Ideal Lenses in EMs
- Practical Electron Microscopy and Database -
- An Online Book -

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This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

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An ideal lens in EMs would have no effect on the electron wave except focusing the spherical wave fronts coming from a point in the object plane to a point in the image plane. In this case, incident electrons coming from an object point converge at a single image point. In the equivalent wave picture, the spherical wave coming from a point object is transformed by the ideal lens to a spherical wave converging at the image point.

For an ideal objective lens, the incident electron probe simply forms an Airy disc in the back focal plane of the lens. This disc is the Fourier transform of the uniformly illuminated condenser aperture. Furthermore, for the ideal lenses the phase shift induced by objective lens, χ(α), is equal to 0.

 

 

 

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