Abstract:
A forensic light source uses a pair of filter wheels to achieve a combination of the characteristics of filters on different wheels and may include a housing which supports the light, filter wheels and other parts with shock absorbing members such as rubber washers or the like to achieve a shock resistant housing. A light source and a plurality of light filters are contained within the housing. The light source is powered by an external power supply, thus making the light source light weight.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the priority of U.S. provisional patent application No. 60/259,192 filed Dec. 29, 2000, the disclosure of which is hereby incorporated herein by reference thereto. 

   TECHNICAL FIELD 
   The present invention relates to light sources useful for illuminating and thus detecting the presence of forensic materials at a crime scene using light of wavelengths selected to enhance the likelihood of detecting such materials. 
   REFERENCE TO GOVERNMENT FUNDING 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   Description of Related Art 
   Recent advances in DNA testing have rendered the gathering of forensic materials of increasing importance. However, even before the advent of DNA testing, the detection of forensic materials such as blood, perspiration, bone, skin, and the like has always been of great importance to crime fighters. For example, bone fragments that can be matched to a corpse would show that the individual who had suffered the crime may have been at a particular location. Fingerprints would identify individuals because of their unique characteristic. Loose hairs on a victims clothes could identify a possible assailant. 
   But as important as forensic evidence was in the past, it was only one of numerous circumstantial and objective sources of evidence which were weighed by juries and judges in their search for the truth and implementation of criminal justice objectives aimed at punishing and/or preventing criminal activities. 
   However, with the advent of DNA Testing, forensic material begins to approach, more closely than ever, a determination with certainty respecting certain types of criminal activity and particularly reliable circumstantial evidence with respect to other types of criminal activity. For example, in rape cases, identification of seminal fluids substantially amounts to a basis to convict or a basis to acquit. This is especially the case where only the victims and the accused have their DNA patterns in the sample. 
   Accordingly, the detection of forensic materials at a crime scene is of the utmost importance whether to make an almost positive connection between a criminal and a crime scene or to exonerate innocent people. One of the primary tools in detecting forensic materials is the use of light having particular wavelength characteristics. More particularly, a light that is produced by various types of forensic light sources which include means to direct the light onto various parts of a crime scene. One typical device, for example, comprises a light source and a six foot long fiber optic member which directs light from the light source to a point in which the end of the fiber optic member is pointed. A wheel containing a number of filters is mounted at the end of the fiber optic light pipe. In order to select various wavelengths, the wheel is rotated thus interposing different filters in front of the output of the light pipe. The result is that the filters filter the light as it comes out of the light pipe and allow only the light of a particular wavelength to fall on an object or area to be illuminated. Such devices are relatively heavy and the long fiber optic light pipe is of particular advantage because it allows the light source to be put down on the floor and the light direction and source to be manipulated to the manipulation of the very light and easy to manipulate fiber optic bundle light type. This is what represents one of the easiest to use instruments and, a particularly effective embodiment of a forensic light source. However, the bundles necessary for such a device are relatively expensive and the use of a plurality of filters results in a particularly large expense. Moreover, the fiber optic bundle is also a relatively expensive item and contributes significantly to the cost. In addition, losses occur during transmission along the fiber optic bundle and, accordingly, light sources of especially high strength are needed to provide sufficient illumination energy at the output of the light bundle and filters. 
   However, such systems are relatively expensive to manufacture. In addition, the filter assembly is at the end of a relatively fragile fiber optic bundle and both the filter assembly and fiber optic bundle are subject to abuse and shock, and need to be protected. 
   Other approaches suffer from even greater problems. For example, in one system, an array of filters located in a housing which contains the light source are operated by remote control using an electrical switch located at the end of the light pipe opposite the light source and filters. The result is the need for an electrical connection and electrical control circuitry for activating additional motor systems needed to move the filters. This has the result of decreasing reliability and system life, while at the same time increasing the cost of the system. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a forensic light source is provided which combines the easy maneuverability of a simple fiber optic bundle without the use of a fiber optic bundle while at the same time preserving the flexibility of control with the same hand that is moving the light source. In addition, the relatively light weight nature of the system which is encountered by the hand used to scan the crime scene is also maintained. Moreover, the same is achieved without the high cost of an electrical control circuitry to control placement of filters as source. In addition, these objects are achieved in a format which is particularly resistant to shock and abuse. Finally, all the above advantages and objects of the invention are achieved in a configuration which allows low cost and also provides for compounding filtering characteristics to achieve versatility in the operation of the system. 
