USRE37136E1

Movatterモバイル変換

Info

Publication number: USRE37136E1
Application number: US09/275,895
Authority: US
Inventors: Nicholas Vezard
Original assignee: Horiba Jobin Yvon Inc
Current assignee: Horiba Instruments Inc
Priority date: 1994-07-22
Filing date: 1999-03-24
Publication date: 2001-04-17
Anticipated expiration: 2014-07-22
Also published as: US5613752A

Abstract

In accordance with the present invention an improved forensic light source comprising a source of light and support structure for supporting the source of light is provided. A light guide having first and second ends is coupled to the source of light at the first end to receive light from the source of light and transmit the light to the second end. The light guide is mounted on the support structure. A filter support member supports a plurality of filters. A movable light directing assembly is mounted on the second end of the light guide for movably supporting the filter support member for movement to a plurality of positions. Each of the positions corresponds to the coupling of a selected one of the filters to the second end, whereby the light is filtered by the selected filter. A heat sink may be coupled to the first end of the light guide.

Description

TECHNICAL FIELD

The present invention relates to light sources for illuminating forensic depositions or other evidence with an improved light cable for transmitting selectable wavelength ranges.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application of Purcell Ser. No. 08/076,916, filed Jun. 14, 1993, U.S. Pat. No. 5,515,162 and entitled “LOW NOISE LIGHT SOURCE FOR FORENSIC EXAMINATION”, and U.S. patent application Ser. No. 08/227,962, which is abandoned, the subject matter of which are hereby incorporated herein by reference.

BACKGROUND

Starting at the end of the nineteenth century, crime fighters began to use and develop what has grown into a substantial body of technological tools designed to detect and/or enhance physical evidence. One of the earliest techniques of this kind to receive widespread application is the dusting of fingerprints. Light sources were also among the first tools used in this field. Hence the classic icon of the gumshoe, flashlight in hand, searching for evidence at the dimly lit crime scene.

When a fingerprint is fresh, the oil which forms the print generally follows the pattern of the fingerprint ridges in the finger which made the print. If a fine dust is applied to the surface of a fresh print, the dust tends to adhere to the oils in the fingerprint, thus forming a pattern which generally reveals the pattern of the fingerprint.

Fingerprint dusts were initially selected for their color contrasting qualities as compared to the background. Thus white dust was used to enhance a fingerprint on a black object and vice versa. Even where the oils of a fingerprint have lost their tackiness due to aging or other phenomena, the amino acids into which they break down do cause a minute etching of many surfaces. While this etching is often not visible to the naked eye, and may not become visible with the application of a colored powder, extremely fine fluorescent dusting powders will reveal the fingerprint pattern when illuminated under high intensity light.

Today, many materials, such as dyes, in addition to fluorescent dusting powders are used. Inspection of the evidence is done with specialized light sources. These light sources usually comprise a high intensity source and a filter which passes light having a limited range of wavelengths. Depending upon the material used, which material may be either a fluorescent dusting powder, dye, or other marker material, light having a wavelength which substantially coincides with a known excitation wavelength of the marker is employed. The characteristic of the marker is that, upon illumination with light at one of its excitation wavelengths, it will fluoresce, or emit light. Such fluorescence is typically at a longer wavelength as compared to the excitation wavelength.

Examination of evidence is also enhanced through the use of color filtering glasses or barrier filters, whose color filtering characteristics are tuned to maximize the image to be detected. As noted above, the excitation wavelength is varied through the use of filters at the source. While such devices are very efficient in filtering light, every filter has its own fixed characteristics. These include its center wavelength, bandwidth and transmission coefficient. Thus, if one wishes to have flexibility, it is necessary to have a wide range of filters having different center wavelengths and different bandwidths. This is both cumbersome and expensive. Moreover, as new dyes and powders are introduced, old filters can become obsolete or unnecessary.

In an attempt to provide convenience and flexibility, some light sources used for forensic examination come with a mechanical filter assembly, which allows the introduction of one of about a half dozen filters into the path of the light source to provide the desired wavelength illumination. While this does solve the problem of providing a convenient and easy way to use a light source, obsolescence and limited wavelength and bandwidth selection remain.

