Zoom lens system

Abstract

Abstract PURPOSE:To realize the infocus state to an approximate object, by shifting the lens group at the back of the diaphragm of a fixed rear group in a magnification and reduction system comprising a fixed front group, a magnification and reduction lens group including a variator and a compensator and the above-mentioned fixed rear group respectively. CONSTITUTION:A zoom lens system comprises a fixed front groupI, a variation and reduction lens group II including a variator and a compensator and a rear group III which is totally fixed and contains a diaphragm S at its front or inside part in that order from the side of an object. A mobile lens group F having the positive refractive power is provided at the side of an image from the diaphragm in the group III, and this group F is shifted toward the object to perform the focusing to an approximate object. The ratio between the focal distance fF of the group F and the focal distance of the group III is set at 0.2-2, and as a result a well- balanced compensation is possible to the aberration fluctuation caused by the focusing.

Inventors

• 👤 Hisayuki Masumoto
• 👤 Masaichi Shimomura

Bibliographic Details