   In accordance with the present invention, these objectives are achieved in the context of a system which comprises a light source contained within a housing. The housing includes a handle attached to the housing which allows the housing to be grasped by a user. Light is output from the housing through a filter wheel mounted on the housing. The filter wheel is positioned to allow for filter adjustment using the thumb of the hand which is grasping the housing while the other four fingers engage the handle to hold the housing in position. The same is achieved by having the filter wheels mounted in front of the output of the light source within the housing which is grasped by the hand. At the same time, power to the system is supplied not by an internal battery pack or internal power supply incorporating a transformer. Rather, a power supply or battery pack is coupled by a cable to the housing containing the light source. During use, the power supply is placed on the floor and the light source, relatively light because of the absence of the power supply components, is manipulated to direct light wherever one wishes to direct light. Likewise, when a battery pack is used, the battery pack is also coupled by a long wire to the housing of the inventive forensic light source. The result is that the weight of the battery pack is also kept off the hand doing the work of directing the light source in various directions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages, and the system and apparatus of the present invention will be understood from the following description taken together with the drawings, in which: 
       FIG. 1  is a front view taken from above of an embodiment of a forensic instrument constructed in accordance with the present invention; 
       FIG. 2  is a side view of the embodiment of the present invention in  FIG. 1  illustrating a preferred grip position during use of the inventive instrument; 
       FIG. 3  is a side view of the embodiment of the present invention in  FIG. 1 ; 
       FIG. 4  is a rear view of the embodiment of the present invention in  FIG. 1 ; 
       FIG. 5  is a front view of one of the filter wheels useful with the embodiment of the present invention in  FIG. 1 ; 
       FIG. 6  is a front view taken from above with the front cap piece of the embodiment of the present invention in  FIG. 1  removed; 
       FIG. 7  is an interior view of the front cap piece of the embodiment of the present invention in  FIG. 1 ; 
       FIG. 8  illustrates a mechanism for retaining the filter wheel in position; 
       FIG. 9  illustrates a mechanism in  FIG. 8  engaging the filter wheel; 
       FIG. 10  is a side view of an embodiment of the present invention further illustrating the connection of the light source with a battery pack; 
       FIG. 11  is a side view of an embodiment of the present invention further illustrating the connection of the light source with a power supply; 
       FIG. 12   a  illustrates a focusing position for the light output focusing lens mounted in a turret which is slidably mounted to a tubular member of the front cap. 
       FIG. 12   b  illustrates a second focusing position for the light output focusing lens, similar to that illustrated in  FIG. 12   a  mounted in a turret which is slidably mounted to a tubular member of the front cap. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , the inventive forensic light source  10  is illustrated. Forensic light source  10  includes a housing  12  which may be grasped by the user using a handle  14 . More particularly, as illustrated in  FIG. 2 , the user uses a unit by grasping handle  14  with his hand  16 . The unit is controlled by a pair of frequency selector dials  18  and  20  (FIG.  1 ). The user positions his hand  16  in such a manner that thumb  22  on hand  16  may be placed over dials  18  and  20  and the thumb may be selectively used to rotate either dial  18  or dial  20  to a desired position. 
   Referring to  FIG. 3 , handle  14  on housing  12  includes an on/off switch  24 . Switch  24  is used to turn a light source such as lamp  26  on and off. Lamp  26 , which may be mounted in housing  12  on shock absorbing supports, may be any of numerous lamps employed in such instruments, such as for example, a xenon lamp or other suitable source. Suitability for employment in forensic light source  10  is determined by the spectral emission of the lamp. In particular, lamps having sufficiently high spectral output within the desired output range of the instrument are suitable. The exact nature of the xenon lamp or any other suitable lamp is not a feature of this invention. The system also includes a fan  28  may be connected in parallel with lamp  26 , whereby actuation of switch  24  results in turning both lamp  26  on and turning fan  28  on, thus providing for the cooling of the unit during use. Fan  28  is mounted adjacent to a port  30  for the circulation of air on the rear of the unit as illustrated in FIG.  4 . Port  30  may be a simple circular hole and may be covered by a grille  32  made of wire. Referring back to  FIG. 3 , because there must be a flow of air through the instrument, a set of vents  34  are provided near the opposite end of housing  12 . 
   In connection with venting it is noted that switch  24  may be made to individually control fan  28  and light source  26 . More particularly, if desired, it is also possible for switch  24  to be a three way switch in which the first position has both the fan and the light source off, in a second position sends power only to fan  28  and in a third position sends power to fan  28  and light source  26 . This allows the light source to be turned off while still continuing cooling to occur thus preserving the life of the unit. 
