Position detection device and imaging device

A position detection device comprising:

• a motor configured to rotate a drive target;
• a periodic sensor configured to detect a plurality of periods included in a periodic change generated by rotation of the motor;
• an origin sensor configured to detect an origin of the motor in a rotation direction;
• and
• a controller configured to control the rotation of the motor based on:
• (i) a waveform signal output from the periodic sensor to the controller, the waveform signal having the plurality of periods;
• and (ii) an origin detection signal output from the origin sensor to the controller, the origin detection signal indicating that the origin of the motor is detected,
• wherein:
• a repeated detection error in detecting the origin of the motor by the origin sensor is smaller than a rotation range of the motor corresponding to each period of the plurality of periods detected by the periodic sensor;
• and
• the controller is further configured to:
• calculate, when the origin of the motor is initially set, a first count value that is an integrated value of the plurality of periods when the origin detection signal is acquired and a first intra-period rotation amount that is an intra-period rotation amount of the motor in a period corresponding to the first count value, based on the waveform signal output from the periodic sensor;
• calculate, when the origin of the motor is reset, a second count value that is an integrated value of the plurality of periods when the origin detection signal is acquired and a second intra-period rotation amount that is an intra-period rotation amount of the motor in a period corresponding to the second count value, based on the waveform signal output from the periodic sensor;
• and
• set the origin of the motor using the first intra-period rotation amount, the second intra-period rotation amount, the first count value, and the second count value.