| 摘要 |
PURPOSE:To obtain a natural photographic picture plane nearby a zoom terminal by reducing gradually the rotating speed of a rotation driving means nearly the terminal of the turning range of a lens barrel for operation by an increase of a rotation torque increasing means, and decreasing gradually the zoom speed of a variable power lens system. CONSTITUTION:A motor driving circuit is provided with switches 20a and 20b, and consequently the polarities of a power source 21 for a motor 16 are changed. Those switches 20a and 20b operates associatively with each other to cut off a voltage applied to the motor at a neutral position shown by a broken line. When the switches 20a and 20b are placed to the solid-line position firstly, the motor 16 starts rotating and a zoom operation lens barrel 14 also turns, so that an end surface cam 18 also turns together with the zoom operation lens barrel 14 in one body. A leaf spring 19 shifts in contacting position as the end surface cam 18 turns and when the leaf spring 19 starts contacting a slanting surface 18a, contacting pressure increases gradually to increase the turning torque of the zoom operation lens barrel 14, and the rotating speed of the motor 16 is reduced gradually to reduce the zoom speed gradually. |