   As illustrated in  FIG. 3 , the optical system in forensic light source  10  further comprises a reflector  36  position to couple light output from lamp  26  to focusing optics  38 . Focusing optics  38  serve to concentrate light directly received from lamp  26  and indirectly received from lamp  26  by a reflector  36  to the output of the system. 
   A pair of filter wheel  40  and  42  are positioned within a cap housing  44  (FIG.  1 ). Referring back to  FIG. 3  taken in conjunction with  FIG. 5 , it is seen that the filter wheels, such as filter wheel  40  each have a mounting hole  44  which allows them to be mounted for rotation on a post  46  (FIG.  6 ). More particularly, both wheels  40  and  42  are mounted on post  46  and maybe freely rotated to put one or two filters over the output of focusing optics  38  and thus filter such output. 
   More particularly, light output from focusing optics  38  passes through a hole  48  ( FIG. 3 ) through front wall  50  and then through a filter and filter wheel  40  and a filter and filter wheel  42 , or if no filter is selected through holes in either or both wheels  40  and  42 . 
   This may be better understood with reference to  FIG. 6  where one filter  52  in filter wheel  40  is positioned in a manner coupled to receive the output of focusing optics  38 . Five filters namely filters  52 ,  54 ,  56 ,  58  and  60  in similar fashion wheel  42  has filters  62 - 70  as illustrated in FIG.  6 . 
   There is an alphanumeric designation  72  associated with each of the filters. Each alphanumeric designation  72  such as designation  72  designates the wavelength of its corresponding filter which is radially opposite the location of the alpha numeric designation. For example, alphanumeric designation  72  is opposite filter  56  whereas alphanumeric designation  74  is located opposite to filter  54 . Likewise, another alphanumeric designation  76  is located opposite filter  58  and corresponds to the characteristics of filter  58 . In similar fashion alphanumeric designation  74  corresponds to the characteristics of filter  54 . Other alphanumeric designations on the system are not illustrated but are positioned in similar analogous fashion. 
   In accordance with the preferred embodiment, the system, or more particularly, the filter wheels  40  and  42  have holes, such as hole  78  in wheel  40  which do not include any filter and merely pass all light in order to output an uncolored or “white” light output. Hole  78  is a simple hole, in contrast with holes  80  which support the filters. Holes  80  have a suitable shoulder which supports the filter and are closed by a retainer spring ring  82 , a plurality of which are employed in the system, each associated with one of the holes  80  in filter wheels  40  and  42 , as illustrated in FIG.  5 . 
   Each of the filter wheels includes a mounting hole  83  upon which filter wheels  40  and  42  are mounted for rotation. The filter wheels are maintained in position after being mounted by a closure cap  84 , as shown and positioned in FIG.  2 . Closure cap  84  is shown in perspective in FIG.  7 . 
   As can be seen in  FIGS. 3 and 5 , filter wheels  40  and  42  include a plurality of notches  86 . Notches  86  serve to provide positive stops so that the filter wheels click into place in one of six specified positions. See also FIG.  6 . Filter wheels  40  and  42  may be rotated to any desired position through the use of knurled serrations  88 . In accordance with the preferred embodiment of the invention, the output of light source  26  is outputted at a fixed point on housing  12 . When hole  78 , which has no filter mounted in it, is lined up with the output point, then the unfiltered output spectrum, of the lamp will be output by the system. 
   This may be better understood with reference to  FIG. 6  where it can be seen that filter  52  is overlapping the proper point for lamp  26 . See also FIG.  3 . 
   In accordance with the preferred embodiment of the invention, positive engagement of the wheel and maintenance of the position of the wheel at the desired preset points is achieved through the use of a mechanism which mates with detense or notches  86 . The particular mechanism used in accordance with the present invention is a spring loaded ball bearing. More particularly, as can be seen with reference to  FIG. 8  a block  90  includes a hole  92  into which a spring  94  is positioned. A ball bearing is then pressed over spring  94  and into hole  92  and a filter wheel pressed over it to keep it in position. As the filter wheel is rotated, the ball, not illustrated, is forced into one of the detense or notches  86  resulting in holding the filter in the desired position. The result is illustrated in  FIG. 9  where a ball  96  is shown in phantom lines. 
   In accordance with the present invention, ease of use and light weight is achieved by separating the light unit from the power supply, whether it be a battery pack or an electrical power supply operated by the mains. Such situations are illustrated in  FIGS. 10 and 11 . Referring first to  FIG. 10 , a battery powers the system and the power supplied by a battery pack  98  is connected by a five or six foot length of cord  100  to the forensic power source  10 . Thus the weight of the battery pack is not a burden to the user, the battery pack being simply put down on the floor or a piece of furniture during use of the inventive system  10 . 
