Chapter

Phase contrast, contrast transfer function (CTF) and high‐resolution electron microscopy (HRTEM)

Xiaodong Zou, Sven Hovmöller and Peter Oleynikov

in Electron Crystallography

Published in print August 2011 | ISBN: 9780199580200
Published online January 2012 | e-ISBN: 9780191731211 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780199580200.003.0006

Series: International Union of Crystallography Texts on Crystallography

Phase contrast, contrast transfer function (CTF) and high‐resolution electron microscopy (HRTEM)

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Phase contrast, the contrast transfer function (CTF), kinematical scattering and the weak-phase object approximation are central concepts for image formation. The physics is described in great detail with one hundred formulas, leading up to the fundamental relation between electron wave phases and structure factor phases. Through-focus series are discussed as a means to collect all the information from a structure projection – some data may be lost in one HRTEM image because it falls on a node (= zero cross-over of the CTF) but this data can be obtained from another image taken at another defocus value. It is shown that singly and doubly scattered electron waves are transferred differently by the objective lens to the image. Thus, they can be separated in image processing, especially if a few images of different focus are combined.

Keywords: phase contrast; contrast transfer function; CTF; kinematical scattering; phase object; weak-phase object; image formation; through-focus series; multiple scattering; Scherzer defocus; structure factor; high-resolution electron microscopy; structure image

Chapter.  12858 words.  Illustrated.

Subjects: Crystallography

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