Investigation of a Dual-Wavelength Solid-State Laser Self-Mixing Vibration Measurement Method

Regarding the contradiction between high resolution and complex structure in traditional laser self-mixing measurement systems, the co-axial dual-wavelength solid-state laser self-mixing technology was proposed and studied. LD pumped the Nd:YVO4 crystal and doubled the frequency to generate two wavelengths laser of 1064nm and 532nm, and a co-axial dual-wavelength laser self-mixing measurement system was constructed. A 90° phase difference of the two wavelengths was produced by adjusting the angle of incidence of the parallel glass plate. As a result, a set of orthogonal signals was built to distinguish the direction of the displacement for the target. The results of experiment show that the measuring system can adapt to different vibration waveform and the frequency measurement upper limit can be reached by 7kHz. With a peak-to-peak average error below 10 nm, a minimum reconstructable displacement of less than 10 nm, and a short-term resolution better than 2 nm, the system demonstrates high precision in displacement measurement.