Fig. 1. As of December 30, 2019, the discovered exoplanets

Fig. 2. Brightness distribution of the main star of the direct imaging exoplanet system

Fig. 3. Layout of the 2nd prototype sodium beacon AO

Fig. 4. Design schematic of a phase mask coronagraph system

Fig. 5. Relationship between halo contrast and WFS integration time

Fig. 6. Influence function of the DM

Fig. 7. Coronagraph in simulation experiment

Fig. 8. Halo contrast and wavefront closed-loop residual error with WFS integration time. The blue solid line is the theoretical analysis of the halo contrast and the blue inverted triangle is the simulation result, the red circle is the residual wavefront error

Fig. 9. Relationship between planetary/star stellar brightness ratio and planetary angular interval required to reach SNR = 5 in 3 h

Fig. 10. Relationship between planetary/star stellar brightness ratio and planetary angular interval required to reach SNR = 5 in 2 h. The green circle indicates the brightness ratio of the planet to the star; the purple solid line indicates the Robo-AO exoplanet detection capability; the blue solid line indicates the sodium beacon AO exoplanet detection capability

Fig. 11. Focal anisoplanatism phases of ROBO-AO Rayleigh guide star and Lijiang 1.8 m sodium guide star