为了评估万焦耳级激光装置不同打靶透镜构型的远场光束质量, 采用弱光取样、分束放大成像的探测方法, 在横向放大系数相同而光强衰减系数不同的条件下, 通过两台16位科学CCD在主瓣光路和旁瓣光路对3ω激光束的焦斑进行采集；基于纹影测量激光焦斑数学模型, 获得了动态范围为1 151.7∶1的远场焦斑重构图像；并对CCD动态范围、分束光路相对放大系数、系统噪声等因素对焦斑诊断的影响进行了分析.实验表明, 该方法能够实现高动态范围远场焦斑的精确测量, 对于重构图像的拼接边缘误差小于1 pixel, 满足打靶要求.

In order to evaluate the far-field beam quality of 10 kJ-level laser facility with different off-axis wedged focus lens, by utilizing the methods of the sampling of weak light beams and amplification imaging of splitting beams, the focal spot data of 3ω laser was collected by two 16-bit scientific-grade CCD cameras in the paths of main lobe and side lobe under the conditions of that the lateral magnification coefficient is the same but the intensity attenuation coefficient is different. One CCD obtained main lobe of far-field image, the other acquired its side lobe. The far-field focal spot was reconstructed based on the mathematical model of schlieren method, and the dynamic range is 1 151.7∶1. The influence of CCD dynamic range, relative magnification ratio and system noise on reconstructed image was analyzed. Experimental results show that, the method can achieve a high dynamic range far-field accurate measurement of focal spot, the stitching error is less than one pixel, which meets the requirements of targeting experiments in experimental precision.