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Designing the phase grating for Talbot-Lau phase-contrast imaging systems: a simulation and experiment study

2016; Optica Publishing Group; Volume: 24; Issue: 12 Linguagem: Inglês

10.1364/oe.24.013357

1094-4087

Jens Rieger, Pascal Meyer, Georg Pelzer, Thomas Weber, Thilo Michel, Jürgen Mohr, G. Anton,

Laser-Plasma Interactions and Diagnostics

The performance of a Talbot-Lau interferometer depends to a great extent on its visibility. This means, to obtain high quality phase-contrast and dark-field images a high visibility is mandatory. Several parameters influence the visibility of such a system, like for example the x-ray spectrum, the inter-grating distances or the parameters of the three gratings. In this multidimensional space, wave field simulations help to find the optimal combination of the grating specifications to construct a setup with a high visibility while retaining a fixed angular sensitivity. In this work we specifically analyzed the influence of the G1 grating duty cycle in simulations and experiments. We show that there is a lot of room for improvement by varying the duty cycle of the phase-shifting grating G1. As a result, by employing a third-integer duty cycle we can increase the visibility to up to 53 % in a laboratory setup with a polychromatic spectrum. The achieved visibility is more than two times higher compared to the result with a standard-type setup. This visibility gain allows a dose reduction by a factor of 5 preserving the same image quality.