Fig. 1. Flow chart of CCD camera collecting grating fringe image

Fig. 2. Phase error analysis results. (a) Standard sinusoidal input and non-sinusoidal output; (b) ideal phase main value and actual output phase main value; (c) phase error caused by Gamma nonlinearity

Fig. 3. Simulated fringe patterns captured by a CCD camera. (a) Standard sinusoidal fringe γ₀=1; (b) distorted fringe γ₀=0.6; (c) distorted fringe γ₀=1.5; (d) distorted fringe γ₀=2.1

Fig. 4. Comparison of the sine characteristics of fringes with different Gamma values

Fig. 5. Spectrograms of the 300th line under different Gamma distortions. (a) γ₀=1; (b) γ₀=0.6; (c) γ₀=1.5; (d) γ₀=2.1

Fig. 6. The lowest power ratio search curves in the frequency domain under different Gamma distortions. (a) γ₀=0.6; (b) γ₀=1.5; (c) γ₀=2.1

Fig. 7. The lowest power ratio search curve in the frequency domain when γ₀=2.1

Fig. 8. Comparison before and after single-line fringe correction. (a) Gray scale comparison; (b) phase error comparison

Fig. 9. Grating fringe projection measurement system. (a) Structure diagram of the measurement system; (b) actual measurement equipment

Fig. 10. Comparison before and after the distortion grating fringe correction. (a) Captured grating fringes before correction; (b) captured grating fringes after correction

Fig. 11. Single-line spectrograms before and after the distortion grating fringe correction. (a) Spectrogram of the 500th line of grating fringes before correction; (b) spectrogram of the 500th line of grating fringes after correction

Fig. 12. Phase error of the 500th line under different phase correction methods

Fig. 13. Absolute phase maps before and after phase error correction. (a) Before correction; (b) after correction

Fig. 14. Absolute phase restoration of plaster vase. (a) Measuring object; (b) uncorrected absolute phase; (c) absolute phase after monotonic smoothing correction; (d) absolute phase after double four-step correction; (e) absolute phase after correction by the proposed method

Fig. 15. Absolute phase error of plaster vase under different correction methods