Fig. 1. Typical light path for three-dimensional surface shape measurement using fringe-projection method

Fig. 2. Spherical crown to be measured

Fig. 3. Simulated fringe patterns. (a) Original fringes; (b) modulated fringes

Fig. 4. Results of surface simulation. (a) Calculated value; (b) comparison between theoretical and calculated values on cross section at y=256 pixel; (c) relative error between theoretical and calculated values on cross section at y=256 pixel

Fig. 5. Simulated irregular fringe patterns. (a) Fringes before deformation; (b) fringes after deformation

Fig. 6. Results of optical flow method using irregular fringe patterns. (a) Calculated surface shape distribution; (b) comparison between theoretical and calculated values on the cross section at y=256 pixel; (c) relative error between theoretical and calculated values on cross section at y=256 pixel

Fig. 7. Fringes in experiment. (a) Fringes before modulation; (b) fringes after modulation

Fig. 8. Phase distributions of mask. (a) Phase shift method; (b) optical flow method

Fig. 9. Three-dimensional phase distributions of surface shape of mask. (a) Phase shift method; (b) optical flow method; (c) comparison of results calculated by phase shift method and optical flow method on cross-section at y=290 pixel