7. Controls

Controls are dialogues, windows, menu items or sliders that allow to change the calculation parameters. 


7.1 Microscope dialogue

The microscope parameters, accelerating voltage, chromatic and spherical aberration coefficients, defocus (positive for under focus as the Oz axis points to the electron gun), camera length, acceptance angle,  incident beam convergence, radius of the objective aperture and position of the optical axis are all controlled by the microscope dialogue. This dialogue also have some predefined values for a range of different microscopes. Figure 7.1 shows the dialogue as it appears when the crystal has not yet been defined:

Figure 7.1 (Microscope dialogue, crystal not yet defined)

Figure 7.2 (Microscope dialogue, crystal is defined)

The upper panel offers a selection of predefined microscope parameters, the lower "Diffraction" sub-panel allows a change of the camera length, the acceptance angle and the convergence of the incident beam. The "Objective aperture" panel and the "Optical Axis" panel are employed to size and center the objective aperture and to set the optical axis position with respect to the zone axis diffraction pattern of the specimen.


7.2 Specimen dialogue

    The specimen dialogue is made of 5 panels for controlling the coarse specimen orientation (zone axis), the fine specimen orientation (Laue circle center), the number of reflections for diffraction pattern display and Blochwave based dynamical calculation (but for multislice calculation), the normal to the foil and the number of Laue zones to include in the drawings/calculations. The toolbox of the zone axis panel contains a tool to increase,, or decrease,, the number of zone axis that can be selected with the mouse and a tool that stop the rotation of the stereogram,. The rotation makes access to [u,v,w] indices possible. The tool freezes the stereogram and gives indices to the selected zone axis. Moving the mouse "down" on the stereogram provides the indices of the zone axis that the mouse points to.

Figure 7.3 (Specimen dialogue : zone axis selection)

The 4 other panels are show on figure 7.4 a,b,c and d.


Figure 7.4 a, b, c and d (Specimen settings)

These 4 panels also have controls for adjusting the Center of Laue Circle, the deviation parameter, the foil normal or the number of Laue zones. The green cross of the CLC panel can be selected and moved under mouse control, or using the little arrows, down, up, left, right and centered with . A combination of Alt, Ctrl, Shift and the keyboards arrows can also be used to adjust with high precision the CLC. The controls of the 3 other panels are pretty obvious.


7.3 Perspective window

The 3D window has been designed to use opengl. Unfortunately, the Java API to opengl is not yet available on the Macintosh so I decided not to use it also on the Windows NT PC.. This tool uses very simples graphic primitives to draw the atoms in perspective view. As soon as the Java 3-D API will be available, this tool will be upgraded. Figure 7.5 shows the 3-D tool.

Figure 7.5 (Perspective tool)

The size of the balls are controlled (for BeO) by the Be and O panels. The "Direction" panel (Figure 7.6) changes the viewer point of view, the "Distance" panel the observer -crystal distance, the resolution panel the size of the color lookup table used to draw the balls. More than one unit cell can be displayed. A frame can help to visualize the crystal structure.

Figure 7.6 (Changing the observer direction)


7.4 RPS code editor

Figure 7.7 shows the RPS code editor that is employed to define the symmetry operators of the space-group. The entered code is not verified except for the determinant of the rotation part of the symmetry operator.

Figure 7.7 (RPS code editor)

For example Si, space-group Fd3m (non centric) could also be described with space-group F-43m or just by specifying two atoms in a face centered cubic lattice. One Si will be in (0, 0, 0) and the other at (x + 1/4, y + 1/4, z + 1/4).

Figure 7.8 (RPS code for Si)


7.5 Stereographic projection window

Figure 7.9 shows a stereogram. At present it provides only the angle between 2 [u,v,w] zone axis.

Figure 7.9 (Stereographic projection)

The stop,, tool freezes the stereogram.


7.6 Image loader

jems provides a very simple format to save images (see .ems images). The "Image" + "Load" menu item loads saved .ems images, , (figure 7.10).

Figure 7.10 a, b (CBED image saved in .ems data format)

7.7 Brightness and gamma correction

Brightness and gamma correction are available during HREM image map or montage calculation. One must know that these controls acts on all displayed images.

Figure 7.11 (Default brightness and gamma correction)

Figure 7.12 (Brightness and gamma correction)