Single-Pixel Phase-Corrected Fiber Bundle Endomicroscopy With Lensless Focussing Capability

In this paper a novel single-pixel method for coherent imaging through an endoscopic fiber bundle is presented. The use of a single-pixel detector allows greater sensitivity over a wider range of wavelengths, which could have significant applications in endoscopic fluorescence microscopy. First, the principle of lensless focussing at the distal end of a coherent fiber bundle is simulated to examine the impact of pixelation at microscopic scales. Next, an experimental optical correlator system using spatial light modulators (SLMs) is presented. A simple contrast imaging method of characterizing and compensating phase aberrations introduced by fiber bundles is described. Experimental results are then presented showing that our phase compensation method enables characterization of the optical phase profile of individual fiberlets. After applying this correction, early results demonstrating the ability of the system to electronically adjust the focal plane at the distal end of the fiber bundle are presented. The structural similarity index (SSIM) between the simulated image and the experimental focus-adjusted image increases noticeably when the phase correction is applied and the retrieved image is visually recognizable. Strategies to improve image quality are discussed.