Lightwave interference measurement apparatus that calculates absolute distance using lightwave interference

摘要

A lightwave interference measurement apparatus includes a wavelength-variable laser which periodically performs wavelength scanning between first and second reference wavelengths to emit light beam, a wavelength-fixed laser which emits light beam having a third reference wavelength, a light beam splitting element which splits the light beams into reference light beam and light beam under test, a phase detector which detects a phase based on an interference signal of the reference light beam and the light beam under test, and an analyzer which sequentially determines an interference order of the third reference wavelength based on the third reference wavelength, first and second synthetic wavelengths, an integer component of a phase change amount in the wavelength scanning, and interference orders of the first and second synthetic wavelengths, and calculates an absolute distance between the surface under test and the reference surface.