State of the Art of X-ray Speckle-Based Phase-Contrast and Dark-Field Imaging

Zdora, Marie-Christine

doi:10.3390/jimaging4050060

Cited by 105 publications

(104 citation statements)

References 178 publications

(263 reference statements)

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“…The shift (s) and attenuation (M) signals could then be extracted by adding and subtracting Eqns. (29) and (30), giving consistent results as in the scenario described above for grating interferometry.…”

Section: Edge Illuminationsupporting

confidence: 82%

Applying the Fokker–Planck equation to grating-based x-ray phase and dark-field imaging

Morgan

Paganin

2019

Sci Rep

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X-ray imaging has conventionally relied upon attenuation to provide contrast. In recent years, two complementary modalities have been added; (a) phase contrast, which can capture low-density samples that are difficult to see using attenuation, and (b) dark-field x-ray imaging, which reveals the presence of sub-pixel sample structures. These three modalities can be accessed using a crystal analyser, a grating interferometer or by looking at a directly-resolved grid, grating or speckle pattern. Grating and grid-based methods extract a differential phase signal by measuring how far a feature in the illumination has been shifted transversely due to the presence of a sample. The dark-field signal is extracted by measuring how the visibility of the structured illumination is decreased, typically due to the presence of sub-pixel structures in a sample. The strength of the dark-field signal may depend on the grating period, the pixel size and the set-up distances, and additional dark-field signal contributions may be seen as a result of strong phase effects or other factors. In this paper we show that the finite-difference form of the Fokker–Planck equation can be applied to describe the drift (phase signal) and diffusion (dark-field signal) of the periodic or structured illumination used in phase contrast x-ray imaging with gratings, in order to better understand any cross-talk between attenuation, phase and dark-field x-ray signals. In future work, this mathematical description could be used as a basis for new approaches to the inverse problem of recovering both phase and dark-field information.

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Section: Edge Illuminationsupporting

confidence: 82%

Applying the Fokker–Planck equation to grating-based x-ray phase and dark-field imaging

Morgan

Paganin

2019

Sci Rep

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“…Equation (6) serves well in the limit where H and w 1=2 H approach 0 and is employed in a number of XST-based techniques. For example, in the UMPA approach [see equation 9of Zdora (2018)] the governing equation is given by…”

Section: The Speckle Tracking Approximationmentioning

confidence: 99%

“…Others in the XST field use correlation-based approaches, where the geometric mapping between a small region of the distorted image and the reference is determined by the point which provides the greatest correlation coefficient (Zdora, 2018). The approach outlined in this work was employed because of its simplicity and ease of implementation.…”

Section: Rèðxþ ¼mentioning

confidence: 99%

“…Additionally, XST can be employed to measure the phase profile of an object's transmission function. Thanks to the simple experimental setup, high angular sensitivity and compatibility with low-coherence sources, this method has since been actively developed for use in synchrotron and laboratory light sources [see Zdora (2018) for a recent review].…”

Section: Introductionmentioning

confidence: 99%

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Ptychographic X-ray speckle tracking

et al. 2020

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A method is presented for the measurement of the phase gradient of a wavefront by tracking the relative motion of speckles in projection holograms as a sample is scanned across the wavefront. By removing the need to obtain an undistorted reference image of the sample, this method is suitable for the metrology of highly divergent wavefields. Such wavefields allow for large magnification factors that, according to current imaging capabilities, will allow for nanoradian angular sensitivity and nanoscale sample projection imaging. Both the reconstruction algorithm and the imaging geometry are nearly identical to that of ptychography, except that the sample is placed downstream of the beam focus and that no coherent propagation is explicitly accounted for. Like other X-ray speckle tracking methods, it is robust to low-coherence X-ray sources, making it suitable for laboratory-based X-ray sources. Likewise, it is robust to errors in the registered sample positions, making it suitable for X-ray free-electron laser facilities, where beam-pointing fluctuations can be problematic for wavefront metrology. A modified form of the speckle tracking approximation is also presented, based on a second-order local expansion of the Fresnel integral. This result extends the validity of the speckle tracking approximation and may be useful for similar approaches in the field. research papers J. Appl. Cryst. (2020). 53, 760-780 Andrew J. Morgan et al. Ptychographic X-ray speckle tracking 761 research papers J. Appl. Cryst. (2020). 53, 760-780 Andrew J. Morgan et al. Ptychographic X-ray speckle tracking 763 ! ; ð64Þ research papers J. Appl. Cryst. (2020). 53, 760-780 Andrew J. Morgan et al. Ptychographic X-ray speckle tracking 773

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“…We carried out wavefront measurements to characterize the aberrations of the MLLs by two different methods: ptychography [40][41][42] and speckle tracking [34,43]. Both methods were carried out in the "nanoprobe" configuration.…”

Section: Wavefront Characterization and Resolutionmentioning

confidence: 99%

Multilayer Laue lenses at high X-ray energies: performance and applications

Murray¹,

Pedersen²,

Mohácsi³

et al. 2019

Opt. Express

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X-ray microscopy at photon energies above 15 keV is very attractive for the investigation of atomic and nanoscale properties of technologically relevant structural and bio materials. This method is limited by the quality of X-ray optics. Multilayer Laue lenses (MLLs) have the potential to make a major impact in this field because, as compared to other X-ray optics, they become more efficient and effective with increasing photon energy. In this work, MLLs were utilized with hard X-rays at photon energies up to 34.5 keV. The design, fabrication, and performance of these lenses are presented, and their application in several imaging configurations is described. In particular, two "full field" modes of imaging were explored, which provide various contrast modalities that are useful for materials characterisation. These include point projection imaging (or Gabor holography) for phase contrast imaging and direct imaging with both bright-field and dark-field illumination. With high-efficiency MLLs, such modes offer rapid data collection as compared with scanning methods as well as a large field of views.

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State of the Art of X-ray Speckle-Based Phase-Contrast and Dark-Field Imaging

Cited by 105 publications

References 178 publications

Applying the Fokker–Planck equation to grating-based x-ray phase and dark-field imaging

Applying the Fokker–Planck equation to grating-based x-ray phase and dark-field imaging

Ptychographic X-ray speckle tracking

Multilayer Laue lenses at high X-ray energies: performance and applications

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