Rear focus type zoom lens

Details Rear focus type zoom lens Rear focus type zoom lens

1993-06-28

1995-07-04

Sugarman, Scott J.

Optical: systems and elements

Lens

With variable magnification

359687, G02B 1514

Patent

active

054305764

ABSTRACT:
A zoom lens of the rear focus type is disclosed, comprising, from front to rear, a first lens unit of positive power, a second lens unit of negative power, a third lens unit of positive power and a fourth lens unit of positive power, zooming being performed by moving the second and fourth lens unit and focusing being performed by moving the fourth lens unit, while the first and third lens units remain stationary. The first lens unit comprises, from front to rear, a negative meniscus lens and a bi-convex lens, and the second lens unit comprises, from front to rear, a bi-concave lens and a positive lens. The first and second lens units each have at least one asphric surface. The zoom lens satisfies the following conditions: ##EQU1## where f.sub.2, f.sub.3 and f.sub.4 are the focal lengths of the second, third and fourth lens units, respectively, and f.sub.W and f.sub.T are the shortest and longest focal lengths of the entire lens system, respectively.

REFERENCES:
patent: 4802747 (1989-02-01), Horiuchi
patent: 4998809 (1991-03-01), Tsuji et al.
patent: 5009492 (1991-04-01), Hamano
patent: 5050972 (1991-09-01), Mukaiya et al.
patent: 5134524 (1992-07-01), Hamano et al.
patent: 5138492 (1992-08-01), Hamano et al.
patent: 5285316 (1994-02-01), Miyano et al.

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