Patent ID: 6157494
Filing Date: 2000-12-05
Classification: G02B

Abstract:
A zoom lens system, comprising;a negative lens group having a magnification variance greater than other lens groups of the zoom lens system; anda positive lens group located on an image side thereof,a surface in said positive lens group, which surface is located nearest to an object side of said zoom lens system, satisfying the following condition (1) and,a surface in said positive lens group, which surface is located nearer to the image side, having a diffractive surface:0.2<R.sub.a1 /f.sub.S <3.0 (1)where f.sub.S is f.sub.S =.sqroot.(f.sub.W .times.f.sub.T) wherein f.sub.W is a d-line focal length of said zoom lens system at a wide-angle end thereof and f.sub.T is a d-line focal length of said zoom lens system at a telephoto end thereof, and R.sub.a1 is a paraxial radius of curvature of a surface in said lens group having a diffractive surface, which surface is located nearest to an object side of the zoom lens system.