   It is advantageous that the inventive forensic light source  10  also be powered by house current. In this case a power supply  102  is used and power supply  102  may be connected by a length of line cord  104  to house current source  106 , as illustrated in FIG.  11 . Here again a length of electrical cable  108  perhaps six or eight feet long is used to connect power supply  102  to the ruggedized forensic light source  10 . 
   The separation of the power supply or the battery from the remainder of the system also contributes to the ruggedized nature of the system. More particularly, because the weight of the battery is not connected to the delicate bulb and filter assembly, when the same is dropped the momentum of the system is minimal and the damage caused by the impact is reduced, thus resulting in a more rugged, more hearty and more reliable system under normal police use which may in fact involve substantial abuse. 
   In accordance with the present invention, filter wheel  40  has an open hole, which passes all light, and a plurality of filters. The filters in filter wheel  40  have the following characteristics: a bandpass filter with a center wavelength of 440 nm with a relatively broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength 490 nm with a relatively broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 540 nm with a relatively broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 590 nm with a relatively broad bandwidth in the range of 40 to 50 nm; and a short pass filter with a maximum pass wavelength of 540 nm (which functions as a crime scene scanning filter). The 540 nm filter is known as a crime scene scanning filter because it is most useful in searching over wide areas of a crime scene in order to identify areas for inspection under light of various wavelengths. Of course, in accordance with the present invention, it is also contemplated that a crime scene will be searched under white light and under light of various wavelengths, particularly in those areas of the crime scene likely to contain various types of the evidence. In addition, to the extent that it is known that various specific types of evidence are most visible under the light of one wavelength or another, it is anticipated that in accordance with the invention that area will be examined on the light of the applicable wavelength or wavelengths. 
   Filter wheel  42  also has an open hole, which passes all light, and filters with the following characteristics: a bandpass filter with a center wavelength of 415 nm with a relatively broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 465 nm with a relatively broad bandwidth in the range of 40-50 nm; a bandpass filter with a center wavelength of 515 nm with a relatively broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 565 nm with a relatively broad bandwidth in the range of 40 to 50 nm; and a bandpass filter with a center wavelength of 615 nm with a relatively broad bandwidth in the range of 40 to 50 nm. 
   In accordance with yet another embodiment of the invention, it is contemplated that the system will incorporate a third filter wheel which has a number of very narrow band reject filters. These may be selected to reject wavelengths which excite certain commonly occurring wavelengths which constitute noise and present the possibility of overpowering wavelengths which one wishes to detect or photograph. 
   Any suitable filters may be used in accordance with the invention, including, filters made by holographic processes, dielectric coating, glass plates coated with layers of materials incorporating dyes, and so forth. While lamps of other power may be used, it is anticipated that the inventive system  10  will be used with a 100 watt lamp. 
   It accordance with the invention, it is contemplated that it may be desired to vary the optical characteristics of the light output by the system. The same is achieved to the use of a lens  112  ( FIG. 12   a ), mounted in a turret  114 , which is slidably mounted in a tubular member  116  secured to cap  84 . Turret  114  may be positioned in various positions as illustrated in  12   a  and  12   b  in solid and phantom lines. In particular, a screw  118  which passes through a slot  120  is used to hold turret  114  in position. Rotation of turret  114  causes turret  114  to move into or out of tubular member  116 , thus varying the distance between lens  112  and the lamp, and focusing the light into beams having different characteristics. Once adjusted in the desired manner, turret  114  is held in position by tightening screw  118  which mates with a tapered hole in turret  114 . 
   When it is decided to use the inventive system, the power supply  102  or battery pack  98  is put on a table or on the ground at the crime scene. If the power supply is used, the same is plugged into standard house current. 
   An individual then grasps the light source using his hand  16 , as illustrated FIG.  2 . The thumb  22  of hand  16  may be used to rotate filter wheel  40  or  42  to put a desired filter or no filter at all into the path of light output from lamp  26 . 
   The user uses light of different wavelengths to inspect the crime scene for materials which will only the revealed by light of a particular wavelength, or which will be revealed in a better and easier to identify fashion by light of a selected wavelength. 
