Patent ID: 8019037

Claim:
A phase difference detection device detecting a phase difference between a reference signal and a detection signal in accordance with a rotation position of a measured object comprising: a reference counter performing a count in synchronization with a predetermined first clock pulse and reset when a phase of the reference signal becomes a predetermined reference phase; a velocity detection unit acquiring velocity information capable of specifying a rotation velocity of the measured object; a pulse conversion unit outputting a second clock pulse by using a time specified based on the velocity information and required for rotation of the measured object by an angle corresponding to 1 count of the reference counter as a pulse interval; and a phase count unit configured to be able to latch the count value counted by the reference counter every time a phase of the detection signal becomes the reference phase, count a number of pulses of the second clock pulse after the phase of the detection signal becomes the reference phase, and output at least one of a sum or difference of the latched count value and the counted number of pulses.