Polarization-based structured light 3D measurement for metallic surfaces under time-varying ambient illumination

Area of Science:

• Optical Metrology
• Surface Characterization
• Industrial Measurement

Background:

• High reflectivity of metallic surfaces causes saturation and low fringe contrast in FPP.
• Time-varying ambient light interference (TVALI) degrades phase retrieval accuracy in FPP.
• Existing FPP methods struggle with accuracy on metallic surfaces due to these challenges.

Purpose of the Study:

• To develop a robust FPP method for accurate measurement of metallic surfaces.
• To address limitations imposed by high reflectivity and TVALI.
• To improve measurement efficiency and simplify system calibration.

Main Methods:

• Proposed a polarization-modulated illumination recovery model (P-MIRM).
• Utilized Fresnel reflection principles and polarization properties of metallic surfaces.
• Employed a polarization camera to decouple ambient light from modulated signals in a single image.
• Leveraged response differences across four camera channels for pixel-wise signal separation.

Main Results:

• Significantly reduced standard deviation of plane-fitting residuals by approximately 73%.
• Decreased error in adjacent step height differences by approximately 47%.
• Demonstrated markedly improved robustness under unstable illumination conditions.

Conclusions:

• P-MIRM effectively overcomes challenges of metallic surface measurement in FPP.
• The method offers a simplified, efficient alternative to conventional techniques without mechanical rotation.
• Achieved substantial improvements in accuracy and robustness for industrial metrology applications.