Projection zoom lens having a long back focal length

Details Projection zoom lens having a long back focal length Projection zoom lens having a long back focal length

1998-04-20

1999-08-10

Sugarman, Scott J.

Optical: systems and elements

Lens

With variable magnification

359649, 359754, G02B 1514

Patent

active

059367806

ABSTRACT:
A projection zoom lens having a long back focal length is provided which can produce excellent image quality. The projection zoom lens comprises: a front lens group including a first lens that is a convex lens, a second lens and a third lens, both of which are meniscus negative lens having a convex surface that is directed toward the object side, a fourth lens that is a meniscus lens having a surface which has a larger radius of curvature toward the image side; and a rear lens group including a fifth lens that is a plano-convex lens having a plane surface directed toward the object side, a sixth lens that is a biconvex lens, a seventh lens that is a meniscus negative lens, forming a doublet with the sixth lens, having a surface that has a larger radius of curvature directed toward the image side, an eighth lens that is a meniscus negative lens, a ninth lens that is a plano-convex lens, and a tenth lens that is a biconvex lens; wherein the projection zoom lens conforms to the following conditions: ##EQU1## where, f.sub.A is the focal length of the front lens group, f.sub.B is the focal length of the rear lens group, f.sub.W is the focal length of the projection zoom lens at the wide-angle side, N.sub.3 is the refractive index of the third lens, and V.sub.3, V.sub.6 and V.sub.7 are the Abbe numbers of the third lens, the sixth lens and the seventh lens, respectively.

REFERENCES:
patent: 4190323 (1980-02-01), Ogawa et al.

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