Patent ID: 7920332

Claim:
A variable-focal-length lens system comprising, in order from an object side: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having negative refractive power; and a fifth lens group having positive refractive power, wherein as a lens position state changes from a wide-angle end state to a telephoto end state, an air space between the first lens group and the second lens group increases, an air space between the second lens group and the third lens group decreases, an air space between the third lens group and the fourth lens group changes, an air space between the fourth lens group and the fifth lens group increases, the first lens group moves monotonously to the object side, the second lens group is fixed in an optical axis direction, and the third lens group and the fourth lens group move to the object side, and the following conditional expressions (1) and (2) are satisfied 0.2 <D 23 w/ft< 0.4 (1) 0.1 <f 2 /f 4<0.4 (2) where D 23 w is an air space between the second lens group and the third lens group in the wide-angle end state, ft is a focal length of the variable-focal-length lens system as a whole in the telephoto end state, f2 is a focal length of the second lens group, and f4 is a focal length of the fourth lens group.