Resolution cascade: simulated MTF of a coherent fiber bundle-based microendoscopic system

Despite advances in miniaturization of CMOS sensors, current submillimeter diameter microendoscopic systems rely on coherent fiber bundles to transfer the image from its collection point to the detector. Determining the resolution of an endoscopic optical system that employs a fiber bundle is nontrivial, and there is limited published information about how to calculate the theoretical modulation transfer function (MTF) of a system that may include a distal lens, fiber bundle, relay optics, and a camera sensor. While the fiber bundle is frequently considered the resolution-limiting element, greater information may be gained from computing the full system MTF. In this paper, we describe a resolution cascade method that calculates theoretical MTFs for common components, as well as for the entire microendoscopic system. These theoretical calculations compare favorably to experimentally gathered data for four different optical configurations. The software developed for these calculations is freely available to predict the MTF of other coherent fiber bundle-based systems. Brief instructions and necessary assumptions/conditions are described.