Fig. 1. Schematic of subset before and after deformation. (a) Reference image; (b) deformed image

Fig. 2. Optical path diagram of deflectometry

Fig. 3. Schematic of SPD test setup

Fig. 4. Schematic of image deformation. (a) Image reflected by reference surface; (b) image reflected by surface to be tested; (c) displacement of inspection point

Fig. 5. Reflection of light on reference surface

Fig. 6. Experimental setup

Fig. 7. Curves of mean intensity gradient versus number of speckle

Fig. 8. Pictures taken in experiment (inner circle area is used for surface measurement). (a) Captured using planar crystal; (b) speckles captured using acrylic plastic plate; (c) fringe captured in PMD

Fig. 9. Displacement of pixel points in effective area. (a) Displacement in x direction; (b) displacement in y direction

Fig. 10. Slope measurement results. (a)(b) Slope memeasured by SPD in x and y directions, respectively; (c)(d) slope measured by PMD in x and y directions, respectively

Fig. 11. Surface shape reconstruction results. (a) Result of SPD; (b) result of PMD; (c) surface difference between the two methods