Driver for optical deflector using two modified synchronous saw-tooth drive voltages and method for setting the same

In an optical deflector comprising a mirror (1), a movable frame (2) for supporting the mirror, a support body (5) surrounding the movable frame, and a first group of piezoelectric actuators (6a-1, 6a-3, 6b-1, 6b-3) serving as cantilevers and a second group of piezoelectric actuators (6a-2, 6a-4, 6b-2, 6b-4) serving as cantilevers alternating with the first group of piezoelectric actuators, the piezoelectric actuators (6a-1, 6a-2, 6a-3, 6a-4, 6b-1, 6b-2, 6b-3, 6b-4) are folded at every actuator and connected from the support body to the movable frame. Each of the piezoelectric actuators is in parallel with one axis of the mirror. A driver combines first and second original saw-tooth waves having the same waveform into first saw-tooth waves. The driver generates a first drive voltage (V Y1 ) having the first saw-tooth waves and applies the first drive voltage to the first group of piezoelectric actuators. The driver generates a second drive voltage (V Y2 ) having second saw-tooth waves opposite in phase with the first saw-tooth waves, and applies the second drive voltage to the second group of piezoelectric actuators. A difference in phase (” Æ ) between the first and second original saw-tooth waves is a predetermined value to suppress a natural frequency (f c ) of a mechanically-vibrating system of the mirror with respect to the axis thereof depending upon the piezoelectric actuators.