Patent ID: 7173771

Claim:
A variable power optical system, that forms an optical image of an object on a light receiving surface of an image sensor for converting an optical image into an electric signal and changing gaps between lens groups in an optically axial direction so as to vary power of the optical system, the optical system including from an object side: a first lens group having negative optical power; a second lens group having positive optical power; and a third lens group having a positive optical power, wherein when the power of the optical system is varied from a wide-angle end to a telephoto end, a gap between the first lens group and the second lens group is narrowed, the first lens group is composed of two or more lenses, at least three lens groups are composed only a single lens or a lens where countered lens surfaces in the lens group are in close contact with each other without providing a gap; and wherein a gap between the second lens group and the third lens group is widened when the power of the optical system is varied from the wide-angle end to the telephoto end.