PURPOSE: To secure a high-accuracy detection for the displacement amount with a simple constitution by using the phase between the pseudo wave and the phase modulation signal.
CONSTITUTION: Reference pulse RP of a fixed frequency is counted 22 and 27 to deliver the reference wave, and at the same time pulse RP is counted 23 and 31 via control gate G1 to deliver the pseudo wave. Then phase comparison 25 is given every fixed cycle to the phase relation between the pseudo wave and the phase modulation signal delivered from displacement phase converter 20. And in case the phase modulation signal features the gained phase, the pahse gain signal is delivered; while in the case of the lost gain, the loss phase signal is delivered respectively. While the loss phase signal is delivered, gate G1 is closed to stop counting of counter circuits 23 and 31. And while the phase gain signal is delivered, the output counted 24 pulse RP is added to circuits 23 and 31 by the next comparison. In this way, the displacement amount of mobile object 12 is detected directly via the phase difference caused through the phase comparison to send out the pulse.
OWA KAORU
OOMURA HARUO
