Dual phase grating interferometer for tunable dark-field sensitivity

Hard X-ray dark-field and phase contrast imaging using grating interferometry have shown great potential for medical and industrial applications. However, the wide spread applicability of the method is challenged by a number of technical related issues such as relatively low dose and flux efficiency due to the absorption grating, fabrication of high quality absorption gratings, slow data acquisition protocol and high mechanical stability requirements. In this paper, the authors propose an interferometric method for dark-field and differential phase contrast imaging based on phase shifting elements only with the purpose to improve the dose and flux efficiency and simplify the setup. The proposed interferometer consists of two identical phase gratings of small pitch (1.3 mu m), which generate an interference fringe at the detector plane with a large enough pitch that can be resolved directly. In particular, the system exhibits flexible and tunable dark-field sensitivity which is advantageous to probe unresolvable micro-structure in the sample. Experiments on a micro focal tube validated the method and demonstrated the versatility and tunability of the system compared to conventional Talbot grating interferometer. Published by AIP Publishing.