Light coupling and distribution system

Abstract: A light coupling and distribution system includes a plurality of light sources (44) are used to generate light. The lighting system further has an optical fiber (18) and a light coupler (16) optically coupling the light sources (44) to the fiber (18). The light coupler (16) has a body (30) and a plurality of lenslets (48) corresponding to a respective light source (44). Each lenslet (48) directs light through the body (30) to the optical fiber (18).

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. US 4,496,211 describes, with reference to Figure 21, a simple light diode. Light from a first male optical coupler is directed to a second male optical coupler via two lenses in series which focus the light onto the wide mouth of a tapered glass rod. The light is funneled through the rod by internal reflection to a narrow first optical window which is in turn fused to the end of an optical mixer. Light enters the optical mixer and expands to fill the volume thereof, reaching a second optical window uniformly distributed across the optical mixer cross-section. The light then enters the second male optical coupler together with any backflow light that might be present. Light is substantially prevented from travelling from the second optical connector to the first by reflection from a mirror which is adjacent the first optical window. EP 0 596 865 describes, with reference to Figure 8, LED light irradiating apparatus wherein LED light reaches a light irradiating lens via a bunch of optical fibres in a laminated structure. The light enters the bundle of fibres at inlet ports and exits via outlet ports. The collection of output ports has a square contour, so that an irradiated light is projected through the lens onto a screen or the like with an image similar to a square. 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 Figure 1 is a side cutaway view of an automotive vehicle having a light distribution system according to the present invention. Figure 2 is a perspective view of a light coupler according to the present invention coupled to an optical fiber. Figure 3 is a top view of the light coupler Figure 3. Figure 4 is an enlarged partial view of light sources and coupler. Figure 5 is a perspective view of the lenslets of the light coupler. Figure 6 is a cross-sectional view of a lenslet of Figure 5. Figure 7 is a ray trace diagram of a light coupler according to the present invention. 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 Figure 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 Figure 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. Side surfaces 40, 42 have an angle 54 with respect to the axis to the optical fiber of about 8°. Referring now to Figures 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 Figure 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 Figure 6, a cross-sectional view through line 6-6 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.

Claims: A lighting system (12) comprising: a plurality of light sources (44) generating a light; an optical fiber (18) and a light coupler (16) optically coupling said light sources (44) to said fiber (18), said coupler (16) having a monolithic structure comprising a body (30) and a plurality of lenalets (48), with each lenslet (48) corresponding to a respective light source (44), and each lenslet (48) directing light through the body (30) to said optical fiber (18). A lighting system (12) as recited in claim 1 wherein said body (30) has sides (40, 42) with a predetermined angle with respect to a face (50) of said optical fiber (18). A lighting system (12) as recited in claim 1 wherein the light sources (44) comprise laser diodes. A lighting system (12) as recited in claim 1 wherein the light sources (44) comprise a wafer having a plurality of laser cavities. A lighting system (12) as recited in claim 1 wherein each of said plurality of lenslets (48) have a wedge shape. A lighting system as recited in claim 5 wherein said wedge shape has an angle directing light to a face (50) of said optical fiber (18). A lighting system (12) as recited in claim 6 wherein said angle increases as a distance from a center emitter increases. A lighting system as recited in claim 1 wherein said plurality of lenslets (48) collimated light in a first direction. A lighting system as recited in claim 1 wherein said plurality of lenslets (48) have a curved cross section.

Inventors: FOHL TIMOTHY, ISHIKAWA TOMONARI, NOLD JEFFREY PAUL, ONEIL DAVID ALLEN, FOHL, TIMOTHY, ISHIKAWA, TOMONARI, NOLD, JEFFREY PAUL, ONEIL, DAVID ALLEN
Applicants: VISTEON GLOBAL TECH INC, VISTEON GLOBAL TECHNOLOGIES, INC.
Application year: 2000
Main classification: F21V8
IPC codes: H01S5, F21V8, G02B6