Image pickup system

Abstract

The invention has for its object to use a zoom system that comprises a reduced number of lens elements, is compact and simplified, and has high image-formation capability, thereby achieving thorough size reductions in video cameras or digital cameras. A zoom lens for use on an image pickup system comprises a first lens group Gnegative power comprising an aspheric negative lens element and a positive lens element, a second lens group Gcomprising a positive single lens element, a positive doublet wherein a positive and a negative lens element are cemented together in this order and which is in a meniscus form convex toward an object side of the zoom lens and a positive single lens element, wherein two or more surfaces except the cementing surface of the doublet are each defined by an aspheric surface, and a third lens group Gcomprising one positive lens component. For zooming from the wide-angle end to the telephoto end of the zoom lens, the second lens group Gmoves only toward the object side of the zoom lens, and the third lens group Gmoves in a locus different from that of the second lens group G. For focusing, the third lens group Gmoves. Condition (1) for the shape factor of the object side-positive lens element in the second lens group Gand condition (2) for the magnification of the second lens group Gare satisfied.