US20080252619A1 - System for Providing a Frustrated Total Internal Reflection Touch Interface - Google Patents

Abstract

A system for providing a touch interface on a display are described. The system include providing an emitter on a first side of the display and providing a detector on a second side of the display. The emitter provides an electromagnetic signal to the display. The electromagnetic signal has a path from the emitter to the detector through the display in the absence of a user's touch such that the electromagnetic signal is detected by the detector in the absence of the user's touch. The path includes at least one total internal reflection in the display. The emitter and the detector are configured such that the user's touch at any of the at least one total internal reflection alters the path such that a portion of the electromagnetic signal does not reach the detector.

Description

• Under 35 USC §120, this application is a continuation application and claims the benefit of priority to U.S. patent application Ser. No. 10/991,668 filed Nov. 17, 2004, entitled “Method for Providing a Frustrated Total Internal Reflection Touch Interface”, all of which is incorporated herein by reference.
FIELD OF THE INVENTION
• The present invention relates to computer system interfaces and more particularly to a system for providing a touch interface using frustrated total internal reflection as a detection mechanism.
BACKGROUND OF THE INVENTION
• Touch interfaces are used in a variety of computer systems.FIG. 1A depicts a side view of a portion of aconventional touch interface10 in the absence of a user's touch. Theconventional touch interface10 includes ascreen20,emitter30, anddetector40. Although only oneemitter30 and onedetector40 are depicted, theconventional touch interface10 typically includes emitters on first and second sides of thescreen20 and corresponding detectors on the third and fourth sides of thescreen20 that are opposite to the first and second sides, respectively.
• In operation, theemitter30 emits an electromagnetic signal that is typically an infrared signal. The infrared signal follows thepath50 to thedetector40 in the absence of a user's touch. When a user is not touching thescreen20, thedetector40 detects the infrared signal. Thus, infrared signals between the emitters and detectors form a grid over thescreen50 when a user is not touching thescreen20.
• FIG. 1B depicts theconventional touch interface10 when a user touches thescreen20. When the user touches thescreen20, thepath50 of the infrared signal is changed to thepath50′. Thus, becausepath50′ does not reach thedetector40, the infrared signal does not reach thedetector40. As a result, the user's touch is detected. A touch that interrupts any of the infrared signals between the emitter and detector pairs will be detected. Thus, theconventional touch interface10 allows the user to interact with the computer system employing theconventional touch interface10.
• Referring toFIGS. 1A and 1B, although theconventional touch interface10 functions, one of ordinary skill in the art will readily recognize that theconventional touch interface10 is subject to detecting false positives for unintentional touches. Unintentional touches occur when items other than a user touch the screen. Unintentional touches can interrupt thepath50 between theemitter30 anddetector40. For example, items other than the user depicted inFIG. 1B can result in thepath50′ that does not reach thedetector40. For example, clothing such as ties, flies, or other items touching thescreen20 result in thepath50′. Consequently, theconventional touch interface10 detects such unintentional touches, resulting in false positives for the unintentional touches.
• Accordingly, what is needed is a mechanism for providing a touch interface that reduces the false positives that are detected. The present invention addresses such a need.
BRIEF SUMMARY OF THE INVENTION
• The present invention provides a system for providing a touch interface on a display. The system comprise providing an emitter on a first side of the display and providing a detector on a second side of the display. The emitter provides an electromagnetic signal to the display cover. The transparent display cover is of sufficient density and thickness to create the conditions required for total internal reflection. The electromagnetic signal has an internally reflected path from the emitter to the detector through the transparent display cover in the absence of a user's touch such that the electromagnetic signal is detected by the detector in the absence of the user's touch. The emitter and the detector are configured such that the user's touch on the transparent cover frustrates the total internal reflection path reducing the portion of the electromagnetic signal that reaches the detector. A loss of transferred electromagnetic energy from the emitter to the detector below a specified threshold is perceived as a valid touch.
• According to the system disclosed herein, the present invention provides a touch interface which is sensitive to the user's touch, and results in reduced false positives due to unintentional touches.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
