基于二元光学元件的相位延迟表达式，推导出谐衍射光学元件在光束斜入射时的相位延迟表达式以及衍射效率表达式，定性分析了谐衍射光学元件衍射效率与光束入射角度的关系.分析表明：在可见光范围内，谐衍射光学元件的谐波长随入射角增大而向长波方向漂移，并且短波部分变化较长波部分更为明显；对于单色光，随着入射角变化，出现不同衍射级次更替现象；对于普通衍射元件，随入射角增大波峰漂移速度远大于谐衍射元件衍射波峰速度；入射角对短波段的衍射效率影响更大.

According to phase shift method of binary optics, the phase delay expression and the diffraction efficiency of Harmonic Diffractive Optical Element (HDOE) at oblique incidence were derived. And the relationship between the diffraction efficiency and the beam incident angle was qualitatively analyzed. The results show that in the visible spectral range, resonant wavelength of HDOE becomes longer with incidence angle increasing, otherwise in the short-wave part wave crest drift more violently; with incident angle of monochromatic light increasing, the diffraction order sequence appears; with the incidence angle increasing, the wave crest of ordinary binary element drift much faster than HDOE; beam incidence angle has a greater impact on diffraction efficiency of short wave.