级联自适应光学：两级控制器对比度性能的数值模拟分析
Cascade adaptive optics: contrast performance analysis of a two-stage controller by numerical simulations
摘要：
通过添加第二个AO校正级（具有自己的波前传感器、可变形镜和实时控制器），可以提高当前极限自适应光学（XAO）系统的对比度性能。我们建立了一个这样的级联AO（CAO）系统的动力学模型，两个阶段，每个控制的标准积分器，并研究其控制特性。我们研究如何这样的配置可以改善现有的系统，而无需修改的第一阶段。我们分析的CAO架构一般，并显示部分的干扰是如何从低到高的时间频率与邪恶的影响第二阶段的积分器过冲，并建议可能的方法来减轻这一点。我们还进行了数值模拟的特定情况下的第一阶段AO使用夏克-哈特曼波前传感器和第二阶段AO与较小的变形镜运行在一个较高的帧速率，以减少时间误差。在这种情况下，我们表明，第二阶段提高了一个数量级的成像对比度，并缩短了去相关时间的大气湍流散斑甚至更大的因素。结果表明，CAO提出了一种有前途的和相对简单的方法来升级一些现有的XAO系统，并实现改进的成像对比度，促进了大量的科学案例，包括系外行星的直接成像。
英文摘要：
The contrast performance of current eXtreme Adaptive Optics (XAO) systems can be improved by adding a second AO correction stage featuring its own wavefront sensor, deformable mirror, and real-time controller. We develop a dynamical model for such a cascade AO (CAO) system with two stages each controlled by a standard integrator, and study its control properties. We study how such a configuration can improve an existing system without modifying the first stage. We analyze the CAO architecture in general and show how part of the disturbance is transferred from low to high temporal frequencies with a nefarious effect of the second stage integrator overshoot, and suggest possible ways to mitigate this. We also carry out numerical simulations of the particular case of a first stage AO using a Shack-Hartmann wavefront sensor and a second stage AO with a smaller deformable mirror running at a higher framerate to reduce temporal error. In this case, we demonstrate that the second stage improves imaging contrast by one order of magnitude and shortens the decorrelation time of atmospheric turbulence speckles by even a greater factor. The results show that CAO presents a promising and relatively simple way to upgrade some existing XAO systems and achieve improved imaging contrasts fostering a large number of science cases including the direct imaging of Exoplanets.
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