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Compact high-resolution endomicroscopy based on fiber bundles and image stitching.

In this Letter, we report a compact endomicroscope (ϕ=2.8  mm) based on a fiber bundle and a two-axis piezoelectric tube scanner, achieving a resolution of ∼1  μm and an imaging speed of 30-120 fps. Compared with distal end scanning systems, typical fiber-bundle-based endomicroscopes achieve a more compact envelope (ϕ∼1.5  mm) at the expense of compromised imaging quality. The resolution of fiber-bundle-based systems is largely limited by the diameter of the constituent fibers (ϕ∼5.0  μm), where each fiber serves as a single pixel, i.e., a sampling point, in the imaging system. To retrieve the lost information, we integrate a piezo tube scanner at the tip of the fiber bundle. Next, we rapidly scan the fiber tip over a range of ±2.5  μm and combine the signals obtained at different inter-fiber locations. Direct alignment and feature-based registration methods are applied to register the raw images. Imaging experiments are performed on a resolution target and biological samples to demonstrate the performance enhancement.