Abstract:
The present invention relates to a low profile, handheld inspection lamp with a unique configuration. Light of different wavelengths is emitted along different portions of the length, and an opaque slider allows the user to select the preferred wavelength of light for a particular task.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This is a continuation-in-part of application Ser. No. 11/284,153, filed Nov. 21, 2005, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to lamps, and especially, but not exclusively, to a lamp of compact shape for handheld use in fluorescence analysis and/or germicidal detection.  
       BACKGROUND  
       [0003]     Fluorescence is generally understood to be a property that enables certain materials to absorb light energy and radiate visible light at a longer wavelength than the absorbed light. Without being limited to any specific theory, it is widely accepted that electrons in fluorescent materials are excited upon being illuminated by light energy of a specific wavelength, and light energy of a longer wavelength is radiated from these materials as the electrons return to the unexcited or ground state. The specific excitation and radiation wavelengths are characteristics of the particular fluorescent materials. The apparent brightness of a fluorescent material&#39;s luminescence is dependent, among other factors, on the wavelength emitted by the material and the intensity of the incident radiation that excites the material. A fluorescent material that has its excitation peak at a specific wavelength may quickly emit a much reduced luminescence as the wavelength of incident light deviates from the excitation peak, and will lose the ability to fluoresce when the incident light does not have enough energy within the specific excitation range.  
         [0004]     Lamps emitting radiation that excites fluorescence have been used for a wide variety of purposes, including, but not limited to, forensic inspection, readmission control, counterfeit currency detection, contamination inspection, non-destructive testing, and detecting leaks in air conditioning and other fluid-containing systems. The lamplight is commonly in the ultraviolet (UV) or in the visible blue-violet range, exciting a fluorescence somewhere in the visible range. The fluorescent material may be deliberately provided. For example, some banknotes have a fluorescent marker embedded in the paper and the UV light is used to detect the otherwise hidden marker. In another example, one method for detecting leaks in an air conditioning system is through the use of fluorescent dyes that are added to and mixed with the refrigerant in the system, with the combination of refrigerant and dye circulating through the air conditioning system. This method was first pioneered by Spectronics Corporation, the assignee of the present invention. In these leak detection systems, the dye circulates through the system, eventually seeping out at the source of the leak. When exposed to a suitable light source, such as an ultraviolet (UV) light, the dye fluoresces, thus highlighting the source of the leak. Stamps using an ink that is visible only by fluorescence under an ultraviolet lamp are used as re-admission stamps at entertainment events.  
         [0005]     The fluorescence may be an incidental property of some material that it is desired to detect, measure, or observe. For example, many biological materials, including rodent hair and urine, are naturally fluorescent. Other examples of the use of fluorescence include the detection of counterfeit currency and other documents. Many minerals can be recognized or distinguished by their levels and colors of natural fluorescence.  
         [0006]     Ultraviolet lamps may also be used to produce an effect on an object, for example, in sterilization, erasing EPROMs, or DNA/RNA cross-linking or otherwise setting or hardening various plastic materials.  
         [0007]     Additionally, ultraviolet lamps have been used for germicidal detection and decontamination. One successful example of such a device was developed by Spectronics Corporation, the assignee of the present invention, and is described in U.S. Pat. No. 6,953,940.  
         [0008]     The visibility of the fluorescent response is increased when the intensity of other visible light is reduced, so that the fluorescent response is not masked or washed-out by other light. Thus, ultraviolet lamps directed in otherwise dark conditions at a system containing a UV responsive fluorescent material may reveal the fluorescent material glowing against the dark background.  
         [0009]     Many current fluorescence-exciting lamps emit light in long wave ultraviolet (UV-A) wavelength range of about 320 nm to about 400 nm, for example, around 365 nm, or in the medium wave ultraviolet (UV-B) range from about 280 nm to about 320 nm, for example, around 315 nm, or in the short wave ultraviolet (UV-C) range, for example, around 254 nm, or in the visible violet/blue range from about 400 nm to about 480 nm within the electromagnetic spectrum.  
