| 摘要 |
PURPOSE:To provide a control system for a back focus driving type autofocusing single lens reflex camera using an ultrasonic motor which rotates at low speed with high torque and has large holding torque when it is still as a driving mechanism, having an easy control system and capable of accurately bringing a camera main body movable block which is heavy in weight to a focusing point at high speed. CONSTITUTION:A rotary direct acting conversion mechanism in which the ultrasonic motor 32 is set as a driving source and which is constituted of receiving parts 29 and 30, a guiding bar 28 and a wire 31 is driven by the start of AF so as to positionally move a flange back on the camera main body movable block side. In the case moving amount to the focusing point is larger than the width(resolution) of the slit 18 of an encoder slit moving plate 17, a control circuit counts an encoder signal from a photocoupler 15 and drives the flange back to an encoder generating point being at a distance that the distance to the focusing point is smaller than the width of the slit 18. Furthermore, the flange back is brought to the focusing point by generating the pulses of calculated number by arithmetic calculation so that it is finely moved. |
