Patent ID: 7180683
Filing Date: 2007-02-20
Classification: G02B

Abstract:
1. A zoom lens system comprising, in order from an object: a first lens group having negative refractive power; a second lens group having positive refractive power; and a third lens group having positive refractive power; the first lens group consisting of a negative lens element and a positive lens element, the second lens group including at least two positive lens elements and at least one negative lens element, and the third lens group consisting of one lens element, wherein the second lens group includes at least one aspherical surface, a positive lens element of said at least two positive lens elements in the second lens group is cemented with the negative lens element in the second lens group, no other cemented lens exists in the second lens group, and when a state of lens group positions varies from a wide-angle end state to a telephoto end state, a distance between the first lens group and the second lens group decreases, a distance between the second lens group and the third lens group increases, and the third lens group is fixed, the following conditional expression being satisfied: where TL denotes the distance between the most object side lens surface of the zoom lens system and the image plane, fw denotes the focal length of the zoom lens system in a wide-angle end state, and ft denotes the focal length of the zoom lens system in a telephoto end state.