Patent ID: 8564887

Claim:
A zoom lens comprising: in order from an object side to an image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power, wherein the second and third lens units are configured to move in an optical axis direction for a magnification variation, and the first lens unit is configured to move in the optical axis direction to reduce an image-plane fluctuation associated with the magnification variation, wherein the third lens unit is configured to move to the object side in zooming from a wide-angle end to a telephoto end, and wherein the following conditions are satisfied: −0.83 ≦f 1 /f 2≦−0.40; −4.6 ≦f 1 /fw≦− 2.5; and 0.01≦|β2 w/β 2 t|≦ 0.35, where f 1 is a focal length of the first lens unit, f 2 is a focal length of the second lens unit, fw is a focal length of the entire zoom lens at the wide-angle end, β2w is an imaging magnification of the second lens unit at the wide-angle end, and β2t is an imaging magnification of the second lens unit at the telephoto end.