【作者】 张玉燕；

【导师】 王玉田；

【作者基本信息】 燕山大学 ， 测试计量技术及仪器， 2006， 博士

【摘要】 基于光反馈效应的激光自混合干涉技术是近年来兴起的、具有应用前景的技术。重新注入激光腔的激光与腔内的光混合引起输出功率变化和频率变化,该性质可应用于各种传感器,实现对速度、距离、位移或振动等物理量的非接触、高精度测量。基于半导体激光器LD的自混合干涉效应,开展了对位移和速度测量技术的研究。采用Lang-Kobayashi速率方程方法和三镜法-珀腔模型,阐述了LD自混合干涉的机理,得到了出射光频率和光强表达式以及通用数学模型。针对LD自混合干涉位移测量系统,建立了弱反馈、适度反馈和强反馈机制下的LD的工作模型,对输出光功率信号进行了数值模拟与分析。根据不同条件下模拟的输出光功率信号波形,分析了各种测量参数的影响及外腔位移调制方式的影响规律。设计了基于半导体激光器自混合干涉的位移测量系统,实验验证了理论分析的结果。应用垂直腔面发射激光器的自混合效应对激光多普勒测速方法进行了研究,设计了一种结构紧凑的激光多普勒测速装置。采用快速傅立叶变换方法对自混合干涉信号进行频谱分析,可获得多普勒频率信息,从而获得运动物体沿光学轴向的速度分量信息。实验结果表明当被测物体速度在70～400mm/s范围时,相对误差小于2%。为了有效减小因温度不稳定而造成的LD输出功率不稳定、输出波长发生漂移等不良影响,对光源LD内部温度的高精度控制技术进行了研究。分别采用半导体热敏电阻和半导体热电制冷器作为感温元件和控温执行元件,提出了一种模糊控制理论与数字PID参数自适应调整相结合的增量式控制算法。实验结果表明,该方法的控温稳定度优于0.1℃,有效地抑制了LD波长的温度漂移。光反馈所引起的非线性现象很大程度上影响LD的特性,应用卡尔曼滤波算法更适于处理自混合效应的非线性问题,且能提高测量精度。提出了一种基于扩展卡尔曼滤波器的信号处理方法,适用于弱光反馈强度的自混合干涉位移测量系统。实验结果表明该方法可有效地实时重构目标反射体的位移波形,测量分辨力为λ20。更多还原

【Abstract】 Based on the use of optical feedback that occurs in a semiconductor laser diode when the optical beam is back reflected toward the cavity and then re-introduced inside, the self-mixing interference has been demonstrated to be suitable for non-contact and high-accuracy sensing applications. This is an emerging and promising technique enabling notably displacement, distance, vibration and/or velocity measurements to be performed. The techniques of displacement and velocity measurement based on self-mixing interference in a laser diode have been studied in this thesis.By using the rate equations first derived by Lang and Kobayashi and the model of a three-mirror cavity, the mechanics of the self-mixing interference effect can be analyzed. The general expression of the optical frequency and power emitted by the laser diode are obtained, and then the mathematical model of the common self-mixing can be established. The displacement sensing properties have been numerically simulated and analyzed by using Matlab tools. In order to represent the self-mixing interference phenomenon occurring in different optical feedback regime, a behavioral model of a laser diode described by schematic block diagrams is presented. By virtue of this behavioral model, the simulation of output power of a self-mixing sensor can be performed. The simulated fluctuation waveforms of the power shows that how the parameters associated with the external target movement have influence on the self-mixing interference signal, as well as that the dependence of the self-mixing interference signals on the external cavity vibration modulated by different waveforms.The measuring systems of displacement and velocity base on self-mixing effect have been designed. Correspondingly, the optical path and experimental setups have been established.A simple and compact laser Doppler velocimeter is developed based on self-mixing effect in a vertical-cavity surface-emitting laser (VCSEL). The monitor photodiode mounted on the back facet of the VCSEL acts as a transducer and it generates the self-mixing current signal. The FFT technique is applied to analyze self-mixing interferometric signal. The power spectrum of this signal can be acquired and analyzed to extract the Doppler frequency and the information relative to the velocity measurement. The target velocity component projected along the optical axis of the laser beam is calculated. The experiment results show that the accuracy of velocity measurement is high with relative error of Doppler frequency lower than 2%, while for the velocity higher than 70mm/s.In order to eliminate the output power and wavelength shift of LD caused by temperature instability, A temperature control method of LD with high accuracy is proposed, which adopts thermistor and thermo-electric cooler as temperature sensor and execute component of temperature control respectively. A control algorithm based on fuzzy theory and digital PID control is proposed. The experimental results show that the precision of controlled temperature is better than 0.02℃, and the response characteristic of the system with Fuzzy-PID control is better than that of with general PID control.Although the nonlinear phenomena can govern the global behavior of the laser diode, we concluded that Kalman filtering techniques could also be popular to deal with this problem and increase the measurement precision of self-mixing interferometry. In this paper, a new signal processing method based on Klaman filter is presented for the self-mixing displacement sensor. Based on the approximate linearized model of a LD, the robust Kalman filter is designed for an estimation of the system parameters and the target displacement in the wake feedback regime. The simulation analysis and experiments have been done to illustrate the validity and the effectiveness of the method. These results show that the displacement estimation is good with little noise and the estimated resolution of aboutλ20 is achievable.更多还原