Numerical Techniques for Ray Tracing and Calculation of Aberrations

Abstract

Once the focusing fields have been determined (see Chapter 3), one can proceed to trace the particle trajectories according to Chapter 4 and then calculate the aberration coefficients (Chapter 5). Although it is quite possible to solve the general ray equation (4-21) directly by numerical methods, usually we restrict the treatment to paraxial trajectories, which are totally adequate t o determine the aberrations as well. Then we only have to know the axial potential and flux density distributions to gain complete information about the optical properties of the given focusing system.