Zoom finder of real image type and real image type zoom finder c

Details Zoom finder of real image type and real image type zoom finder c Zoom finder of real image type and real image type zoom finder c

1993-04-09

1995-09-05

Nguyen, Viet Q.

Optical: systems and elements

Compound lens system

Telescope

359774, 359687, 359676, 359643, 359686, 359432, G02B 1514

Patent

active

054484006

ABSTRACT:
A zoom finder of a real image type has an objective lens having positive refracting power and an eyepiece having positive refracting power. The objective lens is constructed by first, second, third and fourth lens groups sequentially arranged from an object side. The first lens group has positive refracting power. The second lens group has negative refracting power. The third lens group has positive refracting power. The fourth lens group has positive refracting power. The zoom finder is constructed such that a real image is focused and formed by the objective lens between the fourth lens group and the eyepiece and is observed through the eyepiece. A magnification of the zoom finder is increased by moving the second lens group from the object side to an eyepiece side. A change in diopter caused by this increase in magnification is corrected by moving the fourth lens group. In accordance with the above structure, an entire length of the zoom finder is short and is not changed in a zooming operation. Further, the structure of a mechanical mechanism for displacing lenses in the zooming operation is simplified and no diopter of the zoom finder is changed in the zooming operation.

REFERENCES:
patent: 5144480 (1992-09-01), Oshita
patent: 5184252 (1993-02-01), Miyauchi et al.
patent: 5193030 (1993-03-01), Nozaki et al.
patent: 5233471 (1993-08-01), Nakamura et al.

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