Fig. 1. Flow chart for designing the freeform TIR lens

Fig. 2. Equalize the luminous flux and the target plane ( : the cone angle of the sampling rays; R: the radius of the target plane; : the radius of each annulus on target plane)

Fig. 3. Schematic diagram of the freeform TIR lens (1: a circular plane; 2: a freeform surface to be designed; 3: a cylindrical surface inside; 4: a freeform TIR surface to be designed; 5: an annular plane)

Fig. 4. Optical geometry of freeform surface

Fig. 5. Schematic diagram of Fresnel lens (R: the half-diameter of the lens; d: the width of each annulus; : the half inside-diameter of the jth Fresnel annulus; the half outer-diameter of the jth Fresnel annulus)

Fig. 6. 2D cross-section diagram of two types of TIR lens

Fig. 7. Illuminance distribution of two types of TIR lens

Fig. 8. 3D models of two types of TIR lens