Carre(カレ)の手法を用いた半導体レーザー位相シフト干渉計測法

抄録

Optical interferometry with laser has been developed for noncontact profiling of surfaces and noncontact diagnostics of precision systems.1) We have proposed phase-shifting interferometers with a frequency-modulated laser diode (LD).2) The phase shifts were easily produced at high speed by changing the wavelength of the LD on an unbalanced interferometer through the variation of injection current.3) The phase measurement without making calibration of the phase shifts has been realized by Carre technique4) in which phase shifts at regular intervals are produced by stepwise current modulation of the LD. A phase error caused by the power change of the LD has been analyzed theoretically and a phase extraction algorithm which is insensitive to changes in laser power associated with current variation has been newly developed.5) A new algorithm for LD phase-shifting interferometer with Carre technique is proposed and a phase without the error caused by the power change can be obtained.