Patent ID: 8611016

Claim:
A zoom lens system comprising a plurality of lens units, each lens unit comprising at least one lens element, wherein the plurality of lens units include a plurality of movable lens units which individually move along an optical axis at the time of zooming from a wide-angle limit to a telephoto limit during image taking, at least two of the movable lens units are focusing lens units which move along the optical axis at the time of focusing from an infinity in-focus condition to a close-object in-focus condition in at least one zooming position from a wide-angle limit to a telephoto limit, and among the focusing lens units, a lens unit having the absolute value, which is not the greatest absolute value, of a wobbling value at a wide-angle limit represented by the following expression (a) is a wobbling lens unit which senses a moving direction of the focusing lens units at the time of focusing by wobbling itself in a direction along the optical axis: W= 1 /e+β WO /( Sb×f WO )−1/((β R ×f R ) (a) where W is a wobbling value at a wide-angle limit (wobbling incremental magnification sensitivity), Sb is a focus sensitivity of the wobbling lens unit represented by the following expression Sb =(1−β WO 2 )×β R 2 , e is an exit pupil position of the entire system at a wide-angle limit, β WO is a paraxial lateral magnification of the wobbling lens unit at a wide-angle limit in an infinity in-focus condition, f WO is a focal length of the wobbling lens unit at a wide-angle limit in an infinity in-focus condition, β R is a paraxial lateral magnification of a system on the image side relative to the wobbling lens unit at a wide-angle limit in an infinity in-focus condition, and f R is a focal length of a system on the image side relative to the wobbling lens unit at a wide-angle limit in an infinity in-focus condition.