Study Of The Vibration Sensing And Measuring Technology Based On Laser Self-Mixing Interference

With the rapid development of micro-electro-mechanical technology and precision machining technology as well as many important applications, many researchers are very interested in micro-vibration sensing and measuring problems. Optical sensing and measuring technologies are non-contacted; they have a lot of advantages such as high accuracy, perfect stability, etc., and play an important part in the field of metrological measurements. Of various optical sensing and measuring methods, laser interferometry is the most widely used. The sensing and measuring technology based on laser self-mixing interference (SMI) has been developed rapidly in recently years; its main advantages include simplicity, compactness and easy alignment, providing a better solution to the problems of complexity and large size of the conventional interferometric systems. Therefore the SMI-based sensing and measuring technology has been investigated extensively and deeply by many researchers at home and abroad.The mechanism and technology of the SMI-based vibration sensing and measuring has been studied theoretically and experimentally in this thesis, the main contents are included as follows:First, the development and present status of the SMI based laser vibration sensing and measuring technology have been briefly introduced.Secondly, the mechanics of the SMI effect has been studied theoretically. The laser system's stable condition and frequency function are obtained by virtue of the theoretical model of a three-mirror F-P cavity and Lang-Kobayashi rate equations theory, and the mathematical model of common SMI effect is established. The theoretical result is deduced that the phase sensitivity of the SMI based measurement is the same as that of the two-beaminterference measurement, which has supplied a foundation for the simulations, analyses and experimental studies in this thesis. The inclinations and the waveform inversions of the SMI fringes are analyzed. The effects of linewidth enhancement factor and feedback strength on the asymmetry and the direction of fringe inclination of the SMI signal are investigated.Thirdly, the SMI-based vibration sensing properties have been numerically simulated and analyzed by use of Matlab tools, including the influences of the extra-cavity phase on the frequency, power and line-width of the output light as well as the dependences of the SMI signals on the vibrating object modulated by different waveforms such as sine, triangular and saw-tooth waves.Fourthly, the system based on laser diode SMI effect has been designed and the corresponding experimental setup has been established. The vibration sensing and measuring experiments had been carried out by changing the extra-cavity length of the laser diode and the frequency, amplitude and waveform of the vibrating object, respectively. The corresponding SMI signals had been observed experimentally and the experiment results had been analyzed. The experimental results were good in accordance with the simulated results.Lastly, an improved vibration sensing and measuring system based on laser diode SMI effect has been designed so as to enhance the measurement resolution; the feasibility has been theoretically analyzed.