Self-Mixing Interferometry Based on Improved All-Phase FFT for High-precision Displacement Measurement

In the displacement sensor using laser self-mixing interference, the signal processing method plays an important role. Inherent drawbacks of the spectrum estimation algorithm such as spectrum leakage will influence the measurement of beat frequency and degrade the displacement measurement accuracy. In order to accurately extract the displacement information from self-mixing interference signals, we propose an approach based on improved all-phase fast Fourier transform, which has eminent ability to restrain spectral leakage. The principle of self-mixing interference is presented. A measurement error on the order of nanometer is obtained by experimental measurement, which demonstrates the superiority of the proposed approach in comparison with fast Fourier transform.