Study on signals of in-plane displacement measurement utilizing laser Doppler effect

When utilizing laser Doppler effect to measure in-plane displacement of an object in long distance, the intensity of Doppler signals of scattering light, SNR and quality of signals are very important parameters, and they affect the distance and accuracy of displacement measurement directly. The Doppler differential method, lock-in amplifier and homomorphic filter are studied. A differential optical measuring system with the best effect, a lock-in amplifier with high sensibility and high Q and a homomorphic system that can reconstruct the lost signals are designed. So the transverse displacement measurement of object in distance of 50 m is accomplished with the maximal relative error of 1.5%.