Zoom lens and focusing method

Details Zoom lens and focusing method Zoom lens and focusing method

1990-01-22

1991-08-27

Dzierzynski, Paul M.

Optical: systems and elements

Lens

With variable magnification

359689, 359676, G02B 1500

Patent

active

050429264

ABSTRACT:
A zoom lens comprises first to third lens groups sequentially arranged from an object side toward an image side and respectively having negative, positive and negative focal distances; a first zoom region for performing a zooming operation from a wide angle side to a telescopic side by moving at least the first lens group onto the image side; and a second zoom region for performing the zooming operation from the wide angle side to the telescopic side by moving all the lens groups onto the object side further from the telescopic end of the first zoom region while the distances between the lens groups are changed with respect to each other; the focal distances of the respective lens groups and the focal distance of the entire lens system at the wide angle end satisfying predetermined inequality conditions. A focusing method in the above zoom lens comprises the steps of performing a focusing operation by moving the second lens group on an optical axis in the first zoom region; and performing the focusing operation by moving the first lens group on the optical axis in the second zoom region.

REFERENCES:
patent: 4198127 (1980-04-01), Itoh
patent: 4636040 (1987-01-01), Tokumaru
patent: 4955700 (1990-09-01), Yamaguchi

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