WAVELENGTH-MULTIPLEXED PHASE-LOCKED LASER-DIODE INTERFEROMETER USING A PHASE-SHIFTING TECHNIQUE

We propose a new signal-processing method for eliminating measurement errors that occur in the wavelength-multiplexed phase-locked laser dio de interferometer. The basic idea proposed here is a very simple but e ffective way to improve measurement accuracy. With our scheme, the pha se in the interference signal is strictly shifted by 2 pi, which enabl es us to eliminate measurement errors, The equivalent wavelength Lambd a is 80 mm, and the measurement accuracy reaches similar to Lambda/600 . A step-height measurement was also carried out in the experiment. (C ) 1997 Optical Society of America.