Patent ID: 7301711
Filing Date: 2007-11-27
Classification: G02B

Abstract:
1. A fast zoom lens system comprises 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, a distance between said positive first lens group and said negative second lens group increases, a distance between said negative second lens group and said positive third lens group decreases, and a distance between said positive third lens group and said positive fourth lens group decreases; wherein said fast zoom lens system satisfies the following conditions: wherein f f fw designates the focal length of the entire fast zoom lens system at the short focal length extremity; wherein said positive fourth lens group comprises three positive lens elements, and wherein at least one of said three positive lens elements is bonded to a negative lens element.