Fig. 1. Measuring points of sapphire in different sizes and path planning

Fig. 2. Principle of vertical scanning white light interference technology

Fig. 3. Principle for autofocus judgement

Fig. 4. Workflow of focusing algorithm

Fig. 5. Workflow of sapphire substrate surface topography measurement and evaluation system

Fig. 6. Photo of sapphire substrate surface topography measurement system

Fig. 7. Physical drawing of R_a standard parts

Fig. 8. Fitting results for error compensation

Fig. 9. Contrast experiment with Zygo7300 3D optical profilometer

Fig. 10. Measurement result of surface profile contrast experiment

Fig. 11. Analysis of focusing algorithm

Fig. 12. Three-dimensional topography of position 3

Fig. 13. Two-dimensional evaluation parameters of 2-inch sapphire substrate

Fig. 14. Three-dimensional evaluation parameters of 2-inch sapphire substrate

Fig. 15. Two-dimensional evaluation parameters of 4-inch sapphire substrate

Fig. 16. Three-dimensional evaluation parameters of 4-inch sapphire substrate