US Patent 7457045 Zoom lens

A zoom lens includes, in order from an object side to an image side, a first lens unit of negative refractive power, a second lens unit of positive refractive power, and a third lens unit of positive refractive power. The first lens unit moves in a locus convex toward the image side and the second lens unit moves toward the object side during zooming from a wide-angle end to a telephoto end. The object side principal point position of the first lens unit is within the first lens unit. The movement locus of the image side principal point position of the first lens unit during zooming from the wide-angle end to the telephoto end intersects with the movement locus of the object side principal point position of the second lens unit during zooming from the wide-angle end to the telephoto end.