Patent ID: 7173769

Claim:
A zoom lens optical system comprising: a first lens group having a positive refractive power; a second lens group having a negative refractive power; a third lens group having a positive refractive power; and a fourth lens group having a positive refractive power, wherein the first, second, third, and fourth lens groups are sequentially arranged from an object, and zooming from a wide angle position to a telephoto position is performed so that the distance between the third lens group and the fourth lens group satisfies the equations: f T f W â¢ > _ â¢ 8.0 0.2 â¢ < _ â¢ ï˜ƒ L III ï˜„ f W Â· f T â¢ < _ â¢ 0.6 where f w denotes the overall focal length of the zoom lens optical system at the wide angle position, f T denotes the overall focal length of the zoom lens optical system at the telephoto position, and L III denotes the amount of movement of the third lens group from the wide angle position to the telephoto position.