Real image type finder

Details Real image type finder Real image type finder

1996-03-13

1998-09-29

Nguyen, Thong

Optical: systems and elements

Compound lens system

Telescope

359422, 359432, G02B 2300, G02B 1306

Patent

active

058153128

ABSTRACT:
The present invention provides a real image type of zoom finder which, albeit having a zoom ratio as high as at least 3, is short in terms of the total length of an objective, is well corrected in terms of aberrations and ensures good viewing, and which comprises, in order from the object side, an objective having a positive refracting power, an optical system for inverting the upper, lower, left and right parts of an image formed by said objective, and an eyepiece having a positive refracting power, wherein the objective consists essentially of a first lens group G.sub.1 having a negative refracting power, a second lens group G.sub.2 having a positive refracting power, a third lens group G.sub.3 having a negative refracting power and a fourth lens group G.sub.4 having a positive refracting power, each consisting of one lens or the second lens group G.sub.2 consisting of two lenses, and conforms to the following conditional inequality (1):

REFERENCES:
patent: 5005955 (1991-04-01), Ohshita
patent: 5173806 (1992-12-01), Ogata
patent: 5231534 (1993-07-01), Kato
patent: 5359377 (1994-10-01), Kamo
patent: 5448411 (1995-09-01), Morooka
patent: 5701199 (1997-12-01), Takato

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