The Self-mixing Interference Velocimetry Study

In this dissertation, the background and the significance of self-mixing interference velocity measurement technique are introduced. The state of the self-mixing interference velocity measurement is reviewed. In order to construct the perfect technique for this measurement, the theoretical analysis and the experimental research are extensively and deeply studied.In theory, the model of self-mixing interference has been build based on the Doppler effects and the compound cavity theory. The principle of self-mixing velocity measurement bas been studied, the problem of upper limit has been discussed carefully, the depth of modulation has been analyzed. At last, the parameters of the fiber-coupled self-mixing interference system how to influence the waveform of self-mixing interference signal have been simulated.The systems of free-space self-mixing interference and all-fiber speckle self-mixing interference have been designed. We put stress on the study of the feasibility using fiber to transmit light and using self-focus lens to collect feedback light. Firstly, we build the model of self-focus lens, and then, we study the collection efficiency of the self-focus lens how to change with radius and working distance, at last, the experiments of collection efficiency have been done. The feasibility of using fiber to transmit light and using self-focus lens to collect feedback light is theoretically proved.The signal processing has been studied. These researches include how to normalize the self-mixing interference signal, how to acquire the velocity from the self-mixing interference signal, and how to acquire the displacement. At last, we compare threshold method and auto-correlation method which are used to process the self-mixing speckle interference signal. At last, we adopt the threshold method to process the self-mixing speckle interference signal.The systems of free-space self-mixing interference and all-fiber speckle self-mixing interference have been constructed, the experiments have been carried through, the ideal signals have been acquired, and at last, the experimental results are given.