| 摘要 |
PURPOSE:To enhance the reliability of a focus mechanism by changing periodi cally a sampling area at the time of the stop of a focus motor, storing an arithmetic output concerning the area and restarting the motor by the comparing result of the memory information concerning the same area. CONSTITUTION:When the focus motor 31 is at the focusing point position, an area control constant changing circuit 19 is shifted from a constant fixing condition to a constant changing condition at the time of driving of the motor. In such a condition, by the output of four state counters 33, the constant to control area control circuits 17 and 18 is changed over to the constant set beforehand, and areas I-IV are set as shown in the figure. Thus, by the output of the counter 33, the area is divided into I-IV, at a arithmetic circuit 15, the level is successively accumulated before every one field for the area, and transferred to a memory 21. the contents are successively transferred up to a memory 28 after one field. When the level changing quantity before four fields at every area exceeds the threshold, a high output is outputted to a discriminating circuit 28 by comparing circuits 34-37. At the circuit 28, when the quantity exceeds at two areas or above, a motor 31 is redriven through an FF 32. |
