Fig. 3 shows the basic arrangement of an interference electron microscope. The electron biprism consists of a fine, positively charged electric filament (represented as a dot in the figure) bracketed by two plate electrodes at ground potential. The filament, generally not more than 1 μm in diameter, is usually a gold-coated quartz fiber. By placing the specimen off-axis in the electron beam, the diffracted specimen wavefront and the reference wavefront combine to create the hologram.
