Patent ID: 7092169

Claim:
A zoom lens system, in sequence from an object side to an image side, comprising: a first lens group having positive refractive power and being fixed for gathering incoming light; a second lens group having negative refractive power for changing a focal length of the zoom lens system; a third lens group having positive refractive power and being made stationary; a fourth lens group having positive refractive power and being movable for eliminating for an optical aberration of the zoom lens system; and a fifth lens group having positive refractive power and being movable for focusing purpose; wherein, during zooming from a wide-angle end to a telephoto end, said second and fourth lens groups are moved independently toward the third lens group in such a manner that a spacing between said first lens group and said second lens group increases and a spacing between said third lens group and said fourth lens group decreases; wherein, the relationship between the fourth lens group and the second lens group satisfies the following condition: 2.3 ≤  f 4 f 2  ≤ 3.9 wherein f 2 and f 4 are focal lengths of the second lens group and the fourth lens group, respectively.