br/>different<br/>denomination being flagged. Assuming the first bill in a stack determines the<br/>relevant denomination and assuming the first bill is a $10 bill, then provided <br/>all the<br/>bills in the stack are $10 bills, the display 63 will indicate the aggregate <br/>value of the<br/>bills in the stack and/or the number of $10 bills in the stack. However, if a <br/>bill<br/>having a denomination other than $10 is included in the stack, the <br/>discriminator will<br/>stop operating with the non-$10 bill or "stranger bill" being the last bill <br/>deposited in<br/>the output receptacle in the case of the discriminator system 62 of FIG. 56 or <br/>10 of<br/>FIG. 1 (or the inspection station of FIGs. 8 and 9). The stranger bill may <br/>then be<br/>removed from the output receptacle and the discriminator is started again <br/>either<br/>automatically or by depression of the "Continuation" key 6~ depending on the <br/>set up<br/>of the discriminator system. An unidentified but otherwise acceptable $10 bill <br/>may<br/>be handled in a manner similar to that described above in connection with the <br/>mixed<br/>mode, e.g., by depressing the $10 denomination selection element 64c, or<br/>alternatively, the unidentified but otherwise acceptable $10 bill may be <br/>removed from<br/>the output receptacle and placed into the input hopper to be re-scanned. Upon <br/>the<br/>completion of processing the entire stack, the display 63 will indicate the <br/>aggregate<br/>value of the $10 bills in the stack and/or the number of $10 bills in the <br/>stack. All<br/>bills having a denomination other than $10 will have been set aside and will <br/>not be<br/>included in the totals. Alternatively, these stranger bills can be included in <br/>the totals<br/>via operator selection choices. For example, if a $~ stranger bill is detected <br/>and<br/>flagged in a stack of $10 bills, the operator may be prompted via the display <br/>as to<br/>whether the $5 bill should be incorporated into the running totals. If the <br/>operator<br/>responds positively, the $5 bill is incorporated into appropriate running <br/>totals,<br/>otherwise it is not. Alternatively, a set-up selection may be chosen whereby <br/>all<br/>stranger bills are automatically incorporated into appropriate running totals.<br/><br/> CA 02215886 1997-11-06<br/>140<br/>~C) Sort Mode<br/> Sort mode is designed to accommodate a stack of bills wherein the bills are<br/>separated by denomination. For example, all the $1 bills may be placed at the<br/>beginning of the stack, followed by all the $5 bills, followed by all the $10 <br/>bills, etc.<br/>The operation of the sort mode is similar to that of the stranger mode except <br/>that<br/>after stopping upon the detection of a different denomination bill, the <br/>discriminator is<br/>designed to resume operation upon removal of all bills from the output <br/>receptacle.<br/>Returning to the above example, assuming the first bill in a stack determines <br/>the<br/>relevant denomination and assuming the first bill is a $1 bill, then the <br/>discriminator<br/>processes the bills in the stack until the first non-$1 bill is detected, <br/>which in this<br/>example is the first $5 bill. At that point, the discriminator will stop <br/>operating with<br/>the first $5 being the last bill deposited in the output receptacle. The <br/>display 63 may<br/>be designed to indicate the aggregate value of the preceding $1 bills <br/>processed and/or<br/>the number of preceding $1 bills. The scanned $1 bills and the first $5 bill <br/>are<br/>removed from the output receptacle and placed in separate $1 and $5 bill <br/>stacks. The<br/>discriminator will start again automatically and subsequent bills will be <br/>assessed<br/>relative to being $5 bills. The discriminator continues processing bills until <br/>the first<br/>$10 bill is encountered. The above procedure is repeated and the discriminator<br/>resumes operation until encountering the first bill which is not a $10 bill, <br/>and so on.<br/>Upon the completion of processing the entire stack, the display 63 will <br/>indicate the<br/>aggregate value of all the bills in the stack and/or the number of bills of <br/>each<br/>denomination in the stack. This mode permits the operator to separate a stack <br/>of bills<br/>having multiple denominations into separate stacks according to denomination.