Telephoto zoom lens

Details Telephoto zoom lens Telephoto zoom lens

1997-10-21

2000-04-18

Mai, Huy

Optical: systems and elements

Lens

With variable magnification

G02B 1514

Patent

active

060522356

ABSTRACT:
A telephoto zoom lens includes a first positive lens group, a second negative lens group, a third positive lens group and a fourth lens group. A resultant refractive power of the third and fourth lens groups are moved from an image side to an object side upon zooming from a short focal length extremity to a long focal length extremity, so that a distance between the first and second lens groups increases, a distance between the second and third lens groups decreases, and a distance between the third and fourth lens groups becomes smallest at an intermediate focal length. The zoom lens satisfies a condition specified by (0.1<X.sub.3 /X.sub.1 <0.5), wherein X.sub.1 represents a distance between a position at the short focal length extremity and at the long focal length extremity of the first lens group on an optical axis, and X.sub.3 represents a distance between the positions at the short focal length extremity and at the long focal length extremity of the third lens group on the optical axis, respectively.

REFERENCES:
patent: 4662724 (1987-05-01), Moriyama
patent: 5061053 (1991-10-01), Hirakawa
patent: 5572277 (1996-11-01), Uzawa et al.

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