High-efficiency dynamic three-dimensional shape measurement based on misaligned Gray-code light

The combination of Gray-code method with phase-shifting algorithm has been widely used in three-dimensional (3D) shape measurement. However, the non-uniform surface reflectance, the defocus of the projector and the object motion will cause order jump error at the boundary of adjacent Gray-code. This paper proposes a 3D shape measurement method based on misaligned Gray-code (MGC) light to avoid this kind of error. In this method, all the traditional Gray-code patterns are pre-moved by half fringe period before projection so that the edges of the decoding order and the wrapped phase are staggered exactly, and then each period of decoding order is divided into four sub-regions to construct correct phase order and unwrap the wrapped phase. In addition, the fringe period number can be further expanded by introducing the virtual plane to improve the measurement efficiency and accuracy simultaneously. Two sets of comparative experiments on static scenes confirm that our method can successfully avoid the order jump error without projecting additional Gray-code pattern. And the dynamic experimental results demonstrate that proposed method can especially realize high-efficiency and high-speed 3D shape measurement at a rate of 2381 fps by labeling 32-period fringe patterns with only 4 misaligned Gray-code patterns.