Abstract:
An electrically powered image intensifier having an output and an input is optically coupled to the lens to receive the focused light image from the lens and provide at the output of the image intensifier an intensified light image. A chassis is configured to support the intensifier and to mainly engage the lens by engaging the mounting structure. The lens is engaged by the mounting structure in a use position. A power source is coupled to the image intensifier by an electrical switch having an open and a closed state. The switch is connected to couple electrical power from the power source to the image intensifier in the closed state and to decouple electrical power from the power source from the image intensifier in the open state. The electrical switch comprises an operator for configuring the electrical switch in the open state in an open operator position or in a closed state in a closed operator position. The operator is biased in the open operator position. The operator is urged in the use position into the closed operator position by the mounting structure.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is directed to the detection of fingerprints and other forensic evidence employing an image intensifier. More particularly, the present invention is directed to a damage resistant light imaging system that photographs and provides viewing of fingerprints and other evidence.  
         BACKGROUND OF THE INVENTION  
         [0002]    Special tools are frequently used by law enforcement personnel when evaluating a crime scene to collect forensic evidence that may be hard to see or invisible to the human eye. Examples of such evidence include bodily fluids, fingerprints on porous and non-porous surfaces, forged documents, explosive residue, and trace evidence e.g., hair, fibers, etc.  
           [0003]    One commonly used tool is a forensic light source that utilizes fluorescent light to detect and record forensic evidence. Subjects illuminated by a forensic light source may be viewed through light filtering goggles, and the output of the source may be filtered to achieve a range of diverse functionalities and corresponding capabilities, with and without the use of chemical developers, powders and dyes.  
           [0004]    A recently introduced tool complementary to the forensic light source is a tool that relies on intensified short-wave ultraviolet (or “uv”) reflectance instead of fluorescence. Such an ultraviolet light tool can reveal otherwise undetectable or difficult to detect evidence on non-porous surfaces where a forensic light source is not useable or the subject requires processing with powders or fluorescent dye. Such systems can increase the area that can be efficiently inspected at a crime scene.  
           [0005]    In some conventional forensic tools that utilize ultraviolet light reflectance from an ultraviolet light source a traditional photograph is taken at the output of an intensifier tube. However, photography at the output of an intensifier is limited in resolution by the number of line pairs/mm in the specification of the intensifier.  
           [0006]    One ultraviolet light tool that does not rely on the output of an intensifier to obtain a photograph is the “SceneScope” (trademark) ultraviolet light imager or forensic viewer, which is a system with a modified Nikon FM2 camera. This product is available from J Y Horiba, Inc. The Scenescope utilizes an intensifier and a modified 35 mm camera to provide both non-intensified photography of reflectance of fingerprints on various backgrounds, and simultaneous intensified image focusing and viewing. An intensifier is useful to obtain the focus when using an invisible light source such as ultraviolet light (200-400 nm) or infrared (above 700 nm) since ultraviolet light or infrared images will not be visible to, and may be harmful to, the naked eye. The intensifier operates electronically to increase the luminescence of the image and provide a visible wavelength output for example on a video screen.  
           [0007]    In a device of this type, as disclosed in U.S. Pat. No. 6,392,238 (the disclosure of which is incorporated by reference), an ultraviolet forensic viewer comprises a camera having a focusable camera lens to input ultraviolet light images to the camera, the camera being loadable with a film to capture images received from the camera lens. The spacing of the camera lens from the film, when loaded, is adjustable to focus an input ultraviolet image on the film. A camera mirror has an ultraviolet-reflective surface to reflect and image light received from the camera lens to provide a reflected ultraviolet image for use in focusing the camera lens. An image intensifier is optically coupled to the camera to receive the reflected ultraviolet image from the camera mirror and provide a viewable output. The reflected ultraviolet image is focused to the viewable output of the intensifier.  
           [0008]    In this device, the camera lens incorporates optical elements which are ultraviolet-transmissive, optionally quartz, and one may employ an ultraviolet filter with the camera lens. The camera (optionally a single lens reflex camera) may comprise a viewing lens system to receive an ultraviolet image reflected by the camera mirror and project that ultraviolet image to the image intensifier. Optionally, an eyepiece or a video camera may be coupled to the intensifier.  
