自适应光学实时信号处理及优化控制技术研究

发布时间：2017-12-30 18:03

本文关键词：自适应光学实时信号处理及优化控制技术研究　出处：《中国科学院光电技术研究所》2017年博士论文　论文类型：学位论文

【摘要】：自适应光学系统能够实时探测和补偿由于大气湍流等传输介质和光学系统扰动带来的波前畸变,因此其在高分辨力成像、激光大气传输等众多应用领域得到了广泛应用。波前控制系统作为自适应光学系统的核心和枢纽,对自适应光学系统的校正性能起着至关重要的作用,本文主要围绕波前控制系统的实时性,准确性和稳定性几个方面展开了研究工作。首先,针对自适应光学实时信号处理系统的特点,提出了自适应光学系统对实时信号处理的基本需求,分析了波前控制系统的运算量和传输特性,构建了实时信号处理系统的总线架构,研究了基于时间流水和空间并行相结合的实时信号处理方法,设计了基于双DSP+FPGA硬件架构的自适应光学实时信号处理平台。实验结果表明,该平台能够满足自适应光学系统的实时性要求,并在多套自适应光学系统中得以应用,具有可靠性高,适用性强等优点。其次,针对夏克-哈特曼波前传感器中采用一阶矩法提取光斑质心时,系统噪声严重影响一阶矩算法质心提取精度的问题,分析了波前传感器系统中噪声的特点,提出了一种以滑动窗口内像素均值及图像信号的局部梯度作为参数,构造噪声权重函数来获得子孔径阈值最优估计值的方法。详细分析了算法的基本原理和实现过程,在不同信噪比,不同光斑大小的条件下,进行了数值仿真并搭建了实验平台对算法进行了验证。仿真和实验结果表明,本文提出的阈值估计方法,在各种实验条件下均能取得优于传统阈值处理方法获得的结果。然后,针对光束在传输的过程中受大气湍流等传输介质及平台振动等因素的影响,使得到达目标靶面中心的光束发生漂移和抖动的问题,分析了常规控制系统存在的不足,对高速倾斜镜的模型进行了辨识,提出了一种基于两级高速倾斜镜串联控制的方法。该方法利用前级光束稳定系统校正由于平台机械谐振带来的大幅度、高频率窄带扰动,后级光束稳定系统校正由于传输介质引起的宽带扰动。仿真和实验表明,本文提出的系统结构和控制方法能够有效的抑制光束稳定系统中存在的扰动。最后,针对典型自适应光学系统中经常使用方形孔径排布的波前传感器,受波前传感器测量噪声、传感器和变形反射镜布局不匹配等因素的影响,容易产生棋盘效应降低闭环控制稳定性的问题,提出了一种同时对重构电压施加惩罚函数和对控制电压进行投影的方法,利用该方法对方形孔径排布自适应光学系统中存在的棋盘效应进行抑制。针对变形镜的不同参数,利用数值仿真分析对比了各阶像差与棋盘效应之间的耦合关系,并构建了实验系统,在实际大气湍流条件下,对靶点信标进行了闭环验证实验。实验结果表明本文提出的方法能够有效地抑制方形孔径排布自适应光学系统中存在的棋盘效应,提高系统的稳定性。
[Abstract]:Capable of real-time detection and compensation for wavefront distortion caused by atmospheric turbulence and other transmission media and optical system of adaptive optical system, so the high resolution imaging, laser atmospheric transmission and many other application fields has been widely used. The wavefront control system as the core and hub of adaptive optical system, plays a vital role in the performance of the adaptive correction the optical system, this paper mainly focus on the real-time wavefront control system, the accuracy and stability of several aspects of the research work. Firstly, according to the characteristics of adaptive optics real-time signal processing system, proposed an adaptive optical system of the basic needs of real-time signal processing, analysis of the computation and transmission characteristics of wavefront control system, construct bus architecture for real-time signal processing system, studies the time and space of parallel flow based on the combination of real time signal Methods of signal processing, the design of adaptive optics real-time signal processing platform based on dual DSP+FPGA hardware architecture. The experimental results show that the platform can meet the real-time requirements of adaptive optical system, and can be used in multiple sets of adaptive optics system, has advantages of high reliability, strong applicability. Secondly, based on Hartmann Shack wavefront sensor by the moment method of centroid extraction, system noise seriously affect the accuracy of the first-order moment algorithm centroid extraction, analysis of the characteristics of noise of wavefront sensor in the system, put forward as a parameter to smooth local gradient pixels in the window and moving average image signal, to construct noise weighting function to estimate parameters the optimal threshold method of sub aperture. The basic principle and implementation process of the algorithm is analyzed in detail under different SNR conditions, different beam sizes, numerically The simulation and experimental platform verifies the algorithm. Simulation and experimental results show that the method proposed in this paper to estimate the threshold, can get better than the traditional thresholding method the results obtained under various experimental conditions. Then, the beam affected by the atmospheric turbulence transmission medium and platform vibration and other factors in the process of transmission so, reach the target of the center beam drift and jitter problems, analyzes the shortcomings of conventional control system, the fast steering mirror model identification, proposes a method of two stage high speed tilting mirror series based on the control. Before the beam stability correction system due to the mechanical resonance caused by platform by using this method, the high frequency narrowband disturbance, secondary beam stability correction system with broadband transmission medium caused by disturbance. The simulation and experimental results show that the proposed system. The structure and the control method can suppress the disturbance beam stabilization system effectively. Finally, according to the arrangement of square aperture wavefront sensor is often used in typical adaptive optical system, the measurement noise of wavefront sensor, sensor and deformable mirror do not match the layout and other factors, easy to produce the chessboard effect to reduce the stability of the closed-loop control problem. At the same time, proposes a method of penalty function is applied to the reconstruction of the projection and the voltage control voltage, to suppress the effect of square aperture arrangement board in adaptive optical system by using this method. According to the different parameters of the mirror and the comparative analysis of the coupling relationship between aberration and checkerboard effect by numerical simulation, and construction in the experimental system under actual atmospheric turbulence, the closed loop verification experiment was carried out on the target beacon. Experimental results show that the proposed The proposed method can effectively suppress the chessboard effect in the square aperture arrangement adaptive optical system and improve the stability of the system.

【学位授予单位】：中国科学院光电技术研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN911.74

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