Improvement of Undersaturated Regions in Structured Light 3D Measurement

In structured light three-dimensional measurement technology, the low reflectivity of black or dark surfaces leads to insufficient reflection, causing phase information undersaturation and severely affecting reconstruction accuracy. To address this issue, an improved algorithm combining high-brightness sinusoidal projection with regional masking is proposed. First, high-brightness sinusoidal fringe patterns are employed to enhance the projected light intensity in low-reflection areas. A mask is generated based on the ratio of background intensity to modulation amplitude to adaptively distinguish between undersaturated and oversaturated regions. The phase extraction in the target area is optimized through a phase fusion strategy. Second, the Gray code decoding method is improved by introducing a regional weighted filtering algorithm, which corrects binary encoding errors through neighborhood weight analysis. Experimental results demonstrate that the proposed algorithm increases the point cloud density of a black planar object from 463,637 to 571,324 (a growth rate of 23.23%) and reduces the root mean square error from 0.004594 to 0.003475 (a decrease of 24.3%). The planarity of the point cloud is significantly improved. In the reconstruction results of practical targets (e.g., a black keyboard), the missing areas are reduced, and the surface continuity is enhanced.