Patent ID: 7595836

Claim:
A drive controller comprising: an electromechanical transducer that extends and contracts along a direction; a drive member fixed to one end of the electromechanical transducer in the direction; and a driving pulse control unit that controls a supply of a driving pulse to the electromechanical transducer, the driving pulse control unit causing the drive member to extend and contract along the direction by controlling the supply of driving pulse in such a way as to make an extension speed and a contraction speed along the direction of the electromechanical transducer differ to cause the electromechanical transducer to extend and contract, so as to move a driven member along the direction, the driven member being made to be in frictional engagement with the drive member and including a lens, wherein the driving pulse control unit comprises: a AF evaluation value-measuring section that, while the driven member is moved by a number of driving pulses in a driving direction of the driven member during a focusing operation of the lens, measures an AF evaluation value obtained from an image photographed via the lens for each movement of the driven member; a return pulse number-calculating section that calculates a maximum value-presuming position, which is presumed to be a position where a maximum value of the AF evaluation value is obtained, based on a measured maximum value obtained by the AF evaluation value-measuring section and that calculates a return pulse number to return the driven member to the maximum value-presuming position; a reverse movement-control section that controls the supply of driving pulses in such a way as to return the driven member in a reverse direction based on the return pulse number; a threshold calculating section that calculates an evaluation value threshold specifying whether to move the driven member to a preset fixed focus position, based on the measured maximum value; a measurement and determination section that remeasures an AF evaluation value at a position where the driven member stops after the driven member is returned by the reverse movement-control section and that determines whether the AF evaluation value remeasured is equal to or larger than the evaluation value threshold; and an AF evaluation value-remeasuring section that, while the driven member is moved in the reverse direction by a number of driving pulses, remeasures an AF evaluation value for each movement of the driven memeber until the measurement and determination section determines the AF evaluation value remeasured to be equal to or larger than the evaluation value threshold.