Patent ID: 7593165

Claim:
A zoom lens for forming an optical image of an object on a sensing surface of an image sensor at a variable magnification, the zoom lens comprising, in order from an object side to an image side: a first lens group having a positive optical power; a second lens group having a negative optical power; a third lens group having a positive optical power; a fourth lens group having a negative optical power; and a fifth lens group having a positive optical power, wherein between the second lens group and the fourth lens group, an optical aperture stop is located, and wherein the fourth lens group is composed of one negative lens element having at least one aspherical surface and having a paraxial radius of curvature of an image side surface smaller than a paraxial radius of curvature of an object side surface, and satisfies conditional formula (1) below: −1.15 <f 4/ √{square root over (fw·ft)}< −0.5 (1), where f4 represents a focal length of the fourth lens group; fw represents a focal length of the entire zoom lens at a wide-angle end; and ft represents a focal length of the entire zoom lens at a telephoto end.