| 摘要 |
PURPOSE:To prevent the degradation in performance for macro-photographing of a lens by providing the first moving means and the second moving means and compensating aberrations of the lens simultaneously with focusing in a macro-area. CONSTITUTION:When an operation ring 1 for macro is rotated, a straight going barrel 5 is not rotated but is moved straight along the optical axis in accordance with double helicoid screws 2 and 3. A linear cam groove 25 is provided in a cylinder part of the second moving cylinder 15, and the third sliding pin 26 provided on the third moving cylinder 18 is engaged with this groove 25. A key groove 27 is provided on the outside peripheral surface of the moving cylinder 18, and a projecting key 28 provided on the operation ring 1 is engaged with this groove, and the moving cylinder 18 is displaced along the linear cam groove in the direction of the optical axis while rotating through the key 28 when the operation ring 1 is rotated. When an operation ring 11 is rotated from the wide angle position to the telephoto position, the second positive lens group L2 and a lens group L4 between which the third immobile negative lens group L3 are moved left to change the resultant focal length from a short value to a long value in cooperation with the first negative lens group L1. The lens group L1 compensate the movement of the image surface. |
