GB564306A - Improvements in or relating to photographic objectives - Google Patents

Abstract

564,306. Photographic objectives. KODAK, Ltd. June 23, 1943, No. 10163. Convention date, July 7, 1942. [Class 97 (i)] In an objective consisting of two positive meniscus cemented-triplet components, each with the more highly curved of the two cemented surfaces concave to the diaphragm position, and each comprising a positive element II between negative elements I, III, or a negative element between positive elements, the refractive indices of the elements increasing with their relative distances from the diaphragm position, the weaker cemented surface has a positive or negative radius numerically greater than half the focal length F of the whole objective, and the refractive index of element I is greater than 1.68; the dispersive index of this element may be greater than 35 ; if the intermediate element is positive, the radius R3 may be greater than F, and, if it is negative, the radius R2 may be F greater than -, R4-R1 being greater than 2 .03 F. The highest refractive index may exceed the lowest by 0.18 or more, and either of them may differ from the intermediate refractive index by one and a half times as much as does the other. The space between the triplets may be between 0.06 F and 0.15 F. Complete data are set out for three examples, one of which is unsymmetrical.