         [0010]     For many purposes, a battery operated hand-held lamp that can be directed at less-accessible areas is desirable. Existing lamps powered by an external AC or DC power source have a trailing power lead that hinders maneuvering of the lamp, and cannot be used where a suitable power source is not available. Many existing battery powered lamps are heavy and bulky. The size and shape of the lamp typically hinders maneuvering of the lamp, makes the lamp awkward to grasp in the hand, or both. Small lamps do exist, for example, the UV-4B Series battery operated ultraviolet lamps manufactured and sold by Spectronics Corporation are only about 16 cm long by 2.5 cm wide by 5 cm from front to back. Those lamps are deep from front to back, with the actual light source positioned along one narrow side of the lamp unit.  
         [0011]     A smaller, hand-held UV lamp was developed by Spectronics Corporation and is described in U.S. Pat. No. 6,953,940, referred to above and which is incorporated herein by reference in its entirety. That lamp is light and easily maneuverable. However, the small area of illumination generated by the lamp makes inspection of larger areas more time consuming. More particularly, the narrow width of the unit permits light from the surrounding environment to sometimes overpower the fluorescent response in brightly lit rooms, thus making detection difficult.  
         [0012]     A need, therefore, exists for a battery-powered inspection lamp that is compact, easy to hold, and provides higher output (microwatts/cm 2 ) of the desired wavelength.  
       SUMMARY OF THE INVENTION  
       [0013]     One embodiment of the present invention is directed to a lamp with a housing having a front, a back, sides, and ends. An elongated light source is located within the housing and configured to emit light along a length that is part of the distance from end to end of the housing. A window is provided in the front of the housing along the length for light from the light source to exit the housing. The light exiting the housing is of a first spectral composition along a first portion of the length and of a second spectral composition different from the first spectral composition along a second portion of the length. An opaque shutter is slidable along the front of the housing between a first position in which the shutter blocks light emitted along the first portion of the length and a second position in which the shutter blocks light emitted along the second portion of the length.  
         [0014]     Another embodiment of the present invention is directed to a lamp that includes a housing having a front, a back, sides, and ends. The height of the housing from front to back is less than the width of the housing from side to side, and the width of the housing is less than the length of the housing from end to end. A light source is located within the housing and configured to emit light along at least a portion of the length direction of the housing. At least one receptacle (battery holder) for a battery extends along the length direction of the housing alongside the light source. The receptacle is spaced from the light source in the width direction of the housing.  
         [0015]     In one embodiment of the invention, a reflector is mounted in the housing around the light source. In this embodiment, there may be two receptacles for batteries, one receptacle positioned on either side of the reflector.  
         [0016]     In one embodiment, the light source is preferably configured to emit UV light.  
         [0017]     These and other objects, aspects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description, when considered in conjunction with the appended claims and the accompanying drawings briefly described below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     For the purpose of illustrating the invention, the drawings show a form of the invention which is presently preferred. However, this invention is not limited to the precise arrangements and instrumentalities shown in the drawings.  
         [0019]      FIG. 1  is a front view of one embodiment of a lamp according to the invention.  
         [0020]      FIG. 2  is a front view of the lamp shown in  FIG. 1  with its housing removed.  
         [0021]      FIG. 3  is a rear view of the lamp shown in  FIG. 1 .  
         [0022]      FIG. 4  is a rear view of the lamp shown in  FIG. 1  with the housing removed.  
         [0023]      FIG. 5  is a side view of the lamp shown in  FIG. 1 .  
         [0024]      FIG. 6  is a perspective view of the lamp shown in  FIG. 1 .  
         [0025]      FIG. 7  is a schematic cross-section through the lamp shown in  FIG. 1 .  
         [0026]      FIG. 8  is a perspective view of a second embodiment of a lamp according to the invention.  
         [0027]      FIG. 9  is a is a schematic cross-section through a third embodiment of a lamp according to the invention, looking in a lengthwise direction.  
         [0028]      FIG. 10  is a is a schematic cross-section through a fourth embodiment of a lamp according to the invention, with the housing removed, looking in a front-to-back direction.  
