US Patent 7289283 Lens barrel and image pickup apparatus

A lens barrel includes a lens moving frame configured to hold an image pickup lens; a barrel member configured to support the lens moving frame for back and forth linear movement along the direction of an optical axis of the image pickup lens; the lens moving frame having a magnetized face magnetized alternately with N poles and S poles along the direction of the back and forth linear movement; and, a magnetic resistance sensor apparatus. The magnetic resistance sensor apparatus has a magnetic resistance sensor, a body, a single screw, and a plurality of resilient pieces. The resilient pieces are formed such that, in a state wherein the resilient pieces are resiliently deformed all by the same amount, the sum of moments by the resilient pieces which act upon the location of the body at which the screw is fitted is zero.