Phase-Shifting Structured Illumination with a Polarization-Encoded Metasurface.

Phase-shifting structured illumination is a powerful technique used across diverse imaging modalities including 3D surface measurement, quantitative phase imaging, and super-resolution microscopy. However, conventional implementations often rely on mechanically or optoelectronically driven complex systems, limiting the compactness, stability, and integration. Here, we present a polarization-controlled dielectric metasurface that generates phase-shifting fringe patterns in the visible spectrum, enabling compact and robust structured light projection. The metasurface encodes distinct phase gratings for orthogonal polarizations, producing fringe patterns with lateral displacements that vary with the transmitted polarization. We experimentally demonstrate high-quality fringe generation and apply the structured illumination in a fringe projection profilometry system for the 3D surface measurement of different objects. The metasurface integrates multiple phase-shifting steps into a single static device, offering a millimeter-scale footprint and compatibility with polarization multiplexing. This approach introduces a compact, passive solution for structured light generation with broad potential in optical metrology and computational imaging.