         [0029]      FIG. 11  is a view similar to  FIG. 10  of a fifth embodiment of a lamp according to the invention.  
         [0030]      FIG. 12  illustrates an alternate embodiment of the invention which includes a dual wavelength light source. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     Referring to the drawings, and initially to FIGS.  1  to  7 , one form of lamp according to an embodiment of the invention is shown, indicated generally by the reference numeral  20 . The lamp include a housing  22  having a front  24 , a back  26 , two sides  28 ,  30  and two ends  32 ,  34 . The front  24  and back  26  are preferably generally flat, and a window  36  of at least partially transparent material, such as glass or plastic, is preferably set into or attached to the front  24 . The two sides  28 ,  30  preferably have a generally semicircular or curved cross section, which is convex outwards. Recesses  38  are preferably set into or formed in the sides  28 ,  30 . The recesses  38  occupy approximately the middle third of the height of the housing  22  from front to back, and are curved with a radius similar to the radius of the sides  28 ,  30 . The two ends  32 ,  34  are preferably generally semicircular in cross section, which is also convex outwards. The corners where the ends  32 ,  34  meet the sides  28 ,  30  are preferably spherically curved. Accordingly, the sides and ends of the lamp housing provide gently contoured surfaces which facilitate handling and holding by the user.  
         [0032]     In the interior of the housing  22  is a light source  40 , which is shown in  FIGS. 1, 2 , and  7  as a discharge tube, extending along the housing  22 , aligned approximately along the middle of the housing, for most of the length of the lamp  20 . However, as will be apparent, the light source  40  can be configured and mounted in a variety of ways within the housing. The light source  40  and the window  36  occupy roughly the same part of the length of the lamp  20 . In the illustrated embodiment, the light source  40  is not centered lengthwise. This is due in part to the packaging of the lamp in the illustrated embodiment as discussed below. However, other configurations can include a centered lamp.  
         [0033]     At one end  32  there is a circuit board  42  containing a switch  44  and circuitry  46  needed to drive the light source  40 . For example, where the light source  40  is a discharge tube, the circuitry  46  may include components such as an oscillator, a transformer, and a choke. The switch  44  on the circuit board  42  is connected to a switch actuator  48  on the outside of the back  26  of the housing  22 . In order to provide a convenient package design, the other end  34  of the housing  22  preferably includes only the necessary mechanical supports and electrical connectors.  
         [0034]     The light source  40  is located within a reflector  50 . The reflector  50  may be hyperbolic or semi-cylindrical. However, in the illustrated embodiment, the reflector includes a flat back panel  52  between the light source  40  and the back  26  of the housing  22 . Two angled side panels  54  are attached to the flat back panel and spread apart from the side edges of the back panel  52  to positions just behind the side edges of the window  36 . The face of the reflector panels  52 ,  54  towards the light source  40  is preferably highly reflective, and may be white, polished (mirrored), such as an anodized vapor deposition coating, or in between.  
         [0035]     Outside the reflector panels  54 , between the reflector  50  and the housing sides  28 ,  30 , are holders  56  for batteries  58 . The battery holders  56  are formed in one piece with the reflector  50 . The batteries  58  are cylindrical, with their length along the end-to-end direction of the housing  22 . As is best shown in  FIG. 4 , each of the battery holders  56  can hold more than one battery end to end. As is best shown in  FIG. 7 , the batteries  58  lie side by side with the light source  40 , aligned in the side-to-side direction, and the whole combination of light source  40 , reflector  50 , battery holders  56 , and batteries  58  has a very compact shape. In the front to back direction, the height of the combination is only the height of the reflector, which exceeds the diameter of the light source  40  only by the clearance provided for air circulation to avoid overheating of the light source. In the side to side direction, the width of the combination is only a little more than the combined diameters of the light source  40  and two batteries  58 . The housing  22  fits closely found the combination of light source  40 , reflector  50 , battery holders  56 , and batteries  58 , and can thus be both compact in cross-sectional area and flat in shape.  
