Abstract:
A coherent optical fiber bundle is used in place of a lens for imaging. The input end of the bundle is shaped into the shape of a desired area for receiving light. The light is received and modified according to the shape. The other end can be flat and pressed directly against an image sensor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the U.S. Provisional Application No. 60/171,849, filed on Dec. 22, 1999. 
    
    
     BACKGROUND 
     Conventional imaging has relied on high-quality bulk optics for certain optical functions such as focusing and beam shaping. High-quality bulk optics can be expensive, and fragile, and can also limit the applications which can be carried out. 
     SUMMARY 
     The present application teaches optical imaging using optical fiber bundles. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other aspects will now be described in detail with reference to the accompanying drawings, wherein: 
     FIG. 1 shows a lens formed from a coherent optical fiber bundle with a contoured light receiving end; 
     FIG. 2 shows a bundle of tapered fibers; 
     FIG. 3 shows a bundle formed from a group of tapered fibers. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows forming a lens using a coherent optical fiber bundle. An optical fiber bundle with a relatively low numerical aperture is used. The fiber bundle  100  may have a contoured input end  110 , and a flat output end  120 . The contoured end may be a convex or concave or slanted edge. 
     Flat output end  120  is abutted against a sensor  130  which can be an image sensor, e.g. a complementary metal oxide semiconductor, CMOS image sensor. For example, an active pixel sensor of the type disclosed in U.S. Pat. No. 5,471,215 may be used. The shape and arrangement of the input end of the fiber bundle determines its imaging properties. And, each of the fibers is substantially constant in diameter, and therefore the outer surface of the fiber bundle may be cylindrical, as shown. 
     FIG. 1 shows the lens with incoming light  150  which may be from a single direction as shown, or may be from many different directions, strikes the contoured end of the lens. The way that the light enters the fiber bundle is determined by Snell&#39;s law. Within each fiber of the bundle, only those beams that enter at a specific proper angle are guided by specified fiber of the bundle. Again this is all dictated by Snell&#39;s law, and can be mathematically modeled ray by ray. Each ray, from a different angle and/or different location, can be messed. By determining if each ray will be passed through the bundle or otherwise, the profile of the light can also be determined. 
     For example, each of a plurality of rays entering the specified contour can be handled in different ways depending on the contour of the input end. 
     The guided beams propagate down the bundle to the far end  120  which can be a flat end. Once exiting the flat end, the light is substantially immediately capture by the sensor  130 . 
     Another embodiment is shown in FIG.  2 . In the FIG. 2 embodiment, the bundle can include tapered fibers such as  200 . Each tapered fiber has a thicker end  205  and thinner end  210 . The bundle is formed by a tapered fiber. The entrance to the bundle may be at the end  205 . The bundle itself is shown in FIG.  3 . Incoming light shown as  300  is input to the input end  310  of the bundle. The output end  320  is again abutted against an image sensor  330 . Therefore, the input end includes large diameter fibers, while the output end includes small diameter fibers. The rate of taper, as well as the contouring of the fibers, determines the imaging properties of the lens. 
     The imaging using this system depends on the shaping of the bundle. The input end is shaped and the output end may be flat. The input end can be convex, concave, angled, or any complex combination of all of these. Each input end can be modeled using numerical modeling to determine the result of the output. 
     While this system discloses the output end being flat, the output end can also be contoured or shaped in any desired way to meet any desired goal. For example, if the input surface of the sensor array is curved, then the bundle may also be correspondingly curved. In addition, this system can be used to obtain light from an angular location in which case the bundle may be curved instead of flat as shown. 
     Although only a few embodiments have been disclosed in detail above, other modifications are possible. All such modifications are intended to be encompassed within the following claims, in which: