Digital confocal microscopy through a multimode fiber

TL;DR

This paper presents a novel method for confocal microscopy through multimode fibers, digitally engineering wavefronts and virtual pinholes to enhance imaging contrast and resolution in deep biological tissues.

Contribution

It introduces a combined confocal imaging technique via multimode fibers with digital wavefront control and virtual pinholes, improving deep tissue imaging contrast.

Findings

Achieved lateral resolution of 1.5μm and axial resolution of 12.7μm.

Enhanced image contrast significantly compared to traditional methods.

Point-scanning rate limited to 20Hz by the spatial light modulator.

Abstract

Acquiring high-contrast optical images deep inside biological tissues is still a challenging problem. Confocal microscopy is an important tool for biomedical imaging since it improves image quality by rejecting background signals. However, it suffers from low sensitivity in deep tissues due to light scattering. Recently, multimode fibers have provided a new paradigm for minimally invasive endoscopic imaging by controlling light propagation through them. Here we introduce a combined imaging technique where confocal images are acquired through a multimode fiber. We achieve this by digitally engineering the excitation wavefront and then applying a virtual digital pinhole on the collected signal. In this way, we are able to acquire images through the fiber with significantly increased contrast. With a fiber of numerical aperture 0.22, we achieve a lateral resolution of 1.5um, and an axial resolution of 12.7um. The point-scanning rate is currently limited by our spatial light modulator (20Hz).