Fig. 1. Schematic of r distribution of the target surface

Fig. 2. Design idea of double freeform surface lens

Fig. 3. Surface design based on uniform illumination distribution

Fig. 4. Simulation results under uniform illuminance distributions

Fig. 5. Schematic of uniformity region

Fig. 6. Simulation results of uniformly distributed array

Fig. 7. Design illuminance distribution of "parallel-down"

Fig. 8. Comparison of illuminance curves of "parallel-down" distributions

Fig. 9. Design illuminance distribution of "up-parallel"

Fig. 10. Comparison of illuminance curves of "up-parallel" distribution

Fig. 11. Illuminance distribution of "up-parallel-down" design

Fig. 12. Comparison of illuminance curves of "up-parallel-down" distribution

Fig. 13. Optimized design of illuminance distribution

Fig. 14. Optimization of illuminance distribution and simulation results

Fig. 15. Schematic of light tracing

Fig. 16. Surface profile of bottom microstructure

Fig. 17. Array simulation results after optimization of bottom surface