Telephoto type zoom lens

Details Telephoto type zoom lens Telephoto type zoom lens

1977-03-02

1978-08-29

Clark, Conrad J.

350187, 350212, G02B 1518

Patent

active

041100069

ABSTRACT:
The present invention relates to a focusing lens group of a telephoto zoom lens having a long range of focal length. The focusing lens group consists of four sub-groups, wherein first, second, and fourth sub-groups are fixed while a third sub-group can be shifted for focusing.
And the first sub-group has a positive refractive power and the second sub-group has a negative refractive power. The third sub-group has a positive refractive power and the fourth sub-group has a negative refractive power. As a result, the variation in the image quality at a time when the telephoto zoom lens is focused will be eliminated and the diameters of the lenses in the second, third and fourth sub-groups will be smaller than that of the first sub-group.

REFERENCES:
patent: 3594066 (1971-07-01), Cook et al.
patent: 3598476 (1971-08-01), Merigold
patent: 3632188 (1972-01-01), Nakamura
patent: 3682534 (1972-08-01), Cook et al.

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