In an attempt to overcome some of these disadvantages, earlier forensic illumination systems have attempted to achieve a measure of tunability by mounting an interference filter for angular rotation. Generally, such angular rotation results in a change in angle of incidence with respect to the filter input and a relatively small variation in the encountered path length between the functional layers in the interference filter for light passing through the filter in a fixed direction. In accordance with Bragg's Law, this results in different wavelengths being passed by the filter.

In the above-referenced disclosure of Purcell, a system is disclosed which provided a high intensity light source which is continuously adjustable to vary the center frequency of a band of wavelengths. At the same time, the flexibility of varying the bandwidth of this band was also possible. The same was done with a single light source and a single filtering apparatus. At the same time that was achieved with a mechanical configuration that is both reliable and rugged. Finally, that system was easily portable, and capable of outputting light sufficient for close up analysis of surfaces bearing such material as oils, semen, blood and so forth.

In that system, a method and apparatus for illuminating a deposition of organic material such as, blood, sweat or oil for forensic examination was also provided. A light source emitted light having a range of wavelengths. A first optical coupler or light pipe was positioned and configured to reflect the light toward a reflective diffraction grating. A supportable structure supported, at a selectable relative position, an exit slit and the grating to pass a desired band of wavelengths of output light from portions of the light reflected by the grating. A bendable second optical coupler was coupled to the exit slit and directed the output light toward the deposition to be examined. The bendable second optical coupler comprised a liquid fiber optic member. The support structure rotated the grating. An electronic control and a hand held remote control pad was coupled to the support structure and controlled the support structure.

As can be seen from the above, numerous advantages are provided in such a continuously adjustable diffraction grating based system. Naturally, it is desirable to have the possibility of the highest possible intensity output light at the selected wavelength. However, such a brute force approach results in increased power consumption and excessive heat energy, stressing the rest of the system. In an attempt to achieve better results without aggravating this problem, the above disclosure of Purcell utilizes an infrared blocking filter to filter the light source thus allowing only filtered and relatively low intensity light to fall on the grating. This, however, also has an adverse impact on the amount of energy output by the forensic light source, particularly in the ultraviolet range. In addition, the use of the filters, because they are exposed to a high intensity source, results in there being another element subject to deterioration and replacement.

In accordance with the latter of the two above applications, a filter is used to achieve maximum throughput of energy. Improved signal-to-noise ratio is achieved using other filters at the detection end. In order to protect the filters at the light output side, protection is provided by infrared reflecting filters which reflect unwanted infrared radiation away from the bandpass filters used in the system. However, they also attenuate the desired output light. These bandpass filters are located in the housing and relatively proximate to the source of light which is filtered to output the desired filtered light at the selected wavelength.

SUMMARY OF THE INVENTION

In accordance with the present invention an improved forensic light source comprising a source of light and support structure for supporting the source of light is provided. A light guide having first and second ends is coupled to the source of light at the first end to receive light from the source of light and transmit the light to the second end. The light guide is mounted on the support structure. A filter support member supports a plurality of filters. A movable light directing assembly is mounted on the second end of the light guide for movably supporting the filter support member for movement to a plurality of positions. Each of the positions corresponds to the coupling of a selected one of the filters to the second end, whereby the light is filtered by the selected filter.

The filter support member comprises a wheel with a plurality of filters mounted around a point of rotation. Mounting structure is provided for rotatably mounting the wheel for rotation about the point of rotation.

The filter support member defines a plurality of detentes and further comprises a spring member mounted on the movable light directing assembly. It is positioned to releasably engage the detentes. The detentes are positioned to correspond to alignment between one of the filters and the second end, when engaged by the spring member, each of the detentes corresponding to a respective one of the filters.

The source of light may be a xenon lamp, a tungsten lamp or a metal halide lamp. A heat sink may be coupled to the first end of the light guide. The light guide may be a liquid light guide or a fiber optic light guide. A lens for focussing light from the second end through a selected filter may be provided and a securing member may be used to adjust the position of the second end relative to the lens.

