Abstract
Two-dimensional (2D) Talbot array illuminators (TAIs) were designed, fabricated, and evaluated for high-resolution high-contrast x-ray phase imaging of soft tissue at 10-20 keV. The TAIs create intensity modulations with a high compression ratio on the micrometer scale at short propagation distances. Their performance was compared with various other wavefront markers in terms of period, visibility, flux efficiency, and flexibility to be adapted for limited beam coherence and detector resolution. Differential x-ray phase contrast and dark-field imaging were demonstrated with a one-dimensional, linear phase stepping approach yielding 2D phase sensitivity using unified modulated pattern analysis (UMPA) for phase retrieval. The method was employed for x-ray phase computed tomography reaching a resolution of 3 µm on an unstained murine artery. It opens new possibilities for three-dimensional, non-destructive, and quantitative imaging of soft matter such as virtual histology. The phase modulators can also be used for various other x-ray applications such as dynamic phase imaging, super-resolution structured illumination microscopy, or wavefront sensing.
Highlights
Various imaging techniques based on x-rays have opened unique insights into three-dimensional (3D) structures at the micro- and nanometer scale and even enabled the capture of time-resolved volumetric data due to recent innovations in x-ray sources, optics, detectors, high precision metrology, and advanced post-processing and reconstruction algorithms
Optimized modulators should have a high x-ray transmission and a strong resistance to high radiation doses. They should be easy to fabricate with current microprocessing technologies and adaptable in period in the sub10-μm range to operate at high visibility with a given detector point spread function (PSF). Considering these factors, we propose and demonstrate a 2D periodic phase-shifting grating for the x-ray regime, known as Talbot array illuminator (TAI) from visible light literature [25,26,27]
Note that the highest visibility does not have to be necessary on the exact position of the fractional Talbot distance, since strong focusing occurs even before and after dT /6 as the simulations show
Summary
Various imaging techniques based on x-rays have opened unique insights into three-dimensional (3D) structures at the micro- and nanometer scale and even enabled the capture of time-resolved volumetric data due to recent innovations in x-ray sources, optics, detectors, high precision metrology, and advanced post-processing and reconstruction algorithms. While propagation-based methods provide good edge visibility [2], analyzer-based [3], interferometric [4,5], aperture-based [6,7], and speckle-based methods [8,9,10] enable us to retrieve the attenuation, phase, and dark-field signals separately from a measurement at one single propagation distance. The latter techniques rely on various diffractive and absorptive beam modulator optics creating a defined intensity pattern after propagation in space.
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