Copying zoom lens

Details Copying zoom lens Copying zoom lens

1988-01-22

1989-03-21

Corbin, John K.

350464, G02B 1500, G02B 962

Patent

active

048137731

ABSTRACT:
A copying zoom lens comprising, in order from the object side, a first lens unit having a negative focal length, a second lens unit having a positive focal length and a third lens unit having a negative focal length. An axial space between the first and second lens units and an axial space between the second and third lens units are varied while moving an overall lens system and keeping constant a distance between the object and an image surface, thereby performing a zoom effect. The first lens unit is composed of a single negative meniscus first lens element having a concave surface directed to the object. The second lens unit is composed, in order from the object, of positive second lens element, a negative third lens element, a negative fourth lens element and a positive fifth lens element to constitute a three-lens element subsystem. The third lens unit is composed of a single negative meniscus sixth lens having a concave surface directed to the image surface. The second lens unit may be modified that it is composed, in order from the object, of a positive biconvex second lens element, a negative biconcave third lens element, and a positive biconvex fourth lens element to constitute a three-lens element subsystem.

REFERENCES:
patent: 4359269 (1982-11-01), Itoh

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