GB551011A - Improvements in or relating to optical objectives - Google Patents

Abstract

551,011. Optical objectives. KAPELLA, Ltd., WARMISHAM, A., and WYNNE, C. G. July 31, 1941, No. 9725. [Class 97 (i)] In an objective for profile projection comprising a convergent rear member and a divergent front member separated by a distance greater than the equivalent focal length of the objective, the convergent rear member comprises two convergent components of which at least one is compound, and a stop (or its equivalent) is provided substantially in a position at which rays parallel to the axis entering the objective from the rear will come to a real focus on the axis, the objective being corrected with respect to such stop position ; the axial separation between the members may be greater than twice the equivalent focal length. As shown, the convergent rear member comprises a convergent cemented doublet close behind a convergent simple member, the cemented surface R8 being dispersive ; the front member consists of two uncemented elements. A stop G may be provided at the position at which a real axial image of the light source is formed by a collimated beam therefrom incident on the convergent rear member, or the stop may be formed by the image of the light source itself. The nodal planes are both located considerably behind the rear surface R9 of the convergent rear member, thus providing a large clearance between the rear surface and the object plane. Complete data for the lens shown are set out, the spacing S<SP>2</SP> being greater than 2.5F. Specification 388,215 is referred to.