Abstract:
An assembly is disclosed that provides for the installation of an inverted reflector cup over the optical dome of a light emitting diode (LED) package wherein the reflector has a single controlled output opening through which the output of the LED is focused. The reflector assembly is designed to completely cover the light output end of the LED package in order to capture all of the light being emitted from the LED chip. The interior surface of the reflector is curved to redirect as much of the emitted light toward the front of the optical package as possible. The present invention is particularly suited for use a variety of lighting devices including but not limited to flashlights, specialty architectural grade lighting fixtures and vehicle lighting.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is related to and claims priority from earlier filed provisional patent application No. 60/404,489, filed Aug. 19, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a new reflector assembly for use with a light emitting diode (LED) device. More specifically, the present invention relates to an inverted reflector for installation over an LED lamp that collects and concentrates the light emitted from the LED to provide a narrowed and collimated beam output.  
           [0003]    Currently, manufacturers are producing a wide range of high brightness LED packages in a variety of forms. These packages range from conventional LED lamps to LED&#39;s that use emitter chips of much greater size and much higher power consumption. In general, however, the protective dome placed over the emitter chip, while intending to provide a level of optical concentration of the light, generally produces a relatively wide-angle beam. One example of a high brightness LED of this type is the Level 1 Assembly LED, manufactured by Luxeon. The Luxeon LED uses an emitter chip that is four times greater in size than the emitter chip used in standard LED lamps. While this LED produces a much greater light output than the standard LED, it produces a very disperse wide-angle beam that is difficult to capture for efficient collimation and beam imaging in practical application, such as in a flashlight. As a result, a great deal of the output energy is lost as leakage out the side of the LED package.  
           [0004]    Generally, when these high intensity LED&#39;s are incorporated into a flashlight, the manufacturer attempts to image and transfer as much light as possible from the LED to the flashlight beam by using large diameter, long focal length lenses. While this solution provides an adequate output beam in the flashlight, two distinct issues arise. First, the imaged beam is inefficient because as noted above, much of the light in these LED packages escapes from the side of the LED thus being lost within the flashlight and not transferred into the far field beam image captured by the lens. Second, since these lenses are imaging an LED die that is coated With a yellow phosphor layer, the beam inherits a yellowish cast. Therefore, there is a need for an assembly that can successfully concentrate and transfer as much of the available light emitted from an LED into the far field of the flashlight beam.  
           [0005]    In order to capture the light leaking at the sides of the LED package and improve the efficiency of the overall assembly, many manufacturers have placed the LED packages into openings at the rear of traditional parabolic type reflectors as are well known in the art. While these reflectors capture and redirect a great deal of the light output, they provide a low quality image in the far field of the lighting device. These reflectors simply transfer a large image of the LED die into the far field of the beam resulting in poor quality illumination.  
           [0006]    There is therefore a need for a unique reflector design that is tailored for use with high output LED packages that has improved efficiency in capturing and transferring a high percentage of the lamp output, while providing a high quality light image in the far field of the light beam.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    In this regard, the present invention provides for a novel lighting assembly that utilizes a high intensity LED with a unique inverted reflector arrangement to capture and redirect the light output into a collimated and homogenized beam. The assembly is particularly suited for use in compact lighting assemblies such as flashlights.  
           [0008]    In accordance with the present invention, an assembly is disclosed that provides for the installation of an inverted reflector cup over the optical dome of the LED package. The reflector cup has a single controlled output opening through which the output of the LED is focused. The reflector assembly is designed to completely cover the light output end of the LED package in order to capture all of the light being emitted from the LED chip. The interior surface of the reflector is curved in such a manner to redirect as much of the emitted light toward the front of the optical package as possible. This re-direction happens in two ways. First, some of the light escapes the output opening from LED directly or on a single direct bounce from a surface of the reflector. Second, light that does not escape is redirected towards the emitter chip. A portion of this light is then reflected off the surface of the emitter and out of the output opening. The remaining light, that is not reflected as described above, re-excites the emitter chip and phosphor to enhance the light output of the LED.  
           [0009]    As stated above, while the present invention is particularly suited for use in flashlights, the disclosed assembly can be incorporated into a variety of lighting devices including but not limited to flashlights, specialty architectural grade lighting fixtures and vehicle lighting.  
           [0010]    Accordingly, one of the objects of the present invention is the provision of a lighting assembly that includes a high intensity LED and a reflector disposed thereon that homogenizes and collimates the light output from the LED. Another object of the present invention is the provision of a compact lighting assembly that includes a high intensity LED and a reflector that work in conjunction to approximate a point source of illumination. A further object of the present invention is the provision of a compact high intensity LED and reflector lighting assembly that is particularly suited for use in portable lighting devices such as flashlights. Yet another object of the present invention is to provide a compact lighting source that creates a high quality, high intensity output that can be further imaged and focused using optics to provide a focused level of output in the far field of the lighting device.  
