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

1990-07-03

Dzierzynski, Paul M.

350427, 350450, G02B 1500

Patent

active

049385720

ABSTRACT:
A zoom lens system for use in a microfilm projection apparatus, having from 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 and 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. Such structure reduces a distortion as well as a variation thereof during the zooming operation. Moreover, the fixed location of the first lens unit reduces the length of the whole zoom lens system to thereby provide it being compact.

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

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