C. J. Humphreys, J. C.H. Spence

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Resolution and coherence criteria in transmission electron microscopy are discussed, and a contrast transfer function (CTF) is derived for coherent spherical wave illumination. Assuming a disc source, the CTF for spherical wave illumination is identical to that for convergent illumination from an incoherent source. Assuming a Gaussian source, the CTF decays more rapidly for a spherical wave than for an incoherent convergent beam. The implications for high resolution microscopy using a field emission gun are considered and it is shown that, owing to both the reduced energy spread and the increased brightness of a field emission source, point-to-point resolutions of better than 1 A should be possible using existing technology. A simple method of incorporating the CTF in image calculations for perfect or imperfect crystals, which does not involve the usual Fourier transforming, is also given.

Original languageEnglish (US)
Pages (from-to)125-142
Number of pages18
JournalOptik (Jena)
Issue number2
StatePublished - Jan 1 1981
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering


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