# Near, far, wherever you are: simulations on the dose efficiency of holographic and ptychographic coherent imaging

## TL;DR

This study compares the dose efficiency of near-field holography, near-field ptychography, and far-field ptychography in x-ray microscopy, finding similar image quality across methods when using the same fluence, with slight advantages for far-field ptychography.

## Contribution

It provides a numerical comparison of three imaging modes, clarifying their dose efficiency and spatial resolution limits in x-ray microscopy.

## Key findings

- All three methods offer similar image quality at the same fluence.
- Far-field ptychography achieves slightly better spatial resolution.
- Photon fluence limits the spatial resolution regardless of imaging mode.

## Abstract

Different studies in x-ray microscopy have arrived at conflicting conclusions about the dose efficiency of imaging modes involving the recording of intensity distributions in the near (Fresnel regime) or far (Fraunhofer regime) field downstream of a specimen. We present here a numerical study on the dose efficiency of near-field holography (NFH), near-field ptychography (NFP), and far-field ptychography (FFP), where ptychography involves multiple overlapping finite-sized illumination positions. Unlike what has been reported for coherent diffraction imaging (CDI), which involves recording a single far-field diffraction pattern, we find that all three methods offer similar image quality when using the same fluence on the specimen, with far-field ptychography offering slightly better spatial resolution and lower mean error. These results support the concept that (if the experiment and image reconstruction are done properly) the sample can be near, or far; wherever you are, photon fluence on the specimen sets one limit to spatial resolution.