         SUMMARY OF THE INVENTION  
         [0009]    Still other image intensifying viewers generally comprise a T-shaped configuration, generally comprising an elongated member comprising a removable 35 mm lens at the end of a chassis holding an image intensifier. By “35 mm lens” is meant a lens for a 35 mm camera, that is a camera which accepts 35 mm film. If desired, the unit may be used in conjunction with an ultraviolet light source to reveal latent fingerprints or other evidence which is invisible or hard to see using only the unaided human eye.  
           [0010]    However, one problem with image intensifying crime scene viewers is that the image intensifier is vulnerable to damage in the event of direct exposure to common levels of ambient light for a period of time. For example, an operating image intensifier may have a specification that it is able to sustain light at a given level of intensity for a specific short period of time, before suffering damage. This period of time may be on the order of sixty seconds at light levels as little as, for example, fifty millilumens on an area of one millimeter.  
           [0011]    In the event that one wishes to change the lens on such an image intensifying crime scene viewer, the input face of the imager would be subjected to whatever ambient light conditions exist at that time. While, in principle, it is possible to remember to manually remove power from the image intensifying crime scene viewer to avoid damage, in practice this may be forgotten. Even when the user remembers to do this, under the pressure of trying to get a task done in a reasonable amount of time, or in the face of distraction on account of information being gathered or due to some other cause, the state of the image intensifying crime scene viewer may not be correctly noted and damage done to the unit. Based on the foregoing, there is a need for an improved ultraviolet light imaging system.  
           [0012]    In accordance with the invention, an image intensifying forensic viewer, comprises a lens configured to focus light, from an object or surface being imaged, as a focused light image. The lens comprises mounting structure for mounting on the inventive viewer.  
           [0013]    An electrically powered image intensifier having an output and an input is optically coupled to the lens to receive the focused light image from the lens and provide at the output of the image intensifier an intensified light image. A chassis is configured to support the intensifier and to mainly engage the lens by engaging the mounting structure. The lens is engaged by the mounting structure in a use position. A power source is coupled to the image intensifier by an electrical switch having an open and a closed state. The switch is connected to couple electrical power from the power source to the image intensifier in the closed state and to decouple electrical power from the power source from the image intensifier in the open state. The electrical switch comprises an operator for configuring the electrical switch in the open state in an open operator position or in a closed state in a closed operator position. The operator is biased in the open operator position. The operator is urged in the use position into the closed operator position by the mounting structure.  
           [0014]    In accordance with the preferred embodiment of the invention, the lens is moveable, engaged by the mounting structure, between a use position and a release position which allows the release of the mounting structure and the lens.  
           [0015]    In one embodiment of the invention, the lens transmits ultraviolet light, and the electrically powered image intensifier is sensitive to ultraviolet light and the lens is a focusable lens.  
           [0016]    In the preferred embodiment of the invention, the lens has bayonet mounting structure configured to nest into and be rotated into engagement with mating bayonet mounting structure on the chassis.  
           [0017]    Alternatively, the lens may have snap mounting structure configured to snap into engagement with mating snap mounting structure on the chassis. Any other suitable mechanical coupling arrangement may be employed.  
           [0018]    A camera for presenting the output of the image intensifier to photographic film in the camera or an eyepiece functioning as viewing optics for presenting the output of the image intensifier to the eye of a viewer may be used in conjunction with the inventive viewer.  
