Robust real-time imaging through flexible multimode fibers

TL;DR

This paper presents a real-time, flexible multimode fiber imaging system that reconstructs images from speckle patterns using a variational autoencoder, maintaining robustness despite fiber bending and without needing feedback from the fiber's end.

Contribution

It introduces a novel approach combining a variational autoencoder with flexible MMFs for robust, real-time imaging without distal feedback, even under bending.

Findings

Successfully reconstructs images through bent fibers with 50-degree change.

Operates in real-time for objects 20 cm away.

Handles fiber movement of 8 cm without loss of image quality.

Abstract

Conventional endoscopes comprise a bundle of optical fibers, associating one fiber for each pixel in the image. In principle, this can be reduced to a single multimode optical fiber (MMF), the width of a human hair, with one fiber spatial-mode per image pixel. However, images transmitted through a MMF emerge as unrecognizable speckle patterns due to dispersion and coupling between the spatial modes of the fiber. Furthermore, speckle patterns change as the fiber undergoes bending, making the use of MMFs in flexible imaging applications even more complicated. In this paper, we propose a real-time imaging system using flexible MMFs, but which is robust to bending. Our approach does not require access or feedback signal from the distal end of the fiber during imaging. We leverage a variational autoencoder (VAE) to reconstruct and classify images from the speckles and show that these images can still be recovered when the bend configuration of the fiber is changed to one that was not part of the training set. We utilize a MMF 300 mm long with a 62.5 um core for imaging 10 x 10 cm objects placed approximately at 20 cm from the fiber and the system can deal with a change in fiber bend of 50 degrees and range of movement of 8 cm.