Patent ID: 8106649

Claim:
An angle detecting apparatus comprising: a rotor fixed to a rotating shaft, the rotor being such that a distance between two points where a straight line passing through a center of rotation of the rotor crosses an outer periphery of the rotor is constant; a first magnetic sensor and a second magnetic sensor arranged opposite each other and close to the outer periphery of the rotor, the first magnetic sensor detecting a change in a magnetic field corresponding to a change in a first distance between the outer periphery of the rotor and the first magnetic sensor which distance varies periodically in conjunction with rotation of the rotor, thereby outputting a first detection signal, the second magnetic sensor detecting a change in a magnetic field corresponding to a change in a second distance between the outer periphery of the rotor and the second magnetic sensor which distance varies complementarily in conjunction with the variation in the first distance, thereby outputting a second detection signal; differential operation means for performing differential operation on the first detection signal and the second detection signal; and angle calculating means for calculating an angle of rotation of the rotating shaft based on a result of the differential operation by the differential operation means.