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Currently, dual-energy X-ray phase contrast imaging is usually conducted with an X-ray Talbot-Lau interferometer. However, in this system, the two adopted energy spectra have to be chosen carefully in order to match well with the phase grating. For example, the accelerating voltages of the X-ray tube are supposed to be respectively set as 40 kV and 70 kV, with other energy spectra being practically unusable for dual energy imaging. This system thus has low flexibility and maneuverability in practical applications. In this work, dual energy X-ray phase-contrast imaging is performed in a grating-based non-interferometric imaging system rather than in a Talbot-Lau interferometer. The advantage of this system is that, theoretically speaking, any two separated energy spectra can be utilized to perform dual energy X-ray phase-contrast imaging. The preliminary experimental results show that dual-energy X-ray phase contrast imaging is successfully performed when the accelerating voltages of the X-ray tube are successively set as 40 kV and 50 kV. Our work increases the flexibility and maneuverability when employing dual-energy X-ray phase-contrast imaging in medical diagnoses and nondestructive tests., Comment: 18 pages, 5 figures, 1 table

The measurement of the spectral diffraction efficiencies of a diffraction grating is essential for improving the manufacturing technique and for assessing the grating's function in practical applications. The drawback of the currently popular measurement technique is its slow speed due to the hundreds of repetitions of two kinds of time-consuming mechanical movements during the measuring process (i.e., the rotation of the mechanical arm to capture the light beam, and the mechanical variation of the output wavelength of the grating monochromator). This limitation greatly restricts the usage of this technique in dynamic measurement. In this manuscript, we present a motionless and fast measurement technique for obtaining the spectral diffraction efficiencies of a plane grating, effectively eliminating the aforementioned two kinds of mechanical movement. Herein, the proposed solution for removing the first kind of mechanical movement is tested, and the experimental result shows that the proposed method can be successfully used to measure the plane transmission grating's spectral diffraction efficiencies in the wavelength range of 550-750 nm. The method for eliminating the second kind of mechanical movement is not verified in this manuscript; however, we think that it is very straightforward and commercially available. We estimate that the spectral measurement can be achieved on a millisecond timescale by combining the two solutions. Our motionless and fast measuring technique will find broad applications in dynamic measurement environments and mass industrial testing., Comment: 7 pages, 7 figures,2 tables

In this paper, we build an apparatus for measuring the optical transmittance and its uniformity for a semispherical surface at normal incidence; the system is primarily comprised of a traditional double-beam photometric framework and a novel custom-made mechanical structure with multidimensional degrees of freedom. During the measurement process, a key aligning step is adopted to guarantee that the center point of the semispherical surface stands still in the light beam while scanning the hemispherical optical element point by point around the horizontal and vertical axes, which ensures that the laser beam is always normally incident onto the surface of the hemisphere. The experimental results show that the uniformity of the optical transmittance for a semispherical optical glass can be successfully characterized by the system, with a three-cycle repeatability error of 0.026% being demonstrated. Our system solves the problem of traditional spectrophotometers when measuring the spectral property of a hemispherical surface and thus can be popularized in similar applications., Comment: 6 pages, 10 figures

Optical propagation time in matter could reveal fruitful information, such as the velocity of light and the sample's refractive index. In this paper, we build a simple and robust setup for measuring the optical propagation time in matter for a known distance, the system uses high frequency square signal as the signal carrier, and a lock-in amplifier is employed to obtain the phase difference between the reference square signal and the other one penetrating the sample, in this way the optical time of flight in matter can be obtained by a background subtraction process. Primary experimental result confirms the feasibility of the newly proposed measuring theory, which can be used to measure easily in high-speed the speed of light and the refractive index of optical transparent material, compared with the currently popular measuring technique using oscilloscope, potential advantage of our proposed method employing lock-in amplifier is that high accuracy are promising, and in contrast with the presently most popular method for measuring the sample's refractive index based on the minimum deviation angle, superiority of our suggested method is the easy preparation of the sample, the convenient operability and the fast measuring speed., Comment: 10 pages, 3 figures

