Patent ID: 7656590
Filing Date: 2010-02-02
Classification: G02B

Abstract:
1. A zoom lens, comprising, in order from an object side thereof, a first lens group having negative refracting power, a second lens group having positive refracting power, a third lens group having negative refracting power, and a fourth lens group having positive refracting power, wherein: said first lens group consists of one negative lens component wherein one negative lens and one positive lens are cemented together; upon zooming from a wide-angle end to a telephoto end of the zoom lens, said second lens group moves toward the object side, and said third lens group moves, with a decreasing spacing between said first lens group and said second lens group, a changing spacing between said second lens group and said third lens group, and a changing spacing between said third lens group and said fourth lens group; and when a near-intermediate zooming state is defined as any zooming state where a focal length of the whole zoom lens system is from 0.9×√{square root over ( )}(fw·ft) to 1.05×√{square root over ( )}(fw·ft) where fw is a focal length of the whole zoom lens system at the wide-angle end and ft is a focal length of the whole zoom lens system at the telephoto end, said third lens group satisfies the following condition in any near-intermediate zooming state: where Δ3G(s) is a positional difference of the third lens group at the wide-angle end relative to the near-intermediate zooming state provided that plus and minus signs are indicative of directions of travel of the lens groups toward the object side and an image side, respectively.