Double Sinusoidal Phase-Modulating Distributed-Bragg-Reflector Laser-Diode Interferometer for Distance Measurement

A previously proposed double sinusoidal phase-modulating (DSPM) laser-diode interferometer measures distances larger than a half-wavelength by detecting modulation depth. Although it requires a vibrating mirror to provide the second modulation to the interference signal, such vibrations naturally affect measurement accuracy. We propose a static-type DSPM laser-diode interferometer that uses no mechanical modulation. Our experimental results indicate a measurement error of +/-1.6 (mu)m. [Optical Society of America ]