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

1987-04-06

1989-04-25

Corbin, John K.

Radiant energy

Ionic separation or analysis

Static field-type ion path-bending selecting means

250214AL, 350449, G02B 1514, G02B 964

Patent

active

048242365

ABSTRACT:
A zoom lens system for use in microfilm projection apparatus in which the image projection is conducted in a condition of a definite object-image distance, the system comprising from the enlargement side to the reduction side, an aperture stop disposed fixedly, a first lens group of a positive refractive power located near the aperture stop at the longest focal length side, a second lens group of a negative refractive power, and a third lens group of a positive refractive power, wherein the first to third lens groups are moved along the optical axis while increasing a distance between the first and second lens groups and decreasing a distance between the second and third lens groups in an operation of zooming from the longest focal length side to the shortest focal length side.

REFERENCES:
patent: 3360325 (1967-12-01), Gustafson
patent: 4449791 (1984-05-01), Terasawa et al.
patent: 4620775 (1986-11-01), Fujioka

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