以光学系统中的白宝石分光镜为研究对象，利用有限元方法和Zernike多项式对其热变形像差进行了计算和拟合，分别对入射激光的反射相移和信标光的透射相移进行了研究和分析。入射激光的反射相移的主要像差为离焦项；信标光的透射相移的主要像差包含离焦项和主球差项，而主球差的引入主要是由于在激光入射区域边界上轴向温度分布的不均匀性。利用像差比率γnm直观反映入射激光的吸收功率与反射激光和透射信标光的像差的关系，对入射激光而言，其离焦比率γ20=0.0393；对信标光而言，其离焦比率γ20=-0.0011，主球差比率γ40=-0.0033。

Based on the finite element method (FEM) and Zernike polynomial, the thermal deformation aberrations of Al2O3 mirror in an optical system are calculated. The phase shifts of reflected laser beam and transmitted beacon beam are theoretically analyzed, respectively. The defocusing is the major aberration of reflected laser beam and the defocusing and the primary spherical aberrations are the major aberrations of transmitted beacon beam. The primary spherical aberration is induced by the uneven temperature distribution at the boundary of laser irradiation area. The aberration ratio γnm is defined to describe the influence of absorption power on aberration of reflected laser beam and transmitted beacon beam. The defocusing ratio of reflected laser beam γ20 is 0.0393, and the defocusing ratio of transmitted beacon beam γ20 is -0.0011 and the primary spherical ratio γ40 is -0.0033.