使用衍射光学元件（DOE）作为投影光刻照明系统实现离轴照明（OAI）的光束整形匀光器件，能够在保持较高照明效率的基础上精确控制OAI光束的形状及光强分布。在矢量角谱传输方法的基础上，建立了投影光刻用DOE的矢量分析模型，并对标量方法设计的DOE在偏振照明情况下的匀光与整形性能进行了分析。分析结果表明DOE在大角度衍射、单元尺寸与工作波长相近条件下，一般标量近似条件已不满足，仍采用标量迭代方法进行DOE设计，则计算结果存在较大误差。

Diffractive optical element (DOE) which maintains beam shape and intensity distribution precisely with high efficiency of the source is used as the beam shaping and smoothing element for the off-axis illumination (OAI) of lithographic system. A vector analyzing model of DOE for lithography is established based on vector angular-spectrum method, and the performance of DOE designed by using scalar algorithm such as uniformity and beam shaping is analyzed. The results show that the scalar approximation cannot fit the requirement when the diffraction angle of DOE is large and the dimension of DOE is reduced to the working wavelength, or large error of caculations will be caused.