Ring lens assembly for an optical viewing device

Abstract

A ring lens assembly for an optical viewing device is presented. The ring lens assembly includes a ring shaped lens adapted for mounting at the end of an optical viewing device for viewing a remote location. The optical viewing device comprises an objective lens section, a relay lens section and an eye piece section. Further, the optical viewing device has an inner tube wherein the optics is housed and an outer tube. A plurality of optical fibers are disposed between the inner and outer tubes to provide illumination of the field of view. The ring shaped lens is a negative curvature lens or a prism-like lens for increasing the field of illumination. Alternatively, the lens is a flat lens and the optical fibers twisted to increase the field of illumination. Also, a cleaning tube is disposed between the inner and outer tubes. The cleaning tube terminates short of the end of the inner tube. An opening or channel is formed at the end of the inner tube adjacent to the cleaning tube. Accordingly, cleaning fluid travels down the cleaning tube and impacts the inner surface of the ring shaped lens. The cleaning fluid is deflected off of the inner surface of the ring lens, flows through the opening in the inner tube and impacts the outer surface of the first lens in the objective lens section thereby providing cleaning action.