| 摘要 |
PURPOSE:To improve preciseness of positional change of an optical system by changing the braking force of a cam driving means in accordance with the moving direction of a cam and uniforming the distance of over-run. CONSTITUTION:When a cam plate 27 is moved in a direction D so that a roller 24 rises on the inclined surface of the cam plate 27 and reached to a parallel surface 27d, voltage impression to a motor 25 is interrupted. In this case, only the inertia force of the motor 25 is applied to the cam plate 27 because of the movement of the cam plate 27 in the direction D, and at the stop of the motor 25, the cam plate 27 is quickly stopped under the state that the roller 24 is abutted upon the parallel surface 27d. When the cam plate 27 is moved in a direction C so that the roller 24 descends on the inclined surface of the cam plate 27, the exciting force of a spring is applied to the cam plate 27 on the inclined surface and the moving speed is increased. When the cam plate 27 arrives at a required parallel surface 27h, the cam plate 27 is suddenly braked by discharge due to a drive control means, so that the cam plate 27 is not overrun. Thus, the positional change of the optical system can be precisely attained.
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