GB419552A - Improvements in lenses for photographic and like purposes - Google Patents

Abstract

419,552. Lenses. LEE, H. W., and KAPELLA, Ltd., 104, Stoughton Street, Leicester. July 22, 1933, Nos. 20676/33 and 20170/34. [Class 97 (i).] In a photographic &c. lens system comprising a dispersive member between two collective members, the dispersive member is of compound meniscus form and the collective member on the convex side of the dispersive member consists of a number of meniscus collective components with their concave surfaces turned towards the dispersive member. The dispersive member comprises a double convex element of relatively high refractive index in contact with, or close to, a double concave element of higher refractive index, and the ratio of the power of its outer convex surface to that of the system is not substantially less than the ratio of the focal length to the diameter of the entrance pupil. The convex surfaces of the meniscus components of the collective member on the convex side of the dispersive member are of successively greater radius, in order counting from the dispersive member, and also the ratio of the powers of any two of these components does not exceed the value two. The member on the concave side of the dispersive member may be a single collective component as shown, or a number of such components, or a single collective element outside a dispersive component. The system has a large aperture, of the order of f /1, and is corrected for axial and oblique aberrations and field. Data for three examples are given.