Fig. 1. Principle of the grid division. (a) Spatial coordinates of the LED light source; (b) grid division on the receiving surface

Fig. 2. Schematic diagram of the lens surface generation

Fig. 3. Free-form surface data of the uniform rectangular spot

Fig. 4. Solid model of the rectangular spot lens

Fig. 5. Irradiance distribution and profile of receiving surface. (a) Irradiance; (b) profile

Fig. 6. Simulation diagram of the underwater LED transmitting antenna experiment

Fig. 7. Light path diagram of the underwater LED transmitting antenna experiment

Fig. 8. Received optical power in different media

Fig. 9. Structure of the transmitting antenna. (a) Structure of the free-form surface lens; (b) structure of the omni-directional transmitting antenna

Fig. 10. Overall structure of the free-form surface lens

Fig. 11. Irradiance distribution and profile of single transmitting channel on the receiving surface 2. (a) Irradiance; (b) profile

Fig. 12. Irradiance distribution and profile of dual transmitting channel on the receiving surface 2. (a) Irradiance; (b) profile

Fig. 13. Irradiance distribution and profile on receiving surface 1. (a) Irradiance; (b) profile

Fig. 14. Irradiance distribution and profile on receiving surface 3. (a) Irradiance; (b) profile