Image inversion bug in Z-focus
Added by Anonymous almost 20 years ago
Hi Everyone,
I experienced a strange bug within MSI yesterday.
The node was working properly, it was taking the initial image and then doing the beam tilt and taking another image for correlation.
The problem was that the second image was inverted. This rendered z-focus completely useless because it was trying to correlate an image with a negagtive. I saw a nice correlation peak, but it was black instead of white.
Has anyone seen this image inversion problem? I restarted the client, started a new session and the problem persisted.
Thanks,
Jonny
Replies (1)
image inversion in autofocusing - Added by Anchi Cheng almost 20 years ago
The inversion is caused by your beam being clipped partially by the objective aperture. Threee possible reasons:
1. Objective aperture is off-centered.
2. Objective aperture is too small for the beam tilt applied.
3. Beam tilt is not centered before you started tilting.
The third problem is more common during a session because users are normally pretty good with centering apertures and the match between aperture size and beam tilt should be taken care of the very first session. The third one normally happens because leginon is forced to quite in the middle of a beam tilting. It does not remember the original value and does not reset it before the next restart. You will just have to reset it by redo rotation centering. Do remember to adjust to U-centric focus first before doing this, though.