Finder optical device

Details Finder optical device Finder optical device

1988-12-06

1990-10-23

Henry, Jon W.

350572, 350410, 350480, G02B 2314, G02B 906, G02B 2500, G03B 1306

Patent

active

049646869

ABSTRACT:
A secondary image forming type finder opitcal device having an objective lens solely used therefor, comprising, from front to rear, an objective lens unit including at least one positive lens, a relay lens unit formed by arranging a lens of positive refractive power and a lens of negative refractive power in spaced relation, a field lens unit consisting of a positive lens whose front surface is of strong curvature, and an eyepiece lens unit consisting of two positive lenses whose confronting surfaces are of strong curvature, satisfying the following conditions: ##EQU1## where f.sub.P is the focal length of the lens of positive refractive power of the relay lens unit, .nu..sub.P is the Abbe number of its material, R.sub.P is the radius of curvature of a lens surface of the lens of positive refractive power of the relay lens unit which is of strong curvature and faces the lens of negative refractive power of the relays lens unit, f.sub.N is the focal length of the lens of negative refractive power of the relay lens unit, .nu..sub.N is the Abbe number of its material, and R.sub.N is the radius of curvature of a lens surfaces of the lens of negative refractive power of the relay lens unit which is of strong curvature and faces the lens of positive refractive power of the relay lens unit.

REFERENCES:
patent: 2541014 (1951-02-01), Orser
patent: 3045545 (1962-07-01), Korones et al.
patent: 3127809 (1964-04-01), Denk
patent: 3989349 (1976-11-01), Besenmatter et al.
patent: 4270837 (1981-06-01), Baker
patent: 4387967 (1983-06-01), Yamazaki et al.

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