Wataru Yashiro 교수

The reduction in visibility in x-ray grating interferometry based on the Talbot effect is formulated by the autocorrelation function of spatial fluctuations of a wavefront due to unresolved micron-size structures in samples. The experimental results for microspheres and melamine sponge were successfully explained by this formula with three parameters characterizing the wavefront fluctuations: variance, correlation length, and the Hurst exponent. The ultra-small-angle x-ray scattering of these sa

We assesses the efficiency of x-ray Talbot interferometry (XTI), a technique based on the Talbot effect for measuring a wavefront gradient, in terms of how quickly it can capture a high-quality phase image with a large signal-to-noise ratio for a given incident photon number. Photon statistics cause errors in the phase of the moiré fringes and impose a detection limit on the wavefront gradient. The relation between the incident photon number and the detection limit is determined, and a figure of

Novel hard x-ray phase imaging microscopy that simply uses an objective and a transmission grating is described. The microscope generated an image that exhibited twin features of a sample with an opposite phase contrast having a separation of a specific distance. Furthermore, the twin features were processed to generate an image mapping the x-ray phase shift through a simple algorithm. The presence of the grating did not degrade the spatial resolution of the microscope. The sensitivity of our mi

We investigated effects of unresolvable sharp edges on images obtained in a grating-based X-ray differential phase imaging technique. Results of numerical calculations for monochromatic X-rays show that an unresolvable sharp edge generates not only differential-phase contrast but also visibility contrast. The latter shows that the visibility contrast has another major origin other than ultra-small-angle X-ray scattering (USAXS) from randomly distributed unresolvable microstructures, which has be

X-ray grating interferometry has been highlighted in the last decade as a multi-modal X-ray phase-imaging technique for providing absorption, differential phase, and visibility-contrast images. It has been mainly reported that the visibility contrast in the visibility-contrast image originates from unresolvable random microstructures. In this paper, we show that the visibility contrast is even reduced by a uniform sample with flat surfaces due to the so-called "beam-hardening effect", which has

X-ray Talbot interferometry has been widely used as a technique for x-ray phase imaging and tomography. We propose a method using this interferometry for mapping distribution of parameters characterizing anisotropic microstructures, which are typically of the order of $\ensuremath{\mu}\mathrm{m}$ in size and cannot be resolved by the imaging system, in a sample. The method uses reduction in fringe visibility, which is caused by such unresolvable microstructures, in moir\'e images obtained using

An X-ray phase tomogram was successfully obtained with an exposure time of less than 10 ms by X-ray grating interferometry, an X-ray phase imaging technique that enables high-sensitivity X-ray imaging even of materials consisting of light elements. This high-speed X-ray imaging experiment was performed at BL28B2, SPring-8, where a white X-ray beam is available, and the tomogram was reconstructed from projection images recorded at a frame rate of 100,000 fps. The setup of the experiment will make

We successfully realized millisecond-order X-ray phase tomography using a fringe-scanning method in grating-based X-ray interferometry. We obtained phase tomograms with a measurement time of 4.43 ms using a white synchrotron X-ray beam. The use of a fringe-scanning method enables us to achieve not only a higher spatial resolution but also a higher signal-to-noise ratio than that attained by the Fourier transform method. In addition, our approach can be applied to realize four-dimensional or high

We report on millisecond-order X-ray tomography with grating-based X-ray imaging using a white synchrotron X-ray beam. We performed a compressed sensing technique for tomographic reconstruction and successfully obtained a phase tomogram for a polypropylene sphere with a temporal resolution of 2.0 ms. Our approach will make it possible to realize millisecond-order four-dimensional X-ray tomography but also to markedly reduce the radiation damage of samples including polymer and biological materia

Reflection and transmission coefficients of X-rays by a single atomic plane are obtained in the general case where the plane consists of any two-dimensional Bravais lattice and the incident and exit X-ray beams take any direction with respect to the plane. A formula obtained for the coefficients is written in a simple form, different from that obtained by Durbin [Acta Cryst. (1995), A51, 258-268]. This makes it possible to extend Darwin's dynamical theory of X-ray diffraction to general geometri

We report on a hard-x-ray imaging microscope consisting of a lens, a sample, and a transmission grating. After the theoretical framework of self-imaging phenomenon by the grating in the system is presented, equations for the electric field on the image plane are derived for ideal and real lenses and an equation for the intensity on the image plane for partially coherent illumination is derived. The equations are simple and similar to those applying to a projection microscope consisting of a tran

In the 4D world of three-dimensional (3D) space plus time that we live in, there is a vast blue ocean in the spatio-temporal domain of micrometers and milliseconds that has never been accessed even with the most advanced measurement technology, and it is expected to be full of various non-equilibrium phenomena. In this paper, we review recent advances in synchrotron hard X-ray tomography we have made that can be used to explore the 4D frontier.

In X-ray grating interferometry, the fabrication of thick transmission gratings with pitches of several micrometers has been a key subject. We report on a metallic glass imprinting technique for fabricating an interferometer grating. We successfully fabricated an 8-µm-pitch, 10-µm-thick grating (26 mm2) made of Pd42.5Ni7.5Cu30P20 metallic glass by using the technique, and as a demonstration we also performed X-ray phase imaging with the grating. The technique can be applied to fabricate not only

We present a high-speed multi-beam X-ray imaging realized using a detector system and the recently developed multi-beam X-ray optics [Voegeli et al., Optica 7, 514 (2020)]. The detector utilized optical relay lenses and mirrors for connecting four scintillator screens to a CMOS camera, enabling the high-speed simultaneous acquisition of multiple projection images. We successfully acquired nine projection images in 0.5 ms with a spatial resolution of 70 μm. Dynamical behaviors of a light-bulb fil

Abstract A proof-of-concept experiment for sub-millisecond temporal and 10 μ m order spatial resolution 4D X-ray tomography imaging using a multibeam X-ray imaging system is reported. The 3D structure of a tungsten wire during mechanical deformation was reconstructed using a super-compressed sensing-based algorithm from 28 projection images acquired simultaneously with a temporal resolution of 0.5 ms. The multibeam imaging system does not require rotation of the sample, X-ray source or detector.