Patent ID: 8472122

Claim:
An optical system comprising a plurality of lens groups and a variable focus lens that can change the refractive power by changing the shape of the interface that is formed by a first medium and a second medium that have differing refractive indices, wherein, the variable focus lens satisfies the following condition: −0.023≦{( n A −1)/ν A −( n B −1)/ν B }/( n B −n A )≦0.023 where n A and n B respectively denote the d-line refractive indices of the first and second media, and ν A and ν B respectively denote the d-line Abbe numbers of the first and second media; the plurality of lens groups moves in an optical axial direction when changing the magnification from the wide angle end to the telephoto end; and the following condition holds: 0.8 <|f ao |/f w <5 where f ao denotes the composite focal distance at the wide angle end of the part of the optical system from the optical surface of the optical system closest to the object side to the optical surface of the variable focus lens closest to the image side, and f w denotes the focal distance of the entire system at the wide angle end.