Direct vibration waveform extraction based on synthetic wavelength amplitude modulation in an SMI system

This paper proposes an amplitude modulation method based on synthetic wavelength to directly acquire the vibration waveform of targets in a self-mixing interferometry (SMI) system. The vibration waveform of the target is directly extracted from the envelope of the amplitude-modulated SMI signal, which arises from the synthetic differential wavelength. Experimentally, targets with different vibration frequencies were measured, demonstrating an average frequency measurement error of 0.6% and an average coefficient of determination of 0.9938 for waveform agreement. This is the first time, to the best of our knowledge, in the SMI field to extract vibration waveform by using amplitude modulation generated by lasers with different wavelengths. This method provides a simple and accurate approach for measuring target vibration waveforms, significantly simplifying the demodulation process of SMI signals.