<br/>(D) Face Mode<br/> Face mode is designed to accommodate a stack of bills all faced in the same<br/>direction, e.g., all placed in the input hopper face up (that is the portrait <br/>or black<br/>side up for U.S. bills) and to detect any bills facing the opposite direction. <br/>In such a<br/>mode, when a stack of bills is processed by the discriminator, the face <br/>orientation of<br/>the first bill in the stack is determined and subsequent bills are flagged if <br/>they do not<br/>have the same face orientation. Alternatively, the discriminator may be <br/>designed to<br/>permit designation of the face orientation to which bills will be evaluated <br/>with those<br/><br/> CA 02215886 1997-11-06<br/>141<br/>having a different face orientation being flagged. Assuming the first bill in <br/>a stack<br/>determines the relevant face orientation and assuming the first bill is face <br/>up, then<br/>provided all the bills in the stack are face up, the display 63 will indicate <br/>the<br/>aggregate value of the bills in the stack and/or the number of bills of each<br/>denomination in the stack. However, if a bill faced in the opposite direction <br/>(i.e.,<br/>face down in this exampie) is included in the stack, the discriminator will <br/>stop<br/>operating with the reverse-faced bill being the last bill deposited in the <br/>output<br/>receptacle. The reverse-faced bill then may be removed from the output <br/>receptacle.<br/>In automatic re-start embodiments, the removal of the reverse-faced bill <br/>causes the<br/>discriminator to continue operating. The removed bill may then be placed into <br/>the<br/>input receptacle with the proper face orientation. Alternatively, in non-<br/>automatic re-<br/>start embodiments, the reverse-faced bill may be either placed into the input<br/>receptacle with the proper face orientation and the continuation key 65 <br/>depressed, or<br/>placed back into the output receptacle with the proper face orientation. <br/>Depending on<br/>1~ the set up of the discriminator when a bill is placed back into the output <br/>receptacle<br/>with the proper face orientation, the denomination selection key associated <br/>with the<br/>reverse-faced bill may be selected, whereby the associated denomination <br/>counter<br/>and/or aggregate value counter are appropriately incremented and the <br/>discriminator<br/>resumes operation. Alternatively, in embodiments wherein the discriminator is<br/>capable of determining denomination regardless of face orientation, the <br/>continuation<br/>key 65 or a third key may be depressed whereby the discriminator resumes <br/>operation<br/>and the appropriate denomination counter and/or total value counter is <br/>incremented in<br/>accordance with the denomination identified by the discriminating unit. In<br/>discriminators that require a specific face orientation, any reverse-faced <br/>bills will be<br/>unidentified bills. In discriminators that can accept a bill regardless of <br/>face<br/>orientation, reverse-faced bills may be properly identified. The later type of<br/>discriminator may have a discriminating unit with a scanhead on each side of <br/>the<br/>transport path. Examples of such dual-sided discriminators are disclosed above <br/>(see<br/>e.g., FIGs. 2a, 6c, 20a, 26, and 42. The ability to detect and correct for <br/>reverse-<br/>faced bills is important as the Federal Reserve requires currency it receives <br/>to be<br/>faced in the same direction.<br/><br/> CA 02215886 1997-11-06<br/>142<br/>In a mufti-output receptacle discriminator, the face mode may be used to route<br/>all bills facing upward to one output receptacle and all bills facing downward <br/>to<br/>another output receptacle. In single-sided discriminators, reverse-faced bills <br/>may be<br/>routed to an inspection station such as i 690 of FIG. 5'~ for manual turnover <br/>by the<br/>operator and the unidentified reverse-faced bills may then be passed by the<br/>discriminator again. In dual-sided discriminators, identified reverse-faced <br/>bills may<br/>be routed directly to an appropriate output receptacle. For example, in dual-<br/>sided<br/>discriminators bills may be sorted both by face orientation and by <br/>denomination, e.g.,<br/>face up $1 bills into pocket #1, face down $1 bills into pocket #2, face up $5 <br/>bills<br/>into pocket #3, and so on or simply by denomination, regardless of face <br/>orientation,<br/>e.g., all $1 bills into pocket #1 regardless of face orientation, all $2 bills <br/>into pocket<br/>#2, etc.