Real image mode variable magnification finder optical system

Details Real image mode variable magnification finder optical system Real image mode variable magnification finder optical system

1996-05-31

1997-12-23

Nguyen, Thong

Optical: systems and elements

Compound lens system

Variable magnification

359422, 359431, 359686, 396379, G02B 2300, G02B 1514

Patent

active

057011990

ABSTRACT:
A real image mode variable magnification finder optical system has a finder objective for forming an optical path different from a photographic objective, an image erecting optical member for erecting an image formed by the finder objective, and an eyepiece having a positive refracting power. The finder objective includes the first lens unit having a negative refracting power, the second lens unit having a positive refracting power, the third lens unit having a negative refracting power, and the fourth lens unit having a negative refracting power, so that the second lens unit and said third lens unit are movable along the optical axis to change spaces among respective lens units from the first lens unit to the fourth lens unit. In this way, the finder optical system is obtained which bears a high variable magnification ratio, but is compact in size and provides good correction for aberration.

REFERENCES:
patent: 5173806 (1992-12-01), Ogata
patent: 5231534 (1993-07-01), Kato
patent: 5323264 (1994-06-01), Kato
patent: 5359377 (1994-10-01), Kamo

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