Zoom-lens system (varifocal system, variable-focus system)

摘要

A zoom-lens system contains at least three lens groups (lens components) with a first positive lens group which has a first negative lens and a second positive lens, a second positive lens group which has a first negative lens unit and a second positive lens unit, and a third negative lens group. During zoom operation, the first, second and third lens groups are moved from a short focal length to a long focal length in the direction of a subject to be recorded and satisfy the conditions (1) 0 < fW/f1 < 0.5 (2) 1.7 < N1P (3) 1.75 < N2aN (4) 1.7 < N2bP, with fW specifying the focal length of the overall lens system in a wide-angled end position, f1 the focal length of the first lens group, N1P the refractive index of the positive lens of the first lens group, N2aN the refractive index of the negative lens of the first negative lens unit of the second lens group and N2bP the refractive index of the positive lens of the second positive lens unit of the second lens group. <IMAGE>