To measure displacement and speed of an object at high resolution to reduce the time required for measurement.

The physical quantity sensor includes a semiconductor laser 1 radiating laser beam to an object 10, a laser driver 4 driving the semiconductor laser 1, a photodiode 2 detecting electrical signal including interference waveform produced from self-adopted effect of laser beam radiated from the semiconductor laser 1 and return light from the object 10, a current-voltage conversion amplification section 5, a signal extraction section 7 measuring the period of interference waveform contained in the output signal from the current-voltage conversion amplification section 5, and an operation section 8 where, by comparing the period of interference waveform measured at the signal extraction section 7 with a moving average value of the period of interference waveform measured at least at only one of its immediately before and after to correct the period of the interference waveform and compute at least only one of displacement and speed of the object 10 based on each corrected period.

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