Patent ID: 7087889

Claim:
A rotational angle detecting apparatus for detecting a rotational angle of a rotor, comprising: one or a plurality of first targets provided at the rotor; second targets provided at said rotor or another rotor rotating coaxially with said rotor, the number of which is coprime with the number of the first targets; a plurality of sensors, disposed opposite to the first targets, for outputting detection signals having phases different from each other in accordance with each position of the first targets as the rotor provided with the first targets rotates; a plurality of sensors, disposed opposite to the second targets, for outputting detection signals having phases different from each other in accordance with each position of the second targets as the rotor provided with the second targets rotates; and a calculation processing circuit capable of performing operations of: executing a predetermined calculation on the basis of the detection signals respectively outputted from the plurality of sensors; storing a relation between a result of calculation executed in advance and an electrical angle of the detection signal corresponding to each of the positions of the first and second targets; and obtaining an electrical angle of each of the detection signals on the basis of a result of executed calculation by referring to the stored relation between the result of calculation and the electrical angle, wherein a rotational angle of the rotor is detected on the basis of the electrical angle obtained by the calculation processing circuit.