<br/>(E) Forward/Reverse Orientation Mode<br/> Forward/Reverse Orientation mode ("Orientation" mode) is designed to<br/>accommodate a stack of bills all oriented in a predetermined forward or <br/>reverse<br/>orientation direction. For example in a discriminator that feeds bills along <br/>their<br/>narrow dimension, the forward direction may be defined as the fed direction <br/>whereby<br/>the top edge of a bill is fed first and conversely for the reverse direction. <br/>In a<br/>discriminator that feeds bills along their long dimension, the forward <br/>direction may<br/>be defined as the fed direction whereby the left edge of a bill is fed first <br/>and<br/>conversely for the reverse direction. In such a mode, when a stack of bills is<br/>processed by the discriminator, the forward/reverse orientation of the first <br/>bill in the<br/>stack is determined and subsequent bills are flagged if they do not have the <br/>same<br/>forward/reverse orientation. Alternatively, the discriminator may be designed <br/>to<br/>permit the operator to designate the forward/reverse orientation against which <br/>bills<br/>will be evaluated with those having a different forward/reverse orientation <br/>being<br/>flagged. Assuming the first bill in a stack determines the relevant <br/>forwardlreverse<br/>orientation and assuming the first bill is fed in the forward direction, then <br/>provided<br/>all the bills in the stack are also fed in the forward direction, the display <br/>63 will<br/>indicate the aggregate value of the bills in the stack and/or the number of <br/>bills of<br/>each denomination in the stack. However, if a bill having the opposite<br/><br/> CA 02215886 1997-11-06<br/>143<br/>forward/reverse orientation is included in the stack, the discriminator will <br/>stop<br/>operating with the opposite forward/reverse oriented bill being the last bill <br/>deposited<br/>in the output receptacle. The opposite forward/reverse oriented bill then may <br/>be<br/>removed from the output receptacle. In automatic re-start embodiments, the <br/>removal<br/>of the opposite forward/reverse oriented bill causes the discriminator to <br/>continue<br/>operating. The removed bill may then be placed into the input receptacle with <br/>the<br/>proper face orientation. Alternatively, in non-automatic re-start embodiments, <br/>the<br/>opposite forward/reverse oriented bill may be either placed into the input <br/>receptacle<br/>with the proper forward/reverse orientation and the continuation key 65 <br/>depressed, or<br/>placed back into the output receptacle with the proper forward/reverse <br/>orientation.<br/>Depending on the set up of the discriminator when a bill is placed back into <br/>the<br/>output receptacle with the proper forward/reverse orientation, the <br/>denomination<br/>selection key associated with the opposite forward/reverse oriented bill may <br/>be<br/>selected, whereby the associated denomination counter and/or aggregate value <br/>counter<br/>i5 are appropriately incremented and the discriminator resumes operation.<br/>Alternatively, in embodiments wherein the discriminator is capable of <br/>determining<br/>denomination regardless of forwardlreverse orientation, the continuation key <br/>65 or a<br/>the third key may be depressed whereby the discriminator resumes operation and <br/>the<br/>appropriate denomination counter and/or total value counter is incremented in<br/>accordance with the denomination identified by the discriminating unit. In <br/>single-<br/>direction discriminators, any reverse-oriented bills will be unidentified <br/>bills. In dual-<br/>direction discriminators, reverse-oriented bills may be properly identified by <br/>the<br/>discriminating unit. An example of a dual-direction discriminating system is<br/>described above connection with FIGS. 1-7b and in United States Pat. No. <br/>5,295,196.<br/>The ability to detect and correct for reverse-oriented bills is important as <br/>the Federal<br/> Reserve may soon require currency it receives to be oriented in the same<br/>forward/reverse direction.