           [0011]    Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:  
         [0013]    [0013]FIG. 1 is a side view of a high intensity LED package of the prior art;  
         [0014]    [0014]FIG. 2 is a side view of a high intensity LED package of the prior art in conjunction with a conventional lens;  
         [0015]    [0015]FIG. 3 is a side view of a high intensity LED package of the prior art in conjunction with a conventional reflector;  
         [0016]    [0016]FIG. 4 is an exploded perspective view of a high intensity LED package and the reflector of the present invention;  
         [0017]    [0017]FIG. 5 is a perspective view of the interior of the reflector of the present invention;  
         [0018]    [0018]FIG. 6 is a cross-sectional view of the high intensity LED and reflector assembly taken along line  6 - 6  of FIG. 4;  
         [0019]    [0019]FIG. 7 is a cross sectional view thereof shown in combination with a lens; and  
         [0020]    [0020]FIG. 8 is a cross sectional view of a high intensity LED shown with an alternate embodiment of the reflector of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    Referring now to the drawings, FIGS. 1, 2 and  3  illustrate a high intensity LED  10  as described in the present invention, wherein the LED  10  includes a base  12 , an emitter die  14  and an optical housing  16 . While the LED  10  shown includes conventional construction details, the LED  10  could be manufactured as only an emitter die  14  with the optical housing  16  and base  12  eliminated. In such a configuration, the emitter die  14  may be simply mounted onto a circuit board (not shown). In this regard, the particular construction of the LED  10  is not intended to be limiting on the scope of the present invention except as defined by the claims herein. FIGS. 2 and 3 further illustrate prior art attempts to capture and redirect the output from the LED  10  assembly. FIG. 2 shows a traditional optical lens  18 . As can be clearly seen, much of the light is lost as it bleeds to the sides of the LED  10  and is not captured by the lens  18 . FIG. 3 shows a parabolic reflector  20  installed around the LED  10 . While this configuration captures the light emitted from the side of the LED  10 , it simply re-images the emitter die  14  of the LED  10  in the far field image, producing undesirable illumination of the target.  
         [0022]    Tuning now to FIGS. 4 and 5, the inverted reflector of the present invention is illustrated and generally indicated as  22 . The reflector  22  is shown as being disk shaped, and is show in combination with a traditionally constructed LED  10  as described above. The reflector  22  has an inner reflective surface  24  that forms an inverted reflector cup. The reflective surface  24  has an optical axis  26  that generally passes directly through the center of the reflector  22 . Further, the reflective surface  24  has an apex of curvature that is located along the optical axis  26 . An aperture  28  is provided through the reflector disk  22 , is generally located at the apex of the reflective surface  24 , and is centered on the optical axis  26 . As can be best seen in FIG. 4, the reflector  22  is configured to be placed over the output end of the LED  10  and entirely enclose the emitter chip  14  and optical housing  16 . While the reflector  22  is shown as being disc shaped, it can be appreciated that other configurations and shapes would fall within the present disclosure. For example, the reflector  22  may be square or polygonal. Further, the reflective surface  24  may be parabolic, spherical or ellipsoidal. The reflective surface  24  may also be smooth or faceted as is well known in the art. In this manner, the present invention provides for the shape of the reflector  22  and the reflective surface  24  to be tailored to suit the particular LED  10  package with which it will be used.  
         [0023]    Turning now to FIG. 6, the reflector  22  of the present invention is shown in its operative position in conjunction with an LED  10  package. The reflector  22  is placed into overlying relation with the LED  10  so that the entire optical housing  16 , and emitter chip  14  are enclosed entirely within the reflective surface  24 . It can be appreciated that while the LED  10  in this figure is shown to include an optical housing  16 , the optical housing  16  could easily be eliminated without detracting from the scope or performance of the present invention. In this assembled relation, it can be seen that the optical axis  26  of the reflective surface  24  is in substantial alignment with an axis that passes through the center of the LED  10  emitter chip  14 . Further, the aperture  28  at the center of the reflective surface  24  is also aligned on the central axis of the emitter die  14 . The aperture  28  provides an opening through which a predetermined portion of light that emanates from the emitter die  14  is allowed to escape in a concentrated beam having a narrow angle. The portion of light that is not exiting the LED  10  package within the angle required by the aperture  28  in the reflective surface  24  is re-directed back onto the emitter chip  14 . This re-direction happens in two ways. A portion of the re-directed light is reflected directly off the surface of the emitter  14  and out of the aperture  28 . The remaining light, that is not reflected as described above, re-excites the emitter chip  14  to enhance the light output of the LED  10 .  
