光束取样光栅(BSG)是一种重要的用于光束取样诊断的衍射光学元件。以2块取样光栅代替单块光栅作为初始光学结构，运用Zemax光学设计软件采用分步优化的方法设计了具有消像差功能的光栅对结构，此方法比采用Matlab语言编程计算的方法消像差更快捷、更灵活，同时可以验证程序计算结果的正确性。设计结果显示：再现的会聚光经2块光栅衍射后在像平面上点列图中的均方根半径仅为0.506μm，单块取样光栅的均方根半径则为7.284μm，说明2块光栅能够做到像差互相矫正，其像质明显好于单块取样光栅。另外，设计出的双光栅光学系统，可进行远场光斑质量检测，为激光束性能的在线诊断提供了行之有效的技术支持。

Beam sampling grating is an important diffraction optical element for beam sampling diagnosis. Using two gratings as initial optical structure instead of single grating, an aberration-free structure was designed by using Zemax optical design software, which is a faster and more flexible tool for designing aberration-free grating-pair than Matlab. The method can verify the calculation result of the program. Design results show that the RMS radius of the converging light diffracted by two gratings is only 0.506μm in spot pattern image, compared to 7.284μm for the single grating, which indicates that two gratings can reduce aberration and improve image quality. Besides, the optical system can be used to detect far field beam, which provides effective technical support for on-line diagnosis for laser beam characteristics.