Fig. 1. Principle of the photon counting imaging system

Fig. 2. Schematic diagram of echo and reconstruction results under different conditions. (a) Schematic diagram of single-pixel echo; (b) reconstruction result

Fig. 3. Principles of super-resolution imaging and NLOS imaging. (a) Low-resolution image; (b) super-resolution result; (c) principle of the NLOS imaging

Fig. 4. Schematic diagram of the OPN3DR algorithm^[28]

Fig. 5. Reconstruction results of different algorithms under different dwelling times^[28]

Fig. 6. Principle of the non-local neural network reconstruction algorithm^[36]

Fig. 7. Reconstruction results of different algorithms on long-distance targets^[36]

Fig. 8. Target classification results based on multispectral photon counting imaging^[40]

Fig. 9. Three-dimensional reconstruction results of multispectral photon counting under different conditions. (a) Reference image; (b)--(d) SBR is 1, PPP is 10; (e)--(g) SBR is 0.1, PPP is 10^[46]

Fig. 10. Restoration results of nylon net and the hiding target^[7]

Fig. 11. Reconstruction results of long-distance targets for multi-peak signals by different algorithms^[52]

Fig. 12. Super-resolution results of target located at 8.2 km^[54]

Fig. 13. NLOS imaging results of different algorithms. (a) Physical map; (b) echo-time distribution diagram; (c) FBP algorithm; (d) LCT algorithm; (e) f-k algorithm^[64]