Electron microscope with an energy filter having hexapole correctors which are coupled with a projective system downstream of the energy filter

摘要

The invention is directed to an electron microscope having a magnetic energy filter. The energy filter has four deflection regions and seven hexapole correctors for correcting the aberrations of the energy filter. A projection system is mounted downstream of the filter. With the projection system, the achromatic image plane is selectively imaged onto the CCD camera for energy-filtered object imaging or the dispersion plane is imaged on a CCD camera for spectrum detection. For an object registration, the hexapoles are so excited that all geometric aberrations of the second order are corrected in the achromatic image plane and in the dispersion plane. For the spectrum imaging, the excitation of three hexapoles is so changed that the axial chromatic aberration of the filter is corrected while maintaining the correction of the spherical aberration in the achromatic image plane and while maintaining the correction of all geometric errors of the second order in the dispersion plane.