Abstract:
A light coupling and distribution system includes a plurality of light sources are used to generate light. The lighting system further has an optical fiber and a light coupler optically coupling the light sources to the fiber. The light coupler has a body and a plurality of lenslets corresponding to a respective light source. Each lenslet directs light through the body to the optical fiber.

Description:
TECHNICAL FIELD 
     The present invention relates generally to a light coupling system, and more particularly, to a light coupling device for coupling light into a optical fiber. 
     BACKGROUND 
     Conventional light transmission systems used within automotive vehicles use a bulb and reflector system. In a bulb and reflector system, a filament of the bulb is placed at or near a focal point of the reflector. Typically, in an automotive application, a conventional bulb and reflector system collects and reflects only about thirty percent of the light emitted from the bulb filament. 
     Bulb and reflector systems have several disadvantages including aerodynamic and aesthetic styling which is limited by the depth of the reflector. For interior applications, scarce package space is used by the depth of the lighting package. Additionally, thermal energy given off by the bulb during operation must be considered in the development of the components. This is particularly true for lighting systems within an automotive vehicle such as instrument panel lights. 
     Fiber optic systems for light distribution have been explored by automotive manufacturers. Such systems have the advantage of locating the light source in a central location and distributing light through fiber optics to their desired location. To provide illumination for such systems, laser diodes have been proposed. Laser diodes are formed on a large wafer in rows. The rows are referred to as bars. To direct light into a single larger fiber, an array of fibers are typically used. The array of fibers are butt coupled to the individual diode cavities of the wafer. The individual fibers are then coupled together to feed a single larger fiber. 
     Providing a number of fibers butt coupled to the array of diodes, however, is very inefficient and is labor intensive to assemble. 
     Thus, there is a need in the art for an efficient light collector that is also easy to assemble. 
     SUMMARY OF THE INVENTION 
     The present invention is unique and efficient in light collection particularly for use in vehicle lighting. 
     In one aspect of the invention, a plurality of light sources are used to generate light. The lighting system further has an optical fiber and a light coupler optically coupling the light sources to the fiber. The light coupler has a body and a plurality of lenslets corresponding to a respective light source. Each lenslet directs light through the body to the optical fiber. 
     In a further aspect of the invention, the lenslets have a wedge-shaped cross section in the horizontal direction and a circular cross section in the vertical cross section. Thus, light is collimated in the body in the vertical direction and directed toward the optical fiber in the horizontal direction. 
     One advantage of the invention is that the monolithic structure allows the light distribution system to easily be assembled. 
     Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cutaway view of an automotive vehicle having a light distribution system according to the present invention. 
         FIG. 2  is a perspective view of a light coupler according to the present invention coupled to an optical fiber. 
         FIG. 3  is a top view of the light coupler  FIG. 3 . 
         FIG. 4  is an enlarged partial view of light sources and coupler. 
         FIG. 5  is a perspective view of the lenslets of the light coupler. 
         FIG. 6  is a cross-sectional view of a lenslet of  FIG. 5 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following figures the same reference numerals are used to identify identical components in the various figures. Although the present invention is described with respect to a light distribution system for an automotive vehicle, the present invention may be applied to other non-automotive applications such as housing and consumer electronics. Other examples of specific uses of the lighting system of the present invention include pumping other lasers and metal working. 
     Referring now to  FIG. 1 , an automotive vehicle  10  has a lighting system  12 . Lighting system  12  has a light source  14  and a coupler  16 . Light source  14  and coupler  16  are coupled to optical fibers that are used to distribute light to portions of automotive vehicle  10 . Various types of suitable optical fibers are well known to those in the art. 
     Light source  14  and coupler  16  may be used to provide a source of light to headlights  20 , to a dome light  22 , and/or to an instrument panel  24 . These components are merely illustrative of potential applications of the present invention. A switch  26  is illustrated coupled to dome light  22 . Switch  26  is used to control the flow of light to dome light  22 . Although a single switch  26  is illustrated, switches may also be used to control light to instrument panel  24  and headlights  20 . 
