Research On Vibration Measurement And Signal Reconstruction Algorithm Of Laser Self-mixing Interference

Among many vibration measurement technologies,laser self-mixing interference vibration measurement technology has been widely used because of its high accuracy,non-contact,and easy alignment.In recent years,researchers have proposed many processing methods based on laser self-mixing interference vibration measurement,but they inevitably have problems such as complex measurement algorithms,slow processing speeds,and large measurement errors.Therefore,in view of the above problems,this paper has carried out research on laser self-mixing interference vibration measurement and signal reconstruction algorithms,and improved the measurement algorithms and experimental structure to solve the above problems.First,the theoretical analysis of the laser self-mixing interference theory is carried out to derive the power equation and phase equation of the laser self-mixing interference effect.The phase unwinding method,which is a commonly used vibration measurement algorithm in vibration measurement,is researched.The algorithm is used to reconstruct the displacement of the simulation signal and the experimental signal.By analyzing the processing process of the measurement algorithm,it is found that the algorithm is susceptible to interference in the process of finding the jump point,which leads to an increase in reconstruction error.Secondly,in view of the problems in the phase unwrapping method,a laser self-mixing interference displacement reconstruction algorithm based on peak-valley point detection is proposed.The algorithm achieves the purpose of accurately locating the peak and valley points by obtaining the intersection of the derivatives of the two signals,and the algorithm can avoid the reconstruction error due to the threshold setting.Simulation and experimental results show that compared with the reconstruction results of traditional algorithms,this method can accurately obtain the position of peak and valley points,effectively solving the problem of large reconstruction errors caused by inaccurate positioning of peak and valley points in traditional methods..Then,in order to solve the problems of complex algorithm,slow calculation speed and low accuracy in the phase unwrapping method,a laser self-mixing interference displacement reconstruction algorithm based on integral reconstruction is proposed.In the weak feedback condition,the algorithm performs triangular transformation and derivative integration of the power equation to reconstruct the vibration displacement of the target object.Compared with the phase unwrapping method,the integral reconstruction method can avoid phase unwrapping,directly simplifies the algorithm process,and avoids reconstruction errors caused by inaccurate positioning of peak and valley points.Simulation and experimental results show that this method can improve the calculation speed and thereconstruction accuracy slightly.Finally,in order to further improve the reconstruction accuracy,by adding an electro-optic modulator to the original optical path and combining it with an improved phase generation carrier algorithm to demodulate,this algorithm can eliminate unnecessary parameters introduced in the phase generation carrier algorithm,thereby improving demodulation Precision to achieve the purpose of reducing reconstruction errors.