Abstract
A new double-grating-based phase-contrast imaging technique is described. This technique differs from the conventional double-grating imaging method by the image acquisition strategy. The novelty of the proposed method is in lateral scanning of both gratings simultaneously while an image is collected. The collected image is not contaminated by a Moiré pattern and can be recorded even by using a high-spatial-resolution integrating detector (e.g. X-ray film), thus facilitating improved resolution and/or contrast in the image. A detailed theoretical analysis of image formation in the scanning-double-grating method is carried out within the rigorous wave-optical formalism. The transfer function for the scanning-double-grating imaging system is derived. An approximate geometrical-optics solution for the image intensity distribution is derived from the exact wave-optical formula using the stationary-phase approach. Based on the present formalism, the effects of finite source size on the preferred operating conditions and of polychromaticity on the image contrast and resolution are investigated.
Highlights
The conventional and long-standing method for X-ray imaging is based on absorption and dates back to the pioneering work of Röntgen who discovered X-rays in 1895
Differential phase-contrast methods, including analyzer-based imaging (ABI) [4,5,6,7] and grating-based imaging [8,9,10,11,12,13,14,15,16,17,18], which are sensitive to the phase derivative in a certain direction or to the phase gradient; 3
Near-field propagation-based imaging (PBI) [19,20,21] where the image contrast is proportional to the two-dimensional (2D) Laplacian of the phase
Summary
The conventional and long-standing method for X-ray imaging (radiography) is based on absorption and dates back to the pioneering work of Röntgen who discovered X-rays in 1895. Other methods for X-ray imaging have been developed involving phase contrast. These methods are sensitive to the real part of the complex refractive index describing the interaction between electromagnetic radiation and matter. The existing methods for direct X-ray phase-contrast imaging can be classified in terms of their sensitivity to the phase variations in the detected object wave as follows: 1. 4. Resolution is decreased intentionally (in two grating modality) or needs collecting several images using a high-resolution detector with further processing of data (single grating modality [18]) and may involve ambiguities in phase determination.
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