ZOOM LENS SYSTEM

摘要

A zoom lens system includes a positive first lens group and a negative second lens group. The first lens group includes a cemented lens, a diffraction surface having a rotationally symmetric shape satisfying condition (1) formed on a cemented surface of the cemented lens, and condition (2) is satisfied:;130<|fD/RD|<10,000(fD>0)  (1),;and;0.15

主权项

1. A zoom lens system comprising at least a positive first lens group and a negative second lens group, in that order from the object side, wherein a distance between said first lens group and said second lens group increases while zooming from the short focal length extremity to the long focal length extremity,
wherein said first lens group includes at least one cemented lens, wherein a diffraction surface having a rotationally symmetric shape with respect to the optical axis and satisfying the following condition (1) is formed on a cemented surface of at least one of said cemented lens, and wherein the following condition (2) is satisfied:
130<|fD/RD|<10,000(fD>0)  (1),and0.15 fD designates the focal length of said diffraction surface that is formed on said cemented surface of said cemented lens, provided within said first lens group,
fD=−1/(2×P2×λ0), P2 designates a secondary coefficient of an optical path difference function for calculating an optical path length addition amount of said diffraction surface that is formed on said cemented surface of said cemented lens, provided within said first lens group, λ0 designates the d-line (587.56 nm), RD designates the radius of curvature of the substrate surface having said diffraction surface that is formed on said cemented surface of said cemented lens, provided within said first lens group, f1 designates the focal length of said first lens group, and fT designates the focal length of the entire lens system at the long focal length extremity.