Fig. 1. Relative error distribution of H-S algorithm. (a) Range of phase shift is (0, π]; (b) range of phase shift is (0, 9π/50] (relative error is <2%)

Fig. 2. RMSE distributions of H-S algorithm. (a) Range of phase shift is (0, π]; (b) range of phase shift is (0, 9π/50] (relative error is <2%)

Fig. 3. Error distributions of H-S algorithm with iteration rage from 200 to 1500. (a) Relative error; (b) RMSE

Fig. 4. Error distributions of H-S algorithm with iteration range from 300 to 1500. (a) Relative error; (b) RMSE

Fig. 5. Relative error distributions of L-K algorithm with different pyramid layers. (a) Number of pyramid layers is 1; (b) number of pyramid layers is 2

Fig. 6. RMSE distributions of L-K algorithm with different numbers of pyramid layers. (a) Number of pyramid layers is 1; (b) number of pyramid layers is 2

Fig. 7. Error distributions of L-K algorithm when number of pyramid layers is 1, relative error is less than 2%, and phase shift range is [0, 53π/100]. (a) Relative error; (b) RMSE

Fig. 8. Comparison of errors between H-S algorithm and L-K algorithm with different numbers of pyramid layers. (a) Relative error; (b) RMSE

Fig. 9. Comparison of displacement value calculated by H-S algorithm and true value under different phase shifts. (a) 10^-12π; (b) 10^-13π; (c) 10^-14π; (d) 10^-15π; (e) 10^-16π

Fig. 10. Comparison of displacement value calculated by L-K algorithm and true value under different phase shifts. (a) 10^-12π; (b) 10^-13π; (c)10^-14π; (d) 10^-15π; (e) 10^-16π

Fig. 11. Comparison of resolution relative errors of H-S algorithm, L-K algorithm, and four step phase shift

Fig. 12. Relative error distributions obtained by H-S algorithm with noise. (a) Range of phase shift is (0,π]; (b) range of phase shift is (0, 9π/50](relative error is <2%)

Fig. 13. Displacement RMSE distributions obtained by H-S algorithm with noise. (a) Range of phase shift is (0, π]; (b) range of phase shift is (0, 9π/50] (relative error is <2%)

Fig. 14. Displacement relative error distributions obtained by L-K algorithm with noise. (a) Range of phase shift is (0, π]; (b) range of phase shift is (0, 53π/100] (relative error is <2%)

Fig. 15. Displacement RMSE distributions obtained by L-K algorithm with noise. (a) Range of phase shift is (0, π]; (b) range of phase shift is (0, 53π/100] (relative error is <2%)

Fig. 16. Resolution error distributions of H-S algorithm with noise. (a) Relative error; (b) RMSE

Fig. 17. Resolution error distributions of L-K algorithm with noise. (a) Relative error; (b) RMSE

Fig. 18. Resolution relative error distributions of different algorithms. (a) H-S algorithm; (b) L-K algorithm (range of phase shift is [10^-3π, 10^-1π])