Small three-unit zoom lens

Details Small three-unit zoom lens Small three-unit zoom lens

1992-09-02

1994-05-10

Look, Edward K.

Optical: systems and elements

Lens

With variable magnification

359687, G02B 914

Patent

active

053113616

ABSTRACT:
The present invention relates to a zoom lens system which is invariable in terms of the total length during zooming, has a field angle of 50.degree. or more and a coverage from the wide angle to quasi-telephoto region, and is suitable for use with a lens shutter type camera having a waterproof function. This zoom lens system comprises a first lens unit G1 having a positive refracting power, a second lens unit G2 having a negative refracting power and a third lens unit G3 having a positive refracting power. During zooming, the first lens unit remains fixed, while the second and third lens units are moved such that the second lens unit is larger than the third lens unit in terms of the maximum amount of movement, whereby zooming is carried out. The third lens unit is constructed from a front sub-unit G3F having a positive refracting power and a rear sub-unit G3R having a negative refracting power, said rear sub-unit including at least one negative meniscus lens convex on the image surface side.

REFERENCES:
patent: 4299454 (1981-11-01), Betensky
patent: 4462664 (1984-07-01), Moskovich
patent: 4494828 (1985-01-01), Masumoto et al.
patent: 4582399 (1986-04-01), Mihara
patent: 4653874 (1987-03-01), Takahashi et al.
patent: 5061053 (1991-10-01), Hirakawa

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