High-magnification variable-focus system (varifocal system, zoom lens system)

摘要

A description is given of a high-magnification variable-focus system which contains at least three lens groups. Seen from an object to be photographed, the arrangement is a first positive lens group, a second positive lens group and a negative lens group. The three lens groups are moved, during the adjustment of the focal length, from a position of short focal length in the direction of the object towards a position of long focal length. The negative lens group satisfies the relationship 3.3 < mTn < 6 and 2.5 < mTn/mwn < 4, mTn being the lateral magnification of the negative lens group in the case of a long focal length and mwn being the lateral magnification of the negative lens group in the case of a short focal length. <IMAGE>