           [0019]    One embodiment of the present invention is an ultraviolet light imaging system that includes a camera. In this embodiment the chassis and the lens are configured to focus light from an object or surface being imaged and comprise a single lens reflex camera, comprising a camera lens and a camera body. Viewfinder optics of the type customarily used in a single lens reflex camera reflect the focused light image from the output of the image intensifier for viewing of the intensified image on the output of the image intensifier by a user. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:  
         [0021]    [0021]FIG. 1 is a perspective view of the inventive forensic viewer;  
         [0022]    [0022]FIG. 2 is an unexploded perspective view showing the principal parts of the inventive forensic viewer;  
         [0023]    [0023]FIG. 3 is a detail illustrating the operation of a protective switch for the inventive viewer;  
         [0024]    [0024]FIG. 4 is a detail, similar to FIG. 3, showing the switch in the power applying position;  
         [0025]    [0025]FIG. 5 is a perspective view of the inventive viewer illustrating the front of the system; and  
         [0026]    [0026]FIG. 6 is a side plan view of the inventive viewer illustrating use with a camera;  
         [0027]    [0027]FIG. 7 illustrates holding of the inventive viewer;  
         [0028]    [0028]FIG. 8 illustrates an alternative embodiment of the inventive viewer; and  
         [0029]    [0029]FIG. 9 illustrates another alternative embodiment of the inventive viewer. 
     
    
     DETAILED DESCRIPTION  
       [0030]    As illustrated in FIG. 1, the inventive forensic viewer  10  comprises a housing  12  which contains an image intensifier  14 , as can be seen in the exploded perspective view of FIG. 2. Image intensifier  14  has an input face  16  upon which the image of an object being viewed is imaged. The image of the object being viewed is imaged by a 35 mm camera type lens  18 .  
         [0031]    Image intensifier  14  is rigidly supported within a chassis  20 . Chassis  20  is rigidly supported within a housing  12 . Housing  12  comprises two mating housing members  22  and  24 . Mating housing members  22  and  24  are secured by screws (not illustrated) to chassis  20 . These screws pass through holes  28  and anchor into tapped holes  30  in chassis  20 .  
         [0032]    Power to the unit is provided by a battery  32  which is contained within a battery receiving compartment  34  defined by mating half cavities within housing members  22  and  24 . Battery  32  is coupled to the circuit by a positive terminal coupler  36  secured to a battery compartment cover  37  which is slidably held in mating recesses  38  in housing members  22  and  24 . The negative terminal  40  of battery  32  is coupled to negative terminal coupler  42  which includes a loop  44  which extends around and engages wall  46  on housing member  24 .  
         [0033]    Plate  48  is made of metal and slides into positive terminal housing member  24 . Plate  48  comes into electrical contact with coupler  36 , when the battery compartment cover  37  is slidably held in mating recesses  38  in housing members  22  and  24 . Plate  48  also has a small hole in which an electrical wire can be soldered. This wire is then connected to interlock switch  80 , which controls the removal of power from the image intensifier. Plate  48  closes the electrical circuit with coupler  36 , as no wire can be soldered to coupler  36 , because the battery compartment cover  37  is removed to replace the battery, and it is not desirable to have any component or wire attached to it.  
         [0034]    A key  50  is secured to chassis  20  and has a registration rod  52  for guiding the installation of springy friction member  54  and mounting ring  56  through the use of a pair of holes  58  and  60  respectively. In particular, registration rod  52  passes through holes  58  and  60  thus ensuring that they are maintained in proper relationship to each other and the rest of the system. Springy friction member  54  and mounting ring  56  are held in place by three substantially equispaced screws (not illustrated), two of which pass through holes  62  and  64  in mounting ring  56  and springy friction member  54 , respectively.  
         [0035]    Lens  18  includes a focusing cylindrical grip  66  and a number of focusing optical members  68 . Lens  18  is provided with a so-called bayonet mounting comprising a number of circumferential studs  70 , which extend outwardly and radially from the base  72  of the body of lens  18 . Studs  70  are positioned radially to be able to pass through the inner side walls  74  and  76  of mounting ring  56  and springy friction member  54 , respectively, between inwardly extending mating studs  78 . Studs  70  mate with mating studs  78 . More particularly, after insertion of lens  18 , while it is in the angular position illustrated in FIG. 2, lens  18  is rotated clockwise into the mating position where studs  70  have their outwardly facing surfaces bearing against that portion of the outwardly facing surface of springy friction member  54  which overlies the inwardly facing surfaces of circumferential studs  70 .  
         [0036]    During installation of lens  18  onto viewer  10 , rotation of lens  18  beyond the mating position is prevented by registration rod  52 .  
