US Patent 7411740 Zoom lens

Disclosed is a zoom lens, which includes, in sequence from an object side to an image side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, a fifth lens group, a negative sixth lens group and a positive lens group. The first, third, fifth and seventh lens groups are fixed. When the zoom lens is made to zoom from a wide-angle end to a telephoto end, the second and fourth lens groups move toward the third lens group, while the sixth lens group moves toward the seventh lens group. The absolute value of the ratio of the focal distance of the second lens group to that of the sixth lens group is within a range between 0.1 and 0.5.