单光子探测器复用的多光束激光成像技术

Single-photon detection can improve the sensitivity of laser imaging Lidar, and the multi-beam scheme can increase the detecting speed and range. It is an important method for long-distance 3D laser imaging by combining these two techniques. Single-photon detecting arrays had high R&D cost and long cycle, so they were not suitable for the multi-beam scheme which need to change the spatial position distribution of the detecting pixels flexibly. As a result, most multi-beam systems used discrete detectors. However, too many single-photon detectors will greatly increase the difficulty of the system, which is limiting the number of the laser beams. In this proposal, we proposed a method of multi-beam laser imaging with single-photon detector multiplexing technique. All the echo photons can be detected by only one single-photon detector. These photons are from the multi laser beams with high repetition rate and relatively random phase. And the signal photons of each beam can be distilled by the time-correlated single-photon counting technique, because the photons of the other beams can be suppressed as same as the background counts. Meanwhile, the problems of the multi peaks of photon counts and range ambiguity will be resolved by improving the method of multi-repetition rate photon counting. It will overcome the defects of the dead time of the single-photon detectors, and quickly obtain the photon distribution with high fidelity of the complex surfaces, by counting the sparse echo photons of high-repetition-rate laser pulses.

单光子探测技术可提升激光成像雷达的探测灵敏度，多光束结构可提高系统的探测速率和测量范围，两者结合是实现远距离快速激光三维成像的重要方法。由于单光子探测阵列器件研发成本高、周期长，并不适合需要灵活调整空间位置分布的多光束结构。所以，目前多光束系统多采用分立探测器件。然而，单光子探测器是宝贵的系统资源，制约着光束规模。本项目提出单光子探测器复用的多光束激光成像技术，通过发展高速单光子探测技术，仅采用单路单光子探测器，同时探测多束相位随机的高重复频率激光脉冲回波信号，结合时间相关单光子符合计数，将相位随机的各路光子信号等效成背景噪声抑制，实现多光束信号同时探测和分析。同时，发展多重频光子计数方法，解决多回波峰、非模糊距离等问题，从而发挥高重频激光脉冲探测优势，在稀疏光子条件下，克服单光子探测器死时间缺陷，快速、高保真地获取光子分布信息，实现复杂表面快速高灵敏探测。

本项目研究多波束单光子雷达复用技术，提出并发展了多种复用技术，包括：重复频率复用技术、伪随机数复用技术，以及基于波分复用的收发光路。本项目通过研制多波长复用的单光子雷达原理样机，实现了基于时分复用+密集波分复用（DWDM）的16波束单光子成像，实现了基于伪随机数复用+DWDM的8波束单光子成像。本项目进一步发展了重复频率复用技术，20km范围内，验证了延长非模糊距离和多回波甄别的性能，并且提出了Self gating成像技术，为高速单光子成像建立了一种新的单光子数据处理方法。当前，对地测绘激光雷达朝着百波束甚至千波束规模发展，从而快速地获得地面三维信息。随着波束规模的增加，单光子探测器等核心模块的数量不断增多，利用本项目研究的复用技术，可以大幅减小单光子探测器的规模，解决多波束激光雷达的探测难题。