ZOOM LENS

摘要

PURPOSE:To hold an in-zooming focusing state corresponding to optional object image distance by providing a focusing system driving means which controls the position of a focusing system with the output of a zoom position detecting means and the output of a focusing system position detection means. CONSTITUTION:When a zoom lens which is not in autofocus mode or rear focusing zoom lens which is not provided with an autofocus function is mounted, a lens group used to zoom the zoom lens 2 focused on an objected 1 is detected by a zoom lens position detecting means 3 and the position of an image pickup plate 4 is detected by an image pickup plate position detecting means 5. The position of the lens group used for the zooming or part of the lens group corresponds to the focal length of the zoom lens and the position of the image pickup plate 3 corresponds to the quantity of movement of the focusing system. The movement curve of the image pickup plate by the zooming at the object image distance of the object 1 is calculated by an arithmetic means 6 from the two positions and the lens group is moved by an image pickup plate driving means 7 to perform zooming where in the focusing state is held.