High-speed three-dimensional shape measurement based on shifting Gray-code light.

Area of Science:

• Optics and Photonics
• Computer Vision
• Metrology

Background:

• Traditional 3D shape measurement using phase-shifting and Gray-code light excels in static scenes but struggles with high-speed dynamic measurements.
• Phase unwrapping errors commonly occur at Gray-code boundaries due to projector defocus, object motion, and surface reflectivity variations.

Purpose of the Study:

• To develop a robust and high-speed 3D shape measurement method overcoming phase unwrapping errors in dynamic scenarios.
• To enhance the accuracy and reliability of 3D reconstruction for fast-moving or deforming objects.

Main Methods:

• A pixel-wise thresholding approach using average intensity of phase-shifting fringe images to binarize Gray codes and mitigate errors.
• Introduction of a shifting Gray-code (SGC) strategy with staggered decoding word boundaries to prevent residual unwrapping errors.
• Temporal sequence analysis without additional projected patterns to achieve phase unwrapping.

Main Results:

• The method effectively eliminates phase unwrapping errors caused by non-uniform reflectivity, ambient light, and projector defocus.
• The SGC strategy successfully addresses remaining errors at code word edges, ensuring robust phase unwrapping.
• High-quality 3D shape and texture information of randomly collapsing objects was reliably reconstructed at 310 frames per second.

Conclusions:

• The proposed shifting Gray-code method provides a simple, efficient, and robust solution for high-speed dynamic 3D shape measurement.
• This technique significantly improves the accuracy and applicability of 3D shape measurement in challenging dynamic environments.