Patent Publication Number: US-2005135109-A1

Title: Light blade

Description:
BACKGROUND OF THE INVENTION  
      Generally, conventional automotive lighting systems utilize filament bulbs as a lighting source. However, filament bulbs have many drawbacks, including high consumption of electrical power, the generation of great amounts of heat, and readily breakable filaments. Recently, due to these drawbacks, light emitting semiconductor devices (LESDs), such as light emitting diodes (“LEDs”), have been adapted for use in certain automobile lighting systems.  
      LEDs solve many of the problems associated with filament bulbs, because they emit light using a lower voltage and current than used by a filament bulb and are less prone to breakage. However, various other problems are associated with LEDs when used in automobile lighting systems. For example, surface emitting LEDs use a substantially planar luminescent element which radiates high intensity light predominantly in the forward direction, and only minimal light energy is emitted toward the sides. A typical surface emitting LED will actually have peak intensity at +/−20 to 30 degrees off normal. Nonetheless, this type of LED can be generally modeled as a Lambertian source. That is, a source wherein the intensity of the light emitted is subject to the cosine law as given by the formula: 
 
I=I o  cos θ
 
 wherein I is the resultant intensity, I o  is the intensity normal to the surface, and θ is the angle between normal and the viewing direction. 
 
      In a typical automotive application, the light emitted from a light source is collimated, focusing the emitted light into a narrow beam within 10 degrees of the optical axis. Collimators known to be used with LEDs include those that operate according to the principle of total internal reflection (TIR). TIR is reflection that occurs due to refraction when the angle of incidence of light traveling in a given substance strikes a boundary surface in excess of the critical angle. The critical angle is the angle of incidence in a denser medium, at an interface between the denser and a less dense medium, that is defined by the equation: 
 
sin I c =n′/n
 
 where I c  is the critical angle, n′ the refractive index of the less dense medium, and n the refractive index of the denser medium. TIR is a desirable mechanism because it is more efficient in reflecting light than is utilizing a reflective surface, such as a mirror. 
 