         [0036]     At one end of each battery holder  56 , a contact  60  is mechanically attached and electrically connected to the circuit board  42 , and is positioned to contact the nearest battery  58 . The contacts  60  may alternatively be mechanically attached to the battery holders  56  or to the housing  22 . One of the contacts  60  may be electrically connected to the switch  44 , so that opening the switch interrupts the power supply from the batteries. The contacts serve to transmit power from the batteries  58  to the circuit board  42 , from which power is supplied to the light source  40 . Each of the contacts  60  may be an appropriate contact for the batteries  58  that are intended to be used. Where the batteries  58  are of a sort that has differently-shaped contacts at the two ends, the contacts  60  may be correspondingly different. Facing the contacts  60 , and spaced apart therefrom by the length of the two batteries  58  that each battery holder  56  is intended to hold, are a corresponding pair of contacts  62 . The contacts  62  may be of similar form to the contacts  60 . Where the two contacts  60  are different, the contact  62  in each battery holder  56  may be similar to the contact  60  in the other battery holder  56 .  
         [0037]     The two contacts  62  are electrically connected by a bridge  64 , which in  FIG. 4  is in the form of a length of insulated electrical wire passing between housing end  34  and the adjacent end of reflector  50 . Bridge  64  may alternatively pass between housing back  26  and reflector back panel  52 . An electrical path is thus formed from the circuit board  42  through one contact  60 , the batteries  58  in one battery holder  56 , one contact  62 , the bridge  64 , the other contact  62 , the batteries  58  in the other battery holder  56 , and the other contact  60 , back to the circuit board  42 .  
         [0038]     A connector  66  for an external power supply may be used to recharge the batteries  58 , to conserve battery life by powering the light source  40  from the external supply part of the time, or both.  
         [0039]     In an example of dimensions, the housing  22  is about one inch (25 mm) high between the front  24  and the back  26 , about 2¼″ (57.5 mm) wide between the sides  28 ,  30 , and about 9″ (230 mm) long. A housing  22  of this size can be held by an ordinary adult in the palm of one hand, with the back  26  in the palm and with the tips of the fingers resting in the recess  38  along one side, for example, side  28 , and the tip and heel of the thumb resting in the recess  38  along the other side, for example, side  30 . The person holding the lamp  20  can then easily aim the window  36  in almost any direction including being able to reach past a piece of equipment or other bulky object and aim the window  36  at the far side of the equipment.  
         [0040]     The flat shape of the housing  22  not only is ergonomically useful, because it is easy to grasp and maneuver with one hand, but also facilitates insertion of the lamp  20  through narrow gaps between and behind pieces of equipment. Positioning the light source  40  close to one end  34  of the housing  22 , with the circuit board  42  at the other end  32 , also facilitates such maneuvers, because the distance to which the end  34  must be introduced into a gap to provide a desired illumination is reduced.  
         [0041]     In addition, because the housing  22  projects to both sides of the window  36 , when the lamp  20  is held close to the object being examined the housing  22  tends to cast a shadow from any ambient light. The illumination from the lamp  20  is directed into this shadow, and any fluorescence occurs within the shadow. As a result, the visibility of the fluorescence may be improved, especially in well-lit areas where the ambient light might otherwise tend to overwhelm the fluorescence.  
         [0042]     In the illustrated example, the light source  40  and the window  36  are both about 6″ (150 mm) long. Up to six batteries of the size “AA” can be accommodated in this embodiment, with three batteries in a row end to end in each of the battery holders  56 . As shown in  FIG. 4 , fewer than six batteries may be used depending on the power needed and the configuration of the unit. Also, different forms of battery can be used, such as AAA batteries, or rechargeable batteries. The position of the contacts  62  may be changed to accommodate a desired number of batteries of a desired size.  
         [0043]     As shown in the figures, the window  36  may be a transparent or translucent panel set into the front  24  of the housing  22 . The window  36  may comprise a filter that is transparent or translucent only or configured to transmit primarily light of a desired wavelength (and filter out most other light.) For example, where the lamp  20  is intended to excite fluorescent dyes, the window  36  may comprise a filter that transmits light in one or more of the UV-C, UV-B, UV-A, or visible wavelength ranges. The filter may exclude or greatly diminish other visible light, especially green or yellow light, that might drown out the light emitted by fluorescence.  
