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

Three-dimensional (3D) shape measurement serves an important role in many areas, and fringe projection profilometry (FPP) is a widely used 3D measurement technique due to its non-physical contact and high speed. The real measurement scenarios are often mixtures of specular and diffuse reflections, causing overexposed and underexposed areas to co-exist. Currently, utilizing FPP to simultaneously measure overexposed and underexposed areas remains a challenge. To solve this problem, we propose a mixed reflection model and what we believe to be a novel high dynamic range (HDR) 3D measurement method based on polarization and multispectrum co-modulation. In mixed reflection, the fringe images captured by the polarized color camera can be modulated to different intensities between different channels due to the co-modulation effect. By synthesizing all sub-images, high-modulation fringe images are formed and simultaneous reconstruction of overexposed and underexposed surfaces is finally achieved. Compared to conventional methods, the proposed method is more effective for measuring complex reflection situations, especially when objects with specular and diffuse surfaces simultaneously exist in the scene. And what we believe to be a novel no-registration-error calibration framework for multi-channel cameras has also been proposed, which both acquires a significant amount of information in the region with HDR problems and avoids the registration error due to the physical distances between different channels. Experiments were conducted to verify the effectiveness of the proposed method.