ROTARY ENCODER

PROBLEM TO BE SOLVED: To measure a displacement in an axis direction with a simple configuration in a rotary encoder.SOLUTION: An A-phase subtractor 252 outputs a signal obtained by subtracting an output of a magnetic field detection element 251 of A2 from an output of a magnetic field detection element 251 of A1 as an A-phase detection signal VA, and a B-phase subtractor 252 outputs a signal obtained by subtracting an output of a magnetic field detection element 251 of B2 from an output of a magnetic field detection element 251 of B1 as a B-phase detection signal VB. A permanent magnet 3 fixedly provided at an edge of a shaft 1 is magnetized in one direction selected from directions perpendicular to an axis of the shaft 1. A rotation angle/speed calculation part 261 acquires a rotation angle of the shaft 1 by means of an arctan(VA/VB). A displacement calculation part 262 detects a displacement in an axial direction from a neutral position of the shaft 1 on the basis of a magnitude in an amplitude of the A-phase detection signal VA or the B-phase detection signal VB.