| 摘要 |
The invention provides an ultrasonic motor including internal electrodes provided in an ultrasonic vibrator and disposed in regions where electrical charges of the same sign are generated in one vibration mode and where electrical charges of opposite sign and substantially the same amount are generated in another vibration mode; and a control unit configured to detect a phase difference between a vibration detection signal detected on the basis of electrical signals from the internal electrodes and any one of driving AC voltages, and to set a driving frequency such that the phase difference becomes a reference phase difference. Each driving AC voltage with the driving frequency set by the control unit is applied to the ultrasonic vibrator.
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