         [0044]     Alternatively, the light source  40  may be sheathed or integrally coated with the filter. The window  36  may then be simply an opening in the housing  22 , or may be a clear window that is transparent over a wide range of wavelengths.  
         [0045]     Referring now to  FIG. 8 , in which the same reference numerals are used for features already shown in FIGS.  1  to  7 , an alternative form of lamp  80  is similar to the lamp  20  shown in FIGS.  1  to  7 , except that the lamp  80  has a filter carrier  82  attached over the window  36 . The filter carrier  82  can have one or more filters  84  with different spectral transmission characteristics, mounted (or formed) end to end, each overlying a portion of the length of the window  36 . An opaque slider  86  is movable along the filter carrier  82  between end positions such that the slider covers one or more of the filters  84  while leaving one or more of the filters exposed. In an embodiment shown in  FIG. 8 , the filter carrier  82  can have two filters  84 , each occupying half the length of the open area of the filter carrier, and the opaque slider  86  is about half the length of the open area. The opaque slider  86  may then be moved between two end positions, in each of which one of the filters  84  is completely exposed and the other filter is completely covered.  
         [0046]     For example, one of the filters  84  may transmit visible violet/blue light while blocking longer wavelength visible light. The other filter  84  may transmit UV light while blocking most of the visible light. Alternatively, the two filters  84  may transmit UV light of different wavelengths. It is also contemplated that one of the filters  84  may be a clear window or a broad-band filter transmitting white light, for use of the lamp  80  as an ordinary lamp. Of course, for certain uses no filter may be needed, such as germicidal applications. The clear window overlying one portion of the length of the window  36  may then be an open space. In the embodiment shown in  FIG. 8 , the light source  40  emits light over a range of wavelengths including the transmission ranges of both filters  84 .  
         [0047]     Referring now to  FIG. 9 , a third form of lamp  90  is similar to the lamp  20  shown in FIGS.  1  to  7 , except that lamp  90  has two tubular light sources  92  side by side instead of the single discharge tube  40  shown in  FIGS. 1, 2 , and  7 . As may be seen from a comparison of  FIGS. 7 and 9 , the tubular light sources  92  are of smaller diameter than the discharge lamp  40  to avoid increasing the overall width of lamp  90  between sides  28 ,  30  as compared with the width of lamp  20 . However, the smaller diameter of the tubular light sources  92  may permit a smaller thickness between the housing front  24  and the housing back  26 . By doubling the effective length of tube of light sources  92  as compared with single discharge tube  40 , additional light emission is possible. Furthermore, the use of a thinner diameter tube as shown in  FIG. 9  allows for a reduction in the height of the housing  22 .  
         [0048]     Referring now to  FIG. 10 , a fourth form of lamp  100  is similar to the lamp  90  shown in  FIG. 9 . However, in the lamp  100  the light source is a single U-shaped tube  102  instead of two straight tubes side by side. In  FIG. 10 , three batteries  58  are shown in each battery holder  56 . The contacts  62  are close to housing end  34 , and are connected by a solid bridge  104 , which may be formed from metal strip, mounted in an insulating mounting  106  at the end of reflector  50 .  
         [0049]     Referring now to  FIG. 11 , in a fifth form of lamp  110  the source of light is an array of light emitting diodes (LEDs)  112 . LEDs capable of producing light in the long wave ultraviolet (UV-A) wavelength range of about 320 nm to about 400 nm, or in the visible violet/blue range from about 400 nm to about 480 nm, are known. LEDs capable of producing whitish light are also known. The LEDs  112  may be arranged, for example, as a row of LEDs  114  optimized to produce ultraviolet light, a row of LEDs  116  optimized to produce visible violet/blue light, and a row of LEDs  118  optimized to produce white light. An on/off switch  120  may then be a multi-position switch arranged to selectively activate a desired row, or combination of rows, of LEDs. Other arrangements are possible, for example, only one or two of the three sorts of LEDs  114 ,  116 ,  118  may be provided, or more than three sorts of LEDs may be provided to give a wider choice of wavelengths. For example, a single set of LEDs may emit both UV-A and visible violet/blue light. For example, the LEDs may be arranged in a pattern other than a row or rows. Because LEDs  112  are smaller than the diameter of the discharge tube  40  or  92 , a further reduction in the size of the housing  22  is possible.  
