SIRA calibration

Author: John Minter (jrminter at rochester dot rr dot com)

Precise calibration of electron images is greatly aided by IPLT. The following script was developed to calibrate images of the SIRA 2160 line/mm grating. The basic script was patterned after Andreas Schenk’s extract subimage tutorial and the examples in the ex module. Execute the script with ‘giplt analyze_sira.py’ to display the main dialog (figure 1).

Figure 1: Main dialog

Notice the task-bar on the left. Press the ‘Load Image’ button and choose the desired image file from the dialog. The routine displays the image (figure 2).

Figure 2: SIRA displaying image

The routine displays the full image and computes the largest FFT that will fit in the image. Pressing the ‘Get Spacing’ dialog (figure 3) displays a dialog that presents the default spacing for the 2160line/mm grating and lets the user change it if a different spacing was used.

Figure 3: Get spacing dialog

Pressing the “Analyze Image” crops a region from the center of the image (figure 4)

Figure 4: Cropped image

and computes the power spectrum, and fits a lattice (figure 5). One can normalize the display with the usual commands by selecting a region and pressing N. It also outputs the results to the result window window and to a file with the image file name with ‘_ana.txt’ appended.

Figure 5: Fourier transform

see the source code analyze_sira.py and the test image sira.tif.