Periodic Artifacts Generation and Suppression in X-ray Ptychography

As a unique coherent diffraction imaging method, X-ray ptychography has an ultrahigh resolution of several nanometers for extended samples. However, ptychography is often degraded by various noises that are mixed with diffracted signals on the detector. Some of the noises can transform into periodic artifacts (PAs) in reconstructed images, which is a basic problem in raster-scan ptychography. Herein, we propose a novel periodic-artifact suppressing algorithm (PASA) and present a new understanding of PAs or raster-grid pathology generation mechanisms, which include static intensity (SI) as an important cause of PAs. The PASA employs a gradient descent scheme to iteratively separate the SI pattern from original datasets and a probe support constraint applied in the object update. Both simulative and experimental data reconstructions demonstrated the effectiveness of the new algorithm in suppressing PAs and improving ptychography resolution and indicated a better performance of the PASA method in PA removal compared to other mainstream algorithms. In the meantime, we provided a complete description of SI conception and its key role in PA generation. The present work enhances the feasibility of raster-scan ptychography and could inspire new thoughts for dealing with various noises in ptychography.