• FIG. 1A is a diagram depicting a side view of a portion of a conventional touch interface when a user is not touching the screen.
• FIG. 1B is a diagram depicting a side view of a portion of a conventional touch interface when a user is touching the screen.
• FIG. 2 is a diagram depicting a top view of a portion of one embodiment of a touch interface in accordance with the present invention when a user is not touching the display.
• FIG. 3A is a diagram depicting a side view of a portion of one embodiment of a touch interface in accordance with the present invention when a user is not touching the display.
• FIG. 3B is a diagram depicting a side view of a portion of a one embodiment of touch interface in accordance with the present invention when a user is touching the display.
• FIG. 4 is a diagram depicting a side view of a portion of another embodiment of a touch interface in accordance with the present invention when a user is not touching the display.
• FIG. 5 is a diagram depicting one embodiment in accordance with the present invention for providing a touch interface.
DETAILED DESCRIPTION OF THE INVENTION
• The present invention relates to touch interfaces. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiments and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein.
• The present invention provides a system for providing a touch interface on a display. The system comprises providing an emitter on a first side of the display and providing a detector on a second side of the display. The emitter provides an electromagnetic signal to the display. The electromagnetic signal has a path from the emitter to the detector through the transparent cover of the display in the absence of a user's touch such that the electromagnetic signal is detected by the detector in the absence of the user's touch. The path includes total internal reflections in the display. The path does not include any non reflected energy such as energy that does not travel through the transparent cover as well as straight through or zero mode paths. The emitter and the detector are configured such that the user's touch on the transparent cover frustrates the total internal reflection such that it reduces the portion of the electromagnetic signal that reaches the detector below the detection threshold.
• The present invention will be described in terms of a particular touch interface using certain emitters and detectors in particular positions. However, one of ordinary skill in the art will readily recognize that the method and system can be utilized for other touch interfaces not inconsistent with the present invention. Furthermore, although the present invention is described in the context of particular computer system, nothing prevents the method and system from being used in conjunction with other computer systems.
• FIG. 2 is a diagram depicting a top view of a portion of atouch interface100 in accordance with the present invention when a user is not touching the display. Thetouch interface100 includes adisplay110,emitters120, anddetectors130. Thedisplay110 is termed a display because the user preferably views images depicted by the system with which thetouch interface100 is used through thedisplay100. However, note that in one embodiment, described below, thedisplay110 is placed on top of a screen that is already in place. The electromagnetic signals from theemitters120 to thedetectors130 havepaths150 forming a grid across thedisplay110. Note, however, that for clarity only two of thepaths150 are marked inFIG. 2. In a preferred embodiment, the electromagnetic signals are infrared signals. However, in another embodiment, another type of signal might be used. Further, although thepaths150 are depicted as lines inFIG. 2, the paths can be considered to have a finite width.
• Theemitters120 anddetectors130 are arranged such that a user's touch on any portion of interest on thedisplay110 can be detected. Thus, the spaces between thepaths150 should be small enough that a user's finger touching thedisplay110 always contacts at least part of one of the electromagnetic signals. However, the paths are also sufficiently separated that the user's touch results in a sufficient reduction of signal to be detectable. Also in a preferred embodiment, only one pair of emitters120-detectors130 are active at any one time. As a result, components may be placed in very close proximity without resulting in issues due to interference. Stated differently, time domain multiplexing or scanning is preferably employed. In a preferred embodiment, theemitters120 anddetectors130 are placed such that the paths are one to one and one half centimeters apart. However, in another embodiment, the electromagnetic signals may be separated by a different distance. In addition, although thepaths150 are depicted as forming a rectangular grid between opposing sides of thedisplay110 is depicted inFIG. 2, nothing prevents another arrangement of theemitters120 anddetectors130. Further, although a particular number ofemitters120 anddetectors130 are shown for clarity, nothing prevents the use of another number ofdetectors130 and/or emitters.
