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首页> 外文期刊>Journal of the Optical Society of America, A. Optics, image science, and vision >Methods for correcting tilt anisoplanatism in laser-guide-star-based multiconjugate adaptive optics
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Methods for correcting tilt anisoplanatism in laser-guide-star-based multiconjugate adaptive optics

机译：基于激光导星的多共轭自适应光学器件中校正倾斜各向异性的方法

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摘要

Multiconjugate adaptive optics (MCAO) is a technique for correcting turbulence-induced phase distortions in three dimensions instead of two, thereby greatly expanding the corrected field of view of an adaptive optics system. This is accomplished with use of multiple deformable mirrors conjugate to distinct ranges in the atmosphere, with actuator commands computed from wave-front sensor (WFS) measurements from multiple guide stars. Laser guide stars (LGSs) must be used (at least for the forseeable future) to achieve a useful degree of sky coverage in an astronomical MCAO system. Much as a single LGS cannot be used to measure overall wave-front tilt, a constellation of multiple LGSs at a common range cannot detect tilt anisoplanatism. This error alone will significantly degrade the performance of a MCAO system based on a single tilt-only natural guide star (NGS) and multiple tilt-removed LGSs at a common altitude. We present a heuristic, low-order model for the principal source of tilt anisoplanatism that suggests four possible approaches to eliminating this defect in LGS MCAO: (i) tip/tilt measurements from multiple NGS, (ii) a solution to the LGS tilt uncertainty problem, (iii) additional higher-order WFS measurements from a single NGS, or (iv) higher-order WFS measurements from both sodium and Rayleigh LGSs at different ranges. Sample numerical results for one particular MCAO system configuration indicate that approach (ii), if feasible, would provide the highest degree of tilt anisoplanatism compensation. Approaches (i) and (iv) also provide very useful levels of performance and do not require unrealistically low levels of WFS measurement noise. For a representative set of parameters for an 8-m telescope, the additional laser power required for approach (iv) is on the order of 2 W per Rayleigh LGS.
机译：多共轭自适应光学（MCAO）是一种用于在三个维度而不是两个维度上校正湍流引起的相位畸变的技术，从而大大扩展了自适应光学系统的校正视场。这是通过使用多个可变形的反射镜实现的，这些反射镜与大气中的不同范围共轭，并且执行器命令是根据来自多个引导星的波前传感器（WFS）的测量结果计算得出的。必须使用激光导星（LGS）（至少在可预见的将来），以在天文MCAO系统中获得有用的天空覆盖度。就像单个LGS不能用于测量整个波前倾斜一样，在同一范围内的多个LGS星座无法检测到倾斜各向异性。仅此错误会严重降低基于单个倾斜自然导星（NGS）和多个在相同高度上去除倾斜的LGS的MCAO系统的性能。我们针对倾斜各向异性的主要来源提出了启发式的低阶模型，该模型提出了消除LGS MCAO中这种缺陷的四种可能方法：（i）来自多个NGS的倾斜/倾斜测量，（ii）LGS倾斜不确定性的解决方案问题，（iii）来自单个NGS的其他高阶WFS测量，或（iv）来自钠和瑞利LGS在不同范围内的高阶WFS测量。一种特定的MCAO系统配置的样本数值结果表明，如果可行，方法（ii）将提供最高程度的倾斜各向异性。方法（i）和（iv）还提供了非常有用的性能，并且不需要不切实际的WFS测量噪声。对于8米望远镜的一组代表性参数，方法（iv）所需的额外激光功率约为每个Rayleigh LGS 2W。

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