Fig. 1. (a) Freeform surface model based on a Zernike polynomial; (b) fitted CAD model.

Fig. 2. Spiral center: (a) on the workpiece surface; (b) out of the workpiece surface.

Fig. 3. Schematic of the inclined-axis rotary ultrasonic grinding method.

Fig. 4. Grinding of the freeform SiC mirror: (a) machine tool; (b) testing of shape error; (c) machining results.

Fig. 5. CNC lapping and polishing of the freeform silicon carbide mirror: (a) photo of machine; (b) convergence rate of surface error with lapping cycles.

Fig. 6. (a) Testing optical path; (b) region function distribution of CGH; (c) photo of CGH; (d) testing results.