Order-shifting temporal phase unwrapping using uneven duty gray-code for high-accurate and high-efficient 3D...

Area of Science:

• Optical Metrology
• 3D Imaging and Reconstruction
• Computer Vision

Background:

• Higher-frequency fringe projection offers superior 3D measurement accuracy due to shorter wavelengths.
• Conventional Gray-code (GC) methods struggle with encoding numerous fringe orders, limiting efficiency in high-frequency systems.
• Complex auxiliary patterns in GC methods hinder rapid 3D reconstruction.

Purpose of the Study:

• To develop a novel method for efficient and accurate high-frequency 3D measurement.
• To overcome the limitations of conventional Gray-code methods in fringe order encoding.
• To improve the efficiency and robustness of 3D reconstruction for complex geometries.

Main Methods:

• Introduction of order-shifting temporal phase unwrapping (OSTPU) utilizing uneven duty cycle Gray-code (GC).
• Encoding relative order shifts at high frequencies (≥76) within the measurement range.
• Reducing required codewords from 76 absolute orders to 12 order-shift codewords using only 3 patterns.

Main Results:

• OSTPU relaxes the strict one-to-one mapping between GC word and fringe order, enabling spatial repetition and reducing system complexity.
• Achieved high-fidelity 3D reconstruction of complex color geometry.
• Reduced fringe count from 7 to 3, improving projection efficiency by over 57%.

Conclusions:

• OSTPU provides an accurate, efficient, and robust solution for high-frequency 3D measurement.
• The proposed method significantly enhances projection efficiency compared to conventional techniques.
• OSTPU simplifies the encoding process, making high-frequency 3D measurement more accessible.