High dynamic range 3D measurement based on polarization and multispectrum co-modulation.

Area of Science:

• Optical Engineering
• Metrology
• Computer Vision

Background:

• Three-dimensional (3D) shape measurement is crucial in various fields, with fringe projection profilometry (FPP) being a popular non-contact, high-speed technique.
• Real-world measurement scenarios frequently involve mixed specular and diffuse reflections, leading to co-existing overexposed and underexposed regions, which challenges conventional FPP.
• Simultaneously measuring surfaces with both overexposed and underexposed areas using FPP remains a significant technical hurdle.

Purpose of the Study:

• To address the limitations of FPP in mixed reflection environments.
• To propose a novel high dynamic range (HDR) 3D measurement method capable of simultaneously reconstructing overexposed and underexposed surfaces.
• To develop a registration-error-free calibration framework for multi-channel cameras used in HDR 3D measurements.

Main Methods:

• A mixed reflection model was developed to analyze polarization and multispectrum co-modulation effects in fringe images.
• A polarized color camera captured fringe images, leveraging co-modulation to achieve different intensity modulations across channels.
• Sub-images were synthesized to form high-modulation fringe images, enabling simultaneous reconstruction of surfaces with varying reflectivity.

Main Results:

• The proposed method successfully achieved simultaneous 3D shape measurement of overexposed and underexposed surfaces in mixed reflection scenarios.
• Experimental results demonstrated superior performance compared to conventional methods, particularly for objects exhibiting both specular and diffuse reflections.
• A novel no-registration-error calibration framework for multi-channel cameras was introduced, enhancing data acquisition in HDR regions and eliminating registration errors.

Conclusions:

• The proposed polarization and multispectrum co-modulation based HDR 3D measurement method effectively overcomes the limitations of traditional FPP in complex reflection environments.
• The developed technique enables accurate 3D reconstruction of objects with simultaneous specular and diffuse surfaces.
• The novel calibration framework ensures precise multi-channel camera registration, contributing to the overall accuracy and reliability of the HDR 3D measurement system.