| 摘要 |
PURPOSE:To provide the driving mechanism of the AF single-lens reflex camera of a back focus control system capable of precisely bringing a rear part moving part to a focal position at a high speed. CONSTITUTION:An out-of-focus quantity is calculated by the signal of an AF sensor 3c. The rotational output of an FB rough driving motor 7a of a rough driving section based on the out-of-focus quantity is reduced in speed and transmitted to a lead screw 7d via gears 7e and 7f. On the other hand, the rotational output of an FB precision driving motor 7b of a precision driving section is transmitted via a gear to a precision driving gear 7c. Driving of the motors 7a and 7b is simultaneous and the coarse driving section is driven by a large step. The precision driving motor is driven by a small step. As a result, the rear part moving section moves at a high speed and good accuracy to the focal position. |
