Patent ID: 8416387
Filing Date: 2013-04-09
Classification: G01J,G03F

Abstract:
1. A wavelength shift measuring apparatus which measures a shift of a wavelength of a light beam emitted from a light source relative to an initial wavelength of the light beam, the wavelength shift measuring apparatus comprising: an optical system configured to split the light beam emitted from the light source into two light beams and to cause the two light beams to interfere with each other to generate a plurality of interference light beams having phases different from each other, wherein the optical system includes diffraction gratings and a spacer separating the diffraction gratings by a spacing to provide a predetermined difference between an optical path length of one of the two light beams and an optical path of the other of the two light beams; a plurality of photoelectric sensors configured to respectively detect the plurality of interference light beams generated by the optical system; and a processor configured to output a shift of the wavelength based on outputs from the plurality of photoelectric sensors.