| 摘要 |
PURPOSE:To prevent malfunction in a photographing optical system from occurring, by controlling a period where no focus adjustment of the photographing optical system is performed corresponding to the degree of the change of an object due to panning, etc. CONSTITUTION:When the counted value of a counter 38 is larger than a threshold value TH1 (in other words, the change quantity of the object is larger), both monostable multivibrators(MM) 44 and 46 generate pulses simultaneously, but, since the pulse width of the MM44 is larger, the pulse generated from the MM44 is supplied to a motor driving circuit 20 as a prohibiting signal via an OR gate 48. When the counted value of the counter 38 is smaller than the threshold value TH1 but is larger than a threshold value TH2, the pulse is generated only from the MM46 by the output of a comparator 42, and the short pulse of the MM46 is impressed on the motor driving circuit 20 as the prohibiting signal via the OR gate 48. Also, when the counted value of the counter 38 is smaller than the threshold value TH2(that is, the change of the object is very small), no pulses are generated from the MMs 44 and 46, thereby, no prohibiting signal is generated. In such a way, it is possible to prevent the malfunction in the photographing optical system from occurring. |
