| 摘要 |
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 G1 of negative refracting power, a second lens group G2 of positive refracting power and a third lens group G3 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 G2 moves toward the object side alone of the zoom lens, and the third lens group G3 moves in a locus different from that of the second lens group while the spacing between adjacent lens groups varies. The second lens group G2 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.
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