      However, as the intensity of LEDs increases through various technological advances, the focusing of the emitted light creates a total emission that can exceed the desired intensity. It is, of course, possible to simply use an LED with a lower output. However, it is also desired to reduce the total number of light sources required for a vehicle. Accordingly, it would be beneficial to split the emitted beam into a plurality of beams, either to provide additional ornamentality or to reduce the total number of light sources required for a given application, while minimizing reflection losses.  
      Therefore, a need exists for an automotive lighting system that provides for the use of LEDs within the lighting system while reducing the number of LEDs needed. It is preferred that the system efficiently create a plurality of light beams. It would be further beneficial if the system used commonly available materials and minimized the number of parts in the system.  
     BRIEF SUMMARY OF THE INVENTION  
      In accordance with the present invention, a light assembly is provided which overcomes the disadvantages of the prior art by providing for partial redirection of a beam of collimated light. A lens is provided that allows some of the collimated light to pass through, while another portion of the collimated light is diverted from the original beam. According to one embodiment, the collimated beam is split by using the principle of TIR. Thus, a portion of the collimated beam provides the main beam of a taillight, while another portion of the collimated beam is used to provide a design feature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross-sectional view of a light subassembly.  
       FIG. 2  is a cross-sectional view of a light assembly in accordance with the present invention incorporating the light subassembly of  FIG. 1 , taken along line B-B of  FIG. 3 .  
       FIG. 3  is a top plan view of the light assembly of  FIG. 2 .  
       FIG. 4  is a cross-sectional view of the light assembly of  FIG. 2 , taken along line C-C of  FIG. 3 .  
       FIG. 5  is a perspective view of the light assembly of  FIG. 2 .  
       FIG. 6  is a perspective view of an alternative embodiment of a light assembly according to the present invention.  
       FIG. 7  is a perspective view of an alternative embodiment of a light assembly according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Shown in  FIG. 1  is a cross-section view of light subassembly  100 . Light sub assembly  100  comprises LED  102  and collimator  104 . Collimator  104  comprises ledge  106 , side  108 , LED mating area  110  and top  112 . Collimator  104  is manufactured from a clear substance such as acrylic. Suitable collimators are available from Lumileds Lighting, LLC of San Jose Calif., such as model LXHL-NX05-Luxeon™ Collimator.  
      LED mating area  110  includes vertical wall  114  and convex wall  116 . Vertical wall  114  is designed to refract light from LED  103  so that light entering collimator  104  through vertical wall  114  impinges on side  108  at an angle in excess of the critical angle. Accordingly, light entering collimator  104  through vertical wall  114  will be internally reflected by side  108 . Side  108  is angled so that the light reflecting off of side  108  is collimated, and travels parallel to the optical axis of LED  102  which is indicated in  FIG. 1  by line A-A. Convex wall  116  is designed so that light entering collimator  104  through convex wall  114  is refracted and collimated, and travels parallel to optical axis A-A. Accordingly, a collimated beam of light passes through top  112 .  
      One embodiment of the present invention comprising the light subassembly of  FIG. 1  is described in reference to  FIGS. 2-4 .  FIG. 2  is a cross sectional view of light assembly  200  taken along line B-B of  FIG. 3 .  FIG. 3  is a top plan view of light assembly  200 . Referring now to  FIG. 2 , light assembly  200  includes light sub assembly  100  and lens  202 . In this embodiment, lens  202  includes semi-parabolic wall  204 , planar wall  206 , semi-parabolic wall  208 , planar wall  210 , side walls  212 ,  213 ,  215  and  216 , bottom  214 , and inner walls  220  and  222 . Bottom  214  is designed to fit over top  112  of collimator  104  and be secured against ledge  106 . As shown most clearly in  FIGS. 2, 3  and  FIG. 5 , semi-parabolic wall  204  and semi-parabolic wall  208  are wedge shaped sections having a semi-parabolic curve toward the center of lens  200 . Planar wall  201  and planar wall  204  are also wedge shaped as viewed in  FIG. 3 , and are flat.  FIG. 4  is a cross sectional view of light assembly  200  taken along line C-C of  FIG. 3 . Shown in  FIG. 4  are side walls  212  and  215 , planar wall  210  and semi-parabolic wall  208 .  
      The shape of semi-parabolic walls  204  and  208  are selected such that light from LED  102  that exits top  112  of collimator  104  and enters bottom  214  of lens  202  will impinge semi-parabolic walls  204  and  208  at an angle in excess of the critical angle. Accordingly, light impinging on semi-parabolic walls  204  and  208  is reflected by TIR and does not pass through semi-parabolic walls  204  and  208 . The shape of planar walls  206  and  210  are selected such that some of the light from LED  102  exits top  112  of collimator  104  and enters bottom  214  of lens  202 , passes through lens  202  and impinges planar walls  206  and  210  at an angle less than the critical angle for planar walls  206  and  210 . Accordingly, light impinging on planar walls  206  and  210  may be refracted, but will pass through planar walls  206  and  210 .  
      The splitting of a collimated light beam entering bottom  214  of lens  202  is shown with reference to  FIG. 5 . The collimated light that does not strike semi-parabolic walls  204  and  208  passes through planar walls  206  and  210  as indicated by light rays  402  and  404 . Light impinging on semi-parabolic walls  204  and  208 , however, is reflected. The angle at which the reflected collimated light impinges side walls  212  and  213  is less than the critical angle. Accordingly, as shown by light rays  406  and  408 , the collimated light reflecting off of semi-parabolic walls  204  and  208  respectively, passes through side walls  213  and  212  along a plane normal to optical axis A-A shown in  FIG. 1 .  
      Those of skill in the art will recognize that in accordance with the present invention, the shape of the lens and the overall shape of the light assembly could be varied to generate a variety of unique appearances, provided that the optical and photometric requirements of the light assembly are still satisfactory. By way of example, but not of limitation,  FIG. 6  shows an alternative shape of a light assembly incorporating lens  600 . Moreover, once portions of the collimated light have been redirected, they may be further redirected for use such as providing ornamental appeal to a vehicle. For example, as shown in  FIG. 7 , the light from light assembly  700  may be directed into shaped light pipes  702  and  704 , so as to cause the light pipes to “glow”. Of course, the shape of the light pipes is a design choice. Moreover, the light pipes may be formed as an integral part of the lens.  
      Moreover, while the embodiment of  FIGS. 1-5  allows approximately fifty percent of the light from LED  102  to pass through walls  206  and  210 , this can be altered within the scope of the present invention. For example, the amount of light emitted through the lens in the direction of the optical axis of the LED may be greater than or less than fifty percent. Additionally and/or alternatively, there may be a fewer or a greater number of walls. In yet another embodiment, the light passing through the walls is refracted, so as to direct the emitted light off of the optical axis of the LED or other light source.  
      Those of skill in the art will realize that as described herein, the present invention provides significant advantages over the prior art. The invention provides a light assembly which provides for the use of LEDs within the lighting system of a vehicle while reducing the number of LEDs needed. Moreover, the present invention efficiently create a plurality of light beams. Additionally, the present invention uses commonly available materials without unduly increasing the number of parts in the lighting system.  
      While the present invention has been described in detail with reference to certain exemplary embodiments thereof, such are offered by way of non-limiting example of the invention, as other versions are possible. It is anticipated that a variety of other modifications and changes will be apparent to those having ordinary skill in the art and that such modifications and changes are intended to be encompassed within the spirit and scope of the invention as defined by the following claims.