Angle detecting apparatus for detecting angle of inclination of scanning mirror provided on Michelson interferometer

摘要

A laser beam from a laser beam oscillator (21) is guided to an incidence light path of a beam splitter (11) of a Michelson interferometer by means of a first guide mirror (20), reflected by a fixed mirror (12) and a scanning mirror (13) of the Michelson interferometer, and returned to the beam splitter (11), thus obtaining an interference light beam. The interference laser beam is guided to first and second laser beam detectors (231, 232) by means of a second guide mirror (22) to detect variations in intensity of the interference laser beam. On the basis of the variations in intensity of the interference laser beam, an angle of inclination (θ) of the scanning mirror (13) is measured.