Compact non-line-of-sight imager at long range

Non-line-of-sight (NLOS) imaging can detect hidden targets via bypassing obstacles, which holds great potential for imaging and vision applications. Existing research has focused primarily on short-range indoor scenarios. However, in the context of practical use, long-range outdoor NLOS imaging remains challenging, mainly due to photon loss and high background noise, particularly under daylight conditions. Here, we report a compact and integrated NLOS imaging prototype for outdoor scenarios. The prototype achieves high-efficiency and low-noise photon collection by integrating the key techniques of optimized optical design, adaptive gating, high-transmittance optical devices, and fast control electronics. With this prototype, we demonstrate daylight kilometer-range NLOS imaging at a rate of 2 frames per second, four orders of magnitude faster than previous art. These results provide a solid foundation for the widespread applications of NLOS imaging in real-world scenarios.