Using fiber-bending generated speckles for improved working distance and background-rejection in lensless microendoscopy

Lensless flexible fiber-bundle based endoscopes allow imaging at depths beyond the reach of conventional microscopes with a minimal footprint. These multicore fibers provide a simple solution for widefield fluorescent imaging when the target is adjacent to the fiber facet. However, they suffer from a very limited working distance and out-of-focus background. Here, we carefully study the dynamic speckle illumination patterns generated by bending a commercial fiber-bundle, and show that they can be exploited to allow extended working distance and background rejection, using a super-resolution fluctuations imaging (SOFI) analysis of multiple frames, without the addition of any optical elements.