基于FPGA的半导体激光器调频非线性校正技术研究

发布时间：2018-07-04 20:32

本文选题：线性调频连续波 + DFB半导体激光器　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：线性调频连续波(LFMCW,Linear Frequency Modulated Continuous Wave)绝对距离测量技术是一种新兴的测距技术,具有无靶标、无盲区、非接触等其他传统测距手段不具备的优势。正因如此,该技术可用于一些复杂大尺寸工件的加工和检测,同时测量精度更高、效率更快。尽管调频连续波测距技术优点突出,但缺点是作为光源的激光器调频非线性程度对测距精度和测距分辨率影响严重。只有激光器调频线性度非常高时才能获得高测距精度和测距分辨率,所以有必要对激光器的调频非线性校正技术进行研究。本文主要围绕DFB激光器的调频非线性校正技术进行研究,首先,介绍了FMCW测距的原理,给出了相应参数的计算公式,分析了调频非线性对测距精度和测距分辨率的影响,简要说明了DFB激光器调频非线性产生的原因;其次,对调频非线性校正方法进行了调研,确定了使用迭代校正方法进行初步大带宽范围的非线性校正,给出了DFB激光器调频非线性度的等价评判指标,设计了一种基于割线法的迭代校正算法,并说明了其数学模型、物理意义以及算法流程;根据本课题对信号相位准确度的要求确定了采取FIR滤波器来实现迭代算法中部分数学处理手段,并介绍了FIR滤波器的基本理论及其在FPGA中的实现方法;然后详细介绍了基于FPGA的迭代校正算法具体实现方案,根据实验参数进行了器件选型,设计了基于FPGA最小系统及相应的外围电路;对其中关键等效环节进行了设计并对其幅频响应和相频相应进行了验证。最后,搭建了基于FPGA的激光器调频非线性校正系统,实验验证了迭代算法的校正效果对电流调谐半导体激光器的调频非线性有了明显改善,并进行了重复性测试,证明该迭代校正算法具有良好的重复性和稳定性;结合所提出的校正原理、硬件电路以及光路结构等分析了校正系统的噪声及误差来源。
[Abstract]:Linear Frequency Modulated continuous Wave (LFMCW) absolute distance measurement is a new ranging technique, which has the advantages of no target, no blind area, no contact and other traditional ranging methods. Because of this, the technology can be used to process and detect some complex and large size workpieces, and at the same time, the measurement accuracy is higher and the efficiency is faster. Although the advantages of FM CW ranging technology are outstanding, the disadvantage is that the nonlinearity of frequency modulation laser as a light source has a serious impact on ranging accuracy and ranging resolution. Only when the frequency modulation linearity of the laser is very high, high ranging accuracy and ranging resolution can be obtained. Therefore, it is necessary to study the FM nonlinear correction technology of the laser. In this paper, the frequency modulation nonlinear correction technology of DFB laser is studied. Firstly, the principle of FMCW ranging is introduced, the calculation formula of corresponding parameters is given, and the influence of frequency modulation nonlinearity on ranging precision and ranging resolution is analyzed. The cause of nonlinear frequency modulation of DFB laser is briefly explained. Secondly, the nonlinear correction method of frequency modulation is investigated, and the iterative correction method is used to correct the nonlinear problem in a wide bandwidth range. The equivalent evaluation index of frequency modulation nonlinearity of DFB laser is given, an iterative correction algorithm based on Secant method is designed, and its mathematical model, physical meaning and algorithm flow are explained. According to the requirement of signal phase accuracy, Fir filter is adopted to realize some mathematical processing methods in iterative algorithm, and the basic theory of Fir filter and its implementation method in FPGA are introduced. Then the implementation scheme of the iterative correction algorithm based on FPGA is introduced in detail. According to the experimental parameters, the device selection is carried out, and the minimum system based on FPGA and the corresponding peripheral circuit are designed. The key equivalent links are designed and the amplitude-frequency response and phase frequency are verified. Finally, a nonlinear tuning system of laser frequency modulation based on FPGA is set up. The experimental results show that the iterative algorithm can improve the frequency nonlinearity of current-tuned semiconductor lasers obviously, and the repeatability is tested. It is proved that the iterative correction algorithm has good repeatability and stability, and the noise and error sources of the correction system are analyzed based on the proposed correction principle, hardware circuit and optical circuit structure.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN248.4

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