【作者】 颜召军；

【导师】 李新阳；

【作者基本信息】 中国科学院研究生院（光电技术研究所） ， 光学工程， 2013， 博士

【摘要】 自适应光学系统是一类时间延迟的伺服系统，时间延迟极大的限制了系统的性能。目前系统中采用的各路相同固定控制参数的经典控制算法没有自适应性，系统校正效果不理想，控制带宽也受到很大的限制。多层共轭自适应光学技术可以突破大气非等晕性误差的限制，有效扩大系统的校正视场。美国的大双目望远镜LBT采用了多层共轭技术。若因某种原因导致了LBT的次镜偏离了其正常工作时的位置，将会导致LBT的两路光学系统具有不同的“底片比例”（platescale），最终会影响LBT正常干涉。如何利用多个波前传感器探测到的波前来对视场内大气湍流进行三维的波前重建是实现星向多层共轭自适应光学技术的关键，此外还需要解决观测目标倾斜量的探测问题。对于自适应光学系统，科学相机与变形镜之间的光学器件会引入非共光路静态像差，该像差会影响系统的成像质量。针对自适应光学系统中存在的以上问题，本文对自适应光学系统中的预测控制以及多层共轭技术进行了深入的研究。主要的研究内容和取得的成果有以下几点：1.提出了一种对变形镜控制电压进行线性预测以减少时间延迟对自适应光学系统校正效果影响的算法。仿真结果表明该预测控制算法比比例积分控制算法可以更有效的降低系统时间延迟引起的误差。2.提出并在理论上推导了自适应光学闭环系统中一种实用的实时多路自适应预测控制算法。利用数值仿真对该算法的收敛性、控制效果、控制带宽进行了研究和分析。仿真结果表明该算法较比例积分控制算法和普通的预测控制算法可以更有效的提高系统的校正效果和控制带宽。3.实现了对层向多层共轭自适应光学系统的数值仿真。4.开展了对LBT中platescale变化问题的仿真分析研究。提出了一种利用LBT中高层波前传感器上未重叠区域的波前信息来探测platescale变化的方法，并对该方法进行了仿真验证。仿真结果证明了该方法可以用来对platescale的变化进行探测。5.完成了星向多层共轭自适应光学系统中大气三维波前重建算法的推导，并进行了相关的仿真实验。在仿真中，利用该算法成功地对两层和三层相位屏实现波前重建。6.推导了一种对观测目标方向倾斜量进行探测的算法，并对该探测算法进行了仿真。仿真结果验证了该探测算法的正确性，同时还研究了导星的星等、导星与观测目标的角距离、探测波前时采用的泽尼克阶数对该算法探测精度的影响。7.提出了一种改进的相位差法，并完成了仿真和实验验证。实验结果表明：采用改进的相位差法测量光学系统静态像差得到的各阶泽尼克系数与采用传统相位差法得到的各阶泽尼克系数之差都在10个纳米以内。本文提出的自适应光学闭环系统中的预测控制算法对提高系统的校正效果和校正带宽具有重要的意义。对多层共轭自适应光学相关技术的研究为以后发展多层共轭自适应光学系统提供了有益的参考和帮助。更多还原

【Abstract】 The adaptive optics (AO) systems are time-delay servo systems and their performances are limited by the time lag in the systems. The traditional control algorithms used in AO systems do not have good performances and high control bandwidths since these algorithms have fixed control parameters and are not themselves adaptive. The technology of multi-conjugate adaptive optics (MCAO) can overcome the limitation of anisoplanatism and compensate the atmospheric turbulence over a very large field of view. The Large Binocular Telescope (LBT) in USA uses this technology. The secondary mirrors in LBT may have mechanical displacement in a way that would make the plate scale of the two MCAO systems change and cause trouble for LBT. The key to success of star-oriented MCAO is how to reconstruct the3D map of turbulence above the telescope and how to determine the tip and tilt over the observation object. Non-common path aberrations between the science camera and the wave-front sensor (WFS) in AO system are unseen by the WFS and therefore are not corrected in closed loop that will affect the performance of the system.The dissertation concentrates on prediction control algorithms and multi-conjugate technologies for AO system. The main contents and results are concluded as follows.Firstly, a linear prediction control algorithm used to predict the voltages of deformable mirror of AO system in advance has been studied. Numerical simulations are carried out to show the significant improvements brought by this algorithm.Secondly, a multichannel adaptive prediction control algorithm which can be applied to practical real-time closed-loop AO system has been investigated. Analyses on convergence, control performance and bandwidth of this algorithm have been made. Compared with the classical proportional-integral control and traditional prediction algorithm, simulation results show that the new algorithm can improve control properties and the closed-loop bandwidth of the system efficiently.Thirdly, the simulation of layer-oriented MCAO system has been implemented successfully.Fourthly, a method used to measure the plate scale change of LBT by use of the unoverlapping wave-front from the middle high WFS is proposed and relative simulations have been made to show the validity and the potential ability of this method.Fifthly, an algorithm used to reconstruct the3D map of turbulence for star-oriented MCAO is derived. The validity of this algorithm has been by demonstrated by simulations in which two and three layer phase screens are respectively reconstructed successfully.Sixthly, an algorithm to measure the tip and tilt over the observation object is proposed and has been validated by the relative simulations. The accuracy of this algorithm in terms of guide stars’magnitude, separation distance and the number of Zernike modes has been analyzed.Finally, a modified phase diversity technique used to measure the internal non-common path optical static aberrations is proposed and the relative simulations and experiments have been made to show the validity and the potential ability of this technique. The study shows that the method is very flexible and has the same accuracy as the traditional phase diversity.The prediction control algorithms for closed-loop adaptive optics systems proved by theory and simulations are meaningful on improving the performances and control bandwidths. The theory analysis and simulated results for multi-conjugate adaptive optics provide significant guidelines and help for developing MCAO system in the future. In general, for future high performance AO systems, the work in the dissertation may be of interest to achieve the challenging science goals.更多还原