大气湍流对有限带宽波前补偿系统的影响

Effect of Atmospheric Turbulence on the Finite bandwidth of a Wavefront Compensative System

利用高灵敏度湍流探空仪的测量结果，给出了几种典型情况下大气湍流的特征模式。着重讨论冬、夏两季平面波通过大气湍流对有限带宽的自适应光学补偿系统的影响。分析了当自适应光学闭环的频率响应传递函数为Ｈ（ｆ）时，不同带宽波前系统的补偿效果。结果表明：当系统带宽为４０Ｈｚ时，Ｓｔｒｅｈｌ比可高于０．８５。冬季虽高空风速强于４０ｍ／ｓ，但Ｓｔｒｅｈｌ比没有显著减小。

In this paper, several models of the vertical profile of C 2 n were given using home made high sensitivity micro temperature apparatus. We discussed mainly the effect of atmosphere turbulence on the finite bandwidth of a wavefront compensative system when the wavefront phase of the plane wave went through the atmospheric turbulence in summer or in winter. The Strehl ratios for various bandwidths of the wavefront compensative system were given when a closed loop transfer function H(f) was used as a model of a closed loop control system that processed the turbulence induced wavefront distortions. For the low control bandwidth f c=40 Hz, the Strehl ratio could be larger than 0.85. Although the wind speed of the free atmosphere in the winter was 40.0 m/s, much stronger than in summer, the difference of the Strehl ratio in the two seasons was small.