Laboratory-based edge-illumination phase-contrast imaging: Dark-field retrieval and high-resolution implementations

Abstract

Abstract-Edge illumination is an X-ray phase-contrast imaging technique capable of quantitative retrieval of phase and amplitude images. The retrieval of the ultra-small-angle X-ray scattering was recently developed and implemented with the area-imaging counterpart of an edge-illumination system, sometimes referred to as coded-aperture. This is an incoherent and achromatic technique, well suited for translation of the potential of X-ray phase contrast imaging into efficient laboratory-scale setups. We report on recent advances of these developments along two main directions. One relates to the expansion of the technique with respect to the data analysis and corrections that are required when non-ideal optical elements are used and optimized sampling strategies. The second is directed towards high-resolution and high-energy implementations. A laboratory-based prototype for high-energy X-ray phase-contrast microscopy was built and its performance was modelled and experimentally characterized.

Detection of individual sub-pixel features in edge-illumination x-ray phase contrast imaging by means of the dark-field channel

“…of the sample by measuring the illumination curve with and without the sample in place [26][27][28]. While this procedure yields the above three images sampled at a pitch equal to the detector pixel size, finer sampling pitches can also be accessed by displacing the sample in sub-pixel steps (sample dithering in figure 2(a)), repeating the above procedure at each step, and interleaving the subsequent acquisitions to obtain the oversampled images.…”

“…X-ray phase contrast imaging (XPCI) can obtain high contrast for samples presenting a weak x-ray attenuation, and consequently it has been actively studied over recent years. Several XPCI approaches have been developed to date, including free-space propagation (propagation-based imaging) [1][2][3][4][5][6], Bonse-Hart interferometry (crystal interferometry) [7][8][9], analyzer-based imaging (sometimes referred to as diffraction-enhanced imaging) [10][11][12][13][14], Talbot interferometry (grating-based imaging) [15][16][17][18][19][20][21][22] and edge illumination (EI, sometimes referred to as the coded aperture technique) [23][24][25][26][27][28][29]. Details on the various approaches can be found in a series of reviews that were recently published [30][31][32].…”

“…Of these methods, Talbot interferometry and EI have attracted particular attention due to the possibility to implement them with extended sources, which is one of the key requirements in terms of translation from high-end synchrotron facilities to standard laboratories and, ultimately, commercial systems. This paper focuses on EI, mostly because of its implementation not requiring source collimation [24][25][26][27][28], its achromatic properties [33], and its robustness against vibrations and thermal drifts [34]. The edge-illumination technique was first developed in Elettra Synchrotron, Italy in the late 1990s [35].…”

“…The edge-illumination technique was first developed in Elettra Synchrotron, Italy in the late 1990s [35]. To date, many experimental results have been reported, mostly based around applications in the biohealth and industrial fields [23][24][25][26][27][28][29]. These highlight the technique's potential in terms of application to market, within which hard x-ray dark-field imaging with incoherent sample illumination [26][27][28][29] can carve its own niche due to its ability to visualize micro-structures in the sample using laboratory-scale systems, similarly to what has been demonstrated for dark-field imaging in analyzer-based imaging [36] or Talbot interferometry [37].…”

Edge illumination X-ray phase contrast imaging for impact damage detection in CFRP

“…EI XPCi uses a pair of coded aperture masks to translate X-ray refraction into a variation in detected intensity; the acquisition of at least three images allows the quantitative separation of attenuation, refraction, and dark field signals [31]. The latter corresponds to the ultra-small angle scattering due to features on the sub-pixel scale [32] which, in the case of CFRP, can represent micro-cracks or fibre misalignment that are on a scale below the system resolution [33]. EI XPCi was found to be robust against both vibrations and energy variations [34].…”