Get position refinement working in near-field ptycho. - #86
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…good position refinement
allevitan
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Jul 15, 2026
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Still looks good a few days later, going to merge
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Basically, position refinement has never really been working with near-field ptycho. At the last HIKA beamtime, I realized that the issue was due to the fact that the default subpixel shifting algorithm for doing the probe-object interaction returns a shifted version of the exit wave as it's output.
This is correct for far-field ptycho, where it just causes a phase ramp to appear in the wavefield at the detector, but to do near-field ptycho properly it must be shifted back. I've implemented a fix, and this also dramatically improves the quality of the near field reconstructions on test data. I updated the near-field ptycho test to reflect this, lowering the acceptable loss value from 18 to 6.