Patent ID: 8305695

Claim:
A high magnification compact zoom lens comprising: a first lens group of positive refractivity, a second lens group of negative refractivity, a third lens group of positive refractivity, and a fourth lens group of positive refractivity, in order from the object side; the second lens group being movable toward the imaging plane and the fourth lens group being movable to compensate for a varied position of the resultant image while the first and third lens groups have their respective positions fixed along the optical axis, when the entire lens optics of the zoom lens are displaced from the wide-angle end to the telephoto end; wherein the zoom lens satisfies the requirements as defined in the following formulae: f 3 /f 4>2.0 (13) v 4>65 (14) where f 3 is a focal length of the third lens group, f 4 is the focal length of the fourth lens group, and v 4 is an average of Abbe constants of all positive lens pieces in the fourth lens group; and wherein the third lens group has a fixed lens subset of a convexo-concave cemented lens followed by a movable lens subset of a concavo-convex cemented lens, the movable lens subset being shifted in directions orthogonal to the optical axis so as to cause incident beams to be imaged in shifted position, and the fixed lens subset has its convex surface of the greater curvature faced closest to the subject and its concave surface of the greater curvature faced closest to the imaging plane, and wherein the zoom lens satisfies the requirements as defined in the following formulae: H 31 >H 32 (18) −0.12<( R 31 −R 32)/( R 31 +R 32)<0.12 (19) where H 31 is a height of part of incident beams on the foremost surface of the leading lens piece in the fixed lens subset of the third lens group on or above the optical axis at the wide-angle end, and H 32 is the height of part of the incident beams on the foremost surface of the leading lens piece in the movable or image-stabilizing lens subset of the third lens group on or above the optical axis at the wide-angle end, and where R 31 is a radius of curvature of the convex surface of the leading lens piece closest to the subject in the fixed lens subset of the third lens group, and R 32 is the radius of curvature of the concave surface of the trailing lens piece closest to the imaging plane in the fixed lens subset of the third lens group.