Zoom lens system

摘要

A zoom lens system includes a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group. Upon zooming from the short to the long focal length extremities, the distance between the first and second lens groups decreases, the distance between the second and third lens groups increases, and the distance between the third and fourth lens groups decreases. The following conditions (1) and (2) are satisfied:
−2.50wherein
f1, f2 and f3 designate the focal lengths of the first, second and third lens groups, respectively, and f3B designates the focal length of a bonding surface in the cemented lens of the third lens group.

主权项

1. A zoom lens system comprising a negative first lens group, a positive second lens group, a negative third lens group, and a positive fourth lens group, in that order from the object side,
wherein upon zooming from the short focal length extremity to the long focal length extremity, the distance between said first lens group and said second lens group decreases, the distance between said second lens group and said third lens group increases, and the distance between said third lens group and said fourth lens group decreases, wherein said third lens group includes a cemented lens provided with a positive lens element and a negative lens element, and wherein the following conditions (1) and (2) are satisfied:
−2.50 f1 designates the focal length of said first lens group, f2 designates the focal length of said second lens group, f3 designates the focal length of said third lens group, and f3B designates the focal length of a bonding surface in the cemented lens of said third lens group, wherein said fourth lens group comprises a positive lens element having a convex surface on the image side, a positive lens element having a convex surface on the image side, and a negative lens element having a concave surface on the object side, in that order from the object side, and wherein the following condition (11) is satisfied:
νdp4>80  (11),wherein
νdp4 designates the Abbe number with respect to the d-line of the positive lens element provided with a convex surface on the image side that is provided closest to the object side within said fourth lens group.