在采用啁啾脉冲放大技术的高功率短脉冲激光装置中，终端衍射光栅的损伤阈值是限制装置输出能力的瓶颈之一。提出了测量大口径光栅损伤阈值的方法。该方法通过在线监测采集大口径光斑的同发近场光强分布情况和相应的光栅损伤图像，并经过一系列后期图像数据处理，建立起能量与损伤点的对应关系，经过一个测试光斑便可获得所有通量下的光栅损伤特性。该测量方法对光斑均匀性没有硬性要求，为损伤测量装置中难以解决的光斑均匀性问题提出了新的应对思路和方法。

In chirped pulse amplification laser systems, the damage threshold of the final grating in the pulse compressor seriously limits the energy output. This paper proposes a measurement, by which the exact correlation between the local fluence and local damage characteristics can be established. This method collects the near-field intensity distribution of a cm-sized beam spot and its corresponding raster damage image through on-line monitoring and image processing, and then matches the pixels on the two images to each other. Finally the gray level in the damage image is converted in terms of damage density by microscope observation. It does not strictly require the spatial uniformity of the beam. Moreover, since the intensity fluctuation is taken into account, the damage densities versus the fluence can be extracted within one shot.