GB1350999A - Photographic lenses - Google Patents

Abstract

1350999 Optical objectives POLARIOD CORP 8 July 1971 [8 July 1970] 32224/71 Heading G2J A photographic objective lens system consists of three axially aligned components, and has an overall length from the entrance surface to the exit surface less than one-eighth of its nominal focal length and a Petzval sum not exceeding 0À300, the first component having an AbbÚ value at least 20% greater than the AbbÚ value of the second component, the components being arranged as follows from the long conjugate side:- a convergent first component I having a convex surface towards the long conjugate; a bi-concave divergent second component; and a convergent third component having a convex surface towards the short conjugate. The first component I may be movable for focussing. Surfaces R 3 and/or R 4 may be aspheric, and may be formed by moulding a plastics lens, or by laminating a plastics layer having the aspheric surface on to a glass lens. Components I, II and III are preferably singlets, but may be doublets. The AbbÚ value of a compound lens is defined as the AbbÚ value of a single-element lens having the same dispensive power as the compound lens. Components I and III may be, inter alia, of diamond, and component II may be, inter alia, of LaSF 7 , KI or a mixture of Y and Th oxides. Optical data are given for ten examples.