Hard X-Ray Zernike-Type Phase-Contrast Imaging with a Two-Block Crystal System

Abstract

A novel scheme for Zernike-type hard X-ray phase-contrast imaging is proposed. The scheme relies on X-ray dynamical diffraction in a two-block crystal system with parallel crystal plates of equal thickness. A phase shifter providing a $π/2$ phase shift is placed in the inter-block gap of the crystal system. The method operates in a scanning geometry. The proposed imaging setup is compact and does not require conventional focusing optics. Numerical simulations of phase-contrast image formation are performed.

Figures (2)

• Figure 1: Schematic layout of the phase-contrast imaging setup and the corresponding ray paths. The dotted lines indicate the boundaries of the wave packet not diffracted at the entrance slit and the test object, while the dashed lines show the boundaries of the diffracted wave packet. $\text{S}^{\prime}$ and $\text{S}^{\prime \prime}$ are the entrance and exit slits, respectively; PS is the phase shifter; TO is the test object; D is the image detector; $\text{B}_1$ and $\text{B}_2$ are the blocks of the LL system. Note that in a real experimental setup, the slits $\text{S}^{\prime}$ and $\text{S}^{\prime \prime}$, the phase shifter PS, the image detector D, and even the sample TO may be arranged perpendicular to the X-ray beams incident on them, with appropriate scaling of their widths.
• Figure 2: Numerical simulation of phase-contrast imaging for a test object in the form of a one-dimensional binary phase grating with a phase jump of $\pi / 2$ and periods of (a) 6, (b) 30, (c) 70, and (d) $180 \, \upmu\text{m}$. Solid lines represent the phase-contrast images (left scale), while dashed lines show the phase-shift distributions of the test object (right scale). The $x$-axis corresponds to the coordinate in the scattering plane, parallel to the surfaces of the crystal plates. The slight image shift in panel (a) is due to the finite pixel resolution of the detector.