Zoom lens

Details Zoom lens Zoom lens

1980-10-03

1982-08-24

Corbin, John K.

G02B 1516

Patent

active

043458211

ABSTRACT:
A zoom lens for use with an SLR camera the focal length of which is approximately 400 mm at a telephoto end, which has a zoom ratio of two or more, substantially the same brightness as a fixed focus lens, and substantially the same performance and compactness as a fixed focus lens. The zoom lens system includes, in order from the object side, a first zoom lens having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power and a fourth lens group having a negative refractive power. The second lens group is movable along the optical axis to vary the focal length of the composite zoom lens system while at the same time the third lens group is movable along the optical axis to maintain the image position constant. The fourth lens group is composed, in order from the object, of a negative lens, a positive lens, at least one negative lens, and at least one positive lens.

REFERENCES:
patent: Re28591 (1975-10-01), Nakamura
patent: 3615125 (1971-10-01), Higuchi et al.
patent: 4094586 (1978-06-01), Sato et al.
patent: 4110006 (1978-08-01), Ikemori

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