Further comparisons between the conventional and the modified Schwarzschild objectives

The performance of the modified Schwarzschild objective configuration in comparison with the ordinary configuration is further investigated, completing the analysis presented in a previous work, which was concerned with the trend of the image-plane resolution against the numerical aperture. Here, we compare the third-order aberration coefficients in both configurations, illustrating the dependence of each coefficient on both the on-axis object position and the numerical aperture. This conveys the tolerances of the two configurations to lateral and mirrors’ axial misalignments. Also, the nonconcentric mirror configuration is considered and the relative performance confronted with that of the modified configuration.