Projection lens system

U.S. Patent Number: 5388003

Abstract: A projection lens system which produces a smaller amount of residual chromatic aberrations and which will exhibit satisfactory performance even if it is used as a long-focus lens. The projection lens system is composed of a front group and a rear group. The front group includes, in order from the object side, a positive first lens element, a positive second lens element and a negative third lens element. The lens system satisfies the following conditions: where .theta.2 and .nu.2 denote the dispersion index of the second lens element and .theta.3 and .nu.3 denote the dispersion index of the third lens element, with .theta. and .nu. being defined by: where ng, nF, nC and nd denote the refractive indices of a lens element at the g, F, C and d lines, respectively.

Inventors: Naganuma; Kazuhiro (Tokyo, JP), Arai; Yasunori (Saitama, JP)

Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha (Tokyo, JP)

Application Number: 08/242,063

Issued: 1995-02-07

Expired: 2007-02-07

Classes: 359/649 ; 359/758; 359/760

Field of search: 359/758,760,649

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