| 摘要 |
PROBLEM TO BE SOLVED: To reduce impact force for a lens system by providing a slide adjusting means for decelerating the slide of a direction separating from ground and accelerating the slide of the direction approaching to the ground at the time of switching visual field in relation to a driving means. SOLUTION: A torsion coil spring 50 is attached to the output shaft 20 of a motor as the slide adjusting means. A parallel movement load is made nearly equal to the case ofθ=0 deg., because the gravitational acceleration component of the mass of a lens assembly 2 acting in the direction where a movement is prevented in the case of switching the visual field from the wide visual field to the narrow visual field, namely, the motor shaft conversion torque Tm of mgsinθis negated by the torque Tx of the torsion coil spring 50. The increase of the rotational speed of the motor is eliminated so that it is negated by the gravitational acceleration component of the mass of the lens assembly (parallel movement load) 2 acting in the direction where the movement is accelerated in the case of switching the visual field from the narrow visual field to the wide visual field, namely, the motor shaft conversion torque Tm of mgsinθis cancelled by the torque Tx of the spring 50, so that the parallel movement load is made nearly equal to the case ofθ=0 deg..
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