Patent ID: 8098442

Claim:
A zoom lens system that forms an optical image of an object with variable magnification, the zoom lens system comprising, in order from an object side to an image side: a first lens unit having negative optical power; a second lens unit having positive optical power; and a third lens unit having positive optical power, wherein: in zooming from a wide-angle limit to a telephoto limit, the first, second and third lens units move respectively along an optical axis in such a manner that an interval between the first lens unit and the second lens unit decreases while an interval between the second lens unit and the third lens unit varies so that the variable magnification is achieved, the first lens unit is composed of one object side lens element and one image side lens element, the image side lens element of the first lens unit has positive optical power, the most image side lens element constituting the second lens unit is a lens element composed of a resin and having at least one aspheric surface, the third lens unit consists of one bi-convex lens element having at least one aspheric surface, and the following conditions (II-1), (II-6) and (II-7) are satisfied: 0.7 <f 2 /f 2r <1.5 (II-1), f 3r /f T <1.5 (II-6), T 3 /Y< 0.8 (II-7), and ω T <15, where, f 2 is a composite focal length of the second lens unit, f 2r is a focal length of the most image side lens element of the second lens unit, f 3r is a focal length of the bi-convex lens element of the third lens unit, f T is a focal length of the entire system at a telephoto limit, T 3 is a center thickness of the third lens unit, Y is a maximum image height of the zoom lens system, and ω T is a half view angle at a telephoto limit.