Fig. 1. Schematic diagram for the extraction of the synthetic-wavelength interferogram

Fig. 2. Flow chart for the synthetic-wavelength phase retrieval with the double phase shift strategy

Fig. 3. Simulated results. (a) One frame initial dual-wavelength interferogram; (b) The corresponding Fourier spectrum for the dual-wavelength interferogram; (c) The Fourier spectrum of the dual-wavelength STF; (d) The obtained synthetic-wavelength interferogram with original size; (e) The residual error for the retrieved wavefront

Fig. 4. Separated spectral distances for different methods. (a) ATM method; (b) FT method; (c) CCFC method; (d) DCD method

Fig. 5. Demodulated error curve with the variation of fringe number at \begin{document}$ {\lambda _{\text{s}}} $\end{document} for three methods. (a) PV; (b) RMS

Fig. 6. Measured data for the test step in experiment. (a) Dual-wavelength interferogram; (b) Fourier spectrum of the dual-wavelength interferogram; (c) Fourier spectrum of the dual-wavelength STF; (d) The extracted synthetic-wavelength interferogram with original size

Fig. 7. Results of the test step with about 4 fringes for the synthetic wavelength. (a) DCD method; (b) CCFC method

Fig. 8. Measured data for the test step in experiment with lower carrier condition. (a) Dual-wavelength interferogram; (b) Fourier spectrum of the dual-wavelength interferogram; (c) Fourier spectrum of the dual-wavelength STF; (d) The extracted synthetic-wavelength interferogram with original size

Fig. 9. Results of the test step by the proposed DCD method with about 1 fringes for the synthetic wavelength

Fig. 10. The result of the test step measured by white light interferometer (Veeco NT9100)