JPS6474520A - Zoom lens - Google Patents

Abstract

PURPOSE:To offer a high performance zoom lens whose variable magnification rate is low, but when is compact and has a large aperture by constituting the titled zoom lens of three groups of a first positive group, a second negative group and a third positive group, constituting the third group of four pieces of positive, positive, negative and positive, fixing the first group, and moving the second and the third groups. CONSTITUTION:The first group I is constituted of two pieces of a negative meniscus lens being convex to an object side and a biconvex lens whose strong face has been turned to the object side, and has positive refracting power. The second group III is constituted of two pieces of a negative lens whose strong face has been turned to an image side and a positive meniscus lens being convex to the object side, and has negative refracting power. The third group III is constituted of four pieces of a positive lens whose strong refracting face has been turned to the image side, a positive lens whose strong refracting face has been turned to the object side, a biconcave lens whose strong refracting face has been turned to the image side, and a biconvex lens, in order from the object side, and has positive refracting power as a whole. In this state, at the time of zooming, the first group I is immobile, the second group II moves on an optical axis and brought to variable power, and the third group III follows it up and moves so as to keep the image face constant.