Optical metrology by phase-based methods reaches high accuracy and robustness because the information of interest is encoded as a phase distribution rather than intensity. Interferometry and fringe-projection profilometry are two examples of this approach. However, in some applications, the well-established phase demodulation algorithms fail or are not applicable. For example,
- when the phase shift is nonlinear and unknown,
- when the background and modulation lights are time-varying,
- when the spectral content of the background light overlaps with the spectrum of interest,
The phase demodulation algorithms developed in our research group covers four main topics: intensity normalization, phase-shifting, Fourier fringe analysis, and phase-unwrapping. The following list summarizes some results of our research in this project.
- A full scheme for phase evaluation.
- Unbiased envelope estimation of noisy sinusoidal signals.
- Intensity normalization.
- Generalized phase-shifting for inhomogeneous phase shifts.
- Fourier fringe-normalized analysis.