点衍射干涉仪中小孔对准误差是影响衍射参考波面质量最主要的误差源。基于瑞利索末菲矢量衍射理论，建立了非傍轴高斯光束经小孔衍射的严格数学描述，对不同对准误差下的小孔衍射波面误差进行了分析，在分析中特别考虑了会聚光斑大小的影响。研究表明：小孔对准误差的引入使得衍射波面偏差迅速增大，且衍射波面偏差随对准误差的增大呈线性增长；相同对准误差下，衍射波面偏差随会聚光斑半径的增大而减小，要获得同等衍射波面偏差，允许的对准误差随会聚光斑的增大呈近同倍数增长。给出了0.5~3 μm小孔在不同会聚光斑直径和小孔对准误差下的衍射波面误差分布数据，研究结果可为点衍射干涉仪中会聚透镜的选取、小孔对准精度要求的确定以及小孔衍射波面误差的估计提供重要参考数据。

Alignment error of the pinhole is the main error factor that affects the quality of diffraction reference wavefront in a point diffraction interferometer. Based on Rayleigh-Sommerfeld vector diffraction theory, a theoretical model of non-paraxial Gaussian beams diffracted through a pinhole is established, and diffraction wavefront error caused by different alignment errors is numerically analyzed. The influence of focusing spot size is especially considered. The research results show that the introduction of even a small alignment error can make the diffraction wavefront error increases quickly, diffraction wavefront error increases linearly as the alignment error increases; under same alignment error, the bigger the focusing spot size, the smaller the diffraction wavefront error. In order to reach the same level of diffraction wavefront accuracy, the allowable alignment error increases nearly in same multiples as the focusing spot size increases. Diffraction wavefront error distribution of 0.5~3 μm pinholes in different spot size and alignment error are acquired in the analysis, it can provide favorable reference data for the selection of focusing lens, determination of pinhole alignment accuracy requirements and the evaluation of diffraction wavefront error in certain condition.