Stigmatic condition for electrostatic core-lens by using diagram of axis intercept

This paper clarifies a method for finding the stigmatic operating condition of electrostatic core-lenses applied to a large tilting optical system. The core-lens has many operating parameters such as configurations of electrodes and their voltage and it is important that how to search the suitable parameters systematically. For this purpose, the diagram of axis intercept is newly defined and applied. It is shown that the core-lens can realize the negative aperture aberration impossible for usual round lenses.