Patent ID: 6853496
Filing Date: 2005-02-08
Classification: G02B

Abstract:
1. A zoom lens system comprising a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in this order from an object, wherein upon zooming from the short focal length extremity to the long focal length extremity, all said lens group are movable in a manner that the distance between said positive first lens group and said negative second lens group increases, the distance between said negative second lens group and said positive third lens group decreases, the distance between said positive third lens group and said positive fourth lens group increases, and the distance between said positive first lens group and said positive third lens group does not change; wherein upon zooming from the short focal length extremity to the long focal length extremity, said positive fourth lens group first moves toward an image and thereafter moves toward said object in a U-turn path; and wherein said zoom lens system satisfies the following condition: wherein fw designates the focal length of the entire the zoom lens system at the short focal length extremity; and ΔX