A method for obtaining complete point cloud of tongue surface based on fringe projection trinocular system

The traditional tongue diagnosis process has the problem of poor objectivity. Applying computer vision technology to tongue diagnosis can effectively promote its objectivity. Binocular stereo vision combined with structured light fringe projection technology is a common method for 3D measurement. However, in the measurement scenario of tongue diagnosis, due to the presence of saliva and fluids on the tongue surface, there are high-reflectance areas with significant random distribution in the fringe images, leading to errors in phase calculation and point cloud loss. A trinocular measurement system was proposed based on fringe projection, where a trinocular system and three binocular subsystems were composed of three cameras. Dual-epipolar constraint based on phase and order constraints was introduced to enhance the accuracy of trinocular stereo matching. Supplementary matching points were utilized to optimize the trinocular matching point sets, reconstructing point clouds in high-reflectance areas. The results indicated that, compared to traditional binocular systems, this system achieved improved matching and reconstruction accuracy. Particularly in real tongue surface measurements, it could generate point clouds with clear textures and complete features. It could effectively measure the highly reflective area of the tongue surface and facilitate objective tongue diagnosis.