ELECTRON HOLOGRAPHY - OPTIMUM POSITION OF THE BIPRISM IN THE ELECTRON-MICROSCOPE

More for technical rather than for physical reasons, off-axis electron holograms are usually taken with the biprism positioned in the select ed area aperture holder. Since the quality of the holograms has to be optimized in every respect for high performance electron holography, t he influence of the biprism position in the electron microscope on the hologram quality is studied in more detail. The results show that the re is an optimum geometric arrangement of the biprism in the column of the electron microscope characterized by a minimum biprism deflection angle required for a hologram with given width and fringe spacing.