利用大气湍流对光束的扩展、背投成像原理和卡塞格林望远系统，提出了一种适用于大气激光通信捕获、对准和跟踪系统的光束对准检测方法，并对其进行理论分析和实验验证。该方法利用光斑形状和光斑形心位置综合解算光束的横向偏移量和轴向偏转量，解决了一般方法无法分辨出光斑在接收焦平面的移动是由于光束横向偏移还是轴向偏转引起的问题，以及光束横向偏移量无法被精确检测的问题。实验结果表明，该方法可有效地对光束对准状态进行检测，最终实现分辨率为2.2 μrad的角度偏转量和分辨率为0.25 mm的横向偏移的检测。

A method of beam alignment detection is proposed for the acquisition, pointing and tracking system in atmospheric laser communication based on extension of beam propagating in atmospheric turbulence, back projection imaging principle and Cassegrain telescoping system. The method is analyzed theoretically and verified experimentally. Based on the shape and centroid of the beam spot, the transverse deviation and the axial deflection of the beams are calculated comprehensively. As a result, the problems with the general method are solved, one of which is that the beam spot fluctuation is caused by transverse displacement or axial displacement, and another is that the transverse displacement can not be calculated by the general method. The experimental results show that the method can detect effectively the beam alignment state, and realize finally resolution ratio with 2.2 μrad in axial deflection and 0.25 mm in transverse deviation.