Wide-angle variable magnification viewfinder

Details Wide-angle variable magnification viewfinder Wide-angle variable magnification viewfinder

1996-10-23

1998-02-24

Nguyen, Thong

Optical: systems and elements

Compound lens system

Variable magnification

359422, 359431, 359676, 359686, G02B 2300, G02B 1514

Patent

active

057216380

ABSTRACT:
A wide-angle variable magnification viewfinder comprises from an object side: an objective lens group of a positive refractive power, including a fixed first lens unit of a negative refractive power, a movable second lens unit of a negative refractive power for compensating the change of a view angle, a movable third lens unit of a positive refractive power for changing the magnification of the optical system, a prism for erecting an image, a fixed fourth lens unit of a positive refractive power; and an eyepiece lens group of a positive refractive power; wherein the objective lens group forms an actual image of an object and the actual image can be observed through the eyepiece lens group; and wherein -1.20<L.sub.t /f.sub.1 <-0.75, 0.04<m2w.times.m2.sub.t <0.13; where f.sub.1 represents a focal length of the first lens unit of the objective lens group, L.sub.t represents a distance from the first lens surface of the objective group to a focal point of the objective lens group, m2w represents the magnification of the second lens unit of the objective lens group at a wide-angle position, and m2.sub.T represents a magnification of the second lens unit of the objective lens group at a telephoto position.

REFERENCES:
patent: 4842395 (1989-06-01), Sato et al.
patent: 5086353 (1992-02-01), Mukai et al.
patent: 5231534 (1993-07-01), Kato
patent: 5235460 (1993-08-01), Abe
patent: 5323264 (1994-06-01), Kato
patent: 5448400 (1995-09-01), Kikuchi et al.
patent: 5555431 (1996-09-01), Kim

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