Full-color 3D visualization with Janus metafiber.

Fiber endoscopic imaging system exhibits high-precision imaging capability in extreme scenarios due to its flexibility and compatibility. The fiber bundles are naturally suitable to collect 2D intensity information, but it is difficult to directly obtain depth or angle information. Therefore, a large number of complex optical components are usually required to achieve dual-function imaging. In this work, we propose a single round-trip system with metasurface-integrated fiber bundle, namely the so-called Janus metafiber system. With the forward and reverse switching of the same optical path, we simultaneously achieving passive 2D imaging in the visible regime and active 3D depth sensing. The experiment shows high imaging fidelity and noise resilience benefiting from time-division acquisition between single-wavelength array scanning and polychromatic illumination. Especially, a 60° FOV and a divergence angle less than 2° has been verified in the interpolation optimized 3D depth imaging. Furthermore, the enhanced broadband depth-resolved synthetic imaging and edge detection are demonstrated combining the bimodal data. Our work enlightens potential applications in real-time biomedical diagnostics, LiDAR, and industrial inspection.