Fig. 1. Uniformly-distributed circular light spot

Fig. 2. Gaussian-distributed circular light spot

Fig. 3. Uniformly-distributed elliptical light spot

Fig. 4. Gaussian-distributed elliptical light spot

Fig. 5. Gaussian-distributed ring light spots

Fig. 6. Schematic diagram of QD

Fig. 7. Schematic diagram of internal structure of LUCE terminal

Fig. 8. Schematic block diagram of LCE

Fig. 9. Structure diagram of BLISL system

Fig. 10. Schematic diagram of laser tracking system based on quadrant APD

Fig. 11. Schematic diagram of KODEN receiver

Fig. 12. Schematic diagram of experimental device

Fig. 13. Basic block diagram of SLT

Fig. 14. Optical path diagram of LLST

Fig. 15. QD output values under different spot modes

Fig. 16. QD output values under different spot radius

Fig. 17. QD output values under different deadband widths

Fig. 18. QD output values under different scales of background light

Fig. 19. Variation curve of standard deviation of spot position under different SNR

Fig. 20. Simulation comparison under different positioning algorithms

Fig. 21. Effect of different quadrant response uniformity on QD output

Fig. 22. Offset of X and Y axis under different spot models

Fig. 23. Structure diagram of beam-alignment detection system

Fig. 24. Missing spot detection image

Fig. 25. Complete spot detection image

Fig. 26. QD output diagram during adjustment process

Fig. 27. Tracking and communication composite detection system

Fig. 28. Structure diagram of micro nano laser communication terminal system