[3dem] How to calculate tilt angles in Saxton acquisition scheme?

Charlotte Hamngren Blomqvist charlotte.hamngren.blomqvist at chalmers.se
Fri Mar 31 06:03:31 PDT 2017

Dear all,

I got the suggestion from two other list members that there is a typo, and that “cos(alpha_0)” should read “cos(alpha_n)”. With this change (and some now solved MATLAB-confusion regarding degrees and radians) I now managed to reproduce the tilt scheme given in the FEI-software Xplore3D, which was my objective!

Thank all of you who answered and shed light on the matter, the 3dem-list delivers once again!

If anyone is interested in the code, just let me know.

Best regards

Från: 3dem <3dem-bounces at ncmir.ucsd.edu> på uppdrag av Charlotte Hamngren Blomqvist <charlotte.hamngren.blomqvist at chalmers.se>
Datum: fredag 31 mars 2017 11:22
Till: "3dem at ncmir.ucsd.edu" <3dem at ncmir.ucsd.edu>
Ämne: [3dem] How to calculate tilt angles in Saxton acquisition scheme?

Dear all,

I am currently trying to print out all the tilt angles in a tilt series using the Saxton scheme. I find the reference Saxton 1984 unsatisfactory in how to actually calculate the values. Also, in “Electron tomography”, edited by J. Frank p. 143, it says:
“In this [Saxton] scheme, the tilt angle varies as alpha_n+1 = alpha_n + arcsin(sin(alpha_0)*cos(alpha_0)).“

As I interpret this expression, the last term on the right-hand side is a constant, and hence the tilt angles are distributed with an even angular increment throughout the series. This should not be constant!

Please, can anyone shed some light on this? What am I missing here?

Best regards,
Charlotte Hamngren Blomqvist

Charlotte Hamngren Blomqvist, PhD

Department of Physics
Eva Olsson group
Chalmers University of Technology
SE-41296 Gothenburg, Sweden
Tel +46-(0)31 772 51 80
E-mail: charlotte.hamngren.blomqvist at chalmers.se<mailto:charlotte.hamngren at chalmers.se>

Visiting address: Fysikgränd 3, room F4417b

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