GB593362A - Improvements in or relating to lens systems - Google Patents

Abstract

593,362. Lens systems. JEFFREE, J. H. Oct. 17, 1944, Nos. 20096/44 and 30510/45. [Class 97 (i)] A lens system for use as an anastigmatic objective comprises two or more components with convex outer surfaces and two adjacent inner concave surfaces, separated by an air space, one or both of which are segments of oblate ellipsoids whose minor axes lie in the optical axis of the system ; one or both of the convex outer surfaces also may be of similar ellipsoidal form. Some or all of the components may be of moulded plastic material or partly of such material and partly of glass. Thus, the system may consist of four components, the two outer components being of positive power and formed from polymethyl methacrylate, while the two inner components are of negative power and are formed from polystyrene, which has a relatively higher refractive index. The outer components, which may have spherical or aspherical forms, may be of glass when the spherical form is adapted, in order to correct for temperature changes as described in Specification 561,503. The outer and inner components may be cemented together on one or both sides or not at all. In examples : (1) the outer components 12, 16, Fig. 1, of polymethyl methacrylate have spherical convex outer surfaces while the inner components 13, 15, having inwardly directed concave surfaces of ellipsoidal form, are of polystyrene ; (2) the arrangements are as in example (1), but the convex outer surfaces of components 12, 16 are segments of oblate ellipsoids. Optical data are given in the Specification. Specification 570,694, [Group XXII], also is referred to.