Towards a mobile quantitative phase imaging microscope with smartphone phase-detection sensors

TL;DR

This paper presents a novel single-shot quantitative phase imaging method using smartphone-like quad-pixel sensors, enabling cost-effective, rapid, and robust phase map reconstruction of transparent samples without complex optics.

Contribution

The work introduces Quad-Pixel Phase Gradient Imaging ($QP^{2}GI$), a new single-exposure QPI technique leveraging quad-pixel sensors, simplifying the process and reducing equipment complexity.

Findings

Successful reconstruction of phase maps from microbeads and biological samples

Single-shot imaging achieves comparable results to multi-frame methods

Low-coherence illumination enhances robustness by reducing noise

Abstract

Quantitative phase imaging (QPI) enables visualization and quantitative extraction of the optical phase information of transparent samples. However, conventional QPI techniques typically rely on multi-frame acquisition or complex interferometric optics. In this work, we introduce Quad-Pixel Phase Gradient Imaging ($QP^{2}GI$), a single-shot quantitative phase imaging method based on a commercial quad-pixel phase detection autofocus (PDAF) sensor, where each microlens on the sensor covers a $2\times2$ pixel group. The phase gradients of the sample induce focal spot displacements under each microlens, which lead to intensity imbalances among the four pixels. By deriving the phase gradients of the sample from these imbalances, $QP^{2}GI$ reconstructs quantitative phase maps of the sample from a single exposure. We establish a light-propagation model to describe this process and evaluate its performance in a customized microscopic system. Experiments demonstrate that quantitative phase maps of microbeads and biological specimens can be reconstructed from a single acquisition, while low-coherence illumination improves robustness by suppressing coherence-related noise. These results reveal the potential of quad-pixel PDAF sensors as cost-effective platforms for single-frame QPI.