Patent ID: 7382548

Claim:
A variable magnification optical system for forming an optical image of an object on a light-receiving surface of an image sensor with variable magnification, the variable magnification optical system comprising at least four lens units, namely, from an object side, a first lens unit, a second lens unit, a third lens unit, and a fourth lens unit, at least two of which move to perform the variable magnification; wherein the first lens unit has at least one negative lens element and at least one positive lens element; wherein the second lens unit has at least one negative lens element and at least one positive lens element; wherein a bending optical element for bending an optical axis is provided between the second lens unit and the third lens unit, and wherein conditional formulae (11), (12), and (13) below are fulfilled: 0.2<φ3/φ W< 1.0 (11) 1.5<φ3/φ T< 10.0 (12) −2.0< M 4/ M 3<2.0 (13) where φ 3 represents an optical power of the third lens unit, φW represents an optical power of the entire system at a wide-angle end, φT represents an optical power of the entire system at a telephoto end, M 3 represents an amount of relative movement of the third lens unit in variable magnification from the wide-angle end to the telephoto end, with movement toward the object side being defined as positive, and M 4 represents an amount of relative movement of the fourth lens unit in variable magnification from the wide-angle end to the telephoto end, with movement toward the object side being defined as positive.