Fiber endoscopy using synthetic wavelengths for 3D tissue imaging

Optical endoscopes utilizing multi-core fiber (MCF) bundles offer the capability to image deep within the human body, making them well-suited for imaging applications in minimally invasive surgery or diagnosis. However, the optical fields relayed through each fiber core can be significantly affected by phase scrambling due to variations in fiber length or the presence of multimode cores. Moreover, obtaining high-quality endoscopic images commonly requires the fiber tip to be placed close to the target or relies on the addition of lenses. Furthermore, imaging through scattering layers after the fiber tip is commonly difficult. In this work, we address these challenges by integrating Synthetic Wavelength Imaging (SWI) into fiber endoscopy. This novel approach enables the endoscopic acquisition of holographic information from objects obscured by scattering layers, such as biological tissue. The resulting endoscopic system eliminates the need for lenses, allows for single-shot 3D imaging and is inherently robust against phase scrambling caused by scattering and fiber bending. Using this technique, we successfully demonstrate the endoscopic imaging of ~750μm features on an object positioned behind a scattering layer. This advancement holds significant potential for enabling spatially resolved three-dimensional imaging of objects concealed beneath tissue using fiber endoscopes, expanding the capabilities of these systems for novel medical applications.