Fig. 1. Schematic diagram of phase measuring deflection (PMD) structure

Fig. 2. LCD structure diagram

Fig. 3. Phase gradient mapping of refraction effect of transparent layer of display screen

Fig. 4. Measurement flow chart

Fig. 5. PMD system

Fig. 6. Plane flat crystal surface residuals before and after compensation. (a) PV is 0.83 µm and RMS is 0.15 µm before compensation; (b) PV is 0.59 µm and RMS is 0.12 µm after compensation

Fig. 7. Spherical mirror surface residuals before and after compensation. (a) PV is 1.14 µm and RMS is 0.22 µm before compensation; (b) PV is 0.71 µm and RMS is 0.14 µm after compensation