Variable magnification viewfinder optical system

Details Variable magnification viewfinder optical system Variable magnification viewfinder optical system

1990-11-20

1992-02-04

Henry, Jon W.

Optical: systems and elements

Compound lens system

Variable magnification

359422, 359676, 359643, G02B 2500, G02B 2314, G02B 1515, G03B 1302

Patent

active

050863533

ABSTRACT:
The present invention provides a variable magnification viewfinder optical system, comprising from the object side: objective lens group of a positive refractive power, including a first lens unit of a negative refractive power and a second lens unit of a positive refractive power, said first and second lens units being shiftable along the optical axis of the optical system for changing the magnification of the optical system; condenser lens group of a positive refractive power; and eyepiece lens group of a negative refractive power; wherein the objective lens group forms a real image of an object and the real image can be observed through the eyepiece lens group; and wherein the optical system fulfills the following conditions;

REFERENCES:
patent: 2353565 (1944-07-01), Kaprelian
patent: 3227042 (1966-01-01), Smejkal et al.
patent: 3438689 (1969-04-01), Wehr
patent: 3788731 (1974-01-01), Sugiuva et al.
patent: 4249793 (1981-02-01), Uehava
patent: 4779969 (1988-10-01), Sato et al.
patent: 4842395 (1989-06-01), Sato et al.
Fundamentals of Optics, International Student Edition, McGra-Hill Kogakusha, Ltd. (1976).
The Focal Encyclopedia of Photography, Focal Press, London and New York (8/1957).

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