Dynamic 3-D Shape Measurement Using Bidirectional Spatial Sequence Gray-Code Light

The Gray-code method combined with the phase-shifting algorithm is widely used in noncontact 3-D shape measurement. However, when the period number of fringe is high, a large number of Gray-code patterns are often required, which limits their application in dynamic scenes. To overcome this limitation, this article proposes a bidirectional spatial sequence Gray-code (BSSGC) algorithm to enhance encoding efficiency. This new method uses a BSSGC encoding strategy to generate a unique set of Gray-code patterns, with decoded numbers that no longer correspond one-to-one with fringe orders. It leverages multiple spatial features, such as neighborhood fringe order information, neighborhood statistical data, and invalid points, to transform the ambiguous order map into a fringe order map. By integrating these techniques, the method reduces spatial information redundancy while maintaining the high noise resistance and point-to-point calculation benefits of Gray-code methods. Besides, it achieves phase unwrapping with only four Gray-code patterns for 57-period fringe. Both the static and dynamic experiments demonstrate that the proposed method performs well in various complex scenarios.