Fig. 1. Multi depth layer division method

Fig. 2. Weighted filling method for empty pixels

Fig. 3. Calculation method of null pixel signal set

Fig. 4. Depth maps of simulation experiment.(a) Reference depth map of simulation scene; (b)-(f) depth maps estimated by MLE, PCA, SPISTA, SHIN, and proposed method, respectively

Fig. 5. Schematic of long-range single-photon lidar system

Fig. 6. Depth maps of complex scene 1.(a) Visible band map of complex scene 1; (b) reference depth map; (c)-(g) depth maps estimated by MLE, PCA, SPISTA, SHIN, and proposed method, respectively

Fig. 7. Depth maps of complex scene 2. (a) Visible band map of complex scene 2; (b) reference depth map; (c)-(g) depth maps estimated by MLE, PCA, SPISTA, SHIN, and proposed method, respectively

Fig. 8. RSNR of depth maps estimated by different methods at different PPP levels