Patent ID: 8087835
Filing Date: 2012-01-03
Classification: G02B,G03B

Abstract:
1. A lens barrel comprising: at least three lens groups; a fixed cylinder; a first moving cylinder to which a first lens group frame that holds a first lens group arranged closest to an object side among the three lens groups is fixed and which has a cam groove formed in an inner surface thereof and is movable in a straight line in an optical axis direction; second and third lens group frames that respectively hold second and third lens groups among the three lens groups, are movable in a straight line in the optical axis direction, have diameters smaller than that of the first moving cylinder, and include cam pins formed on the outer surfaces thereof; a cam cylinder that is movable in the optical axis direction while being rotated about the optical axis with respect to the fixed cylinder, is provided between the inner surface of the first moving cylinder and the outer surfaces of the second and third lens group frames, and includes a cam pin which is provided on the outer surface and is fitted to the cam groove provided in the inner surface of the first moving cylinder and a cam groove which is provided in the inner surface and to which the cam pins provided on the outer surfaces of both the second lens group frame and the third lens group frame are fitted; a second moving cylinder; a key ring; wherein the fixed cylinder has a cam groove and a straight-ahead key groove provided in an inner surface thereof, the second moving cylinder includes a straight-ahead key groove that is provided in an inner surface thereof and a cam pin that is provided on an outer surface thereof and is fitted to the cam groove provided in the inner surface of the fixed cylinder, the second moving cylinder is moved in the optical axis direction while being rotated when the cam pin is moved along the cam groove by a driving force, the key ring includes a cam groove that passes through the key ring from an inner surface to an outer surface and a straight-ahead key groove that is provided in the inner surface thereof, the key ring is fitted to the straight-ahead key groove that is provided in the inner surface of the fixed cylinder and is moved integrally with the second moving cylinder in the optical axis direction, without being rotated, when the second moving cylinder is rotated, the cam cylinder further includes a cam pin that is provided on the outer surface so as to protrude toward the outside, is fitted to the cam groove passing through the key ring from the inner surface to the outer surface, protrudes from the cam groove to the outside, and has a leading end portion which protrudes toward the outside and is fitted to the straight-ahead key groove provided in the inner surface of the second moving cylinder, and the cam cylinder is moved along the cam groove of the key ring in the optical axis direction while being rotated integrally with the second moving cylinder when the second moving cylinder is rotated; and a third moving cylinder that is fitted to the straight-ahead key groove provided in the inner surface of the key ring and is moved integrally with the cam cylinder in the optical axis direction, without being rotated, when the cam cylinder is rotated, wherein the third lens group frame is fitted to the straight-ahead key groove provided in the inner surface of the key ring and is moved in the optical axis direction, without being rotated, when the cam cylinder is rotated, the second lens group frame has a straight-ahead key groove provided in the inner surface thereof, the third lens group frame is fitted to the straight-ahead key groove of the second lens group frame, the second lens group frame is moved in the optical axis direction, without being rotated, when the cam cylinder is rotated, and the first moving cylinder is fitted to the straight-ahead key groove provided in the inner surface of the third moving cylinder and is moved in the optical axis direction, without being rotated, when the cam cylinder is rotated.