Filtering Chromatic Aberration for Wide Acceptance Angle Electrostatic Lenses

Chromatic aberration is a major issue for imaging mainly with large acceptance angle electrostatic lenses. Its correction is necessary to take advantage of the outstanding spatial and angular resolution that these lenses provide. We propose a method to eliminate the effect of chromatic aberration on the measured images by determining the impact resulting from higher and lower kinetic energies. Based on a spectral image sequence and a matrix, which describes the transmission function of the lens, a system of linear equations is solved to approximate the 2D spectral intensity distribution of the sample surface. We present the description of our method and preliminary test results, which show significant contrast and image quality improvement. The presented algorithm can also be applied as a software-based energy analyzer.