         [0037]    Alternatively, other lens mounting structures may be used such as screw or snap mounts.  
         [0038]    Power is coupled from battery  32  to image intensifier  14  by a single-pole single-throw switch  80  which is capable of assuming either a closed or open state. The state of switch  80  is controlled by operator  82  which is a lever which is pivotally mounted at one end and is terminated at the other end in a plastic cam follower  84 . As illustrated most clearly in FIG. 3, when lens  18  is not mounted in viewer  10 , cam follower  84  bears against that portion of inward surface of springy friction member  54 , which faces its respective stud  78 .  
         [0039]    When lens  18  is inserted into the bayonet mounting formed by studs  78  on mounting ring  56 , and rotated, studs  70  pass underneath studs  78 . In the case of studs  70   a  and  78   a , stud  70   a  passes between cam follower  84  and that portion of springy friction member  54  which overlies stud  78   a , resulting in advancing lever arm  86  in the direction of arrow  88 , moving arm  86  from the position illustrated in FIG. 3 to the position illustrated in FIG. 4. This results in the depression of switch button  90 , causing switch  80  to assume the close state and conduct electricity to image intensifier  14 , thus powering the image intensifier and allowing the system to operate.  
         [0040]    Conversely, when lens  18  is rotated in the counterclockwise direction, stud  70   a  is also rotated in the counterclockwise direction pulling it out, from in between cam follower  84  and stud  78   a , causing lever arm  86  to spring back from the position illustrated in FIG. 4 to the position illustrated in FIG. 3.  
         [0041]    Support plate  92  is inserted into and maintained in position when housing members  22  and  24  are assembled together. Additionally, two screws (not illustrated) maintain support plate  92  in position in viewer  12 . Support plate  92  is taped with a ¼×20 thread. This thread size is standard on any photographic camera. Support plate  92  is used to fix the viewer on any tripod or copy-stand when a photo must be shot and mates with the tripod camera securing belt.  
         [0042]    Bracket  94  includes a pair of holes  96  through which the screws, which secure mating housing member  24  to chassis  20 , pass. Bracket  94  also includes a pair of strap engaging loops  98  which pass through holes  100  in mating housing member  24 . This allows them to extend out of the housing when the inventive viewer  10  is assembled in the manner illustrated in dashed lines in FIG. 2. Bracket  94  also includes a pair of holes  99 , through which screws, which secure bracket  94  to chassis  20 , pass.  
         [0043]    A rubbery soft comfort cowl  102  overlies a relatively stiff plastic cover  103 . Cowl  102  includes gripping surfaces  104  on both its sides, and also bears against a pair of elongated holes  106  through which strap engaging loops  98  extend when the inventive viewer  10  is fully assembled.  
         [0044]    As is illustrated in FIG. 5, an on off switch  108  is secured in position by a nut  110 . On-off switch  108  is a push button switch which is changed between the open and closed state by repeated depression of its associated push button which extends through mating housing member  24 . In similar fashion, mating housing member  22  has a pilot light  112  mounted in it.  
         [0045]    A strap  114 , which includes a pair of fabric strap loops  116 , completes the structure. Fabric strap loops  116  engage strap engaging loops  98  which may be made of metal, in contrast to most of the other structural parts which may be made of plastic. If desirable, threaded parts and chassis  20  may be made of metal. It is noted that the top surface  118  of cowl  102  is rounded to accommodate the palms and inside surfaces of the fingers of the hand of an operator of the inventive viewer  10 , who has passed his through the strap  114  in the fashion of a video camcorder.  
         [0046]    Viewing by the human eye is accommodated by an eyepiece  120 , which includes threads  122  which engage mating threads  124  on the inside of chassis  20 . The eyepiece  120  also includes a rubbery eyecup  126  to exclude ambient light while at the same time providing comfort to the user.  
         [0047]    In accordance with the preferred embodiment of the invention, it is contemplated that one or more filters  128  may be attached to lens  18 . The system will also accommodate a lens cap  130  which performs the function of protecting the optics of the system.  
