基于迭代分形法的大气波前仿真

大口径望远镜受大气湍流的影响，光学分辨率远远小于其自身光路所决定的衍射极限。为了相应的自适应光学系统设计，首先有必要对大气波动进行仿真以提供环境数据。通常的大气波前仿真方法需要通过计算结构函数，得到功率谱函数，进而得到仿真波前，但该方法存在计算速度慢，中间变量存储空间大的问题，给大口径望远镜或者长时间仿真带来很大不便。介绍了一种可行的基于迭代分形法的波前仿真方法，复杂度达到O（N），可以大大提高波前仿真的速度。

Fast Phase Screen Simulation Based on a Fractal Iterative Method

Under the influence of atmospheric turbulence, a telescope with diameter larger than atmospheric coherence length cannot reach its diffraction limit. Especially, when the telescope aperture is about 10 m or larger atmospheric turbulence will significantly distort the result image. In this case, an Adaptive Optics （AO） system can be used for alleviating the effect. Since an AO system is rather complex, it is necessary to simulate it before actually having it built. Such a simulation normally consists of several parts： the wavefront propagation to the telescope, wavefront reconstruction, wavefront control, and deformable-mirror control. For the first part, a phase screen simulation is traditionally used to provide a series of simulated turbulence layers. Most traditional methods are based on the singular decomposition of the correlation matrix derived from a structure function, their speeds are thus low and the required temporary memory is large. For a simulation of large telescope or of long time, it can be more convenient if the duration of this step is shortened. In this paper, the author adapts a method previously used in wavefront reconstruction, the Fractal Iterative Method complexity of O（N）, to substantially speed up the simulation