Improving the measurement performance for a self-mixing interferometry-based displacement sensing system

TLDR

This paper proposes novel approaches to enhance self‑mixing interferometry displacement measurement, including a real‑time optical‑feedback factor estimator and a combined laser‑phase and feedback‑level algorithm that together improve accuracy over existing methods. The authors study SMI signal characteristics to devise a new laser‑phase estimation procedure, develop a real‑time optical‑feedback factor estimator, and integrate these algorithms into a novel displacement‑measurement technique, which is validated by simulation and experiment. The study identifies the sources of inherent errors in current SMI displacement methods and demonstrates that the proposed technique, verified through simulation and experiments, achieves improved accuracy.

Abstract

Approaches that are, to our knowledge, novel, are proposed in this paper to improve the accuracy performance of self-mixing interferometry (SMI) for displacement measurement. First, the characteristics associated with signals observed in SMI systems are studied, based on which a new procedure is proposed for achieving accurate estimation of the laser phase. The studies also revealed the reasons for the inherent errors associated with the existing SMI-based techniques for displacement measurement. Then, this paper presents a new method for estimating the optical feedback level factor (denoted by C) in real time. Combining the new algorithms for estimating the laser phase and updating C value, the paper finally presents a novel technique for displacement measurement with improved accuracy performance in contrast to existing techniques. The proposed technique is verified by both simulation and experimental data.