GB559379A - Improvements in or relating to high aperture photographic objectives - Google Patents

Abstract

559,379. Lenses. KODAK, Ltd. Aug. 14, 1942, No. 11416. Convention date, Oct. 8, 1941. [Class 97 (i)] In a high-aperture photographic objective comprismg four air-spaced components, the outer ones being positive and the inner ones compound menisci highly concave towards one another, the rear component is a positive doublet, preferably meniscus and concave to the front, and comprises a positive element VI cemented to the front of a negative element VII, the refractive index of element VI being greater than that of element VII by more than 0.12, and preferably by more than 0.15. The third component may be a cemented doublet IV, V of total thickness less than F/10, F being the focal length of the lens, the element V having a refractive index greater than 1.7 and greater than that of element IV by at least .05 as set out in Specification 548,255 ; the radius of R2 is then preferably greater than F/2 and less than 2F. The front surface of the rear component may have a radius R9 greater than 2F, and the rear surface R10 may be convex to the rear. Data for one example are set out. Specification 548,252 also is referred to.