| 摘要 |
PURPOSE:To focus automatically a telephoto lens by providing a manual operation ring which can set optionally the extent of movement of a focusing lens and setting optionally the defocusing quantity of a photographic lens and moving optionally its range from the closest focusing distance side to the far distance side. CONSTITUTION:On a focusing cam cylinder 5, a stop pin 5a is provided in a notched window provided on a manual operation ring 2. One end of a knob 6 is screwed to a stop piece 7; and when the knob 6 is loosened and is moved in a long hole, the piece 7 is moved together, and one end of the piece 7 is projected from the notched window of the ring 2, and the piece 7 is fixed to the ring 2 in a proper position to determine the width of the notched window. When the ring 2 is placed in a determined reference position by a click and the knob 6 is loosened to remove the piece 7 from the window, the pin 5a can be moved in a range (A) from the closest focusing distance of the lens to the infinity. When a range (B) is set by adjusting the knob 6, an apparent defocusing quantity is reduced; and when the ring 2 is placed in a position of this range to perform auto- focus photographing, an object placed at a distance of <=20m is focused quickly. |
