Raster Grid Pathology and Other Ptychographic Ambiguities
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Ptychography with an unknown probe and object is analyzed for the raster scan scheme. The block phases are shown to form an arithmetic progression and the complete characterization of the raster scan ambiguities is given, including: First, the periodic raster grid pathology of degrees of freedom proportional to the squared stepsize and, second, a non-periodic, arithmetically progressing phase shift from block to block. Finally a simple mechanism is demonstrated to remove all ambiguities other than the scaling factor and the affine phase ambiguity which are inherent to any blind ptychography.
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