<br/> In a mufti-output receptacle discriminator, the orientation mode may be used<br/>to route all bills oriented in the forward direction to one output receptacle <br/>and all<br/>bills oriented in the reverse direction to another output receptacle. In <br/>single-direction<br/>discriminators, reverse-oriented bills may be routed to an inspection station <br/>such as<br/>1690 of FIG. 57 for manual turnover by the operator and the unidentified <br/>reverse-<br/><br/> CA 02215886 1997-11-06<br/>1~<br/>oriented bills may then be passed by the discriminator again. In <br/>discriminators<br/>capable of identifying bills fed in both forward and reverse directions ("dual-<br/>direction<br/>discriminators"), identified reverse-oriented bills may be routed directly to <br/>an<br/>appropriate output receptacle. For example, in dual-direction discriminators <br/>bills<br/>may be sorted both by forward/reverse orientation and by denomination, e.g.,<br/>forward $1 bills into pocket #l, reverse $1 bills into pocket #2, forward $5 <br/>bills into<br/>pocket #3, and so on or simply by denomination, regardless of forward/reverse<br/>orientation, e.g., all $1 bills into pocket #1 regardless of forward/reverse <br/>orientation,<br/>all S2 bills into pocket #2, etc.<br/> Suspect Mode<br/> In addition to the above modes, a suspect mode may be activated in<br/>connection with these modes whereby one or more authentication tests may be<br/>performed on the bills in a stack. When a bill fails an authentication test, <br/>the<br/>discriminator will stop with the failing or suspect bill being the last bill <br/>transported to<br/>1~ the output receptacle. The suspect bill then rnay be removed from the <br/>output<br/>receptacle and set aside.<br/> Likewise, one or more of the above described modes may be activated at the<br/>same time. For example, the face mode and the forward/reverse orientation mode<br/>may be activated at the same time. In such a case, bills that are either <br/>reverse-faced<br/>or opposite forward/reverse oriented will be flagged.<br/> According to a preferred embodiment, when a bill is flagged, for example, by<br/>stopping the transport motor with the flagged bill being the Last bill <br/>deposited in the<br/>output receptacle, the discriminating device indicates to the operator when <br/>the bill<br/>was flagged. This indication may be accomplished by, for example, Lighting an<br/>appropriate light, generating an appropriate sound, and/or displaying an <br/>appropriate<br/>message in the display section 63 (FIG. 59). Such indication might include, <br/>for<br/>example, "no call", "stranger", "failed magnetic test", "failed UV test", "no <br/>security<br/>thread", etc.<br/> Referring now to FIGs. 60a-60c, there is shown a side view of a preferred<br/>embodiment of a document authenticating system according to the present <br/>invention,<br/>a top view of the preferred embodiment of FIG. 60a along the direction 60b, <br/>and a<br/><br/> CA 02215886 1997-11-06<br/>r<br/>145<br/>top view of the preferred embodiment of FIG. 60a along the direction 60c,<br/>respectively. An ultraviolet ("UV") light source 2102 illuminates a document <br/>2104.<br/>Depending upon the characteristics of the document, ultraviolet light may be <br/>reflected<br/>off the document and/or fluorescent light may be emitted from the document. A<br/>detection system 2106 is positioned so as to receive any light reflected or <br/>emitted<br/>toward it but not to receive any UV light directly from the light source 2102. <br/>The<br/>detection system 2106 comprises a UV sensor 2108, a fluorescence sensor 21 i0,<br/>filters, and a plastic housing. The light source 2102 and the detection system <br/>2106<br/>are both mounted to a printed circuit board 2112. The document 2104 is <br/>transported<br/>in the direction indicated by arrow A by a transport system (not shown). The<br/>document is transported over a transport plate 2114 which has a rectangular <br/>opening<br/>2116 in it to permit passage of light to and from the document. In a preferred<br/>embodiment of the present invention, the rectangular opening 2116 is 1.375 <br/>inches<br/>(3.493 cm) by 0.375 inches (0.953 cm). To minimize dust accumulation onto the<br/>light source 2102 and the detection system 2106 and to prevent document jams, <br/>the<br/>opening 2116 is covered with a transparent UV transmitting acrylic window <br/>2118.