Shading-based absolute phase unwrapping.

Area of Science:

• Optics and Photonics
• 3-D Imaging and Metrology
• Computer Vision

Background:

• Absolute phase unwrapping is crucial for dynamic 3-D measurements in phase-shifting profilometry (PSP).
• Traditional spatial methods yield relative phase maps, while temporal methods require auxiliary projection sequences.
• Existing techniques face limitations in depth range and measurement complexity.

Purpose of the Study:

• To introduce a novel shading-based absolute phase unwrapping (SAPU) framework.
• To enable in situ 3-D measurements without additional projection patterns or spatial references.
• To overcome limitations of existing phase unwrapping techniques in dynamic 3-D measurements.

Main Methods:

• Calculation of wrapped phase map from three captured images.
• Obtaining a continuous relative phase map using phase histogram check (PHC).
• Deriving absolute phase map candidates and selecting the correct one via shading matching check (SMC).

Main Results:

• The proposed SAPU framework successfully retrieves absolute phase maps.
• Demonstrated validity of the shading matching check (SMC) for absolute phase determination.
• Experimental results confirm the effectiveness of the method for 3-D measurements.

Conclusions:

• The SAPU framework provides a robust solution for absolute phase unwrapping in PSP.
• The method eliminates the need for auxiliary patterns, simplifying dynamic 3-D measurements.
• This approach enhances the capability for large depth range 3-D reconstruction.