Multispectral Quantitative Phase Imaging Using a Diffractive Optical Network

TL;DR

This paper introduces a novel all-optical multispectral quantitative phase imaging system using a diffractive neural network, enabling snapshot, label-free imaging across multiple wavelengths with high efficiency and broad applicability.

Contribution

The work presents a deep learning-optimized diffractive optical processor capable of performing multispectral QPI in a single snapshot, a significant advancement over traditional methods.

Findings

Successfully demonstrated multispectral QPI at 9 and 16 spectral bands.

Maintained uniform performance across all wavelength channels.

Validated generalization on unseen objects like Pap smear images.

Abstract

As a label-free imaging technique, quantitative phase imaging (QPI) provides optical path length information of transparent specimens for various applications in biology, materials science, and engineering. Multispectral QPI measures quantitative phase information across multiple spectral bands, permitting the examination of wavelength-specific phase and dispersion characteristics of samples. Here, we present the design of a diffractive processor that can all-optically perform multispectral quantitative phase imaging of transparent phase-only objects in a snapshot. Our design utilizes spatially engineered diffractive layers, optimized through deep learning, to encode the phase profile of the input object at a predetermined set of wavelengths into spatial intensity variations at the output plane, allowing multispectral QPI using a monochrome focal plane array. Through numerical simulations, we demonstrate diffractive multispectral processors to simultaneously perform quantitative phase imaging at 9 and 16 target spectral bands in the visible spectrum. These diffractive multispectral processors maintain uniform performance across all the wavelength channels, revealing a decent QPI performance at each target wavelength. The generalization of these diffractive processor designs is validated through numerical tests on unseen objects, including thin Pap smear images. Due to its all-optical processing capability using passive dielectric diffractive materials, this diffractive multispectral QPI processor offers a compact and power-efficient solution for high-throughput quantitative phase microscopy and spectroscopy. This framework can operate at different parts of the electromagnetic spectrum and be used for a wide range of phase imaging and sensing applications.