BRIEF DESCRIPTION OF THE DRAWINGS

One way of carrying out the invention is described in detail below with reference to drawings which illustrate only one specific embodiment of the invention and in which:

FIG. 1 is a schematic view of a forensic light source constructed in accordance with the present invention;

FIG. 2 is a detailed view of the coupling between the fiber optic light guide and the light source;

FIG. 3 is a view alonglines3—3 of FIG. 2 illustrating the heat sink of the system of the present invention;

FIG. 4 is a view partially in cross section of a hand-held light directing assembly constructed in accordance with the invention;

FIG. 5 is a view alonglines5—5 of FIG. 4;

FIG. 6 is a top plan view of the filter wheel of the present invention;

FIG. 7 is a top plan view of the filter wheel of the assembly of the present invention with the cover of the housing removed;

FIG. 8 is a side view along lines8—8 of FIG. 6;

FIG. 9 is a front view of the light directing assembly head of the present invention;

FIG. 10 is a top view alonglines10—10 of FIG. 9;

FIGS. 11 and 12 are views similar to the views of FIGS. 4 and 10 of the embodiment of FIGS. 1-10 of an alternative embodiment; and

FIG. 13 is a view of yet another alternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a forensicdeposition illumination system10 constructed in accordance with the present invention is illustrated.System10 generally comprises alight source12 contained in ahousing20, a hand heldlight directing assembly14, and afiber optic cable16 optically coupling thelight source12 to the hand-heldlight directing assembly14.

Light is supplied to the system by alamp18 located withinhousing20 oflight source12. Light fromlamp18 is focused by aparabolic reflector22 also contained withinhousing20. In accordance with conventional technology,housing20 may also contain a fan for cooling the assembly and an appropriate power supply forlamp18. In this respect, reference is made to the above-identified patent applications.

Housing

20 oflight source12 is provided with aflange24 which is secured tohousing20 by a pair ofscrews26, as illustrated in FIG.1. Mounted toflange24 is aheat sink28 which comprises amain body30 andheat dissipating fins32, as can be seen most clearly in FIGS. 2 and 3.

Hand-heldlight directing assembly14 includes ahandle portion34 and afilter housing portion36. Protruding fromfilter housing portion36 is arotatable filter wheel38.

During use, auser40 grasps thehandle portion34 in hishand42 and aims the light at adeposition44 to be examined.Deposition44 may be located on asurface46.

Referring to FIGS. 2 and 3, the construction of theheat sink28 may be more clearly understood. In particular,heat sink28 may be machined out of a single piece of aluminum.Heat sink28 may be finished with a black anodized finish.Heat sink28 includes a tubularforward portion48 which mounts intoflange24 and may be permanently secured thereto using setscrews50.Heat sink28 includes aninner bore52 which communicates optically with light fromlamp18 as reflected byreflector22.Lamp18 may be of any conventional type such as of the incandescent, metal halide, or xenon type.

Alarger bore54 is located at the opposite end ofheat sink28 and is sufficiently large to accommodate thefiber optic cable16. Generally,fiber optic cable16 includes an innerfiber optic member56 and asheathing58. The diameter of the innerfiber optic member56 substantially equals the diameter ofsmaller bore52, while the outside diameter ofsheathing58 substantially matches the inside diameter ofbore54.Fiber optic cable16 is maintained and positioned inbore54 by aset screw60 which has a large knurled head62 (FIG. 3) which allows setscrew60 to be easily and conveniently grasped by the fingers of a user. During use,fiber optic cable16 is inserted intobore54 and setscrew60 is tightened in position thereby securingfiber optic cable16 in position.

Referring to FIG. 4, the construction of the hand-held light-directingassembly14 may be most clearly understood. In particular,assembly14 comprises ahandle portion34.Handle portion34 includes a light guide receiving bore64 which is in optical communication with acentral bore66. Central bore66 is of a diameter which matches the diameter of innerfiber optic member56. This enables the handle to communicate substantially all of the light conducted byfiber optic cable16.Fiber optic cable16 is maintained in position by a handadjustable set screw68 with aknurled head70. During use,fiber optic cable16 is inserted intobore64 and held in position byset screw68.

Handle portion

34 also includes a lens receiving bore72. Alens74 is mounted on anannular shoulder76 inbore72.Lens74 focusses the output light at theoutput end78 offiber optic cable16.

During use, selective focussing of the output fromend78 offiber optic cable16 may be achieved by varying the position ofend78 in the directions shown byarrow80 and setting the position offiber optic cable16 using setscrew68. For example, end78 may be brought to the position shown in phantom lines in FIG.4. Variation of the position ofend78 will result in varying light output cone diameters and varying intensities. High intensity corresponds to smaller diameter light outputs, while larger diameter outputs will result in lower intensity. The advantage of the lower intensity outputs is that wider areas may be illuminated and the same may be particularly useful in searching operations. On the other hand, minute examination of a deposition may require use of a relatively small diameter high-intensity spot of illumination.