<br/>To further reduce dust accumulation, the UV light source 2102 and the <br/>detection<br/>system 2106 are completely enclosed within a housing (not shown) comprising <br/>the<br/>transport plate 2114.<br/> Referring now to FIG. 61, there is shown a functional block diagram<br/>illustrating a preferred embodiment of a document authenticating system <br/>according to<br/>the present invention. FIG. 61 shows an UV sensor 2202, a fluorescence sensor<br/>2204, and filters 2206, 2208 of a detection system such as the detection <br/>system 2106<br/>of FIG. 60. Light from the document passes through the filters 2206, 2208 <br/>before<br/>striking the sensors 2202, 2204, respectively. An ultraviolet filter 2206 <br/>filters out<br/>visible light and permits UV light to be transmitted and hence to strike UV <br/>sensor<br/>2202. Similarly, a visible light filter 2208 filters out UV light and permits <br/>visible<br/>light to be transmitted and hence to strike fluorescence sensor 2204. <br/>Accordingly,<br/> UV light, which has a wavelength below 400 nm, is prevented from striking the<br/>fluorescence sensor 2204 and visible light, which has a wavelength greater <br/>than 400<br/>nm, is prevented from striking the UV sensor 2202. In a preferred embodiment <br/>the<br/>UV filter 2206 transmits light having a wavelength between about 260 nm and <br/>about<br/><br/> CA 02215886 1997-11-06<br/>146<br/>380 nm and has a peak transmittattce at 360 nm. In a preferred embodiment, the<br/>visible light filter 2208 is a blue filter and preferably transmits light <br/>having a<br/>wavelength between about 415 nm and about 620 nm and has a peak transmittance <br/>at<br/>450 nm. The above preferred blue filter comprises a combination of a blue<br/>component filter and a yellow component filter. The blue component filter <br/>transmits<br/>light having a wavelength between about 320 nm and about 620 nm and has a peak<br/>transmittance at 450 nm. The yellow component filter transmits light having a<br/>wavelength between about 415 nm and about 2800 nm. Examples of suitable <br/>filters<br/>are UG1 (UV filter), BG23 (blue bandpass filter), and GG420 (yellow longpass<br/>filter), all manufactured by Schott. In a preferred embodiment the filters are <br/>about 8<br/>mm in diameter and about 1.5 mm thick.<br/> The UV sensor 2202 outputs an analog signal proportional to the amount of<br/>light incident thereon and this signal is amplified by amplifier 2210 and fed <br/>to a<br/>microcontroller 2212. Similarly, the fluorescence sensor 2204 outputs an <br/>analog<br/>signal proportional to the amount of light incident thereon and this signal is <br/>amplified<br/>by amplifier 2214 and fed to a microcontroller 2212. Analog-to-digital <br/>converters<br/>2216 within the microcontroller 2212 convert the signals from the amplifiers <br/>2210,<br/>2214 to digital and these digital signals are processed by the software of the<br/>microcontroller 2212. The UV sensor 2202 may be, for example, an ultraviolet<br/>enhanced photodiode sensitive to light having a wavelength of about 360 nm and <br/>the<br/>fluorescence sensor 2204 may be a blue enhanced photodiode sensitive to light <br/>having<br/>a wavelength of about 450 nm. Such photodiodes are available from, for <br/>example,<br/> Advanced Photonix, Inc., Massachusetts. The microcontroller 2212 may be, for<br/>example, a Motorola 68HC16.<br/>The exact characteristics of the sensors 2202, 2204 and the filters 2206, 2208<br/>including the wavelength transmittance ranges of the above filters are not as <br/>critical<br/>to the present invention as the prevention of the fluorescence sensor from <br/>generating<br/>an output signal in response to ultraviolet light and the ultraviolet sensor <br/>from<br/>generating an output signal in response to visible light. For example, instead <br/>of, or<br/>in addition to, filters, a authentication system according to the present <br/>invention may<br/>employ an ultraviolet sensor which is not responsive to light having a <br/>wavelength<br/><br/> CA 02215886 1997-11-06<br/>147<br/>longer than 400 nm and/or a fluorescence sensor which is not responsive to <br/>light<br/>having a wavelength shorter than 400 nm.