Electron holography

[4] Usually, high spatial and temporal coherence (i.e. a low energy spread) of the electron beam are required to perform holographic measurements.

Positive voltage deflects the electron waves so that they overlap and produce an interference pattern of equidistantly spaced fringes.

The resulting complex image consists of the autocorrelation (center band) and two mutually conjugated sidebands.

Only one side band is selected by applying a low-pass filter (round mask) centered on the chosen side-band.

[6]It is important to shield the interferometric system from electromagnetic fields, as they can induce unwanted phase-shifts due to the Aharonov–Bohm effect.

An illustration to off-axis electron holography in transmission electron microscope.
Inline electron holography scheme.
At this image one can see the electron hologram of a latex sphere on a carbon coating with gold particles (black dots), at the lower part of the image is vacuum. The biprism is approx above the vacuum edge; parallel to this edge one can see the phase planes of the interferogram, which is part of the image and from which the phase information can be extracted.