Open AccessTwo-dimensional Object Functions and Three-dimensional Illumination Functions: their Validity, Interaction and Utility
Author(s) -
Lewys Jones,
Peter D. Nellist
Publication year - 2014
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/522/1/012015
Subject(s) - optical transfer function , convolution (computer science) , point spread function , optics , invariant (physics) , object (grammar) , contrast transfer function , physics , scanning transmission electron microscopy , dark field microscopy , transfer function , focus (optics) , function (biology) , depth of field , artificial intelligence , computer vision , computer science , microscopy , spherical aberration , transmission electron microscopy , electrical engineering , evolutionary biology , artificial neural network , mathematical physics , biology , lens (geology) , engineering
In high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) the data is generally interpreted as the convolution of the sample's sharply-peaked object function with the intensity of the real-valued point-spread function (PSF) of the illumination. As a single image is itself necessarily two-dimensional (2D) it is typically assumed that the object function and PSF can also be accurately described as 2D; this is the so-called 2D-object imaging assumption. Here the validity of these two-assumptions is evaluated using experimental HAADF STEM focal-series. It is found that the contrast contained in each image of the focal-series is accurately described by the convolution of a focus-invariant 2D object with a 2D optical-transfer function (OTF) which describes the illumination at the focus value used for imaging. © Published under licence by IOP Publishing Ltd