Patent ID: 7940473
Filing Date: 2011-05-10
Classification: G02B

Abstract:
1. A zoom lens comprising, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power and configured to move during zooming; a third lens unit having a positive refractive power and including a positive lens element at a position nearest to an object-side end; and a fourth lens unit having a positive refractive power and configured to move during zooming, wherein the second lens unit includes at least three negative lens elements arranged successively and independently along an optical axis and at least one positive lens element, and wherein the zoom lens satisfies the following conditional expressions: where fw denotes a focal length of the zoom lens at a wide-angle end, f 2 and f 3 denote focal lengths of the second and third lens units, respectively, and f 31 denotes a focal length of a positive lens element of the third lens unit nearest to the object-side end.