JPS6474518A - Zoom lens - Google Patents

Abstract

PURPOSE:To offer an inexpensive zoom lens whose overall length is very short, whose aperture is large and whose aberration is also satisfactory, although its variable power rate is low by constituting the titled zoom lens of three groups of a first positive group, a second negative group and a third positive group, and forming the third group as a fixed part constituted of four pieces of positive, positive, negative and positive. CONSTITUTION:The first group I consists 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, and the second group II consists 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 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 such a way, by constituting the third group of positive, positive, negative and positive, an inexpensive zoom lens whose overall length is short enough, whose aperture is large, and whose aberration is also satisfactory can be realized.