Efficient and robust phase unwrapping via virtual gratings and hybrid coding

Area of Science:

• Optics and Photonics
• Computer Vision and Image Processing
• Metrology

Background:

• High-frequency phase unwrapping is crucial for accurate 3D shape reconstruction in fringe projection profilometry (FPP).
• Existing methods often face a trade-off between robustness and efficiency, particularly at high frequencies.
• Robust segmentation of fringe periods and precise phase recovery are persistent challenges.

Purpose of the Study:

• To introduce a novel framework, virtual gratings and hybrid phase unwrapping (VGHPU), for addressing high-frequency phase unwrapping challenges in FPP.
• To enhance the robustness and efficiency of 3D reconstruction in FPP systems.
• To achieve accurate geometric and surface color reconstruction with minimal projection data.

Main Methods:

• Integration of expanded Gray-code (EGC) for robust fringe period segmentation.
• Utilization of virtual grating-based demodulation exploiting spatial phase-shift characteristics.
• Combination of EGC and virtual gratings for hybrid phase unwrapping.
• Employing only three auxiliary projections for phase recovery.

Main Results:

• VGHPU framework successfully achieves reliable high-frequency phase unwrapping.
• The method demonstrates robustness and efficiency in complex object reconstruction.
• Accurate reconstruction of both geometry and surface color was validated using fringe patterns with 76 periods.

Conclusions:

• VGHPU offers a significant advancement in high-frequency phase unwrapping for FPP.
• The framework provides a robust and efficient solution for 3D shape and color measurement.
• The successful reconstruction of complex objects validates the practical applicability of VGHPU.