Zoom lens system for use in microfilm projection apparatus

Details Zoom lens system for use in microfilm projection apparatus Zoom lens system for use in microfilm projection apparatus

1988-12-14

1990-06-19

Dzierzynski, Paul M.

350427, 350450, G02B 1500

Patent

active

049347942

ABSTRACT:
A zoom lens system for use in a microfilm projection apparatus, having from the enlargement side a first lens unit of a negative refractive power, a second lens unit of a positive refractive power and a third lens unit of a negative refractive power and including an aperture stop positioned within the second lens unit or in the vicinity thereof. The first lens unit consists of one or more meniscus lens elements each having a concave surface faced to the reduction side. The second lens unit includes, from the enlargement side, a lens group having at least two positive lens elements,a negative lens element and a positive lens element. The third lens unit consists of one or more meniscus lens elements each having a concave surface faced to the enlargement side. Zooming operation from the longest focal length side to the shortest focal length side is carried out by linearly moving both the second and third lens units to the reduction side along the optical axis while first lens unit is fixed. The zoom lens system fulfills the following condition:

REFERENCES:
patent: 4303311 (1981-12-01), Nakamura
patent: 4449791 (1984-05-01), Terasawa et al.

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