TEM resolution

[Philip Koeck]

Hallo everybody,

I've started wondering about what actually the point resolution of
a TEM in phase-contrast imaging is.

>From Raleigh's criterion I would conclude that for a typical 120 kV
TEM with a numerical aperture of about 20 mrad distances larger than
about  2 Angstrom or 'density waves' with a wavelength longer than
2 Angstrom simply cannot be resolved.

In Scherzer defocus the Phase Contrast Transfer Function (PCTF) has its
first zero at about the same resolution but there seems to be
information
at higher frequencies (even if it is inverted in contrast).

Which is the true resolution limit?

Yours sincerely,

Philip

-- 
Philip Koeck
Karolinska Institutet
Dept. of Bioscience
Novum
S-14157 Huddinge
Sweden
Tel.: +46-8-608 91 86
Fax.: +46-8-608 92 90
Email: Philip.Koeck at csb.ki.se
http://www.csb.ki.se/em
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