Ptychographic reconstruction with wavefront initialization

TL;DR

This paper demonstrates that using a low-resolution wavefront as initialization in ptychographic reconstruction significantly improves computational speed and avoids artifacts, especially for large samples.

Contribution

Introducing a wavefront initialization method that enhances speed and accuracy in ptychographic phase retrieval for large samples.

Findings

Wavefront initialization speeds up reconstruction.

It prevents phase singularity artifacts.

Applicable to non-bulky samples.

Abstract

X-ray ptychography is a cutting edge imaging technique providing ultra-high spatial resolutions. In ptychography, phase retrieval, i.e., the recovery of a complex valued signal from intensity-only measurements, is enabled by exploiting a redundancy of information contained in diffraction patterns measured with overlapping illuminations. For samples that are considerably larger than the probe we show that during the iteration the bulk information has to propagate from the sample edges to the center. This constitutes an inherent limitation of reconstruction speed for algorithms that use a flat initialization. Here, we experimentally demonstrate that a considerable improvement of computational speed can be achieved by utilizing a low resolution sample wavefront retrieved from measured diffraction patterns as initialization. In addition, we show that this approach avoids phase singularity artifacts due to strong phase gradients. Wavefront initialization is computationally fast and compatible with non-bulky samples. Therefore, the presented approach is readily adaptable with established ptychographic reconstruction algorithms implying a wide spread use.