Using Hilbert Transform Method To Measure The Displacement In The Moderate Optical Feedback

The optical feedback self-mixing interferometry (OFSMI) measurement technology can provide high-precision and non-contact measurement. Because of simplicity, compactness and self-aligning, making OFSMI measurement technology has been rapid development in the recent one or two decades. This technology mainly used in object velocity measurement, displacement measurement and laser parameters measurement.In this thesis, Overview the theory of the OFSMI technology, then proposed a displacement measurement based on Hilbert transformation. The main work of the thesis as follows:First, Analyzed the theoretical model of the OFSMI system. Through the computer simulation, obtained three different optical feedback system by analyze relationship of the signal phase. This three different optical feedback named:weak feedback, moderate feedback and strong feedback; Research the laser parameters impact of the laser interference signal.Secondly, In this thesis, the theory of Hilbert transformation has been studied and using Hilbert transformation reconstruct the phase of the signal; Obtained [0,2Ï€] phase reconstruct formula by the arc tangent function, and then completely recover the phase information though the signal turning point, describes the parameters of laser measurement and displacement information measurement of the external objects in the moderate feedback mechanism, based on phase recover theory.Thirdly, In order to improving the measurement accuracy, pre-processing the experimental data. Against the noise of signal characteristics, using the median filtering and FIR filtering removal the signal noise. Verified the algorithm with experimental data, the results show that the relative error of displacement measurement algorithm to reached 0.28%.Finally, summarized this thesis, and the further research issue are point out.