         [0048]    When it is desired to use the inventive system when illuminating a subject with ultraviolet light, an ultraviolet filter, such as filter  128  may be mounted on lens  18  to eliminate all but ultraviolet light from entering the system. Of course, if light produced by other physical effects are being detected, other filters, such as bandpass filters tuned to an expected wavelength range of fluorescent emissions, may be employed on lens  18 .  
         [0049]    During use, light admitted into lens  18  is focused on the front face  16  of image intensifier  14  resulting in the production of a bright image on the output face  130  of the image intensifier. This image is focused by eyepiece  120  for viewing by the human eye.  
         [0050]    As has been alluded to above, it is contemplated that in some, but not all cases, the inventive viewer  10  will be used in connection with the observation of ultraviolet light images. Accordingly, it is desirable that lens  18  have the characteristic of efficiently transmitting ultraviolet light, and that the lens is made of suitable materials, such as quartz, and/or lenses including appropriate coatings will be used in lens  18  where operation in conjunction with ultraviolet images is desired.  
         [0051]    In the event that lens  18  is removed from the inventive viewer  10 , the rotation of lens  18  necessary for removal results in moving switch  80  from the position illustrated FIG. 4 to the position illustrated FIG. 3, resulting in the removal of power from image intensifier  14 . As a result, image intensifier  14  is not subjected to what are likely to be excessive light intensities while under power. Accordingly, with switch  80  in the open position, there is no power applied to image intensifier  14 , and image intensifier  14  can therefore sustain exposure to light without damage.  
         [0052]    If desired, a standard 35 mm SLR camera mounted with a standard photographic lens may be connected directly behind eyepiece  120 . The same way a user of such a camera sees the intensified image with his eye through the eyepiece  120 , a 35 mm SLR camera, equipped with its photographic lens (its eye), will see through the eyepiece the same intensified image. See the description of FIG. 8 below.  
         [0053]    If desired, an adapter which screws into chassis  20  in place of eyepiece  120  may be used to attach to a photographic film camera for permanently recording images produced by the inventive viewer  10 . Referring to FIG. 6, such an adapter  136  has threads  138  that mate with the inside threads in chassis  20 . At the other end, adapter  136  has mounting structure  140  similar to studs  70  which permit the inventive viewer  10  to be attached to an ordinary 35 mm camera  142  in much the same manner as a conventional 35 mm lens. Adapter  136  also includes optics  144  for the focusing the image from image intensifier  14  onto film  146  in the body of 35 mm camera  142  which has been equipped with the inventive viewer, as if the inventive viewer where a specialized lens or other accessory.  
         [0054]    Viewfinder optics  148  of the type customarily used in a single lens reflex camera reflect the focused light image from the output of the image intensifier for viewing of the intensified image on the output of the image intensifier by a user  150 .  
         [0055]    As shown in FIG. 7, then inventive viewer  10  may be comfortably gripped by the hand  180  of a user on account of the round top surface  182  of the same. Comfort and sure grip is promoted by narrow portion  184  and the grippable rubber surface of cowl  102 .  
         [0056]    In accordance with another embodiment of the invention, as illustrated in FIG. 8, inventive system  210  comprises an intensifier unit like that of the earlier embodiment including the inventive protection switch. A camera  214  with a lens  216  is optically and mechanically coupled to the output of intensifier  212 . A lens  218  is coupled to intensifier  212  and when removed opens the protection switch.  
         [0057]    In accordance with another embodiment of the invention, as illustrated in FIG. 9, inventive system  310  comprises an intensifier unit, like that of the earlier embodiment, and including the inventive protection switch. An SLR camera  314  with a modified viewfinder optic  216  provides its viewfinder output to intensifier  312 . Intensifier  312  is optically and mechanically coupled to the viewfinder output. A lens  218  is coupled to camera  314 . When the intensifier  312  is removed from the viewfinder, coupling structure opens the protection switch situated between the intensifier and the viewfinder optic.  
         [0058]    Several embodiments of the present invention are specifically illustrated and/or described herein. However, it will be appreciated that modification and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.