The physical principles of wavelength-shift interferometric laser rangefinders

Abstract

The authors review the recent progress in dynamic interferometry applied to optical distance measurement devices. These techniques are based on modulating laser diodes to obtain a continuous wavelength-shift. Measurements can be done by a fringe counting technique or by detecting the beat frequency that is proportional to the time-of-flight. This paper shows too the importance of the spectral analysis of the photodetected signal. A signal processing allows the use of multiple-beam interferometers with multiple reflectors. It's also possible to determine absolute distances with rough targets from the ratio of the amplitudes of two harmonics.