Patent ID: 7609456
Filing Date: 2009-10-27
Classification: G02B

Abstract:
1. A standard 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, said positive first lens group, said positive third lens group and said positive fourth lens group move toward the object, and said negative second lens group moves toward an image and thereafter moves toward the object; wherein said positive first lens group consists of a negative lens element and a positive lens element; and wherein said standard zoom lens system satisfies the following conditions: wherein f1 designates the focal length of said positive first lens group; f2 designates the focal length of said negative second lens group; and f3 designates the focal length of said positive third lens group.