Vari-focal lens system

Details Vari-focal lens system Vari-focal lens system

1987-11-12

1989-04-04

Corbin, John K.

350423, G02B 1514

Patent

active

048180831

ABSTRACT:
A vari-focal lens system comprising a first lens group having a positive focal length, a second lens group having a negative focal length, a third lens group having a positive focal length, and a fourth lens group having a positive focal length in the order from the object side and arranged that the first and third lens groups are always kept fixed, the second lens group is arranged to be movable when varying the focal length of the lens system as a whole and to be kept fixed at the time of focusing, the fourth lens group is arranged to be movable for the purpose of compensating the displacement of the focal point which occurs when varying the focal length of the lens system as a whole and to be movable also for the purpose of focusing, and the rays coming out from the third lens group becomes approximately afocal, the vari-focal lens system being further arranged that the lens group to be moved for focusing is light in weight and, moreover, arranged to have a large aperture ratio, high vari-focal ratio and high performance.

REFERENCES:
patent: 2741947 (1956-04-01), Back
patent: 4634236 (1987-01-01), Masumoto

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