Patent ID: 7446947

Claim:
A variable magnification optical system comprising lens units that focus a ray of light from an object side on an image sensor, wherein the lens unit located at a first position from the object side toward the image side includes an optical path changing element for changing an optical path, wherein magnification variation is performed by changing gaps between the lens units, and wherein conditional formulae (1) to (3) below are satisfied: 4 < ft/fw Conditional formula (1), 1.72 < n_PR Conditional formula (2), 35 < v_PR Conditional formula (3), where ft denotes a focal length of the entire system at a telephoto end, fw denotes a focal length of the entire system at a wide-angle end, n_PR denotes a refractive index of the optical path changing element for a d-line, and v_PR denotes an Abbe number of the optical path changing element for the d-line, wherein the optical path changing element satisfies conditional formula (4) below: 0.2 < d_PR/ft < 0.4 Conditional formula (4), where d_PR denotes an optical path length of the optical path changing element, wherein the lens unit at the first position includes, in addition to the optical path changing element, one lens element having a negative optical power and two lens elements having a positive optical power.