Addressing phase-curvature in Fourier ptychography

TL;DR

This paper introduces an improved Fourier ptychography model that accounts for phase-curvature effects, enabling accurate wide-field quantitative phase imaging without segmentation and with minimal computational overhead.

Contribution

It presents a simple, efficient extension to the Fourier ptychography model that incorporates phase-curvature effects, enhancing accuracy for wide-field imaging.

Findings

Enables accurate quantitative phase reconstruction over large fields-of-view.

Requires only two multiplications, making it computationally efficient.

Does not require image segmentation for phase retrieval.

Abstract

In Fourier ptychography, multiple low resolution images are captured and subsequently combined computationally into a high-resolution, large-field of view micrograph. A theoretical image-formation model based on the assumption of plane-wave illumination from various directions is commonly used, to stitch together the captured information into a high synthetic aperture. The underlying far-field (Fraunhofer) diffraction assumption connects the source, sample, and pupil planes by Fourier transforms. While computationally simple, this assumption neglects phase-curvature due to non-planar illumination from point sources as well as phase-curvature from finite-conjugate microscopes (e.g., using a single-lens for image-formation). We describe a simple, efficient, and accurate extension of Fourier ptychography by embedding the effect of phase-curvature into the underlying forward model. With the improved forward model proposed here, quantitative phase reconstruction is possible even for wide fields-of-views and without the need of image segmentation. Lastly, the proposed method is computationally efficient, requiring only two multiplications: prior and following the reconstruction.