Patent ID: 8537341

Claim:
A physical quantity sensor comprising: a semiconductor laser which emits laser light to a measurement target; an oscillation wavelength modulating device configured to operate the semiconductor laser such that at least one of a first oscillation period and a second oscillation period repeatedly exists, wherein an oscillation wavelength continuously and monotonically increases during the first oscillation period, and the oscillation wavelength continuously and monotonically decreases during the second oscillation period; a detector configured to detect an electrical signal including interference waveforms, the interference waveforms being caused by a self-coupling effect of the laser light emitted from the semiconductor laser and return light from the measurement target; a signal extracting device configured to measure each cycle of the interference waveforms whenever the interference waveform is input; a cycle correcting device configured to compare each cycle of the interference waveforms received from the signal extracting device with a reference cycle so as to correct the cycles of the interference waveforms; and a calculating device configured to calculate at least one of displacement and velocity of the measurement target based on each of the cycles of the interference waveforms corrected by the cycle correcting device.