Sampling requirements in near-field ptychography

TL;DR

This paper analyzes the sampling requirements for near-field ptychography, extending existing knowledge with a formalism that unifies far- and near-field regimes, supported by simulations to optimize experimental setups.

Contribution

It introduces an analytical framework using fractional Fourier transform to generalize sampling conditions in near-field ptychography, broadening its applicability.

Findings

Unified sampling conditions for near- and far-field regimes

Guidelines for optimizing near-field ptychography experiments

Potential to enable use with low-brilliance sources

Abstract

Ptychography is a robust lensless form of microscopy routinely used for applications spanning life and physical sciences. The most common ptychography setup consists in using a detector to record diffraction patterns in the far-field. A near-field version has been more recently introduced, and its potential is yet to be fully exploited. In this work, the sampling requirements for near-field ptychography are analysed. Starting from the characterisation available in literature, the formalism of the fractional Fourier transform is used to generalise analytically the sampling conditions. The results harmonise the far- and near-field regimes and widen the applications of the technique with respect to the current knowledge. This study is supported by simulations and provides clear guidelines on how to optimise the setup and acquisition strategies for near-field ptychography experiments. The results are key to drive the translation of the technique towards low brilliance sources.