Handle portion

34 is secured to filterhousing portion36 by a plurality ofscrews26 which are disposed inholes82 inflange84, and which threadedly engage tapped holes inmain housing86 offilter housing portion36, as can be seen in FIG.5.Filter housing portion36 housesrotatable filter wheel38.Rotatable filter wheel38 is rotatably mounted withinmain housing86 by being supported on apost88.Rotatable filter wheel38 is maintained in spaced relationship to therear wall90 ofmain housing86 by awasher92.

Referring to FIG. 6, the construction of therotatable filter wheel38 may be seen. In particular,rotatable filter wheel38 comprises a plurality offilter receiving openings94 within which filters96 are located. The circumferential edge ofwheel38 may be smooth as illustrated in FIG. 6 or may include a knurled surface as is shown in dotted lines in FIG.6. Such aknurled surface98 would be disposed around the entire periphery ofrotatable filter wheel38.Rotatable filter wheel38 also includes a plurality ofdetentes100 which are adapted to be engaged by a detente engagingspring member102, as can be seen most clearly in FIG.7. Detente engagingspring member102 is secured by ascrew104 to theinside side wall106 ofmain housing86. It is maintained in place at a location from theinside side wall106 through the use of awasher108.

As can be seen in FIG. 7, thecircumferential edge110 ofrotatable filter wheel38 extends through ahole112 defined inmain housing86 allowing a user to engage the same with his thumb and rotate the rotatable filter wheel to cause engagement with thedetente100 associated with a selectedfilter96, by rotation ofwheel38 in the direction indicated byarrow114.

As can be seen most clearly in FIG. 8, spacing from the forward portion offilter housing portion36 is maintained by an integral centralannular shoulder116 on the rotatable filter wheel. Theforward surface118 ofshoulder116 bears againstfront plate120 ofhousing portion36.Front plate120 defines ahole122 through which light filtered by a selectedfilter96 is allowed to pass to illuminate theforensic deposition44 under examination. As can be seen in FIG. 9,front plate120 also includes ahole124 for receivingpost88. Likewise, a plurality ofscrews126 are used to securefront plate120 to theside walls106 ofmain housing86.

As can be seen in FIG. 10,circumferential edge110 ofrotatable filter wheel38 is easily accessible throughwindow112 for adjustment of a desired filter. The same is of particular interest because during use, the user using a single hand may hold and direct the light source while, at the same time adjusting the filter through which light can pass. In addition, the inventive design is of particular value because the use of a single hand-held light directing assembly frees up the other hand either to hold the light source or to do other tasks such as adjust viewing filters, cameras, painting with developing agents, dusting with appropriate print revealing powders, or the like.

An alternative embodiment is illustrated in FIGS. 11-12. Generally, similar parts or parts performing analogous, corresponding or identical functions to those of the FIGS. 1-10 embodiment are numbered herein with numbers which differ from those of the earlier embodiment, by multiples of one thousand.

An alternative embodiment of the invention is illustrated in FIG.11. Generally, in this embodiment the hand-heldlight directing assembly1014 ofsystem1010 is of similar construction except that aviewing filter1128 is secured to thefront plate1120 offilter housing portion1036 by a supportingbracket1130 having aperture1122. During use, as illustrated in phantom lines in FIG. 1, a viewer looks throughfilter1128 when inspecting the deposition. In addition, provision may be made for adjustable angular positioning offilter1128, also as illustrated in phantom lines in FIG.1. Otherwise operation of the system illustrated in FIG. 11 is identical to that of the system illustrated in FIGS. 1-10. The construction of the filter may be more clearly seen in FIG.12.

As alluded to the above, the inventive system has numerous advantages. In addition to the flexibility provided to the user through the use of the rotatable filter wheel housing which may be operated to adjust the filter and position of the output light beam, the design also accommodates the variation of the intensity and size of the output light beam. In addition, the system of the present invention has superior intensity output on account of the fact that the filters in the rotatable filter wheel do not have to be protected by heat absorbing filter or heat reflecting mirror as used in conventional forensic light sources. In particular, in conventional sources, the output light from the lamp is reduced in intensity by removal of the infrared portion of the source. This is necessary in order to prevent excessive heat buildup in the filter, which would destroy the filter in a relatively short time.

