Fig. 1. System model of the Fresnel lens coupler

Fig. 2. Design diagram of the Fresnel lens coupler

Fig. 3. Design diagram of the fully reflective rotating surface of the free-form surface

Fig. 4. Schematic diagram of the Fresnel rotating surface. (a) Structural diagram of the curved surface; (b) design principle of the single indentation; (c) rays and the indentation shapes of the normal Fresnel lens; (d) rays and the indentation shapes of the centrality; (e) rays and the indentation shapes of the edge

Fig. 5. 3D model of the Fresnel lens coupler

Fig. 6. Light distribution curves of naked LED

Fig. 7. (a) Energy distribution of 3535 LED on the receiving screen; (b) energy distribution of the 3535 LED on the receiving screen with Fresnel lens coupler

Fig. 8. Effect of different coupled distance H on the uniformity of receiving surface of the fiber bundles

Fig. 9. (a) Illumination distribution diagram of side-entry coupling plane and (b) light distribution curves of the Fresnel lens coupler

Table 1. Comparison of the luminous flux of LED-Fresnel lens coupler