The HRSTEM Imager loads a HAADF Object Intensity image (Fig. 2c) and performs a convolution with the
Optical Transfer Function of the microscope (Fig. 2b). The HRSTEM imager uses the metric
and geometry stored in the HAADF intensity image. This makes possible to control the probe shape
(Fig. 2b) by introducing lens Aberrations up to order 8 (Figures 3a,
3b).

Figure 1 HAADF imager, object intensity loaded (graphene).
The HAADF image, Probe and Object intensity tabs display the HAADF image (Fig. 2a),
the Probe shape (Fig. 2b) and the Object intensity (Fig. 2c) respectively.
The slider controlling the HAADF gain is placed on the Imaging pane (2d).
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Figure 2a HAADF image. |
Figure 2b Probe image and profile. |
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Figure 2c Object intensity. |
Figure 2d Imaging controls. |
The imaging parameters controls, optical Aberrations, coherence, drift, ... are grouped in several panes:
Aberrations: as sliders (Fig. 3a) or as a table (Fig. 3b).
Coherence: as sliders (Fig. 3c).
Drift and Noise: as sliders (Fig. 3d).
Microscope: as sliders (Figures 4a, Fig. 4b).
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Figure 3a Sliders to set Aberrations. |
Figure 3b Table of Aberrations. |
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Figure 3c Coherence controls. |
Figure 3d Drift and noise controls. |
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Figure 4a Microscope controls set 1. |
Figure 4b Microscope controls set 2. |
The HADDF intensity map approximates the inverse Fourier transform of power spectrum of the High Angle Annular Dark Field
inelastically scattered electrons.
A popup menu is attached to each figure. It allows to change the color lookup table, to tabulate
the image values or to display the image in 3-D (Figures 4, 5).
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Figure 5a Popup menu attached to the HAADF intensity image. |
Figure 5b Popup menu attached to the Probe intensity image. |
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Figure 5c 3-D view of the probe. |
Figure 5d Popup menu attached to the object intensity. |
Notes
The Aberrations coeeficients can be changed either using sliders (on the left) or directly in the text
fields on the right. When selected the text field background color is yellow. When the text field is
selected (yellow color) using the:
- ↑ Increases the aberration value.
- ↓ Decreases the aberration value.
The formula text field displays the mathematical description of the aberration in orthogonal coordinates.
The notation adopted for the optical Aberrations coefficent follows either the notation of
Krivanek and Haider, as well as a notation describing the wavefront aberration (Wnm). The wavefront
aberration is simpler to remember since n provides the power of the spatial frequency and m the rotational symmetry.
For example W40 is the spherical aberration coefficient C30 or C3 that describes
the deformation of the wavefront:

(no angular dependence).
As another example three fold astigmatism W23 (Krivanek) or A2 (Haider) is labelled
W33 with formula:
that clearly shows that this aberration scales as the third power of the spatial frequency (u3)
and has a rotational symmetry 3.
HAADF image is pretty sensitive to focus changes (6a, 6b).
A larger defocus completey blur the HAADF image (6c, 6d).
It is not possible to simulate images with a very large defocus since under such a condition the probe will
extend farther than the Nyquist limit and consequently the HAADF images will contains many artefacts.
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Figure 6a HAADF image intensity. |
Figure 6b Probe image. |
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Figure 6c HAADF image intensity. |
Figure 6d Probe image. |