System of focusing zoom lens

摘要

A zoom lens includes a front lens group, a zooming lens group and relay lens group arranged in this order from the object side. The zoom lens is focused by moving at least a part of the front lens group and a part of the relay lens group in the direction of the optical axis. The front lens group is moved so that the focusing movement of the front lens group for a given object point is smaller as compared with that by which the front lens group should be moved when the zoom lens is focused by moving solely the front lens group and the focusing error generated by such a movement of the front lens group is larger in the wide-side than the tele-side, and a part of the relay lens group is moved to correct the focusing error.