[01/02/2015] Phys. Rev. Applied: Near-field ptychography on a strongly scattering sample

Near-field ptychography has made its entry a few years ago as a promising alternative to other holographic techniques. The technique combines the concepts and experimental setup of full-field phase-contrast imaging with the robust phase retrieval principles of ptychography. To take one dataset, one simply needs to translate the sample with respect to a structured illumination.

The phase part of the reconstructed Uranium sphere. The scale bar is 25 μm.

In a recent paper by Marco Stockmar, we demonstrate that phase retrieval works even for strongly absorbing and phase-shifting samples — a case known to be extremely problematic for other holographic techniques. In this demonstration we have imaged a Uranium sphere of about 50 microns in diameter. X-rays travelling through the center of the sphere are attenuated by more than 90% and phase-shifted by up to 6π. Yet a quantitative reconstruction could be obtained, showing that the technique can now be applied to a truely large range of possible samples.

The experiment was conducted at the ID22 beamline at ESRF.