GB517271A - Improvements in photographic objectives - Google Patents

Abstract

517,271. Lenses. KODAK, Ltd. May 23, 1938, No. 15264. Convention date, May 22, 1937. Drawings to Specification. [Class 97 (i)] In a photographic objective comprising two dispersive components between two collective components, the refractive index of at least one collective component is greater than 1.70; the curvature of the outer surfaces of the collective components may be greater than that of the inner surfaces, the axial space between the dispersive components being greater than the other axial spacings, or the radius of curvature of the surfaces of the collective components may be greater than 75 per cent of the focal length of the objective, or the collective components may be bi-convex, each dispersive component having a refractive index less than that of the adjacent collective component and at least one divergent component being bi-concave. The refractive index of each collective component may be greater than 1.75, and the adjacent collective and dispersive components may be in contact at their edges. The objective may be highly corrected and have an operative aperture of f2.0. The glass for the collective components may be as described in Specification 462,304, [Group XXIII], Optical data of examples are set out.