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In the X-ray single-grating imaging system, the acquisition of frequency information is the key step of phase-contrast and scattering information recovery. In the process of information extraction, it is easy to lead to the degradation of imaging quality due to the Moire Artifact, thus limiting the development and application of X-ray single-grating imaging system. In order to address the above problems, in this article, based on the theoretical analysis of the generation principle of Moire Artifact in imaging system, the advantages and disadvantages of grating rotation method are analyzed, and a method of suppressing Moire artifacts by adjusting grating projection frequency is proposed. The experimental results show that the method proposed here can suppress the Moire noise in the background noise, resulting in a reduction of more than 50% in the standard deviation of the background noise. High quality phase-contrast and scattering images are obtained experimentally, which is of great value to the development of X-ray single-grating imaging technology.
In the X-ray single-grating imaging system, the acquisition of frequency information is the key step of phase-contrast and scattering information recovery. In the process of information extraction, it is easy to lead to the degradation of imaging quality due to the Moire Artifact, thus limiting the development and application of X-ray single-grating imaging system. In order to address the above problems, in this article, based on the theoretical analysis of the generation principle of Moire Artifact in imaging system, the advantages and disadvantages of grating rotation method are analyzed, and a method of suppressing Moire artifacts by adjusting grating projection frequency is proposed. The experimental results show that the method proposed here can suppress the Moire noise in the background noise, resulting in a reduction of more than 50% in the standard deviation of the background noise. High quality phase-contrast and scattering images are obtained experimentally, which is of great value to the development of X-ray single-grating imaging technology.
In recent years, the X-ray interferometer using dual phase gratings has been reported by a lot of researchers. The large periodic fringes produced by the X-ray interferometer using dual phase gratings can be directly detected by ordinary detectors. At the same time, the X-ray interferometer using dual phase gratings can reduce the radiation dose of the sample without using absorption gratings. Meanwhile, a high fringe visibility is always preferred to achieve a high signal-to-noise ratio for X-ray grating interferometry. However, recent studies have reported that experimental fringe visibility in X-ray interferometer using dual rectangular phase gratings is relatively low. Therefore, it is necessary to further increase the fringe visibility in X-ray interferometry using dual phase gratings. This work focuses on the analysis of fringe visibility in X-ray interferometer using dual triangular phase gratings. Based on the fringe intensity distribution formula of X-ray dual phase grating interferometer, the fringe visibility of the dual triangular phase grating interferometer is investigated as a function of the grating spacing under monochromatic and different polychromatic illumination, respectively. As a comparison, the fringe visibility of the dual rectangular phase grating interferometer was also studied under the same condition. The results show that the maximum fringe visibility of the dual triangular phase grating interferometer increases with an increase with the phase shift regardless of monochromatic or polychromatic illumination. Under monochromatic illumination, the maximum fringe visibility of dual 5<i>π</i>/2 triangular phase gratings is about 21% higher than that of dual rectangular phase gratings. Under different polychromatic illumination, the fringe visibility of dual 5<i>π</i>/2 triangular phase gratings is at least 23% higher than that of dual rectangular phase gratings. Under polychromatic illumination, when the average energy of X-ray deviates from the design energy of grating more, the maximum fringe visibility of the dual phase grating interferometer decreases greater. In addition, with the increase of the focal size of the X-ray source, the maximum fringe visibility of the dual phase grating interferometer decreases, under polychromatic illumination. We hope that those results can be used as guidelines for design and optimization of X-ray interferometer using dual triangular phase gratings.
The transmission X-ray microscope (TXM) is a high-precision, cutting-edge X-ray imaging instrument and a marvel of modern science and technology. It enables non-destructive imaging at the nanoscale, providing a powerful research tool for various scientific fields such as physics, life sciences, materials science, and chemistry. Although many synchrotron facilities domestically and internationally have established Nano-CT experimental stations based on TXM, currently only few companies worldwide can offer commercial TXM instrument based on laboratory X-ray sources. The primary reason is that this instrument involves numerous engineering challenges, including high-brightness laboratory X-ray sources, high-resolution X-ray optical elements, high-precision sample stage system, high-sensitivity detectors, and extremely strict requirements for environmental factors such as temperature and vibration. To push the development of high-end X-ray imaging instruments, it is necessary to overcome the technical bottlenecks encountered in the development of X-ray Nano-CT. This paper mainly discusses the instrument design of a laboratory transmission X-ray microscope with a working energy of 5.4keV and the results of full-field imaging experiments. Firstly, the design of the TXM instrument is introduced in detail. The TXM instrument is equipped with several key components, including laboratory X-ray source, condenser, sample stage module, zone plate, and imaging detector. The TXM instrument adopts a modular vibration isolation design and is equipped with a dedicated temperature control system. The main imaging magnifications of the TXM instrument are 50X, 75X, and 100X, and the optical path parameters and physical photos of the instrument at these three magnifications are introduced. The X-ray source used is a micro-focus X-ray source, operating in Cr target mode, with a focal spot size of 20 μm and a Ka characteristic spectrum brightness of 5*10<sup>9</sup> <i>photos</i>/<i>mm</i><sup>2</sup>/<i>mrad</i><sup>2</sup>/s. The X-ray source provides illumination for the sample after being focused by an ellipsoidal condenser. The outer ring of the condenser's illumination ring corresponds to a numerical aperture (NA) of <i>NA</i><sub>2</sub>=3.196<i>mrad</i>, and the inner ring corresponds to a numerical aperture of <i>NA</i><sub>1</sub>=1.9086<i>mrad</i>. Under these conditions, the TXM instrument's limit resolution is 22nm. The zone plate has a diameter of 70μm, a focal length of 8.7mm, and 616 zones. The TXM instrument uses a high-resolution optical coupling detector equipped with a scientific-grade CMOS camera with an effective pixel size of 7.52μm. The optical coupling detector is equipped with 2X and 10X high numerical aperture objectives. When the TXM instrument magnification is 50X, the effective pixel size of the TXM instrument is 15nm. Secondly, a gold resolution test card was used as the sample to determine the imaging field of view of the TXM instrument by observing the size of the imaging area of the test card on the detector, and to determine the imaging resolution of the TXM instrument by observing the line width of the star-shaped target in the center of the test card. Experimental results show that the TXM instrument has an imaging field of view of 26μm and can achieve clear imaging of line features with 30nm width. The radial power spectrum curve of the Siemens star test card imaging results shows that the TXM instrument's limit resolution is 28.6nm. Finally, we close with a conclusion and outlook. Currently, imaging of line features with 30nm width has been achieved, but the imaging of line-pair features with 30nm half pitch has not yet been achieved, and the limit resolution has not reached the design value. We will continue to explore the potential for upgrading the imaging resolution of the laboratory TXM in future work.
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