Acousto-optic Ptychography

TL;DR

This paper introduces a computational method that enhances acousto-optic imaging resolution to diffraction-limited levels by leveraging speckle correlations and ptychography, enabling high-resolution deep tissue imaging.

Contribution

It presents a novel ptychographic approach using ultrasound focus scanning and speckle correlations to achieve diffraction-limited imaging in acousto-optic systems, surpassing existing resolution limits.

Findings

Achieved 40-times resolution improvement over conventional AOI.

Demonstrated non-invasive imaging of targets beyond the memory-effect range.

Validated the method with experimental results surpassing state-of-the-art approaches.

Abstract

Acousto-optic imaging (AOI) enables optical-contrast imaging deep inside scattering samples via localized ultrasound-modulation of scattered light. While AOI allows optical investigations at depths, its imaging resolution is inherently limited by the ultrasound wavelength, prohibiting microscopic investigations. Here, we propose a novel computational imaging approach that allows to achieve optical diffraction-limited imaging using a conventional AOI system. We achieve this by extracting diffraction-limited imaging information from 'memory-effect' speckle-correlations in the conventionally detected ultrasound-modulated scattered-light fields. Specifically, we identify that since speckle correlations allow to estimate the Fourier-magnitude of the field inside the ultrasound focus, scanning the ultrasound focus enables robust diffraction-limited reconstruction of extended objects using ptychography, i.e. we exploit the ultrasound focus as the scanned spatial-gate 'probe' required for ptychographic phase-retrieval. Moreover, we exploit the short speckle decorrelation-time in dynamic media, which is usually considered a hurdle for wavefront-shaping based approaches, for improved ptychographic reconstruction. We experimentally demonstrate non-invasive imaging of targets that extend well beyond the memory-effect range, with a 40-times resolution improvement over conventional AOI, surpassing the performance of state-of-the-art approaches.