         [0050]     Referring now to  FIG. 12 , a sixth form of lamp  130  is generally similar to the first form of lamp shown in  FIG. 1 , except that the light source  140  is different at its two ends. As shown in  FIG. 12 , the light source  140  is a discharge tube with a fluorescent coating  142  over one half  144  of the length of the light source, and a clear tube over the other half  146  of the length of the light source. Typically, the discharge tube  140  generates light with a large ultraviolet wavelength component, the spectrum of which in the clear half  146  is limited only by the transmissivity of the tube. In the coated half  144 , the fluorescent coating  142  then absorbs some or all of the ultraviolet light, and emits light of lower frequency, for example, visible light, or may absorb UV-B light and emit UV-A light. Alternatively, different parts of the length of the discharge tube  140  may be coated with different fluorescent coatings, to produce light of different spectral compositions.  
         [0051]     The discharge tube  140  shown in  FIG. 12  may be used in combination with the filter carrier  82  shown in  FIG. 8 , and the shutter  86  (not shown in  FIG. 12 ) may be moved to expose either the clear half  146  or the coated half  144  of the tube  140 , or part of each half, as desired. The filter carrier  82  may have a filter  84  over either half  144 ,  146  or both halves of the tube  140 , to further modify the spectral content of the light emitted. Alternatively, either half or both halves of the filter carrier  82  may transmit substantially all the light from the tube  140 . If either half of the filter carrier  82 , that half may contain a clear or diffusing window or broadband filter that transmits substantially all the light from the tube  140 , and acts as a physical protection for the tube, or may be open, with no filter  84 .  
         [0052]     Various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. For example, although the light source  40 ,  92 ,  102 ,  112 ,  140  is shown in the drawings as one or more discharge tubes or arrays of LEDs, other forms of light source may be used that fit within the desired long, narrow profile.  
         [0053]     Although the filter carrier  82  and the tube  140  have been described primarily as being divided into two halves, other arrangements are possible. For example, there could be more than two distinct portions along the length of the lamp.  
         [0054]     Although several embodiments have been described, features from different embodiments may be combined. For example, either the switch  44 ,  48  shown in  FIGS. 1-7  or the switch  120  shown in  FIG. 11  may be on either the side or the back of the housing  22 . Alternatively, the switch  44 ,  48  or  120  may be on the front or the other side of the housing. For example, the two tubular light sources  92  shown in  FIG. 9 , like the rows of LEDs  114 ,  116 ,  118  shown in  FIG. 11 , may be arranged to emit light of different wavelengths, and the on/off switch may be a multi-position switch  120  to selectively switch on one and/or the other light source  92 . For example, the filter carrier  82  of  FIG. 8  may be applied to any of the lamps shown in FIGS.  9  to  11 . For example, the partial coating  144  of the tube  140  of  FIG. 12  may be adapted to the twin light sources  92  of  FIG. 9  or the U-shaped light tube  102  of  FIG. 10 . A similar effect may be achieved in the lamp  110  of  FIG. 11  by placing LEDs  112  of different colors at different portions of the length of the lamp.  
         [0055]     One of the benefits provided by the present invention is that the wider shape of the housing produces a “shadow box” effect. That is, the housing creates a shadow around the area being illuminated. This reduces the amount of surrounding room light that illuminates the area being inspected, thus increasing the fluorescent response. The location of the reflector and thin design also produces enhanced UV intensity of the emitted light, thus providing an improved lamp.  
         [0056]     Although the invention has been described and illustrated with respect to the exemplary embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention.