Widefield lensless endoscopy via speckle correlations
Flexible fiber optic endoscopes provide a minimally invasive solution for imaging at depths beyond the reach of conventional microscopes. Current endoscopes require focusing and/or scanning mechanisms at the distal end, which limit miniaturization and frame rate, and induce aberrations. Alternative lensless solutions are based on adaptive wavefront correction, but are extremely sensitive to fiber bending. Here, we demonstrate a novel endoscopic approach, which enables single shot imaging at a variable working distance through a conventional fiber bundle, without the use of any distal optics. Our approach computationally retrieves the object image from a single speckle pattern transmitted through the bundle, exploiting phase information preserved through inherent angular speckle correlations. Unlike conventional fiber bundle endoscopes, the resulting image is unpixelated, the resolution is diffraction limited, objects can be imaged at variable working distance, and the technique is completely insensitive to fiber bending. Since no optical elements are required, miniaturization is limited only by the bundle diameter.