Patent ID: 7061686

Claim:
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: a distance between the first lens group and the second lens group increases; a distance between the second lens group and the third lens group decreases; and a distance between the third lens group and the fourth lens group increases; 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: a first negative lens element having a concave surface facing to the image; a second negative lens element having a concave surface facing to the image; and a positive lens element having a convex surface facing to the object; and the following conditional expression being satisfied: 3<( R 24+ R 25)/ fw< 5 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: 3< R 11 /fw< 5 where R 11 denotes a radius of curvature of the object side surface of the cemented positive lens in the first lens group.