Another important aspect of the invention is the fact that because the light is first passed through the fiber optic wave guide, no such protective filter is required and the light may be caused to fall directly upon the filters which, instead of being located adjacent to the lamp in the optical wave train, are located at the far end of the fiber optical or liquid optical wave guide. As can be readily understood by those of skill in the art, the flexible optical wave guide does have an attenuation factor. However, because of the placement of the filters at the far output end of the optical wave guide, the additional attenuation factor of the infrared protective filters is avoided. However, because of the fact that light, including a great deal of infrared energy, is passed into the flexible optical wave guide, excessive heat may be caused to be built up within the wave guide, particularly near its input end. Accordingly, the input end is provided with heat-dissipating heat sink.

In accordance with yet another alternative embodiment illustrated in FIG. 13, theheat sink2028 is provided with ahousing2132 housing afan2134 which blows air over thefins2032. This results in extreme cooling which of particular value when very high intensity lamp sources are used.

With respect to a possible flexible fiber optic wave guides, a liquid light guide such as one of the type made by Lumatec of Germany is preferred. This particular light guide will absorb infrared rays to a very great extent (almost 100%) while only attenuating the ultraviolet and visible spectrum to the extent of about 50 or 60%. However, a conventional fiber optic wave guide will provide exceptional performance in the case of lower intensity lamps inasmuch as infrared radiation is reduced by approximately 50%. In the case of lower intensity lamps, this reduction is sufficient to prevent damage to the filters in the rotatable filter wheel. However, if high intensity lamps are used, close to 100% attenuation which is substantially an action of infrared radiation will be necessary to prevent damage to the filters and the use of a liquid light guide is required in order to obtain reasonable filter life.

While an illustrative embodiment of the invention has been described above, it is, of course, understood that various modifications will be apparent to those of ordinary skill in the art. Such modifications are within the spirit and scope of the invention, which is limited and defined only by the appended claims.

Claims

I claim:

1. A forensic light source, comprising:

(a) a source of light;

(b) support structure for supporting said source of light;

(c) a light guide having first and second ends, said light guide being coupled to said source of light at said first end to receive light from said source of light and transmit said light to said second end, said light guide being mounted on said support structure;

(d) a filter support member supporting a plurality of filters; and

(e) a portable hand holdable and movable light directing assembly mounted on said second end of said light guide, said light directing assembly supporting said filter support member and providing for movement of said filter support member to a plurality of positions, each of said positions corresponding to a coupling of a selected one of said filters to said second end, whereby said light emitting from said second and is filtered by said selected filter while the emitted light is directed to various locations through movement of said light directing assembly.

2. A forensic light source as in claim1, wherein said filter support member comprises a wheel with a plurality of filters mounted around a point of rotation and said filter support members further comprises a mounting structure configured to rotatably mount said wheel about said point of rotation, and said wheel is positioned to be rotated by a finger of a user.

3. A forensic light source, as in claim1, wherein said filter support member defines a plurality of detentes and a spring member is mounted on said light directing assembly and positioned to releasably engage one of said detentes, each of said detentes being positioned to correspond to alignment between its respective one of said filters and said second end, when a respective detente is engaged by said spring member, each of said detentes corresponding to a respective one of said filters.

4. A forensic light source as in claim1, wherein said source of light is a xenon lamp.

5. A forensic light source as in claim1, wherein said source of light is a tungsten lamp.

6. A forensic light source as in claim1, wherein said source of light is a metal halide lamp.

7. A forensic light source as in claim1, further comprising a heat sink coupled to said first end of said light guide.

8. A forensic light source as in claim7, wherein said light guide is a liquid light guide.

9. A forensic light source as in claim7, further comprising a lens, said lens positioned to focus said light from said second end through a selected filter.

10. A forensic light source as in claim1, wherein said light guide is a liquid light guide providing light from said second end through a selected filter.

11. A forensic light source as in claim10, further comprising a lens positioned to focus light from said second end through a selected filter.

