Patent ID: 7433584

Claim:
A variable-magnification optical system comprising a plurality of lens groups through which light from an object is imaged on an image sensor, the plurality of lens groups including, from an object side to an image side, at least: 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 the first lens group includes a first optical axis changing element that changes an optical axis, and wherein conditional formula (1) below is fulfilled: 0.1 <|f 2 /√{square root over (fw×ft)}|< 0.45 (1) where f 2 represents a focal length of the second lens group; fw represents a focal length of the entire variable-magnification optical system at a wide-angle end; and ft represents a focal length of the entire variable-magnification optical system at a telephoto end.