High-Counting-Rate Single-Photon LiDAR With Free-Running InGaAs/InP SPAD

Light detection and ranging (LiDAR) with InGaAs/InP Single Photon Avalanche Diodes (SPADs) offers high sensitivity and exceptional temporal resolution, enabling a wide range of applications in target detection, earth mapping, gas detection, and atmospheric exploration. However, it struggles with a long accumulation time to determine the reflectivity and depth of the target. In this article, a high-counting-rate single-photon LiDAR system was developed to decrease accumulation time and improve detection and imaging speed. A Markov-chain steady-state model was introduced for the first time to relate counting rate, signal flux, and laser repetition frequency. This model corrects waveform distortion at high counting rates and substantially enhances the accuracy of both depth and reflectivity measurements. The adjustable laser repetition rates resolve distance ambiguities arising from high counting rates, enhancing detection and imaging range. Simulations and experiments were carried out to verify the performance of the LiDAR and the established model. The LiDAR systems achieved an average photon counting rate of 717 kHz, which was nearing the saturation counting rate of the InGaAs/InP single-photon detector (833 kHz). The LiDAR systems in building mapping were verified by the 3-D imaging and the time consumption of 0.2 ms per pixel, which achieved 3-D imaging of buildings from 40 to 120 m with sub-centimeter depth accuracy when the laser repetition rate was 3.125 MHz (unambiguous range 48 m).