Abstract
An X-ray Talbot-Lau interferometer scanning setup consisting of three transmission gratings, a laboratory-based X-ray source that emits X-rays vertically, and an image detector on the top has been developed for the application of X-ray phase imaging to moving objects that cannot be tested clearly with conventional absorption contrast. The grating-based X-ray phase imaging method usually employs a phase-stepping (or fringe-scanning) technique by displacing one of the gratings step-by-step while the object stays still. Since this approach is not compatible with a scanner-type application for moving objects, we have developed a new algorithm for achieving the function of phase-stepping without grating displacement. By analyzing the movie of the moiré pattern as the object moves across the field of view, we obtain the absorption, differential phase, and visibility images. The feasibility of the X-ray phase imaging scanner has been successfully demonstrated for a long sample moving at 5 mm/s. This achievement is a breakthrough for the practical industrial application of X-ray phase imaging for screening objects carried on belt-conveyers such as those in factories.
Highlights
An X-ray Talbot-Lau interferometer scanning setup consisting of three transmission gratings, a laboratory-based X-ray source that emits X-rays vertically, and an image detector on the top has been developed for the application of X-ray phase imaging to moving objects that cannot be tested clearly with conventional absorption contrast
Among the methods of X-ray phase imaging reported so far, X-ray grating interferometry, such as X-ray Talbot interferometry[5] and X-ray Talbot-Lau interferometry[6], which is an advanced form of X-ray Talbot interferometry, is especially effective for practical X-ray phase imaging in clinical and industrial fields because they operate with conventional X-ray generators in hospitals and factories
When the object is placed in the interferometer, the intensity change is detected through the gratings at each pixel of an image detector. This feature can be seen as a moiré pattern
Summary
The X-ray generator was operated at 60-kV tube voltage and 70-mA tube current. The spatial resolution in the y-direction, which was independent of the motion blur, was evaluated by the FWHM of a sharp edge profile in the refraction image The spatial resolution in the y-direction was almost constant as expected, the slight degradation shown in Fig. 5(b) is considered to be due to the effect of the vibration of the sample stage which increases with the sample speed. This was confirmed by evaluating the moiré movie of the sample scan where an increase in the sample vibration (below one pixel on average) was found with sample speed increment
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