Patent ID: 7630138
Filing Date: 2009-12-08
Classification: G02B

Abstract:
1. A variable-power optical system comprising, in order from an object side: a first lens group that is fixed at a time of varying magnification and at a time of focusing and that has a positive refractive power; a second lens group that is movable at the time of varying the magnification and that has a negative refractive power; a third lens group that is fixed at the time of varying the magnification and at the time of focusing and that has a positive refractive power; a fourth lens group that is movable at the time of varying the magnification, that has a focusing function, and that has a positive refractive power; and a fifth lens group that is movable at the time of varying the magnification and that has a negative refractive power, wherein the following conditional expressions are satisfied: where fw denotes a focal length of the whole system at a wide end, f f