Off-axis holography with a crystal beam splitter

A new method for off-axis holography is presented with a beam splitter crystal in the illumination system of the electron microscope and a biprism in the selected area aperture plane. The method allows high resolution off-axis holography, up to the information limit, combined with a high current level. This high current level can be used to reduce the measurement time or the coherence of the source. Pilot experiments are carried out with a beam splitter crystal located slightly above the specimen. The experiments, performed in a CM300 FEG, show that holograms with a large number of fringes can be obtained with contrast values between 10% and 31%, independent of the coherence of the illuminating beam and with measurement times around 1 s. The measured current values are between 100 and 320 pA. The main factor presently hampering the formation of high contrast hologram fringes is the quality of the beam splitter.