Patent ID: 6671638
Filing Date: 2003-12-30
Classification: G01H,G01N,G01R

Abstract:
A frequency measuring apparatus comprising:a laser resonator that oscillates a laser beam to an object to be measured, and that self-mixes the laser beam reflected by the object, and returned as a return beam, with another laser beam emitted upon reception of the return beam; a laser drive that drives the laser resonator with a laser drive current having a sinusoidal wave; a laser that emits the laser beam, oscillated with a wavelength according to the laser drive current, in the laser resonator and that outputs a beat wave obtained from self-mixing the return beam with the emitted beam upon reception of the return beam; and a signal processor that processes the beat wave output from the laser and that outputs a processing result as an oscillation information, wherein the signal processor includes a frequency difference calculation function for calculating an oscillation frequency of the object according to a frequency change of the beat wave.