Development of a new phase-retrieval algorithm from a single-shot image for X-ray schlieren microscopy

TL;DR

The paper presents a novel phase-retrieval algorithm that reconstructs a phase map from a single schlieren image in hard X-ray schlieren microscopy. By modeling schlieren contrast as a filtered representation of the phase spectrum and applying a Fourier-domain retrieval with a simple sign filter, the method enables rapid, single-shot phase extraction for transparent, weak-phase specimens. A proof-of-principle experiment at KEK demonstrates feasibility using a Fresnel zone plate objective and a knife-edge filter, highlighting potential for high-speed phase-contrast imaging and tomography in hard X-ray full-field microscopy. Applicability to simple optics like FZP and potential extensions to partial coherence and finite-imaging-plane corrections suggest practical impact for high-resolution phase-contrast imaging of light-element or thin samples.

Abstract

In this paper, a new phase-retrieval algorithm from an X-ray schlieren image is proposed. The schlieren method allows phase-contrast imaging with an objective lens and a knife-edge filter placed at the back focal plane of the objective. This method finds a wide range of applications in the visible-light region for transparent specimen visualization. The schlieren contrast does not directly correspond to the phase shift. However, the phase map can be reconstructed from a single-shot schlieren image of a transparent and weak-phase object using the filtered Fourier transform method. A proof-of-principle experiment was performed in the hard-X-ray region at the AR-NE1A beamline of the Photon Factory facility at the High Energy Accelerator Research Organization (KEK).

Figures (6)

• Figure 1: Optical system for schlieren microscopy.
• Figure 2: Schlieren method with inclined plane wave illumination.
• Figure 3: Schematic of the experimental setup for the X-ray microscope installed at the AR-NE1A beamline. The sample-to-detector distance is approximately 6.9 m, and the vacuum duct between the XRM chamber and detector is approximately 5 m.
• Figure 4: (a) Intensity-normalized absorption image of the siemens-star and line-and-space patterns following the calibration standard. The total exposure time is 50 s (5 s $\times$ 10 images) for a 15-mA stored current. (b) Intensity profile at line A-B.
• Figure 5: (a) Intensity-normalized schlieren phase-contrast image of the siemens-star and line-and-space patterns following the calibration standard. The total exposure time is 50 s (5 s $\times$ 10 images) for a 15-mA stored current. (b) Intensity profile at line A-B.