Non–line-of-sight (NLOS) imaging has the ability to reconstruct hidden objects from indirect light paths that scatter multiple times in the surrounding environment, which is of considerable interest in a wide range of applications. Whereas conventional imaging involves direct line-of-sight light transport to recover the visible objects, NLOS imaging aims to reconstruct the hidden objects from the indirect light paths that scatter multiple times, typically using the information encoded in the time-of-flight of scattered photons. Despite recent advances, NLOS imaging has remained at short-range realizations, limited by the heavy loss and the spatial mixing due to the multiple diffuse reflections. Here, both experimental and conceptual innovations yield hardware and software solutions to increase the standoff distance of NLOS imaging from meter to kilometer range, which is about three orders of magnitude longer than previous experiments. In hardware, we develop a high-efficiency, low-noise NLOS imaging system at near-infrared wavelength based on a dual-telescope confocal optical design. In software, we adopt a convex optimizer, equipped with a tailored spatial–temporal kernel expressed using three-dimensional matrix, to mitigate the effect of the spatial–temporal broadening over long standoffs. Together, these enable our demonstration of NLOS imaging and real-time tracking of hidden objects over a distance of 1.43 km. The results will open venues for the development of NLOS imaging techniques and relevant applications to real-world conditions.

非视距 (NLOS) 成像能够从在周围环境中多次散射的间接光路中重建隐藏的物体，这在广泛的应用中引起了极大的兴趣。传统成像涉及直接视线光传输以恢复可见物体，而 NLOS 成像旨在从多次散射的间接光路中重建隐藏物体，通常使用在散射的飞行时间中编码的信息。光子。尽管最近取得了进展，但 NLOS 成像仍处于短距离实现，受到重损失和多次漫反射引起的空间混合的限制。这里，实验和概念创新都产生了硬件和软件解决方案，以将 NLOS 成像的间隔距离从米增加到千米范围，这比以前的实验长约三个数量级。在硬件方面，我们基于双望远镜共焦光学设计，开发了近红外波长的高效、低噪声非视距成像系统。在软件中，我们采用凸优化器，配备使用三维矩阵表示的定制时空内核，以减轻长对峙时时空加宽的影响。总之，这些使我们能够在 1.43 公里的距离内展示 NLOS 成像和隐藏物体的实时跟踪。研究结果将为 NLOS 成像技术的发展和现实世界条件的相关应用开辟空间。