<br/> Calibration potentiometers 2218, 2220 permit the gains of amplifiers 2210,<br/>2214 to be adjusted to appropriate levels. Calibration may be performed by<br/>positioning a piece of white fluorescent paper on the transport plate 2114 so <br/>that it<br/>completely covers the rectangular opening 2116 of FiG. 60. The potentiometers<br/>2218, 2220 may then be adjusted so that the output of the amplifiers 2210, <br/>2214 is 5<br/>volts.<br/> The implementation of the preferred embodiment of a document authenticating<br/>system according to the present invention as illustrated in FIG. 61 with <br/>respect to the<br/>authentication of U.S. currency will now be described. As discussed above, it <br/>has<br/>been determined that genuine United States currency reflects a high level of<br/>ultraviolet light and does not fluoresce under ultraviolet illumination. It <br/>has also been<br/>determined that under ultraviolet illumination counterfeit United States <br/>currency<br/>exhibits one of the four sets of characteristics listed below:<br/>1) Reflects a low level of ultraviolet light and fluoresces;<br/>2) Reflects a low level of ultraviolet light and does not fluoresce;<br/>3) Reflects a high level of ultraviolet light and fluoresces;<br/>4) Reflects a high level of ultraviolet light and does not fluoresce.<br/>Counterfeit bills in categories (1) and (2) may be detected by a currency <br/>authenticator<br/>employing an ultraviolet light reflection test according to a preferred <br/>embodiment of<br/>the present invention. Counterfeit bills in category (3) may be detected by a <br/>currency<br/>authenticator employing both an ultraviolet reflection test and a fluorescence <br/>test<br/>according to another preferred embodiment of the present invention. Only<br/>counterfeits in category (4) are not detected by the authenticating methods of <br/>the<br/>present invention.<br/> According to a preferred embodiment of the present invention, fluorescence is<br/>determined by any signal that is above the noise floor. Thus, the amplified<br/>fluorescent sensor signal 2222 will be approximately 0 volts for genuine U.S.<br/>currency and will vary between approximately 0 and 5 volts for counterfeit <br/>bills<br/>depending upon their fluorescent characteristics. Accordingly, an <br/>authenticating<br/><br/> CA 02215886 1997-11-06<br/>148<br/>system according to a preferred embodiment of the present invention will <br/>reject bills<br/>when signal 2222 exceeds approximately 0 volts.<br/> According to a preferred embodiment of the present invention, a high level of<br/>reflected UV light ("high UV") is indicated when the amplified UV sensor <br/>signal<br/>2224 is above a predetermined threshold. The high/low UV threshold is a <br/>function<br/>of lamp intensity and reflectance. Lamp intensity can degrade by as much as <br/>50%<br/>over the life of the lamp and can be further attenuated by dust accumulation <br/>on the<br/>lamp and the sensors. The problem of dust accumulation is mitigated by <br/>enclosing<br/>the lamp and sensors in a housing as discussed above. An authenticating system<br/>according to a preferred embodiment of the present invention tracks the <br/>intensity of<br/>the LV light source and readjusts the high/low threshold accordingly. The<br/>degradation of the UV light source may be compensated for by periodically <br/>feeding a<br/>genuine bill into the system, Sampling the output of the UV sensor, and <br/>adjusting the<br/>threshold accordingly. Alternatively, degradation may be compensated for by<br/>periodically sampling the output of the UV sensor when no bill is present in <br/>the<br/>rectangular opening 2116 of the transport plate 2114. it is noted that a <br/>certain<br/>amount of UV light is always reflected off the acrylic window 2118. By <br/>periodically<br/>sampling the output of the LTV sensor when no bill is present, the system can<br/>compensate for light source degradation. Furthermore, such sampling could also <br/>be<br/>used to indicate to the operator of the system when the ultraviolet light <br/>source has<br/>burned out or otherwise requires replacement. This may be