Aberration Correction in Electron Microscopy

Most presently available fixed-beam transmission electron microscopes (FBEM) yield a resolution limit close to the theoretically predicted value which is determined by diffraction and by the spherical aberration of the objective lens. The larger the aperture the better is the collection efficiency of the elastically scattered electrons forming the image. To increase the useful objective aperture it is necessary to overcome the spherical aberration. In the case of a phase contrast image it is possible, at least in principle, to compensate the effect of the spherical aberration by subsequent holographic processing of the electron micrograph.