为使发射光束以会聚形式传播，进行了室外450 m和300 m激光聚焦实验。将扩束准直后的光束通过伽利略望远系统，采用精密位移台调整负透镜与正透镜间距，实现不同距离的光斑聚焦。然后用功率计测量450 m焦点处的功率均值为47.67 mW，标准偏差0.67 mW。并利用光束质量分析仪测量聚焦光斑的能量分布。进而采用Matlab中EDGE函数以及Sobel算子进行边界提取，同时进行中值滤波和53H法滤波，最后得到在给定边界提取阈值下的光斑直径为5.56 mm，标准偏差为0.24 mm；光斑中心漂移0.56 mm，占光斑直径10.43%。实验测量聚焦光斑能量损失严重，初步分析为3个因素：受限孔径衍射、激光传输衰减、像差引起光斑弥散。其中衍射和像差引起的衰减占主导，如果进行系统优化设计，可使这两项影响降至最小，通过初步实验研究，为后期进行系统设计提供数据参考。

In order to lead the laser beam transmit in the atmosphere convergently, an experiment of laser focus at a distance of 450 m and 300 m has been operated in outdoor place. The actual manipulations are as follows: Firstly, the laser is collimated by a beam expander, then the near-parallel laser beam transmits through a Galileo telescope system, and the distance between the concave lens and the convex lens can be tuned through a precise displacement platform, so the focus of the system can change due to the tiny displacement of the concave lens. Secondly, the average power of the laser spot can be measured using power meter, and the power is 47.67 mW and the standard deviation is 0.67 mW while the focal length is 450 m. Thirdly, the energy distribution is found through a laser beam analyzer. The spot images are saved by using the beam analyzer, then the saved image can be processed with Matlab software afterwards. The functions named EDGE and Sobel operator are used in the pre-processing of saving image, then method of median filter is used in the course of image de-noising and 53H filter is adopted in the signal analysis. The diameter of laser spot is obtained by the methods above, and the diameter is 5.56 mm and the standard deviation is 0.24 mm. The spot center excursion is 0.56 mm, and it is 10.43% of the total diameter of the laser spot. At last, the key factors of the energy dissipation in the focusing system can be summarized as follows: restriction of the diffraction limit, attenuation in the atmosphere, and geometrical aberration of optical system. The diffraction limit and the geometrical aberration are significant in the three factors above, so we can reduce the impact of the both factors during the design of optical system. The reliable referenced data of the design of the system can be acquired through the primary experimental research.