Fig. 1. Flow chart of variable grouping optimization

Fig. 2. Phase error varying with used period

Fig. 3. Simulation results of two-step phase-shifting method. (a) Environmental light intensity distribution; (b) surface reflectance; (c) height distribution; (d) fringe line image

Fig. 4. Error of different phase solution methods. (a) Method only considering ideal light source; (b) graphical method; (c) method of direct iterative optimization; (d) method of this paper

Fig. 5. Results of verification experiment. (a) Accurate value distribution of wrapping phase; (b) solution value of method in Ref. [15] when phase shift step is π/2; (c) solution value of method in Ref. [11] when phase shift step is π; (d) solution value of method in Ref. [14] when phase shift step is 3π/2; (e)-(g) solution values of proposed method when phase shift steps are π/2,π, and 3π/2, respectively; (h) distribution of phase precise value in first row of image; (i)-(k) solution errors in first row of image when phase shift steps are π/2, π, and 3π/2, respectively