Single-photon lidar has demonstrated significant capabilities in long-range, high-sensitivity detection under conditions of low-pulse-energy laser and small-aperture optical systems. However, certain practical applications face challenges in detecting distant targets within high background noise environments, limiting operational effectiveness. This paper introduces an asynchronous correlation encoding detection method based on the gate-mode operational characteristics of single-photon detectors to enhance the ultimate detection range and improve detection reliability in strong background noise environments. The method executes target detection through alternating operation of the single-photon detector between two states (laser pulse-synchronized detection and asynchronous detection), followed by acquisition and subtraction of raw echo datasets from both states, culminating in cross-correlation operations between the resultant histogram data and correlation codes.

This study presents an asynchronous correlation encoding detection method. Monte Carlo simulations were utilized to compare detection success probabilities between this method and the pulse accumulation detection method under varying relative interference intensities, while analyzing the influence patterns of coding sequences on detection performance. The algorithm architecture was implemented on a field-programmable gate array (FPGA) platform for experimental validation, establishing an asynchronous correlation encoding single-photon lidar system. Outdoor ranging experiments demonstrated enhanced detection performance under strong background noise environments through comparative analysis of lidar measurements across different detection methods and noise levels, validating the method’s effectiveness in improving single-photon lidar ranging systems.

Simulation studies reveal that when the autocorrelation of the encoded sequence approaches similarity, the detection probability of the asynchronous correlation encoding method decreases with increasing code length. This decrease stems from reduced energy allocation to individual echo pulses corresponding to each code element in longer code lengths, adversely affecting system detection performance. However, at fixed code length, the system’s detection performance shows positive correlation with sequence autocorrelation. Under a relative interference intensity of 17.5 dB, the asynchronous correlation encoding method with a code length of 2 achieves a detection success probability of 63.1%, surpassing conventional pulse accumulation single-photon lidar by 22.9 percentage points [Fig. 5(a)], demonstrating superior detection performance under strong background noise interference. An asynchronous correlation single-photon lidar system was constructed for ranging experiments on an outdoor target. Multiple ranging trials were conducted on a building exterior wall at 10 m under varying background noise intensities with an integration time of 0.5 s. At a background noise photon count rate of 1600 s^-1, both detection methods successfully identified the target [Fig. 9(a), Fig. 10(a), Fig. 10(b)]. At 198000 s^-1, while the pulse accumulation method’s signal peak became indistinguishable from noise [Fig. 10(c)], the asynchronous correlation encoding method maintained a distinguishable signal peak [Fig. 10(d)]. In ten repeated trials, the pulse accumulation method achieved no successful detections [Fig. 9(b)], while the asynchronous correlation encoding method achieved five successful detections [Fig. 9(c)]. At 135000 s^-1 background noise photon count rate, with the system repositioned 0.3 m back, the pulse accumulation method achieved six successful detections [Fig. 11(a)], while the asynchronous correlation encoding method achieved eight successful detections [Fig. 11(b)]. These results demonstrate the superior noise suppression capabilities and higher detection probability of the asynchronous correlation encoding detection method under strong background noise interference.

This study presents an asynchronous correlation encoding detection method based on single-photon detectors’ gated-mode operation characteristics and demonstrates the construction of a corresponding lidar system. The system exhibits enhanced detection probability under strong background noise interference. Monte Carlo simulations analyzed detection probability under various methods and conditions, particularly examining code length and autocorrelation effects on system performance. Research indicates optimal detection performance occurs with a code length of 2, where the single-photon detector operates in two states. The method demonstrates reliable target detection under strong background noise interference compared to conventional pulse accumulation of single-photon lidar. Experimental evaluations confirm excellent noise suppression capabilities and higher detection success probability in intense background noise environments compared to traditional methods. This research provides a practical approach for enhancing single-photon lidar system reliability under strong background noise interference, establishing groundwork for applications in challenging environments with intense background noise and long-distance requirements.