Fig. 1. Schematic diagram of two-dimensional planar luminous flux

Fig. 2. Schematic of initial curve construction of double freeform surface lens

Fig. 3. Iterative calculation of internal and external freeform surfaces

Fig. 4. Schematic diagram of solution of tangent line iterative method

Fig. 5. Design flow chart of double freeform surface lens

Fig. 6. Profiles of near field single and double freeform surface lenses

Fig. 7. Three-dimensional models of freeform sufrace lenses. (a) Three-dimensional structure and (b) cross-sectional view of single freeform surface lens; (c) three-dimensional structure and (d) cross-sectional view of double freeform surface lens

Fig. 8. Simulation results on target plane 25 mm away. (a) System ray tracing and (b) simulation result of single freeform lens; (c) system ray tracing and (d) simulation result of double freeform lens

Fig. 9. Comparison of simulation results of single and double freeform surfaces lenses

Fig. 10. Influence of displacement error within ±1 μm on illumination uniformity of discrete points

Fig. 11. Energy utilization and uniformity of system at different distances in near field

Fig. 12. Lens profile of far field double freeform surface design

Fig. 13. Three-dimensional model of far-field lens. (a) Three-dimensional structure; (b) cross-sectional view

Fig. 14. Simulation results on target plane 10 m away. (a) Ray tracing of system; (b) simulation results

Fig. 15. Diagram of normalized illuminance 10 m away

Fig. 16. Error of discrete points at freeform surface with error in range of ±1 μm varying with uniformity

Fig. 17. Illumination energy utilization and uniformity of target surface at different distances in far field