Patent ID: 7164538

Claim:
A zoom lens system comprising, successively from the object side, a first lens group and a second lens group; wherein: the first lens group has negative refractive power and includes a negative meniscus lens with a convex surface facing the object side, and a positive meniscus lens with a convex surface facing the object side, the negative meniscus lens and the positive meniscus lens each has at least one aspherical surface; the second lens group has positive refractive power and includes a first auxiliary group having positive refractive power and a second auxiliary group having positive refractive power, the first auxiliary group includes a bi-convex lens and a bi-concave lens, the second auxiliary group includes a positive meniscus lens with a convex surface facing the object side; and the refractive power of the first group is 1/f 1 , the refractive power of the second group is 1/f 2 , the focal length of the whole lens system f w when the distance between the two lens groups is increased, f T is the focal length of the whole lens system when the distance between the two lens groups is decreased, and they satisfy the following conditional expressions: 0.9 ≦|f 1 |/( f w ·f T ) 1/2 ≦1.1 1.15 ≦|f 1 |/f 2 ≦1.35.