传统光束质量测量装置不能有效测量脉冲激光的M~2因子。为实时检测脉冲激光M~2因子,将正交散焦光栅和短焦透镜密接配合使用,同时测量待测光束9个不同位置处的光强分布,用二阶矩方法计算束宽,并经双曲线拟合得到被测光束的~2因子。根据高斯光束的薄透镜变换理论,分析了被测光束束腰宽度和束腰位置变化对测量精度的影响,得到了正交散焦光栅M~2因子测量系统对测量参数要求低、动态工作范围大等结论。实验测量了1064 nm Nd:YAG固体脉冲激光器单个脉冲的M~2因子、脉冲之间的M~2因子变化和光束M~2因子随电压的整体变化情况。结果表明此系统实现了对脉冲激光M~2因子的测量,并能实时检测激光工作过程中的M~2因子变化。 The traditional beam quality measuring device can not effectively measure the M ~ 2 factor of pulsed laser. In order to detect the pulsed laser M ~ 2 factor in real time, the orthogonal defocus grating and the short focal lens are used in close contact with each other. At the same time, the light intensity distribution at 9 different positions of the light beam to be measured is measured. The beam width is calculated by the second moment method. Hyperbolic fitting gives ~ 2 factors for the beam being measured. According to the thin lens transformation theory of Gaussian beam, the influence of beam waist width and beam waist position on the measurement accuracy is analyzed. The orthogonal measurement of the defocused grating M ~ 2 factor measurement system has low requirements on the measurement parameters, dynamic working range Big conclusion. The experiment measured the M ~ 2 factor of a single pulse of 1064 nm Nd: YAG solid pulse laser, the variation of M ~ 2 between pulses and the overall variation of M ~ 2 factor with voltage. The results show that this system can measure the M ~ 2 factor of pulsed laser and detect the change of M ~ 2 in real time.