Patent ID: 7679837

Claim:
A zoom optical system at least comprising in the order from an object side: a first lens group having a positive optical power; a second lens group having a negative optical power; and a third lens group having a positive optical power, wherein in zooming from a wide angle end to a telephoto end, a distance between the first lens group and the second lens group is increased, and a distance between the second lens group and the third lens group is decreased, and the first lens group includes at least one negative lens element, and the second lens group includes a negative lens element closest to the object side, with a lens surface of the negative lens element closest to the object side being concave toward an image side, and the zoom optical system satisfies the following conditional expressions (1) and (2): vd 2 <30 (1) 50>vd 1n >30 (2) where vd 2 represents the Abbe number of the negative lens element closest to the object side in the second lens group, and vd 1n represents an Abbe number of a negative lens element, or an average Abbe number of negative lens elements in the first lens group, and wherein the negative lens element closest to the object side in the second lens group satisfies the following conditional expression (10): hb/fw≧ 1.5 (10) where hb represents an off-axis ray height on the lens surface closest to the object side in the second lens group, and is a value calculated by paraxial approximation in the case where a ray whose tangent of incident angle is 1.0 is incident onto the zoom optical system in a manner that the ray intersects with an optical axis at a diaphragm position, and fw represents a focal length of an entirety of the zoom optical system at the wide angle end.