Wu Zhiwen, Enmark Anita, Owner-Petersen Mette, Andersen Torben
Lund Observatory, Lund University, Box 43, SE 22100 Lund, Sweden.
Opt Express. 2009 Oct 26;17(22):20575-83. doi: 10.1364/OE.17.020575.
The new generation of extremely large telescopes will have adaptive optics. Due to the complexity and cost of such systems, it is important to simulate their performance before construction. Most systems planned will have Shack-Hartmann wavefront sensors. Different mathematical models are available for simulation of such wavefront sensors. The choice of wavefront sensor model strongly influences computation time and simulation accuracy. We have studied the influence of three wavefront sensor models on performance calculations for a generic, adaptive optics (AO) system designed for K-band operation of a 42 m telescope. The performance of this AO system has been investigated both for reduced wavelengths and for reduced r(0) in the K band. The telescope AO system was designed for K-band operation, that is both the subaperture size and the actuator pitch were matched to a fixed value of r(0) in the K-band. We find that under certain conditions, such as investigating limiting guide star magnitude for large Strehl-ratios, a full model based on Fraunhofer propagation to the subimages is significantly more accurate. It does however require long computation times. The shortcomings of simpler models based on either direct use of average wavefront tilt over the subapertures for actuator control, or use of the average tilt to move a precalculated point spread function in the subimages are most pronounced for studies of system limitations to operating parameter variations. In the long run, efficient parallelization techniques may be developed to overcome the problem.
新一代超大型望远镜将配备自适应光学系统。由于此类系统的复杂性和成本，在建造之前模拟其性能非常重要。大多数计划中的系统将采用夏克-哈特曼波前传感器。有不同的数学模型可用于模拟此类波前传感器。波前传感器模型的选择对计算时间和模拟精度有很大影响。我们研究了三种波前传感器模型对一个为42米望远镜的K波段运行设计的通用自适应光学（AO）系统性能计算的影响。该AO系统在降低波长和降低K波段的r(0)情况下的性能都已得到研究。该望远镜AO系统是为K波段运行设计的，即子孔径尺寸和致动器间距都与K波段中r(0)的固定值相匹配。我们发现，在某些条件下，比如研究大斯特列尔比时的极限导星星等，基于夫琅禾费传播到子图像的完整模型要精确得多。然而，它确实需要较长的计算时间。对于研究系统对运行参数变化的限制，基于直接使用子孔径上平均波前倾斜来进行致动器控制，或者使用平均倾斜来移动子图像中预先计算的点扩散函数的更简单模型的缺点最为明显。从长远来看，可能会开发出高效的并行化技术来克服这个问题。
