Zoom objective of small size

Details Zoom objective of small size Zoom objective of small size

1980-07-17

1983-01-25

Corbin, John K.

G02B 1516

Patent

active

043700314

ABSTRACT:
In the disclosed zoom objective the spacing between divergent front and convergent rear lens groups is varied for zooming. From front to rear, the divergent group consists of a negative meniscus lens of forward convexity, a bi-concave lens and a positive meniscus lens of forward convexity, the bi-concave and positive meniscus lenses defining an air lens which has a converging effect. From front to rear, the convergent group consists of a positive lens with its front surface of strong curvature, two positive meniscus lenses of forward convexity, a negative lens and a positive lens. The zoom objective satisfies the following conditions: ##EQU1## (3) .nu.3 <35 (4) 32 <(.nu.1 or .nu.2) <45.5 ##EQU2## where F1 is the focal length of the divergent lens group; Ft is the longest focal length of the entire system; Et is the interval between the principal points of the divergent and convergent groups when in the telephoto end; .nu.1, .nu.2 and .nu.3 are the Abbe numbers of the 1st to 3rd lenses in the divergent lens group respectively; and N4, N5 and N6 are the refractive indices of the 1st to 3rd positive lenses counting from the front in the convergent lens group.

REFERENCES:
patent: 4168110 (1979-09-01), Itoh
patent: 4294521 (1981-10-01), Doi et al.
patent: 4299452 (1981-11-01), Ikemori

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