Phase-modulated SMI sensor for simultaneous vibration and distance measurements

Abstract

This paper proposes a novel method for simultaneous vibration and distance measurements using triangular wave current modulation in a self-mixing interference (SMI) system. Phase-modulated SMI signal carries both vibration and distance information. A pair of quadrature signals is obtained by sampling and interpolating the modulated SMI signal at the peak and valley points of the triangular wave current signal. The vibration is then reconstructed using the quadrature phase unwrapping method. Meanwhile, the distance is determined by the main frequency estimation of the residual signal obtained by filtering out the vibration-related signal. For the target with non-stationary, the error of vibration reconstruction is 17.1 nm, and the standard deviation of the measured distance is 0.058 cm. This method does not require additional optical components in the optical path, maintaining the advantages of a single optical path and low cost of the SMI system, while also providing a valuable reference for applications involving the simultaneous measurements of vibration and distance.