Optical deflector including narrow piezoelectric sensor element between torsion bar and piezoelectric actuator

In an optical deflector including a mirror (1), a support frame (2) surrounding the mirror (1), at least one torsion bar (3-2, 3'-2) arranged along an axis (X) of the mirror (1) having an end coupled to an outer circumference of the mirror (1), a pair of piezoelectric actuators (4-2a, 4-2b; 4-a, 4-b) arranged between the support frame (2) and the torsion bar (3-2, 3'-2), and a piezoelectric sensor (5, 5') inserted between the torsion bar (3-2, 3'-2) and one of the piezoelectric actuators (4-2a, 4-a), the piezoelectric sensor (5, 5') includes at least one piezoelectric sensor element (5-1, 5-2; 5'-1, 5'-2) having a width being smaller than two-fifths of a width (W) of the one of the piezoelectric actuators (4-2a, 4-a) and being arranged at a wide portion within two-fifths of the width (W) from an inner end of the one of the piezoelectric actuators (4-2a, 4-a).