accomplished, for<br/>example, by means of a display reading or an illuminated light emitting diode<br/>("LED"). The amplified ultraviolet sensor signal 2224 will initially vary <br/>between 1.0<br/>and 5.0 volts depending upon the UV reflectance characteristics of the <br/>document<br/>being scanned and will slowly drift downward as the light source degrades. In <br/>an<br/>alternative preferred embodiment to a preferred embodiment wherein the <br/>threshold<br/>level is adjusted as the light source degrades, the sampling of the UV sensor <br/>output<br/>may be used to adjust the gain of the amplifier 2210 thereby maintaining the <br/>output<br/>of the amplifier 2210 at its initial levels.<br/> It has been found that the voltage ratio between counterfeit and genuine U.S.<br/>bills varies from a discernible 2-to-1 ratio to a non-discernible ratio. <br/>According to a<br/>preferred embodiment of the present invention a 2-to-1 ratio is used to <br/>discriminate<br/><br/> CA 02215886 2000-02-02<br/>149<br/>between genuine and counterfeit bills. For example, if a genuine U.S. bill <br/>generates<br/>an amplified UV output sensor signal 2224 of 4.0 volts, documents generating <br/>an<br/>amplified UV output sensor signal 2224 of 2.0 volts or less will be rejected <br/>as<br/>counterfeit. As described above, this threshold of 2.0 volts may either be <br/>lowered as<br/>the light source degrades or the gain of the amplifier 2210 may be adjusted so <br/>that<br/>2.0 volts remains an appropriate threshold value.<br/> According to a preferred embodiment of the present invention, the<br/>determination of whether the level of UV reflected off a document is high or <br/>low is<br/>made by sampling the output of the UV sensor at a number of intervals, <br/>averaging<br/>the readings, and comparing the average level with the predetermined high/low<br/>threshold. Alternatively, a comparison may be made by measuring the amount of<br/> UV light reflected at a number of locations on the bill and comparing these<br/>measurements with those obtained from genuine bills. Alternatively, the output <br/>of<br/>one or more UV sensors may be processed to generate one or more patterns of<br/>reflected UV light and these patterns may be compared to the patterns <br/>generated by<br/>genuine bills. Such a pattern generation and comparison technique may be <br/>performed<br/>by modifying an optical pattern technique such as that disclosed in United <br/>States Pat.<br/>No. 5,295,196 or in the United States Patent No. 5,652,802 issued July 29, <br/>1997 for a<br/>"Method and Apparatus for Document Identification."<br/> In a similar manner, the presence of fluorescence may be,.performed by<br/>sampling the output of the fluorescence sensor at a number of intervals. <br/>However, in<br/>a preferred embodiment, a bill is rejected as counterfeit U.S. currency if any <br/>of the<br/>sampled outputs rise above the noise floor. However, the alternative methods<br/>discussed above with respect to processing the signal or signals of a UV <br/>sensor or<br/>sensors may also be employed, especially with respect to currencies of other<br/>countries or other types of documents which may employ as security features <br/>certain<br/>locations or patterns of fluorescent materials.<br/> A currency authenticating system according to the present invention may be<br/>provided with means, such as a display, to indicate to the operator the <br/>reasons why a<br/>document has been rejected, e.g. , messages such as "UV FAILURE" or<br/><br/> CA 02215886 1997-11-06<br/>150<br/>"FLUORESCENCE FAILURE." A currency authenticating system according to the<br/>present invention may also permit the operator to selectively choose to <br/>activate or<br/>deactivate either the UV reflection test or the fluorescence test or both. A <br/>currency<br/>authenticating system according to the present invention may also be provided <br/>with<br/>means for adjusting the sensitivities of the UV reflection and/or fluorescence <br/>test, for<br/>example, by adjusting the respective thresholds. For example, in the case of <br/>U.S.<br/>currency, a system according to the present invention may permit the high/low<br/>threshold to be adjusted, for example, either in absolute voltage terms or in<br/>genuine/suspect ratio terms.<br/>
