Two-plus-two fringe projection profilometry based on phase-shifted coding.

Area of Science:

• Optical Metrology
• 3D Imaging
• Computer Vision

Background:

• Fringe projection profilometry (FPP) is a key technique for 3D shape measurement.
• Temporal phase unwrapping in FPP often necessitates a large number of fringe patterns, increasing data acquisition time and complexity.
• Existing methods struggle with efficiency and accuracy when reducing fringe count.

Purpose of the Study:

• To propose a concise absolute phase retrieval algorithm that significantly reduces the number of fringe patterns required.
• To enhance the accuracy and robustness of fringe order mapping in FPP.
• To develop a method that is comparable in accuracy and adaptability to existing techniques but uses fewer fringes.

Main Methods:

• A novel algorithm projecting only four fringes is developed.
• Two orthogonal fringes with high frequency capture initial height data.
• Two additional phase-shifted fringes are used for robust fringe order labeling.
• An average intensity one-time extraction algorithm decodes fringe patterns.
• A universal fringe order correction algorithm addresses common errors and misalignment.

Main Results:

• The proposed method successfully retrieves absolute phase using only four fringe patterns.
• It achieves direct extraction of wrapped and stair-coded phases via arctangent operation.
• The algorithm demonstrates comparable accuracy and adaptability to traditional phase-coding methods.
• The method effectively corrects phase errors and misalignment.

Conclusions:

• The developed algorithm offers a significant reduction in fringe count for temporal phase unwrapping in FPP.
• It provides a robust and accurate method for absolute phase retrieval.
• This technique presents a more efficient and adaptable solution for 3D shape measurement compared to existing methods.