Patent ID: 7960895

Claim:
A drive unit which includes: a vibratory actuator having a piezoelectric element, a driver element provided on the piezoelectric element, a movable body supported by the driver element; and a control unit for supplying first and second voltages at the same frequency to the piezoelectric element, and in which the first voltage and the second voltage having a different phase from a phase of the first voltage by 90° are supplied to the piezoelectric element by the control unit to lead the piezoelectric element to composite vibration of stretching vibration and bending vibration, thereby causing the driver element to make an elliptical motion by the vibration and move the movable body, wherein during a normal mode, a desired movement speed of the movable body is a predetermined speed or more, and during a fine motion mode, the desired movement speed of the movable body is lower than the predetermined speed and the control unit periodically switches the first and second voltages during the fine motion mode between a first state where the first voltage and the second voltage whose phases differ by 90° are supplied and a second state where the first voltage and the second voltage whose phases differ by a predetermined angle θ, where 0°≦θ<90° or 90°<θ≦180°, are supplied.