Correction circuit for deflection aberrations in electron microscopes - compensates third-order energy errors, coma, astigmatism and distortion, by induced distortion from focussing system

摘要

The correction circuit, for deflection aberrations in electron microscopes, corrects given third order or more aberrations. Energy errors and coma are corrected by setting positional angle and exiciting and deflection system comprising two deflection components. The astigmatism of the first component is compensated by the astigmatism of the second such that isotropic astigmatism is adjusted by the position and anisotropic astigmatism by the field length of the first deflect on component. Distortion caused by the deflection components is compensated by the focussing system's induced distortion.