Vari-focal system having short total length

Details Vari-focal system having short total length Vari-focal system having short total length

1991-06-10

1993-02-23

Sugarman, Scott J.

Optical: systems and elements

Lens

With variable magnification

359708, G02B 1514

Patent

active

051895587

ABSTRACT:
A vari-focal lens system having short total length comprising, in the order from the object side, a vari-focal subsystem consisting of a first lens unit having a positive refractive power and a second lens unit having a negative refractive power; and an imaging subsystem consisting of a third lens unit having a positive refractive power and always kept stationary, and a fourth lens unit having a positive refractive power and movable for correcting deviation of image point; said third lens unit being composed of four or a smaller number of lens elements including a positive lens element which is arranged on the object side in the third lens unit and has a convex surface on the object side, and a negative lens element, and said imaging subsystem comprising at least one aspherical surface.

REFERENCES:
patent: 4859042 (1989-08-01), Tanaka
patent: 4906079 (1990-03-01), Mihara et al.

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