Zoom lens system and optical instrument using the same

摘要

A zoom lens system includes a negative first lens group, a positive second lens group, and a positive third lens group, in that order from the object side. The second lens group constitutes a focusing lens group. The following conditions (1) and (2) are satisfied:
0.4<|d12w/f1|<1.06  (1); andd12wwherein f1 designates the focal length of the first lens group, and d12w and d23w designate the air distances between the first and second lens groups, and the second and third lens groups respectively, at the short focal length extremity.

主权项

1. A zoom lens system comprising a negative first lens group, a positive second lens group, and a positive third lens group, in that order from the object side,
wherein said second lens group constitutes a focusing lens group that is moved in the optical axis direction during a focusing operation, and wherein the following conditions (1) and (2) are satisfied:
0.4<|d12w/f1|<1.0  (1); andd12w f1 designates the focal length of said first lens group, d12w designates the air-distance between the surface closest to the image side of said first lens group to the surface closest to the object side of said second lens group at the short focal length extremity, and d23w designates the air-distance between the surface closest to the image side of said second lens group to the surface closest to the object side of said third lens group at the short focal length extremity.