Patent ID: 7199942
Filing Date: 2007-04-03
Classification: G02B

Abstract:
1. A zoom lens system comprising, in order from an object side to an image side: a first lens unit of positive optical power; a second lens unit of negative optical power; a third lens unit of positive optical power, the third lens unit including, a first lens group, the first lens group consisting of three lens elements ordered from the object side to the image side, wherein the three lens elements are a positive lens element, a negative lens element, and a positive lens element; and a fourth lens unit of positive optical power, the fourth lens unit including a second lens group consisting of two lens elements of the second lens group arranged in order from the object side to the image side, the two lens elements being a positive lens element of the second lens group and a negative lens element of the second lens group, wherein the second lens unit and the fourth lens unit are moved during zooming; and the following conditions are satisfied: where β4w is the imaging magnification of the fourth lens unit at a wide-angle end, β4t is the imaging magnification of the fourth lens unit at a telephoto end, f 3 is the focal length of the third lens unit, f 4 is the focal length of the fourth lens unit, fw is the focal length of the zoom lens system at the wide-angle end, and ft is the focal length of the zoom lens system at the telephoto end.