X-ray near-field ptychography for optically thick specimens

Stockmar, Marco, Zanette, Irene, Dierolf, Martin, Enders, Bjoern, Clare, Richard, Pfeiffer, Franz, Cloetens, Peter, Bonnin, Anne and Thibault, Pierre (2015) X-ray near-field ptychography for optically thick specimens. Physical Review Applied, 3 (1), [014005]. (doi:10.1103/PhysRevApplied.3.014005).

Abstract

Inline holography, like other lensless imaging methods, circumvents limitations of x-ray optics through an a posteriori phase-retrieval step. However, phase retrieval for optically thick, i.e., strongly absorbing and phase shifting, specimens remains challenging. In this paper, we demonstrate that near-field ptychography can be used to efficiently perform phase retrieval on a uranium sphere with a diameter of about 46  μm, which acts as an optically thick sample. This particular sample was not accessible by inline holography previously. The reconstruction is based on a statistical model and incorporates partial coherence by decomposing the illumination into coherent modes. Furthermore, we observe that phase vortices, which can occur as artifacts during the reconstruction, pose a greater challenge than in far-field methods. We expect that the methods described in this paper will allow production of reliable phase maps of samples which cannot be accessed by inline holography.

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Contributors

Author: Pierre Thibault

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