Abstract:
One or more layers of LEDs shine light into an array of elliptical reflectors. Each elliptical reflector has an LED at one focal point and shares the second focal point with a larger parabolic reflector that collimates the light. A hole in the center of the parabolic reflector receives additional LEDs, with or without collimation optics.

Description:
BACKGROUND OF THE INVENTION 
     Light Emitting Diode (LED) technology offers advantages in efficiency and life over traditional incandescent or halogen lights. Typical LED lamp design approaches use a planar array of LEDs with one or more collimating optics to achieve the desired photometric distribution. Many LED lamps used as alternatives to Parabolic Aluminized Reflector (PAR) lamps cannot match the photometric performance for a given frontal area compared to the conventional lamps they would replace, particularly for applications that require very high peak intensities such as a PAR64 aircraft landing light or an entertainment stage light. 
     SUMMARY OF THE INVENTION 
     Instead of a simple forward facing planar array that might typically be used for a PAR lamp replacement, the present invention uses depth of the package to increase the total peak intensity. One or more layers of LEDs shine into an array of elliptical reflectors. Each elliptical reflector has an LED at one focal point and shares the second focal point with a larger parabolic reflector that collimates the light. The resulting system has a hole in the center of the parabolic reflector where additional layers of LEDs, with or without collimation optics, are placed to further increase the intensity of the system. This configuration allows the distribution to be adjusted for the application (wavelength, peak intensity and beam spread) by changing the number or type of LED, the focal lengths of the ellipses, the parabola and the collimation optics. 
     In one aspect of the invention, the LEDs are separated to distribute the thermal load over a larger surface area for higher power applications. 
     In still another aspect of the invention, dual-mode capability within the same footprint is provided by replacing some of the visible LEDs with Infrared (IR) LEDs and modifying the drive electronics to control those IR LEDs separately. 
     In yet another aspect of the invention, the system provides variable color output by appropriate placement of various colored LEDs (e.g., red, green, blue, amber and/or white) and separate drive electronics for each group of colored LEDs to allow for color mixing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings: 
         FIG. 1  illustrates a perspective view of a light assembly formed in accordance with an embodiment of the present invention; 
         FIG. 2  illustrates an exploded view of the light assembly shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the light assembly shown in  FIG. 1 ; 
         FIGS. 4-6  are perspective views of components of the light assembly shown in  FIG. 1 ; and 
         FIG. 7  is a wire diagram illustrating light production and reflection of the light assembly shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a perspective view of a light assembly  30  formed in accordance with an embodiment of the present invention. The light assembly  30  is capable of producing a greater intensity of light than that produced by conventional light emitting diode (LED) light assemblies of comparable anterior dimension. The light assembly  30  includes a housing  34  which is capped at one end by a lens  58 . Inside the housing  34  are a large parabolic reflector  36  and a plurality of layers  40 ,  42 ,  44  of LEDs with elliptical reflectors and/or parabolic reflectors. Light produced by the LEDs either passes directly through ends of the large parabolic reflector  36  or the large parabolic reflector  36  collimates light received from the elliptical reflectors. 
       FIG. 2  illustrates an exploded view of the light assembly  30 . In this embodiment, the light assembly  30  includes three LED layers  40 ,  42 ,  44 . The first and second LED layers  40 ,  42  are ring-shaped and the third layer LED layer  44  is sized to fit within an opening of the second LED layer  42 . The first LED layer  40  is held in place within the housing  34  via a first housing section  50  and a second housing section  52 . The second and third LED layers  42 ,  44  are held in place between the second housing section  52  and a third housing section  54 . The various housing sections  50 ,  52 ,  54  are fastened together by suitable means (fasteners, adhesive and/or comparable materials) depending on the thermal, sealing or vibration requirements of the application. In one embodiment, the sections  50 ,  52 ,  54  are attached one to the next as the assembly is built with fasteners that provide significant clamp force to enhance thermal performance. 
     The lens  58  holds the parabolic reflector  36  within the first housing section  50 . The lens  58  may attach to the first housing section  50  in a number of ways, for example threads on the first section  50  and the opposing surface of the lens  38  or an epoxy or other comparable fastener. 
