Zoom lens with hindering device

摘要

A zoom lens is comprised of a fixed barrel, an intermediate barrel coupled to the fixed barrel through helicoid screws, a movable barrel coupled to the intermediate barrel through helicoid screws, a front lens group fixedly held in the movable barrel, and a rear lens group. The position of the front lens group in the optical axis direction is always determined by the axial movement of the intermediate barrel relative to the fixed barrel and the axial movement of the movable barrel relative to the intermediate barrel. The axial position of the rear lens group is determined by the axial movement of the intermediate barrel relative to the fixed barrel and a cam surface formed in an inner periphery of the intermediate barrel. As the axial position of the cam surface within the intermediate barrel changes with the rotational position of the intermediate barrel, the rear lens group moves in the axial direction relative to the intermediate barrel during zooming. But during focusing, a hindering device is activated to hinder the rear lens group from axial movement relative to the intermediate barrel, so that the rear lens group moves by the same amount in the axial direction as the intermediate barrel independently of the cam surface.