Fiber bundle illumination system

Abstract

An improved system for projecting uniform illumination for observation, combining a flexible fiber light guide with a clad cane element which mixes light rays from the fiber bundle to provide uniform brightness across the output face of the clad cane element in a system which lends itself to compactness in design. The fiber light guide comprises a flexible bundle or small, discrete clad fibers, and the bundle receives light from a primary light source at one end. The clad fibers are joined together at the other end to define, along with the spaces therebetween, an output face which forms a source of light of non-uniform brightness. This non-uniform light is received by the clad can element, which has a transparent, homogeneous core with a high refractive index and a thin clad having a low refractive index surrounding the core. The clad cane element is of sufficient size and disposition so that all the light from the bundle is received by the clad cane element, and is of sufficient length so that the light rays from the bundle are internally mixed so that the light is uniform at an output face of the clad cane element. A downstream lens is located at a distance at least equal to its focal length from the output face of the clad cane element, and the lens receives the uniform light therefrom and focuses the image of the output face of the clad cane element on the object plane to be illuminated, in a sharply defined beam with essentially total conservation of brightness.