• FIG. 3A depicts a side view of one embodiment of thetouch interface100 in accordance with the present invention when a user is not touching thedisplay110. Referring toFIGS. 2 and 3A, anemitter120 and acorresponding detector130 are depicted, as well as thepath150 between theemitter120 anddetector130 for the electromagnetic signal. Also depicted inFIGS. 3A and 3B arebarriers140 and142. Although not shown inFIG. 2, eachemitter120 anddetector130 preferably has acorresponding barrier140 and142, respectively.
• As can be seen inFIG. 3A, the electromagnetic signal travels between theemitter120 and thedetector130. Thepath150 traveled by the electromagnetic signal between theemitter120 anddetector130 includes one or more totalinternal reflection152,154, and156 at theupper surface112 and/or lower114 surfaces of thedisplay110. For total internal reflection to occur, the index of refraction outside of thedisplay110 where the totalinternal reflection152,154, or156 occurs is lower than the index of refraction of thedisplay110. The angle of reflection depends upon the ratio of the index of refraction of thedisplay110 and the index of refraction of the region outside of thedisplay110. In a preferred embodiment, air surrounds thedisplay110 at its upper andlower surfaces112 and114, respectively. However, in another embodiment, different materials could surround theupper surface112 and/orlower surface114 of thedisplay110 as long as any of the surrounding material(s) have an index of refraction lower than that of thedisplay110. As can be seen by thepath150, in the absence of a user's touch, the electromagnetic signal from theemitter120 travels to and is, therefore, detected by thedetector130.
• As discussed above, thepath150 traveled by the electromagnetic signal includes at least one total internal reflection, such as the totalinternal reflections152,154, and156. Thebarriers140 and142 prevent the zeroth mode (unreflected) path for the electromagnetic signals from traveling between theemitter120 anddetector130. Consequently, the electromagnetic signal following thepath150 to thedetector130 from theemitter120 is the portion of the electromagnetic signal that is both output by theemitter120 and not blocked by either thebarrier140 or142. Stated differently, thebarriers140 and142 ensure that only the electromagnetic signal undergoing at least one total internal reflection might reach thedetector130.
• FIG. 3B depicts the embodiment of thetouch interface100 in accordance with the present invention when a user is touching thedisplay110. Thus, the situation depicted inFIG. 3B results in a touch being detected by thetouch interface100. Referring toFIGS. 2 and 3B, because the user is touching theupper surface112 of thedisplay110 atregion116, a portion of the electromagnetic signal is transmitted and subsequently scattered or absorbed at theregion116. This is exemplified byreflection154′. Thus, thepath150′ is altered such that a portion of the electromagnetic signal does not reach thedetector130. Instead, the portion of the electromagnetic signal reflecting at theregion116 is transmitted, subsequently scattered or absorbed, and may exit thedisplay110 in a different region, for example at thelower surface114.
• Thus, the portion of the electromagnetic signal that undergoes totalinternal reflection154′ at theregion116 will no longer reach thedetector130. Consequently, the electromagnetic signal at thedetector130 decreases to levels low enough that the user's touch is detected. Thus, the user's touch is detected.
• In one embodiment, thedetector130 is configured such that when the remaining portion of the electromagnetic signal (if any) reaching thedetector130 along thepath150′ is at or below a particular threshold, thedetector130 indicates that no electromagnetic signal has been received. In such an embodiment, an output signal from thedetector130 indicating that no electromagnetic signal has been detected corresponds to a user's touch. In an alternate embodiment, thedetector130 may simply provide an output signal proportional to the amount of electromagnetic signal detected. In such an embodiment, thedetector130 may be coupled to component(s) (not shown) that compare the output signal of thedetector130 to another threshold. If the output signal is at or below this threshold, it is indicated that the user has touched the display. Furthermore, becausemultiple emitters120 anddetectors130 are used, a touch at any portion of interest of thedisplay110 can be detected by thetouch interface100.
• Thus, thetouch interface100 detects the user's touch when thepath150′ is altered such that at least the portion of the electromagnetic signal does not reach the detector. Further, an inadvertent touch, such as by a piece of clothing or a fly, may not result in detection of a false positive by thetouch interface100. For such an inadvertent touch, the reduction in the electromagnetic signal reaching thedetector130 may be small enough that the inadvertent touch is not detected. In particular, the change in the index of refraction outside of the display due to the inadvertent touch may be insufficient or occur over a small enough area that any change in the angle of reflection is small. Consequently, a large portion of the electromagnetic signal still reaches thedetector130. This large portion of the electromagnetic signal is sufficient that no false positive occurs. Thus, thetouch interface100 not only functions, but may also result in fewer false positive detections due to inadvertent touches.
