Fig. 1. Schematic diagram. (a) PMD measurement system; (b) principle of acquiring coordinates of spherical reflection points

Fig. 2. Schematic for generating pre-distortion fringe

Fig. 3. Fringe projected by the LCD and captured by the camera. (a) Standard sine fringe in horizontal and vertical directions, respectively; (b) pre-distortion fringe in horizontal and vertical directions, respectively; (c) fringe captured by the camera when projecting standard sine fringe horizontally and vertically, respectively; (d) fringe captured by the camera when projecting pre-distortion fringe horizontally and vertically, respectively

Fig. 4. Unwrapping phase. (a) (b) Horizontal and vertical unwrapped phases of the fringe captured by the camera when projecting standard sine fringe, respectively; (c) (d) horizontal and vertical unwrapped phases of the fringe captured by the camera when projecting pre-distortion fringe, respectively

Fig. 5. Calculated ROC. (a) ROC obtained by projecting a standard sine fringe; (b) ROC obtained by projecting pre-distortion fringe

Fig. 6. PV and RMS calculated with different ROC values

Fig. 7. Experimental setup for measuring the ROC of spherical element

Fig. 8. Fringe captured by the camera. (a) (b) Fringe captured by the camera when projecting standard sine fringe and pre-distortion fringe in the vertical direction, respectively; (c) (d) fringe captured by the camera when projecting standard sine fringe and pre-distortion fringe in the horizontal direction, respectively

Fig. 9. Contrast of fringe. (a) Contrast of fringe captured by the camera when projecting standard sine fringe; (b) contrast of fringe captured by the camera when projecting pre-distortion fringe

Fig. 10. Mean ROC values measured in the experiment. (a) Result of projection standard sine fringe; (b) result of projection pre-distortion fringe

Table 1. Simulation results of spherical surfaces with different ROC values