Patent ID: 7289280

Claim:
A zoom lens comprising, in order from an object side to an image side; a first lens unit having positive refractive power, which is stationary during zooming; a second lens unit configured to move to perform zooming; a third lens unit configured to move to compensate for variation of an image plane caused by zooming; and a fourth lens unit having positive refractive power, which is stationary during zooming, wherein the first lens unit includes, in order from the object side to the image side, a first lens subunit having positive refractive power, which is stationary during focusing, a second lens subunit having positive refractive power, and a third lens subunit having negative refractive power, which is stationary during focusing, wherein the second lens subunit moves along an optical axis during focusing, and wherein the first lens unit satisfies the following conditions: −4.5< f 1 c/f 1 ab<− 0.8 and 1< f 1 b/f 1 a< 3.0 where f 1 a designates a focal length of the first lens subunit, f 1 b represents a focal length of the second lens subunit, f 1 c denotes a focal length of the third lens subunit, and f 1 ab designates a combined focal length of the first lens subunit and the second lens subunit when focusing is performed at an infinite object distance.