       FIG. 3  illustrates a cross-sectional view of the light assembly  30  shown in  FIGS. 1 and 2 . The parabolic reflector  36  includes first and second open ends. The first open end has a larger diameter than the second open end. The first open end includes an annular flange  60  that surrounds the opening. The flange  60  makes contact with an annular ledge  61  formed at the first open end of the first housing section  50 . The lens  58 , when attached to the first housing section  50 , holds the parabolic reflector  36  in place by placing pressure on the flange  60 . The parabolic reflector  36  rests within a cavity formed within the first housing section  50 . The first housing section  50  also includes first and second open ends wherein the first open end has a slightly larger diameter than the first open end of the parabolic reflector  36  and the second open end has a slightly larger diameter than the second open end of the parabolic reflector  36 . 
     A second ledge  62  formed on a bottom surface of the second open end of the housing section  50  supports an LED board  74  that is part of the first LED layer  40 . The LED board  74  may be attached to the housing section  50  by fasteners or other comparable means. If metal fasteners (e.g. screws) are used then the housing section  50  acts as a heat sink to a metal layer within the LED board  74 . The first LED layer  40  includes first and second open ends. The first open end includes an annular flange  64 . The annular flange  64  and a portion of the LED board  74  securely sits between a first surface  66  of the second housing layer  52  and the second ledge  62 . This allows the first LED layer  40  to sit securely within a cavity formed within the second housing section  52 . 
     A similar type of slot is formed between a second surface  68  of the second housing section  52  and a first surface  70  of the third housing section  54 . The slot formed between the second and third housing sections  52  and  54  receives an outer circumferential flange  72  of the second LED layer  42  and a portion of an LED board  76  of the third housing section  54 . This allows the second LED layer  42  to sit securely within a portion of a cavity formed within the third housing section  54 . The third housing section  54  also includes a second cavity portion that receives the third LED layer  44 . A base of the third LED layer  44  is fastened to an interior base of the third housing section  54  using fastener(s), adhesives or comparable components. 
       FIGS. 4-1  and  4 - 2  illustrate perspective views of the first LED layer  40 . The first LED layer  40  includes the ring-shaped LED board  74  and a plurality of elliptical reflectors  94  mounted to a first side of the LED board  74 . A plurality of LEDs  92  are also mounted to the first side of the LED board  74 . The elliptical reflectors  94  are mounted such that a single elliptical reflector  94  is positioned around a corresponding single LED  92 . The elliptical reflectors  94  are positioned such that light emanating from the LEDs  92  are reflected off of the elliptical reflectors  94  through the opening in the LED board  74 . The light reflecting off the elliptical reflectors  94  reflects off of a predefined section of the parabolic reflector  36 . This will be shown in more detail below with regard to  FIG. 7 . The elliptical reflectors  94  are attached to the LED board  74  (i.e., printed wiring board) by any number of techniques if the elliptical reflectors  94  are not sandwiched between the mated housing sections with a flexible adhesive. There is a keying feature included in the reflector to ensure proper registration with the LEDs for suitable focus. 
       FIGS. 5-1  and  5 - 2  illustrate perspective views of the second LED layer  42 . The second LED layer  42  includes a ring-shaped LED board  76  and a plurality of elliptical reflectors  104  mounted to a first side of the LED board  76 . A plurality of LEDs  102  are also mounted to the first side of the LED board  76 . The elliptical reflectors  104  are mounted such that a single elliptical reflector  104  is positioned around a corresponding single LED  102 . The elliptical reflectors  104  are positioned such that light emanating from the LEDs  102  is reflected off of the elliptical reflectors  104  through the open end in the LED board  76 . The light reflecting off the elliptical reflector  104  is then collimated by the parabolic reflector  36 . This will be shown in more detail below with regard to  FIG. 7 . 
       FIGS. 6-1  and  6 - 2  illustrate perspective views of the third LED layer  44 . The third LED layer  44  includes an LED board  110 , a plurality of LEDs  112  mounted to the LED board  110  and a multi-reflector unit  116  having a plurality of parabolic reflectors  114 . Each of the parabolic reflectors  114  in the reflector unit  116  includes first and second open ends. The first open end has a larger diameter than the second open end. When the reflector unit  116  is mounted to the LED board  110 , via fastener(s), epoxy or comparable means, the second open end is mounted adjacent to the LED board  110 . The reflector unit  116  is mounted such that each of the LEDs  112  mounted on the LED board  110  are exposed via the second open end of a corresponding reflector  114 . The third layer LED  44  includes parabolic reflectors instead of elliptical reflectors because the light emitted by the LEDs  112  is reflected directly through both open ends of the parabolic reflector  36  and do not reflect off of the parabolic reflector  36 . This is shown in more detail in  FIG. 7 . 
