Accurate and fast event-based shape measurement of mixed reflectance scenes

Event-based structured light systems have recently emerged as an exciting alternative to frame-based triangulation for 3D measurement of diffuse surfaces, offering high dynamic range and fast capture speed, but at the cost of reduced data quality. Existing event-based and frame-based 3D imaging systems are typically tailored to a single surface reflectance type, diffuse or specular, and therefore struggle with mixed reflectance scenes. In this work, we present an event-based structured light system for fast and accurate 3D imaging of mixed reflectance scenes. Using epipolar constraints on the captured events, we decompose reflections into diffuse, two-bounce specular, and other multi-bounce reflections. Diffuse surfaces are reconstructed via triangulation and repurposed as a virtual screen for deflectometry to evaluate specular surfaces, requiring only a scanning laser and an event camera. Our system achieves motion-robust 3D reconstructions at  < 600 μm depth accuracy and introduces a fast diffuse-only capture mode operating at 250 Hz.