JPS6446716A - Compact zoom lens - Google Patents

Abstract

PURPOSE:To allow the titled lens to have a full-aperture F-number, to make it light in weight and compact, and to reduce its cost, by constituting said lens of total three groups of a first group having negative refracting power, a second group having positive refracting power, and a third group having positive refracting power in order from an object side. CONSTITUTION:The first group consists of one negative lens component which is stuck with a negative lens and a position lens, the second group consists of two positive lenses, at least one of them is a positive lens component which is stuck with a negative lens and a positive lens, and the third group consists of a front group having negative refracting power as a whole and a rear group having positive refracting power, consisting of a positive lens and a negative lens in order from an object side, so that conditions of expressions I-V are satisfied. In this regard, psiI and psiII denote the refracting power of the first and the second groups, respectively. Also, psiIP, psiIIP, and fW, and psiA denote the refracting power of the surface of the nearest side to the object of the first and the second groups, a composite focal distance of the whole system at a wide end, and composite refracting power of the front group of the third group, respectively. Moreover, D denotes an axial distance extending from an object side face of a positive meniscus lens to an image side face of a negative lens, of the front group of the third group. In such a way, a zoom lens whose bright full-aperture F-number, compact shape, and low cost are satisfied can be obtained.