Harnessing Forward Multiple Scattering for Optical Imaging Deep Inside an Opaque Medium

TL;DR

This paper demonstrates a matrix-based optical imaging method that compensates for multiple scattering in opaque media, enabling three-dimensional imaging deep inside biological tissues with significantly improved penetration depth.

Contribution

It introduces a novel approach using a reflection matrix and wave distortion analysis to digitally de-scatter light, enhancing imaging depth in opaque biological samples.

Findings

Achieved fivefold increase in imaging depth compared to current methods.

Successfully imaged a human opaque cornea in three dimensions.

Demonstrated effective compensation of forward multiple scattering paths.

Abstract

As light travels through a disordered medium such as biological tissues, it undergoes multiple scattering events. This phenomenon is detrimental to in-depth optical microscopy, as it causes a drastic degradation of contrast, resolution and brightness of the resulting image beyond a few scattering mean free paths. However, the information about the inner reflectivity of the sample is not lost; only scrambled. To recover this information, a matrix approach of optical imaging can be fruitful. Here, we report on a de-scanned measurement of a high-dimension reflection matrix R via low coherence interferometry. Then, we show how a set of independent focusing laws can be extracted for each medium voxel through an iterative multi-scale analysis of wave distortions contained in R. It enables an optimal and local compensation of forward multiple scattering paths and provides a three-dimensional confocal image of the sample as the latter one had become digitally transparent. The proof-of-concept experiment is performed on a human opaque cornea and an extension of the penetration depth by a factor five is demonstrated compared to the state-of-the-art.