# Flexible lensless endoscope with a conformationally invariant multi-core fiber

## TL;DR

This paper introduces a novel conformationally invariant multi-core fiber that enables lensless endoscopy without the need for the fiber to remain static, overcoming a key limitation of previous designs.

## Contribution

The authors designed and validated a custom multi-core fiber that maintains its transmission properties despite fiber conformational changes, enabling dynamic lensless endoscopy.

## Key findings

- Experimental validation of fiber invariance under conformational changes
- Theoretical analysis of the fiber's invariance parameters
- Demonstration of imaging through the invariant fiber

## Abstract

The lensless endoscope represents the ultimate limit in miniaturization of imaging tools: an image can be transmitted through a (multi-mode or multi-core) fiber by numerical or physical inversion of the fiber's pre-measured transmission matrix. However, the transmission matrix changes completely with only minute conformational changes of the fiber, which has so far limited lensless endoscopes to fibers that must be kept static. In this letter we report for the first time a lensless endoscope which is exempt from the requirement of static fiber by designing and employing a custom-designed conformationally invariant fiber. We give experimental and theoretical validations and determine the parameter space over which the invariance is maintained.