通过复合电磁同心球系统的理想模型, 探讨了近轴方程特解的近似表示及其近轴横向像差的求解。导出了复合电磁同心球系统近轴方程两个特解的近似表达式, 在此基础上导出了一些特殊类型的近轴横向像差的表达式, 如近轴色球差、近轴放大率色差和近轴各向异性色差。结果表明, 由两个特解的近似解推导得到的近轴横向像差与使用精确解的结果完全一致, 由此证明近似解求解近轴横向像差的方法是可行的。

The approximate expressions of special solutions of the paraxial equation and its paraxial lateral aberrations have been explored by an ideal model of a combined electromagnetic concentric spherical system in this paper. The approximate expressions of two special solutions of the paraxial equation in a combined electromagnetic concentric spherical system have been derived, and on this basis, some special types of paraxial lateral aberrations such as paraxial spherical-chromatic aberration, paraxial magnification chromatic aberration, and paraxial anisotropic chromatic aberration have been deduced. The results show that the paraxial lateral aberration deduced from the approximation of two special solutions is exactly the same as through the exact solution, which proves the feasibility of the approximation to solve the paraxial lateral aberration.