     In one embodiment, the reflectors  94 ,  104 ,  114  are single units formed by a plastic injection molding process. The reflectors  94 ,  104 ,  114  are then coated with a reflective coating, such as, but not limited to, aluminum or silver. Other reflector devices may be used. For example, one or more of the parabolic reflectors  36 ,  114  may be an uncoated, reflective white plastic, such as that produced by Bayer. Also, the boards  74 ,  76 ,  110  may be printed circuit boards that include traces that electrically connect the LEDs  92 ,  102 ,  112  to wires or traces located on or embedded in the housing sections  50 ,  52 ,  54 . In one embodiment, a wiring harness (not shown) connects to mounted headers (not shown) soldered onto the circuit boards at the time the LEDs are installed. A wiring routing channel and pocket (not shown) are included in each of the housing sections  50 ,  52 ,  54  to accommodate the wiring harness and mounted headers. 
     As shown in  FIG. 7 , the light produced by the LEDS  112  reflects off the parabolic reflectors  114  of the third LED layer  44  and directly passes through the parabolic reflector  36 . The elliptical reflectors  94 ,  104  of the first and second LED layers  40 ,  42  share a focal point with the parabolic reflector  36 . Thus, the light produced by the first LED layer  40  reflects off a lower/aft section of the parabolic reflector  36  than does the light produced by the second LED layer  42 . 
     In this example, the light assembly  30  produces light from approximately  37  LEDs with a high percentage of light produced by each LED being reflected either off of the parabolic reflector  36  or passing directly through the parabolic reflector  36  via its own parabolic reflector associated with the LED. In this example, the angular spread of light is approximately 11° to 12° with a production of over 700,000 candelas. Intensity and angular spread of light is adjustable by changing any number of variables: focal length of reflectors, number and type of LEDs, etc. 
     In another embodiment, different LED configurations may be used within the light assembly. The following are non-limiting examples of different LED configurations. 
     White and Infrared lights are included to produce both visual and non-visual light. In one embodiment, the LEDs used are all of a single color (red, amber, green, blue, etc.). 
     In one embodiment, the system includes different colored LEDs (red, green, blue, amber and/or white) distributed throughout the LED boards  74 ,  76 ,  110  with independent drive electronics (not shown) for producing variable color output. The drive electronics independently control the intensity of each color group, resulting in color mixing. 
     In one embodiment, the system is capable of providing variable temperature white. Similar to the aforementioned color mixing method, this embodiment is achieved through the appropriate location on the circuit boards ( 74 ,  76 ,  110 ) of groups of white LEDs selected from two specific “color” bins (a result of the LED manufacturing process) associated with “blackbody color temperatures” found close to, or along, the Planckian locus within a color space such as the CIE 1931 chromaticity diagram. Separate drive electronics control the intensity of each “color” bin of LEDs independently, thus providing the ability to vary the color temperature of the output light along a line between the two white endpoints defined by the selected LED “color” bins. 
     The addition of other white bin groups to the preceding method creates a color temperature polygon (triangle, rectangle, etc.), the boundaries of which are defined by the color points of the selected groups of colored LEDs. Varying the intensities of the component groups changes the output color temperature within the boundaries of the polygon. 
     Monochromatic LED groups, such as red, replace white in the previous embodiment for creating another color space polygon (triangle, rectangle, etc.), the boundaries of which will be defined by the color points of the selected groups of colored LEDs. Varying the intensities of the component groups changes the output color and color temperature within the boundaries of the polygon. 
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. For example, the device could include only two layers of LEDs with associated reflectors and those two layers could have only elliptical reflectors or one layer has elliptical reflectors and one layer includes parabolic reflectors. In another example, the device could include three or more LED and associated reflector “ring” layers. Further, one of the layers may include both elliptical and parabolic reflectors. Also, in one example the parabolic reflector  36  is replaced with a non-parabolic type reflector. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.