Application of x-ray image magnifier and demagnifier to parallel beam x-ray computed tomography

Abstract

X-ray computed tomography (CT) using synchrotron radiation is a powerful technique for qualitatively assessing structural features in various objects. However, the spatial resolution is often limited by the detector, and the size of a sample must be smaller than the viewing field of the detector. We therefore introduced an asymmetrically cut crystal between the sample and the detector to either magnify or demagnify the sample image. For practical usefulness, we adopted a one-dimensional magnification/demagnification scheme rather than a two-dimensional scheme to ensure a high throughput. Actually, a throughput higher than 90% can be obtained by carefully designing the entire optics so that the magnifier/demagnifier forms a nondispersive arrangement with an existing optical element such as a monochromator. Measurements of the modulation transfer function confirmed that the spatial resolution is improved by the magnifier. It was also shown that the magnifier functions properly in x-ray CT experiments. Furthermore, it was demonstrated that the x-ray demagnifier could be used for CT experiments with a sample larger than the viewing field of the detector.