     A controller  28  may also be coupled to light source  14  and coupler  16 . Controller  28  is microprocessor-based and may be used to control the amount of light from light source  14  or the application of power from a power source to light source  14 . Applications in which a controller may be employed include the control of turn signals, headlights and selectively controlling back lighting of instrument panels and radios. 
     Referring now to  FIG. 2 , a perspective view of light source  14  coupled to a coupler  16  is illustrated. Coupler  16  coupled to an optical fiber  18  is illustrated. Coupler  16  has a coupler body  30  having an upper surface  32 , a lower surface  34 , an output end  36 , and an input end  38 . Light source  14  is coupled to input end  38 . Optical fiber  18  is coupled to output end  36 . Coupler body  30  also has angular side surfaces  40 ,  42  that help direct light to output end  36  as described below. That is, the input end  38  is longer than the output end  36  with the angled side surfaces  40 ,  42 , therebetween. Side surface  40 ,  42  have an angle  54  with respect to the axis to the optical fiber of about 8°. 
     Referring now to  FIGS. 3 and 4 , light source  14  is comprised of a plurality of light emitters  44 . In the present example, seven light emitters  44  are illustrated. Light emitters are used to direct light to input end  38  of coupler body  30 . Light emitters  44  are preferably laser diodes. The diodes may be arranged in a row and fabricated on a single wafer  46 . Of course, discrete emitters may also be used. 
     Each light emitter  44  has a respective lenslet  48  through which light is coupled into coupler body  30 . Lenslets  48  are preferably integrally formed with body  30 . Lenslets  48  redirect light emitted by light emitters  44  toward face  50  of optical fiber  18 . 
     The center light emitter  44  is positioned directly opposite (normal to) optical fiber  18  and thus no lenslet is required. As the distance from the center emitter  44  increases, the angle  52  of lenslet with respect to input end  38  increases. For example, the first lenslet has an angle of about 24°, the second has an angle of about 15°, and the third lenslet  48  has an angle of about 4°. Of course, these angles may vary depending on the particular geometry of the overall system. 
     The sizing of optical coupler  16  follows. The light emitters  44  extend for a predetermined length upon the wafer  46 . The input end  38  is sized to extend substantially the length of the emitters. Angle  54  and angle  52  are chosen to direct light by total internal reflection to optical fiber  18 . It is preferred that most of light from emitters  14  is coupled into optical fiber  18 , either directly or through reflection from side surfaces  40 ,  42 . 
     Referring now to  FIG. 5 , a perspective view of input end  38  is illustrated. As shown above in a horizontal cross section, lenslets  48  are wedge-shaped. However, light emitted from light emitters  44  may diverge in a vertical angle by up to a 45° half angle. Such divergence is characteristic with commonly known laser diodes. Thus, providing merely a wedge-shaped lenslet  48  may not allow all the light to be coupled within coupler body  30 . Lenslets  48  have a curved surface  56  that collimates light in the vertical direction. Also, lenslets  48  may be curved slightly in the horizontal direction to collimate light in the horizontal direction as well. The curvature will vary based upon the position of the lenslet and the light source as would be known to those skilled in the art. 
     Referring now to  FIG. 6 , a cross-sectional view through line  5 — 5  illustrates a lenslet  48  with light rays  58  that are emitted from emitter  14  substantially collimated in coupler body  30 . 
     In operation, the number of emitters  44  and therefore the width of coupler body  30  may be adjusted depending on the particular intensity required for the particular application. As one skilled in the art would recognize, the angle of light directed to the surface of optical fiber should not exceed the numerical aperture of the fiber. If varying intensities are required, the controller may be used to selectively operate certain emitters. As the width is adjusted the angles of the lenslets are also adjusted to direct light to the face  50  of optical fiber  18 . In a motor vehicle several couplers  30  and several light sources  14  may be employed. All the light sources and couplers may be maintained in a central location and a plurality of optical fibers  18  may be routed throughout the vehicle where light is desired. 
     While particular embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.