Temporal Phase Unwrapping Based on Unequal Phase-Shifting Code.

Area of Science:

• Optics and Photonics
• 3D Metrology
• Computer Vision

Background:

• Temporal phase unwrapping (TPU) in fringe projection profilometry (FPP) aims to reduce the number of projected patterns for efficiency.
• Accurate 3D shape reconstruction relies on resolving the $2\pi $ ambiguity in phase measurements.

Purpose of the Study:

• To propose a novel TPU method using unequal phase-shifting codes to reduce projected patterns.
• To enhance the speed and robustness of 3D shape reconstruction in FPP systems.

Main Methods:

• Wrapped phase calculation using conventional N-step phase-shifting patterns.
• Generation of a coded pattern with unequal phase-shifting amounts serving as codewords.
• Decoding fringe order using conventional and coded wrapped phases, coupled with a self-correction method.

Main Results:

• Successful implementation of TPU with only one additional coded pattern (e.g., 3+1 pattern projection).
• Determination of fringe order for large numbers, effectively removing $2\pi $ ambiguity.
• Demonstrated high robustness to object reflectivity variations and maintained measurement speed.

Conclusions:

• The proposed unequal phase-shifting code method significantly reduces pattern projection for FPP.
• This technique is highly beneficial for dynamic 3D shape reconstruction applications.
• The method offers a robust and efficient solution for temporal phase unwrapping.