         [0024]    The reflector  22  of the present invention can be adjusted to be used in conjunction with all of the conventional LED  10  colors that are available. Some LED&#39;s  10  are manufactured to include only an emitter die  14  that outputs light in the desired wavelength directly. For example, red, blue and green LED&#39;s  10  all have output wavelengths that are the direct result of simply energizing the emitter die  14 . White LED&#39;s  10  are produced by adding a phosphor coating  30  over the emitter die  14 . When the emitter die  14  is energized, it has an output at one wavelength. Some of the output energizes the phosphor  30  to create additional output at a second wavelength and some of the output bleeds through the phosphor  30  directly. The wavelength of the emitter die  14  and the wavelength of the phosphor  30  are selected so that they are complementary and when combined produce a white light output. For example, a popular, well-known white LED  10  that is available on the market today utilizes a blue emitter chip  14  and a yellow phosphor  30 . In this manner, a coating may be provided on the reflective surface  24  to reflect selective wavelengths of light. When used in conjunction with a White LED  10  having a yellow phosphor  30  coating, the reflective surface  24  may be plated with nickel material or have a slightly blue coating. The light that is directed back onto the yellow phosphor  30  therefore has a bluish cast that counteracts the fact that the reflected light would normally become yellow and results in a white light output. Similarly, when an emitter die  14  is used that does not have a phosphor coating  30 , the color of the coating on the interior of the reflective surface  24  may be closely matched to the output wavelength of the die  14  to further enhance the color of the overall assembly output. For example should an UV emitter chip  14  be used with a white phosphor  30  the spectral shift would not be a factor and a nickel reflector  22  could be used. Similarly, should an LED  10  that does not have a phosphor coating  30  be employed, a reflector color that is matched to the output frequency of the emitter chip  14  can be used.  
         [0025]    The reflector  22  assembly may or may not have a defined thickness T around the perimeter of the aperture  28 . This will be determined by the optical requirements of the system into which the assembly is installed. Should a very low diffusion be desired, a very sharp edge having a thickness T that approaches zero will be provided. Should higher edge diffusion be required, a thicker edge T will be used. Further to improve imaging of the light output from the assembly, the present invention may include a flat black coating on the top, outside surface  32  of the reflector  22 . By providing this coating  32 , a high level of contrast is provided between the beam image that exits the aperture  28  and the background surface  32  of the reflector  22  that produces a high quality image for capture and transfer into the light beam far field.  
         [0026]    Additionally, the present invention can be used as a stand-alone assembly or in conjunction with other optical elements. As can be seen in FIG. 7 for example, a lens  34  can also be used to capture the near field image of the assembly output beam and image it into the far field of the light beam. In this fashion a particularly desirable optical element is an optical drum lens  34  that in addition to having a relatively short focal length, thus allowing the lens to be placed very close to the assembly, the lens  34  assists in further collimating and homogenizing the beam. This type of assembly can therefore produce a highly homogenized light beam with a tight circular appearance while operating with a high level of efficiency.  
         [0027]    An alternate embodiment of the present invention is shown in FIG. 8. In this embodiment, rather than placing a separately machined reflector cup  22  over the LED package  10 , the reflective surface  24  can be created as a reflective layer  100  that is plated onto the outer surface  102  of the LED package  10  at the time of manufacture. The reflective plating  100  would have an opening  104  near the top apex of the LED package  10  through which the light will be allowed to escape. In all other respects, the LED package  10  would operate in accordance with the other features of the invention as described herein. In addition, the plating  100  can be color matched with the wavelength of the emitter chip  14  output to produce the desired overall package output. At the lowest level, the coating  100  could simply consist of a layer of white Teflon provided over the optical housing  16  as a rudimentary reflector assembly. Testing has shown that simply providing a Teflon covering with an opening of approximately 25% of the LED die size provided a luminance boost in the effective LED output of between 10-20%. Further, the coating  100  disclosed herein returns approximately 75% of the light back onto the LED  10  emitter die  14  that produces a boost of nearly 50% for on axis (useable and collimated) illumination. These tests show that the assembly of the present invention provides a LED/reflector assembly that provides a much more efficient and usable illumination assembly for incorporation into lighting devices.  
         [0028]    It can therefore be seen that the present invention provides a compact assembly that captures and redirects a substantial portion of the diffuse light output from a high intensity LED package  10 . The reflector  22  assembly of the present invention greatly enhances the output efficiency of the overall device while creating a compact assembly that can be easily incorporated into a lighting assembly such as a flashlight. Further, the present invention can be modified to accommodate a number of standard LED manufacturing configurations and colors to create an output beam with previously unknown efficiency. For these reasons, the instant invention is believed to represent a significant advancement in the art, which has substantial commercial merit.  
         [0029]    While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.