# Lensless Quantitative Phase Imaging with Bayer-Filtered Color Sensors Under Sequential RGB-LED Illumination

## TL;DR

This paper introduces a new method for high-resolution, lensless imaging using color sensors and RGB-LEDs, enabling detailed biological imaging without labels.

## Contribution

A novel Wirtinger Poly-Gradient Solver (WPGS) that improves phase imaging with Bayer-filtered sensors under RGB-LED illumination.

## Key findings

- The method achieves pixel super-resolution beyond the Nyquist limit using a 1.85 μm pixel-pitch sensor.
- Label-free imaging of HeLa cells and unstained tissue sections was successfully demonstrated.
- The approach suppresses CFA-induced artifacts and enables high-throughput digital pathology.

## Abstract

Lensless on-chip microscopy enables high-throughput, wide-FOV imaging; however, the Bayer color filter array (CFA) in standard color sensors spatially multiplexes spectral channels, introducing sub-sampling and spectral crosstalk that degrade phase retrieval. We propose a Wirtinger Poly-Gradient Solver (WPGS) for quantitative phase reconstruction with Bayer-filtered color sensors under sequential Red–Green–Blue Light-Emitting Diode (RGB-LED) illumination. The method combines Transport of Intensity Equation (TIE)-based initialization with polychromatic Wirtinger optimization to suppress CFA-induced artifacts and enable pixel super-resolution (PSR). Experiments resolve a 2.76 μm linewidth using a 1.85 μm pixel-pitch sensor, exceeding the nominal Nyquist limit imposed by pixel sampling. We further demonstrate label-free imaging of HeLa cells and unstained tissue sections, supporting high-throughput digital pathology and offering potential for longitudinal biological observation.