• 摘要: 提出了一种基于单帧空间多灰阶对称编码的绝对相位展开方法,将每一个条纹周期进行三或五等分并使每个码字呈对称分布。利用对称性特征和相邻码字之间的关联性实现高鲁棒性的条纹级次修正,配合三步相移仅需投影四帧条纹即可实现绝对相位展开。相比于传统空间编码,所提编码方法在条纹存在较多残缺的情况下,仍能利用对称性直接解出条纹级次信息,并从变形条纹图中同步实现了彩色纹理的解调,实现彩色物体的色彩保真三维重构。为了提高实时测量重构效率,提出五帧三步相移加一帧编码条纹的投影策略,将重建率从传统的每四帧投影获得一帧重建结果提升至每六帧投影获得三帧重建结果。实验结果验证了所提绝对相位展开方法和投影策略的有效性和实用性。

       

      Abstract: A method for absolute phase unwrapping based on single frame spatial multi-level symmetric encoding is proposed. This method divides each fringe period into three or five equal parts and makes each codeword symmetrically distributed. The symmetry feature and the correlation between adjacent codewords are used to achieve highly robust fringe order correction. Combined with the three-step phase-shifting profilometry, only four frames of fringes need to be projected to achieve absolute phase unwrapping. Compared to traditional spatial encoding, the proposed encoding method can directly extract fringe order information using symmetry feature even when there are many defects in the fringes, and synchronously demodulate color textures from deformed patterns without additionally capturing specific color image, thereby achieving color fidelity 3D reconstruction of color objects. In order to improve the efficiency of real-time measurement reconstruction, a projection strategy of 5 phase-shifting fringes equipping with 1 code fringe is proposed. The reconstruction rate is increased from the traditional one reconstruction per four patterns to three reconstructions per six patterns. The experimental results have verified the effectiveness and practicality of the proposed absolute phase unwrapping method and projection strategy.