High sensitivity ranging of photon counting lidar with two-dimensional modulation

Traditional lidar sensitivity is not up to the requirements in detecting small long-range targets with weak echo signals. Due to the limitation by the background noise of sunlight and complex climate, the high sensitivity detection cannot be realized by a photon counting lidar with Geiger-mode Avalanche Photodiode Detector (Gm-APD). In this paper, a new system is proposed to improve the performance of photon counting lidar ranging based on two-dimensional modulation. The new system uses two modulation methods to modulate the transmitted signal, which are chirp modulation and photon orbital angular momentum modulation. Chirped modulation is used to adjust the transmitted signal waveform in the frequency domain, and the detection performance improvement of Gm-APD can be improved with response probability correction. Photon orbital angular momentum modulation is used to adjust the transmitted signal waveform in the spatial domain, which is used to filter out background noise. The simulation results show that two-dimensional modulation is independent and do not interfere with each other. Comparing with the traditional lidar, the detection probability increased by 52%; the SNR can be increased by up to 115%, the range accuracy can be up to two-thirds of the traditional range accuracy (means increased by 32%). The new system achieves high sensitivity detection in complex environment.