Portable Pulsed Coherent Lidar for Noncooperation Targets at the Few-Photon Level

The decoherence in coherent lidar becomes serious with the increase in distance. A small laser spot can suppress the decoherence of the echo light from noncooperation targets. However, it is very difficult to keep a small light spot over a long distance. In this paper, a pulsed coherent lidar with high sensitivity at the few-photon level was demonstrated. A phase plate was used to modulate the wavefront of the laser to achieve 100 m focusing which reduced the decoherence effect. Based on coherent detection and time-of-flight (TOF) measurements, long-distance laser ranging and imaging on all days was realized. A signal classification and superposition method was used to extract the echo signal submerged in noise. The system was experimentally demonstrated by ranging different noncooperation targets within 105.0 m. The measurement rate was 10 k/s, and the measurement uncertainty was 1.48 cm. In addition, laser imaging was realized at similar to 50.0 m. The system was simple and portable as well as eye safe, and it may offer new application possibilities in automated vehicle lidar.

Automated summary

The paper presents a few-photon level pulsed coherent lidar, which reduces the decoherence effect over long distances by using a phase plate to achieve 100 m focusing. By applying a signal classification and superposition method, the system successfully extracts echo signals submerged in noise. It is capable of operating at different distances on noncooperation targets, with a high measurement rate and low measurement uncertainty.