26 October 2004 Hard x-ray phase imaging and tomography with a grating interferometer
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Abstract
We have developed a two-grating interferometer for hard X rays that can be used for phase imaging and tomography. A silicon phase grating positioned just downstream of the object under study splits the distorted wavefront into essentially a positive and a negative first-order beam. At a given distance from this beam-splitter grating, where the two beams still mostly overlap, they form a pattern of interference fringes that is distorted according to the wavefront distortions. The fringes may be finer than the resolution of an area detector used to record the signal, but an absorption grating with suitable pitch, put in front of the detection plane, allows the detection of intensity variations that correspond to the derivative of the wavefront phase taken along the direction perpendicular to the grating lines. A combination of this technique with the phase-stepping method, in which several exposures are made which differ in the phase of the fringe pattern, allows to eliminate effects of non-uniform intensity due to inhomogeneous illumination and edge-enhancing inline phase contrast. Several examples of tomograms taken under different experimental conditions are shown, including a polychromatic "pink-beam" setup.
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Timm Weitkamp, Timm Weitkamp, Ana Diaz, Ana Diaz, Bernd Nohammer, Bernd Nohammer, Franz Pfeiffer, Franz Pfeiffer, Torben Rohbeck, Torben Rohbeck, Peter Cloetens, Peter Cloetens, Marco Stampanoni, Marco Stampanoni, Christian David, Christian David, } "Hard x-ray phase imaging and tomography with a grating interferometer", Proc. SPIE 5535, Developments in X-Ray Tomography IV, (26 October 2004); doi: 10.1117/12.569643; https://doi.org/10.1117/12.569643
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