Patent ID: 7630141

Claim:
A zoom lens comprising, in order from an object side to an image side: a first lens unit having a positive refractive power and configured to move along an optical axis during zooming; a second lens unit having a negative refractive power and configured to move with a locus convex towards the image side during zooming; a third lens unit having a positive refractive power; and a fourth lens unit having a negative refractive power, wherein the first lens unit is located closer to the object side at a telephoto end than at a wide-angle end, wherein the second lens unit is located closer to the image side at the telephoto end than at the wide-angle end, and wherein a focal length of the second lens unit (f 2 ), a focal length of the zoom lens at the wide-angle end (fw), and a focal length of the zoom lens at the telephoto end (ft) satisfy the following condition: −0.7< f 2/√{square root over (( fw·ft ))}<−0.2.