Fig. 1. Flow diagram of temporal phase unwrapped algorithm. (a) Phase shifting image; (b) wrapped phase; (c) Gray-code image; (d) order of each period; (e) unwrapped phase

Fig. 2. Period-order coding sequence used in this paper

Fig. 3. Coding phase diagram

Fig. 4. Four-step phase shift fringe images corresponding to adjusted phase

Fig. 5. Phase error for different number of divided segments

Fig. 6. Decoding and phase unwrapping process

Fig. 7. Schematic diagram of influence of occlusion on decoding

Fig. 8. Continuous symbol matching

Fig. 9. Reconstruction process of facial mask. (a) Image of phase-level encoding; (b) wrapped phase obtained by four-step phase-shifting method; (c) absolute phase obtained by decoding algorithm proposed in this paper; (d) side view of reconstructed facial mask

Fig. 10. Analysis of workpiece occlusion. (a)(e) Workpieces placed in two positions; (b)(f) wrapped phase; (c)(g) wrapped phase after removing phase outliers; (d)(h) unwrapping phase

Fig. 11. Experiment of 3D object reconstruction. (a)--(c) Objects to be reconstructed, which can be divided into ceramic pot and workpieces placed in two different ways; (d)--(f) reconstruction results

Fig. 12. Results of 3D plate reconstructed by three methods. (a) Proposed method; (b) multi-frequency heterodyne method; (c) gray-code plus phase-shifting method