Patent ID: 7453649

Claim:
A zoom lens comprising 10 or less lens elements and having a zoom ratio of more than 20×, said zoom lens having first, second, third, and fourth groups of lens elements placed in turn from object side to image side; wherein the first group of lens elements has positive refractive power and is fixed in position during zooming; wherein the second group of lens elements has negative refractive power and is moved in position during zooming; wherein the third group of lens elements has positive refractive power, includes at least one aspheric surface, and is fixed in position during zooming; wherein the fourth group of lens elements has positive refractive power, includes at least one aspheric surface, corrects variations in image surface position during zooming, and performs focusing; and wherein the zoom lens satisfies the following conditional expression (1): 7.8 < dz fw < 8.8 ( 1 ) where dz is the movable distance of the second group of lens elements to perform zooming and fw is the focal distance of the whole lens system at a wide angle end; wherein the third group of lens elements is made of a single lens element having an aspheric convex surface on an object side and an aspheric convex surface on an image side; wherein the fourth group of lens elements is made up of a negative lens element and a positive lens element placed in turn from object side to image side; and wherein the positive lens element located on the image side has an aspheric surface on the image side.