"stabilty" of Leginon calibrations
Added by Anonymous about 18 years ago
Hi,
I had to replace our Fastscan CCD. The Fastcan is mounted at the backside of the camera block, which also holds the 4K CCD used for Leginon. Therefore I had to rotate the camera block to unmount the Fastscan. I guess it will be impossible to bring the 4k CCD exactly back to its original position. I am now wondering how a slight change of the CCD position will interfere with Leginon. Will it be necessary to redo all calibrations? Many calibrations are based on a certain amount of e.g. image shift expressed as a shift measured in pixels. As long as the height of the CCD is not changed, the absolute value for a shift measured in pixel should not change. I fear that it is not that simple in reality.
Thorsten
Replies (1)
- Added by Jim Pulokas about 18 years ago
If the camera is rotated, then several calibrations will have to be done again:
Movement calibrations:
stage position matrix
image shift matrix
beam shift matrix
modeled stage magnification component only (model does not have to be recalculated)
Focusing calibrations:
beam tilt matrix for focus
beam tilt matrices for astigmatism
This would be an interesting feature in Leginon if we could just determine the change in angle by doing only one new calibration, and then update all other calibrations automatically. This just takes a simple matrix multiplication on all matrices. And for the modeled stage magnification component, the angle is stored directly, so it just needs an offset applied to it. I will add this to the list of things to do.
Jim