Fringe double for self-mixing interference based on the narrow transmission spectrum mapping

Abstract

In this work, a novel fringe double scheme with a Fabry–Pérot (F–P) cavity is proposed for self-mixing interferometry based on the narrow transmission spectrum mapping. While the laser beam with self-mixing interference (SMI) propagates through the F–P cavity with the narrow transmission spectrum, the SMI fringe doubles as the optical frequency modulation caused by SMI sweeps the peak of the transmission spectrum of the F–P cavity completely. The doubled SMI signal is very suitable for displacement reconstruction with fringe counting and velocity monitoring with joint time-frequency analysis, since it inherits the merits of the transmission spectrum of the F–P cavity (sharp, neat, and stable). This method has the potential to simplify signal processing and improve the resolution of SMI measurement systems.