• FIG. 4 is a diagram depicting a side view of a portion of another embodiment of atouch interface100′ in accordance with the present invention when a user is not touching the display. Thetouch interface100′ is analogous to thetouch interface100. Consequently, similar components are labeled in an analogous fashion. Thus, thetouch interface100′ includes adisplay110′ having atop surface112′ and abottom surface114′,emitter120′,detector130′,barriers140′ and142′, as well as an electromagnetic signal having apath150″ and totalinternal reflections152′,154″, and156′. Note however, that thedisplay110′ has been placed over aconventional screen170 and is separated from thescreen170 byspacers172 and174. In a preferred embodiment, thespacers172 and174 are merely double-stick tape. Thus, thespacers172 and174 preferably serve the dual purpose of separating thedisplay110′ from thescreen170 and affixing thedisplay110′ in place. Thetouch interface100′ may, therefore, be formed simply by adding thedisplay110′,spacers172 and174, andbarriers140′ and142′ to a conventional system already havingemitters120′ anddetectors130′. Thespacers172 and174 ensure that a gap exists between thedisplay110′ and thescreen170. Thus, thespacers172 and174 ensure that the index of refraction of the material adjacent to thebottom surface114′ of thedisplay110′ is less than the index of refraction of thedisplay110′.
• In addition, thedisplay110′ includes bevelededges118 and119. Thebeveled edges118 and119 are shaped to refract the signal passing through thedisplay110 such that a greater portion of the electromagnetic signal travels through the desiredpaths150′. Note that although a particular shape of thebeveled edges118 and119 is depicted inFIG. 4, nothing prevents the use of another shape that can focus the power in the electromagnetic signal to the desired paths. Furthermore, nothing prevents the use of thebeveled edges118 and119 from being used in another embodiment, such as thetouch interface100.
• Thetouch interface100′ functions in analogous manner to thetouch interface100 and has many of the same advantages including less likely detection of inadvertent touches. Furthermore, thetouch interface100′ may be relatively simply and inexpensive to implement. Thetouch interface100′ may also be added to conventional systems, allowing conventional touch interfaces to be upgraded without incurring significant costs.
• FIG. 5 is a diagram depicting one embodiment of amethod200 in accordance with the present invention for providing a touch interface. For clarity, themethod200 is described in the context of thetouch interface100. However, nothing prevents themethod200 from being used in conjunction with a system not inconsistent with the present invention. An electromagnetic signal is provided from a first side of the display of the touch interface, viastep202. In a preferred embodiment,step202 is performed using theemitters120. The zero mode path between the emitter and the detector for the electromagnetic signal is blocked, viastep204. In a preferred embodiment,step204 is performed using thebarriers140 and142. It is determined whether a sufficient remaining portion of the electromagnetic signal is detected at the second side of thedisplay110 to determine that a user has not touched the screen, viastep206. In a preferred embodiment,step206 is performed using thedetectors130. In addition,step206 is performed such that in the absence of a user's touch, any portion of the electromagnetic signal detected must traverse a path through the display and between the first and second sides and include at least one total internal reflection in thedisplay110. Thus, in the absence of the user's touch,step206 detects a sufficient amount of the electromagnetic signal traversing the path that the user's touch is not detected. Step206 is also performed such that the user's touch at one of the at least one total internal reflection alters the path such that a portion of the electromagnetic signal is not detected on the second side. The portion that is not detected is sufficient large that the user's touch is detected instep206 when the path is so altered. Stated differently, the amount of the electromagnetic signal that is detected in the presence of the user's touch is sufficiently small that the user's touch would be detected instep206. The user's touch, if any, is indicated in response to step206 indicating that the portion of the electromagnetic signal is not detected, viastep208.
• Thus, using themethod200, the touch interfaces100 and100′ can detect the user's touch when thepath150′ is altered such that at least the portion of the electromagnetic signal does not reach the detector. Further, as discussed above, an inadvertent touch, such as by a piece of clothing or a fly, may not result in detection of a false positive by thetouch interface100. Thus, themethod200 not only functions, but may also result in fewer false positive detections due to inadvertent touches.
• A system for providing a touch interface has been disclosed. The present invention has been described in accordance with the embodiments shown, and one of ordinary skill in the art will readily recognize that there could be variations to the embodiments, and any variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.

