Patent ID: 8253845

Claim:
A zoom lens comprising: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power, which are sequentially arranged from the object side of the zoom lens, wherein the magnification of the zoom lens is changed from wide end to tele end by moving each of at least one of the lens groups in such a manner that a distance between the first lens group and the second lens group increases and that a distance between the second lens group and the third lens group decreases, and wherein the first lens group is composed of a negative lens and a positive lens, and wherein when the magnification of the zoom lens is changed from wide end to tele end, the first lens group moves toward the object side, the second lens group moves along a path convex toward the image side of the zoom lens, the third lens group monotonously moves only toward the object side, and the fourth lens group moves along a path convex toward the object side, and wherein the following formulas are satisfied: 0.3< X 1/ ft< 0.5 (1); and 5.0< f 1/ fw< 7.0 (2), where X 1 : the amount of movement of the first lens group when the magnification is changed from wide end to tele end, ft: the focal length of the entire system of the zoom lens at tele end, f 1 : a combined focal length of the first lens group, and fw: the focal length of the entire system of the zoom lens at wide end.