Tecnai on-line help manual -- Options - UT Southwestern

<strong>Tecnai</strong> on-line help Options 157Options Software version 2The following calibration procedures are used :• Magnification calibration• Image-shift calibration• Stage calibration• Stigmator alignment• Focus/stigmator calibrationMagnification calibrationThe software will acquire an image of the cross-grating and analyse that to find the basic spacing. Theanalysis is done using an auto-correlation (at high magnifications) or an FFT (at low magnifications) inwhich the two basic vectors will be outlined by circles.An image of a cross-grating, showing the 463 nm squares.The result of the magnification calibration. The autocorrelationof the cross-grating image (zoomed in 2x) shows the centralpeak pointed at by the line (which has been added manually forclarity). The software adds the two circles around the two basevectors of the pattern. It is important that these circles arelocated at the correct positions and not e.g. at the diagonals ofthe squares. Additional circles are placed at the multiples of thebase vectors used to show how many base vectors were usedtogether for the analysis.Image-shift calibrationThe image-shift calibration procedure performs a calibration of the image shift on the CCD. Thiscalibration must be done for all magnifications in the required range (up to magnifications of ~150kx).Normally the whole range is calibrated in one procedure, but it also possible to (re)calibrate the imageshift for an individual magnification (e.g. when it appears that the calibration in the complete procedurewent wrong for one magnification, that magnification can be redone later).