Claims (9)

1. A system for providing a touch interface including a display comprising:

an emitter on a first side of the display, the emitter providing an electromagnetic signal to the display, wherein the display is transparent; and

a detector on a second side of the display, the display providing the electromagnetic signal a path from the emitter to the detector through the display in the absence of a detectable touch such that the electromagnetic signal is detected by the detector in the absence of the detectable touch, the path including at least one total internal reflection in the display;

wherein the emitter and the detector are configured such that the detectable touch when at any of the at least one total internal reflection is detectable such that a portion of the electromagnetic signal transmitted along the path does not reach the detector.

2. The system ofclaim 1 further including:

a barrier corresponding to the emitter, the barrier residing between the emitter and the display, the barrier for blocking a zero mode path between the emitter and the detector for the electromagnetic signal.

3. The system ofclaim 1 further including:

a detector barrier corresponding to the detector, the detector barrier residing between the detector and the display, the detector barrier for blocking a zero mode path between the emitter and the detector for the electromagnetic signal.

4. The system ofclaim 1 wherein the display includes a third side having an interface between the display and air.

5. The system ofclaim 1 wherein the second side is opposite to the first side.

6. The system ofclaim 1 wherein the detector indicating that the portion of the electromagnetic signal failed to reach the detector corresponds to the detectable touch.

7. The system ofclaim 1 wherein at least one of the first side and the second side of the display includes at least one beveled edge.

8. A system for providing a touch interface having a display comprising:

a plurality of emitters on a first side of the display, each of the plurality of emitters providing an electromagnetic signal to the display, wherein the display is transparent;

a plurality of detectors on a second side of the display, the electromagnetic signal having a path from each of the plurality of emitters to a corresponding detector of the plurality of detectors through the display in the absence of a detectable touch such that the electromagnetic signal is detected by the corresponding detector in the absence of the detectable touch, the path including at least one total internal reflection in the display;

a plurality of barriers corresponding to the plurality of emitters, the plurality of barriers residing between the plurality of emitters and the display, each of the plurality of barriers for blocking a zero mode path between the emitter and the corresponding detector for the electromagnetic signal;

a plurality of detector barriers corresponding to the plurality of detectors, the plurality of detector barriers residing between the plurality of detectors and the display, each of the plurality of detector barriers for blocking the zero mode path between the emitter and the corresponding detector for the electromagnetic signal

wherein the plurality of emitters and the plurality of detectors are configured such that the detectable touch at any of the at least one total internal reflection is detectable as a portion of the electromagnetic signal transmitted along the path does not reach the corresponding detector.

9. The system ofclaim 8 further comprising:

a first plurality of emitters on a third side of the display, each of the first plurality of emitters providing a first electromagnetic signal to the display;

a first plurality of detectors on a fourth side of the display, the fourth side opposing the third side, the first electromagnetic signal having a first path from each of the first plurality of emitters to a corresponding first detector of the first plurality of detectors through the display in the absence of the detectable touch such that the first electromagnetic signal is detected in the absence of the detectable touch, the path including at least one additional total internal reflection in the display;

a first plurality of barriers corresponding to the first plurality of emitters, the first plurality of barriers residing between the first plurality of emitters and the display, the first plurality of barriers for blocking a first zero mode path between the first plurality of emitters and the first plurality of detectors for the first electromagnetic signal,

a first plurality of detector barriers corresponding to the first plurality of detectors, the first plurality of detector barriers residing between the first plurality of detectors and the display, each of the first plurality of detector barriers for blocking the zero mode path between the first emitter and the first corresponding detector for the electromagnetic signal

wherein the first plurality of emitters and the first plurality of detectors are configured such that the detectable touch at one of the at least one additional total internal reflections is detectable as the first electromagnetic signal transmitted along the path does not reach the corresponding first detector.

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