Patent ID: 6657793
Filing Date: 2003-12-02
Classification: G02B

Abstract:
A lens barrel having a zoom lens system, said zoom lens system including a plurality of variable power lens groups which are movable in an optical axis direction for varying the focal length of the zoom lens system; whereinat least one of said variable power lens groups includes a switching lens group having two sub-lens groups, one of said sub-lens groups constituting a movable sub-lens group that is selectively positioned at one of two movement extremities, in the optical axis direction, with respect to the other of said sub-lens groups; said movable sub-lens group of said switching lens group is positioned at one of the movement extremities in a short-focal-length side zooming range from a short focal length extremity to an intermediate focal length, and at the other of the movement extremities in a long-focal-length side zooming range from the intermediate focal length to a long-focal-length extremity; zoom paths of said two sub-lens groups of said switching lens group and the other of said variable power lens groups are discontinuous at the intermediate focal length and are defined so that the zoom lens system forms an image on a predetermined image plane in accordance with a position of said movable sub-lens group; and said switching lens group is a focusing lens group which integrally advances and retreats in the optical axis direction regardless of the zooming range, said lens barrel comprising: a first sub-lens group frame for supporting one of said sub-lens groups; a second sub-lens group frame for supporting the other of said sub-lens groups; a switching lens group frame for supporting said first sub-lens group frame and said second sub-lens group frame in this order from object side in such a manner that allows said first and second sub-lens group frames to move in the optical axis direction; a lens shutter mechanism secured to said switching lens group frame on the image side of said second sub-lens group frame; and a focusing mechanism for making said second sub-lens group frame advance or retreat, depending on the object distance, with respect to a reference position provided by said lens shutter mechanism secured to said switching lens group frame; wherein said first sub-lens group frame is moved along with said second sub-lens group frame in the optical axis direction in the long-focal-length zooming range and in the short-focal-length zooming range via said focusing mechanism.