Spectral division multiplexing-based region projection for 3D measurement under mutual reflection.

Structured-light techniques have demonstrated superior performance in 3D shape measurement. However, measuring multiple objects with diverse reflective properties remains challenging due to mutual reflection interference. This Letter proposes a spectral division multiplexing-based region projection (SRP) technique, where different surfaces are encoded with structured light of distinct spectra, effectively isolating mutual reflection in the spectral domain and fundamentally eliminating indirect reflection artifacts. First, surface location and regional fringe projection can be realized based on the mapping relationship between the camera and the projector. Subsequently, a hetero-spectral division multiplexing strategy is designed, ensuring that different sub-regions within a single frame contain distinct spectral information. As a result, independent phase retrieval for each measured object can be achieved using spectral channel separation, thereby achieving complete high-precision 3D measurement free from interreflection artifacts. Experiments validated the feasibility of the proposed method.