Retrofocus type wide-angle objective

Details Retrofocus type wide-angle objective Retrofocus type wide-angle objective

Filed on

1978-08-04

Date issued

1980-06-10

Examiner

Sacher, Paul A.

Other Related Categories

350207, G02B 964

Type

Patent

Status

active

Patent number

042069734

Description

ABSTRACT:
A retrofocus wide angle objective having an angle of view of at least 82.degree. with a relative aperture of 1:2.8 and whose back focal distance is made longer than 1.4 times the focal length of the entire system. The objective comprises, from front to rear, a first lens of positive power in a forwardly convex meniscus form, a second negative meniscus lens, a third positive lens, a fourth negative lens, a fifth biconvex lens, a diaphragm, a sixth biconvex lens, a seventh biconcave lens, and eighth and ninth positive lenses. In such retrofocus objective with the positive meniscus lens arranged at the front, while the angle of view is maintained increased, the lens system is reduced in dimensions and is properly corrected in particular for distortion and astigmatism.

REFERENCES:
patent: 3877795 (1975-04-01), Yamashita
patent: 4025170 (1977-05-01), Kamamura

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