Absolute distance measurement using a multi-stage evaluation algorithm on sinusoidally phase-shifting interference signals via laser injection current modulation

Abstract

Abstract We present a laser interferometric measurement system for absolute distance measurements based on currentmodulated laser diodes in the telecommunications wavelength range. The sensor system described here uses two lasers with slightly different wavelengths in a point-wise measuring interferometer and enables the determination of absolute distance information without mechanical scanning or an oscillating reference mirror. This work focuses on the experimental setup and its metrological characterization. The system’s performance is demonstrated using step height measurements with a reference step of 75 μm. The successful reconstruction of these step heights particularly highlights the advantage of the absolute measurement principle, which allows for unambiguous distance determination without the phase ambiguity typical of conventional interferometers. Signal evaluation is performed by a multi-stage algorithm that first derives coarse absolute distance values from the frequency estimation of the modulated interference signals and then refines these using phase information. The presented system combines interferometric precision with absolute distance measurement capability in a compact and cost-effective design, making it a promising approach for high-precision optical metrology.