   Moreover, in accordance with the invention, it is contemplated that filters from both filter wheel  40  and  42  may be used simultaneously in order to have a more selective filtering of wavelengths of light output by lamp  26 . For example, if a filter having a center bandwidth of 415 nm is used simultaneously with the filter having a center bandwidth of 440 nm of the other filter wheel, the resultant filtering will have a center wavelength of approximately 427.5 nm and a bandpass characteristic whose largest wavelength is the longest wavelength passed by the 415 nm filter and a shortest wavelength which is the smallest wavelength passed by the 440 nm filter. In this way, inventive system  10 , though it incorporates only nine filters, will provide nine wide bandwidth bandpass characteristics (using one of the filters in one of the filter wheels, with the other filter wheels set for an open hole which passes light all wavelengths) and eight narrow bandwidth bandpass characteristics (using combinations of relatively proximate wavelengths from each of the two filter wheels). The above configuration allows for the individual use of nine broadband filters (415 nm, 440 nm, 465 nm, 490 nm, 515 nm, 540 nm, 565 nm, 590 nm, 615 nm), a short pass filter (crime scene scanning filter) and white light for searching the crime scene. Additionally, with the configuration mentioned above, nine additional commercially useful wavelength filtering functions with relatively narrow bandwidth (20 to 25 nm) can be achieved. These narrow bandpass filtering capabilities at intermediate wavelengths are especially useful for photography at a crime scene and in many instances will provide improved contrast photographs. More specifically, using the 415 nm filter of filter wheel  40  and the 440 nm filter of filter wheel  42 , one obtains a resultant bandpass with a center wavelength of 427.5 nm; using the 440 nm filter of filter wheel  42  and the 465 nm filter of filter wheel  40 , one obtains a resultant bandpass with a center wavelength of 452.5 nm; using the 465 nm filter of filter wheel  40  and the 490 nm filter of filter wheel  42 , one obtains a resultant bandpass with a center wavelength of 477.5 nm; using the 490 nm filter of filter wheel  42  and the 515 nm filter of filter wheel  40 , one obtains a resultant bandpass with a center wavelength of 502.5 nm; using the 515 nm filter of filter wheel  40  and the 540 nm filter of filter wheel  42 , one obtains a resultant bandpass with a center wavelength of 527.5 nm; using the 540 nm filter of filter wheel  42  and the 565 nm filter of filter wheel  40 , one obtains a resultant bandpass with a center wavelength of 552.5 nm; using the 565 nm filter of filter wheel  40  and the 590 nm filter of filter wheel  42 , one obtains a resultant bandpass with a center wavelength of 577.5 nm; and using the 590 nm filter of filter wheel  42  and the 615 nm filter of filter wheel  40 , one obtains a resultant bandpass with a center wavelength of 602.5 nm. 
   Further, using the 590 nm filter of filter wheel  40  and the crime scene scanning filter of filter wheel  42 , one obtains an asymmetrical filtering characteristic that represents the juxtaposition of the two characteristics of the two filters. There is a sharp decline in fluorescence transmission at the high-end while excitation reflection is blocked. This is useful for highly reflective surfaces, such as aluminum. 
   It is further contemplated that three or more filter wheels may be used in accordance with the present invention. The same may be used to provide an increased number of broad band filters. The use of three or more filter wheels will also provide greater flexibility in making combinations of different filters. These filters may also be used together to achieve an increasingly narrow bandpass filtering. In addition, the use of three or more filter wheels will allow selection of bandpass widths. For example, it may be desired in some cases to combine a 590 nm filter with a 565 nm filter having a first bandwidth while at other times to combine the same 590 nm filter with a 565 nm filter having a second bandwidth, in order to bare the resultant bandwidth. This can be accommodated through the use of additional filter wheels, or filter wheels with greater numbers of filters on them. 
   In an alternative embodiment, filter wheel  140  has an open hole, which passes all light, and a plurality of filters. The filters in filter wheel  140  have the following characteristics: a bandpass filter with a center wavelength of 415 nm with a broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength 440 nm with a broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 465 nm with a broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 490 nm with a broad bandwidth in the range of 40 to 50 nm; and a bandpass filter with a center wavelength of 515 nm with a broad bandwidth in the range of 40 to 50 nm. In accordance with this embodiment of the invention, filter wheel  142  also has an open hole, which passes all light, and filters with the following characteristics: a bandpass filter with a center wavelength of 540 nm with a broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 565 nm with a broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 590 nm with a broad bandwidth in the range of 40 to 50 nm; a bandpass filter with a center wavelength of 615 nm with a broad bandwidth in the range of 40 to 50 nm; and a short pass filter with a maximum pass wavelength of 540 nm (crime scene scanning filter). 
   While an illustrative embodiment of the invention has been described, it is, of course, understood that various modifications of the invention will be obvious 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.