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.
X-ray near-field ptychography for optically thick specimens
Pierre Thibault
2015-01-01
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.Pubblicazioni consigliate
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