Zoom lens, and electronic imaging system using the same

Abstract

The invention provides a zoom lens that operates in such a zooming mode and zoom arrangement that the number of lens elements is reduced to make the total thickness of each lens group thin while stable yet high image-formation capability is maintained, thereby achieving thorough size reductions in video cameras or digital cameras, and an electronic imaging system using the same. The zoom lens comprises a first lens group G of negative refracting power, a second lens group G of positive refracting power and a third lens group G of positive refracting power. For zooming from the wide-angle end to the telephoto end of the zoom lens upon focused on an infinite object point, the second lens group G moves toward the object side alone of the zoom lens, and the third lens group G moves in a locus different from that of the second lens group while the spacing between adjacent lens groups varies. The second lens group G is composed of two lens components, i.e., an object side-lens component and an image side-lens component, one of which is composed of a cemented lens component consisting of a positive lens element and a negative lens element, and the other consists only of a single lens component. The object side-lens component satisfies condition (1) concerning the axial radius-of-curvature ratio between the object side-surface and the image side-surface.