12. A forensic light source as in claim11, further comprising a heat sink coupled to said first end of said light guide.

13. A forensic light source as in claim1, wherein said light guide is a fiber optic light guide.

14. A forensic light source as in claim13, further comprising a heat sink coupled to said first end of said light guide.

15. A forensic light source as in claim1, further comprising a lens, said lens being positioned to focus said light from said second end through a selected filter.

16. A forensic light source as in claim15, further comprising a securing member, said securing member providing for an adjustable setting of a position of said second end of said light guide relative to said lens.

17. A forensic light source as in claim1, wherein said movable light directing assembly comprises a housing portion and a handle portion, said housing portion containing said filter support member and said handle portion being configured and dimensioned to be grasped by a hand of a user.

18. A forensic light source as in claim17, further comprising a lens positioned to focus light from said second end through a selected filter.

19. A forensic light source as in claim17, further comprising a securing member, said securing member providing for an adjustable setting of a position of said second end of said light guide relative to a lens.

20. A forensic light source as in claim17, wherein said housing portion allows the user to rotate said filter support member with the user's thumb while gripping said handle portion and directing the filtered light.

21. A forensic light source, as in claim20, wherein said filter support member defines a plurality of detentes and a spring member is mounted on said light directing assembly and positioned to releasably engage one of said detentes, each of said detentes being positioned to correspond to alignment between its respective one of said filters and said second end, when a respective detente is engaged by said spring member, each of said detentes corresponding to a respective one of said filters.

22. A forensic light source as in claim1, wherein said movable light directing assembly comprises a housing portion and a handle portion, said housing portion containing said filter support member and said handle portion being configured and dimensioned to be grasped by a hand of a user.

23. A forensic light source as in claim22, wherein said housing portion is configured to allow the user to rotate said filter support member while gripping said handle portion and directing the filtered light.

24. A forensic light source, comprising:

(a) a source of light;

(b) a support structure for supporting said source of light;

(d) a filter support member supporting a plurality of filters;

(e) a portable hand holdable and movable light directing assembly coupled to said second end of said light guide, said light directing assembly supporting said filter support member and providing for movement of said filter support member to a plurality of positions, each of said positions corresponding to a coupling of a selected one of said filters to said second end, whereby said light emitting from said second end is filtered by said selected filter while the emitted light is directed to various locations through movement of said light directing assembly; and

(f) a heat sink coupled to said first end of said light guide.

25. A forensic light source as in claim24, wherein said light guide is a liquid light guide for providing light from said second end through a selected filter.

26. A forensic light source as in claim25, further comprising a lens, said lens positioned to focus said light from said second end through a selected filter.

27. A forensic light source as in claim24, further comprising a lens positioned to focus light from said second end through a selected filter.

28. A forensic light source as in claim24, wherein said filter support member comprises a wheel with a plurality of filters mounted around a point of rotation and said filter support member further comprises a mounting structure configured to rotate said wheel about said point of rotation.

29. A forensic light source as in claim28, wherein said movable light directing assembly comprises a housing portion and a handle portion, said housing portion being substantially circular in shape to contain said wheel and said handle portion being configured and dimensioned to be grasped by a hand of a user.

30. A forensic light source as in claim29, further comprising a securing member, said securing member providing for an adjustable setting of a position of said second end of said light guide relative to a lens.

31. A forensic light source comprising:

(a)a source of light;

(b)a support structure for supporting said source of light;

(c)a light guide having first and second ends, said light guide being coupled to said source of light at said first end to receive light from said source of light and transmit said light to said second end, said light guide being mounted on said support structure;

(d)a filter support member supporting a plurality of filters, said filter support member being coupled to receive light from said source of light; and

(e)a portable hand holdable and movable light directing assembly mounted on said second end of said light guide, said light directing assembly including a hand or finger operable control member coupled to said filter support member and controlling the movement of said filter support member to a plurality of positions, each of said positions corresponding to a coupling of a selected one of said filters to said source of light, whereby said light emitted from said second end is filtered by said selected filter and the emitted light can be directed to a desired location through movement of said light directing assembly by the same hand which operates said control member.

32. A forensic light source, as in claim31, wherein said filter support member defines a plurality of detents and a spring member mounted to act on said detents and positioned to releasably engage one of said detents, each of said detents being positioned to correspond to alignment between its respective one of said filters to said source of light.

33. A forensic light source as in claim31, further comprising a heat sink coupled to said first end of said light guide.