Fig. 1. Horizontal and vertical grid division

Fig. 2. Grid area and flux ratio

Fig. 3. Shape adjustment of grid nodes. (a) Before adjustment; (b) after adjustment

Fig. 4. Source grids and target grids. (a) Source grid; (b) target grid

Fig. 5. Changes of evaluation function. (a) Change of source evaluation function; (b) change of target evaluation function

Fig. 6. Optical system. (a) Schematic of optical system; (b) free-form surface

Fig. 7. Simulation result