Patent ID: 7061686
Filing Date: 2006-06-13
Classification: G02B

Abstract:
1. A variable focal length lens system comprising four lens groups that are, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power; when the state of lens group positions varies from a wide-angle end state to a telephoto end state, at least the first lens group and the third lens group being moved to the object such that: an aperture stop being arranged in the vicinity of the third lens group; the second lens group being composed of three lens elements that are, in order from the object: the following conditional expression being satisfied: where R 24 denotes the radius of curvature of the image side surface of the second negative lens element in the second lens group, R 25 denotes the radius of curvature of the object side surface of the positive lens element in the second lens group, and fw denotes the focal length of the variable focal length lens system in the wide-angle end state, wherein the first lens group is composed of a cemented positive lens constructed by a negative meniscus lens having a convex surface facing to the object cemented with a positive lens having a convex surface facing to the object, and the following conditional expression is satisfied: where R 11 denotes a radius of curvature of the object side surface of the cemented positive lens in the first lens group.