Portable system for flexible micro-endoscopy using a multi-mode fiber

Advances in imaging through a single multi-mode fiber (MMF) have made it a strong competitor to conventional endoscopic imaging technologies. However, these advancements have predominantly remained confined to laboratory environments. The transition to real-world applications has been hindered by several challenges. In this work, we address three of these challenges: device size and portability, speed and simplicity of calibration, and the robustness of the imaging to fiber flexing. We have developed a fully integrated, compact imaging system housed in a 15 cm×25 cm×35 cm unit. This portable system accommodates power management, serial communication, and optical components, making it suitable for practical deployment outside the laboratory. We use far-field diffuse-reflection imaging through a custom-built dual-fiber needle with a graded-index illumination fiber. We have incorporated a fast fixed-point arithmetic graphics processing unit (GPU) for calculating binary holograms. This enables a setup and calibration in 40 s. Finally, we demonstrate real-time image streaming using a dynamic calibration library, which maintains image quality even under continuous fiber bending. This image quality can be maintained without monitoring or knowledge of the fiber bend. Our innovations in calibration speed, portability, and fiber flexibility open new avenues for MMF use in minimally invasive imaging applications, ranging from minimally invasive medical imaging to the industrial inspection of complex structures.