X-ray phase-contrast imaging has experienced rapid development over the last few decades, and in this technology, the phase modulation strategy of phase-stepping is used most widely to measure the sample's phase signal. However, because of its discontinuous nature, phase-stepping has the defects of worse mechanical stability and high exposure dose, which greatly hinder its wide application in dynamic phase measurement and potential clinical applications. In this manuscript, we demonstrate preliminary research on the use of integrating-bucket phase modulation method to retrieve the phase information in grating-based X-ray phase-contrast imaging. Experimental results showed that our proposed method can be well employed to extract the differential phase-contrast image, compared with the current mostly used phase-stepping strategy, advantage of integrating-bucket phase modulation technique is that fast measurement and low dose are promising., Comment: 14 pages, 6 figures

We reported the usage of grating-based X-ray phase-contrast imaging in nondestructive testing of grating imperfections. It was found that electroplating flaws could be easily detected by conventional absorption signal, and in particular, we observed that the grating defects resulting from uneven ultraviolet exposure could be clearly discriminated with phase-contrast signal. The experimental results demonstrate that grating-based X-ray phase-contrast imaging, with a conventional low-brilliance X-ray source, a large field of view and a reasonable compact setup, which simultaneously yields phase- and attenuation-contrast signal of the sample, can be ready-to-use in fast nondestructive testing of various imperfections in gratings and other similar photoetching products., Comment: 6 pages, 5 figures and 2 tables

Dual-energy X-ray absorptiometry (DEXA) has been widely applied to measure bone mineral density (BMD) and soft-tissue composition of human body. However, the use of DEXA is greatly limited for low-Z materials such as soft tissues due to their weak absorption. While X-ray phase-contrast imaging (XPCI) shows significantly improved contrast in comparison with the conventional standard absorption-based X-ray imaging for soft tissues. In this paper, we propose a novel X-ray phase-contrast method to measure the area density of low-Z materials, including a single-energy method and a dual-energy method. The single-energy method is for the area density calculation of one low-Z material, while the dual-energy method is aiming to calculate the area densities of two low-Z materials simultaneously. Comparing the experimental and simulation results with the theoretic ones, the new method proves to have the potential to replace DEXA in area density measurement. The new method sets the prerequisites for future precise and low-dose area density calculation method of low-Z materials., Comment: 7 pages, 5 figures

X-ray Talbot-Lau interferometer has been used widely to conduct phase contrast imaging with a conventional low-brilliance x-ray source. Typically, in this technique, background correction has to be performed in order to obtain the pure signal of the sample under inspection. In this study, we reported on a research on the background correction strategies within this technique, especially we introduced a new phase unwrapping solution for one conventional background correction method, the key point of this new solution is changing the initial phase of each pixel by a cyclic shift operation on the raw images collected in phase stepping scan. Experimental result and numerical analysis showed that the new phase unwrapping algorithm could successfully subtract contribution of the system's background without error. Moreover, a potential advantage of this phase unwrapping strategy is that its effective phase measuring range could be tuned flexibly in some degree for example to be (-pi+3, pi+3], thus it would find usage in certain case because measuring range of the currently widely used background correction method is fixed to be (-pi, pi]., Comment: 23 pages, 8 figures, english polished

X-ray Talbot-Lau interferometer has been used most widely to perform X-ray phase-contrast imaging with a conventional low-brilliance X-ray source, it yields high-sensitivity phase and dark-field images of sample producing low absorption contrast, thus bearing tremendous potential for future clinical diagnosis. In this manuscript, while changing accelerating voltage of the X-ray tube from 35KV to 45KV, X-ray phase-contrast imaging of a test sample were performed at each integer KV position to investigate the characteristic of an X-ray Talbot-Lau interferometer (located in the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Japan) vs. tube voltage. Experimental results and data analysis show that this X-ray Talbot-Lau interferometer is insensitive to the tube accelerating voltage within a certain range, fringe visibility around 44% is maintained in the aforementioned tube voltage range. This experimental research implies that potential new dual energy phase-contrast X-ray imaging strategy and rough refraction spectrum measurement is feasible with this X-ray Talbot-Lau interferometer., Comment: 9 pages, 7 figures.(English improved and discussion part revised)