Processing Algorithm for Four-Step Phase-Shifting Interferograms

This presents a comprehensive processing algorithm for four-step phase-shifting interferograms. The implementation begins with image preprocessing stages, which include noise filtering using Gaussian or median filters and contrast enhancement through histogram equalization. The core phase extraction module employs frequency-domain methods (such as Fourier transform analysis) and spatial-domain phase unwrapping approaches. Prior to phase unwrapping, phase adjustment algorithms are applied to prevent phase jumps by implementing modulo-2π corrections. The final phase unwrapping stage reconstructs the true phase map using quality-guided or least-squares methods, ultimately revealing accurate surface topography measurements. The provided MATLAB/Python code includes functions for: 1) interferogram calibration, 2) phase calculation via arctangent operations, and 3) robust unwrapping with path-following algorithms. Researchers exploring optical metrology can download this complete implementation for educational and experimental purposes.