Fig. 1. Schematic of refraction - reflection hybrid lens based on point light source

Fig. 2. Schematic of energy grid mapping

Fig. 3. Schematic of refraction part design principle

Fig. 4. Schematic of reflection part design principle

Fig. 5. Designed illumination distribution on the target plane

Fig. 6. Light intensity distribution of extended light source

Fig. 7. Initial profile of refraction-reflection hybrid lens

Fig. 8. Simulation results of initial surface

Fig. 9. Graph of "M" illuminance distribution

Fig. 10. Simulation of "M" shape distribution

Fig. 11. Adjusted profile of the lens

Fig. 12. The optimized lens

Fig. 13. Actual lens

Fig. 14. Practical backlight unit with the designed lenses

Fig. 15. Nine points for uniformity