Retrofocus type wide-angle objective lens

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

1978-03-31

1980-02-12

Sacher, Paul A.

350207, G02B 964

Patent

active

041880927

ABSTRACT:
A retrofocus type lens having an angle of view at least 75.degree. and F number 1:2.0. The lens includes a first lens group of a divergent type, a second lens group of a convergent type and a third lens group of a convergent type. The first lens group includes in the order stated a positive meniscus lens, a negative meniscus lens, a positive meniscus lens and a negative meniscus lens. The second lens group includes a positive lens which is either a single lens or consists of a positive lens and a negative lens cemented to each other and with a front convex face directed toward an object to be photographed. The third lens group includes a positive lens having a rear convex face directed toward an image of the object, a biconcave lens with its front surface radius smaller than its rear surface radius, a positive meniscus lens with a convex surface facing the image and a positive lens. The biconcave lens and the positive meniscus lens are respectively replaceable with cemented doublet lenses. The lens system is characterized in that the first lens group includes meniscus lenses arranged in the order of positive, negative, positive and negative lenses, and particularly in that the third positive meniscus lens serves effectively to correct chromatic distortion aberration and chromatic coma aberration.

REFERENCES:
patent: 3870400 (1975-03-01), Yamashita et al.
patent: 3924935 (1975-12-01), Takahashi
patent: 3938883 (1976-02-01), Takahashi
patent: 3973832 (1976-08-01), Ogura et al.
patent: 4025168 (1977-05-01), Sugiyama

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