受激发射损耗(STED)显微可以打破衍射极限，观测到小于200 nm 的细胞器内部结构。利用径向偏振光通过大数值孔径(NA)成像可以提高STED 系统的分辨率。计算了径向偏振光径向光强分布和纵向光强分布，并分析了数值孔径变化时径向光强分布和纵向光强分布的变化。结果表明：纵向聚焦光斑比径向聚焦光斑小，且随着NA 的增大，径向偏振光径向聚焦光斑和纵向聚焦光斑尺寸均变小，强度曲线图的半峰全宽(FWHM)也变小，光强分布更加集中。因此，增大NA 可以提高STED 显微成像系统的分辨率。

Stimulated emission depletion (STED) microscopy can break the diffraction limit, which enables scientists to discern cell details smaller than 200 nm. By radially polarized beam through the high numerical aperture (NA) lens, the resolution of STED microscopy systems can be improved. The distribution of radial intensity and axial intensity is calculated, furthermore, the effect of NA on the distribution of radial intensity and axial intensity is analyzed. The research shows that the size of axial focal spot is smaller than that of the radial focal spot, the spot size decreases when the NA increases, the full width at half maximum (FWHM) of the depletion beam decreases as well, and the intensity distribution becomes more concentrated. The increase of NA can improve the resolution of STED microscopy systems.