A coarse-fine combined phase unwrapping method

The multi-frequency hierarchical method is a well-established temporal phase unwrapping technique known for its high precision. However, its requirement for numerous images significantly reduces the speed of 3D reconstruction. To address this limitation, we propose a novel coarse-fine combined phase unwrapping method. This method reallocates the actual phase order into sequentially arranged coarse and fine orders. The coarse order provides the primary range for the actual phase, while the fine orders precisely locate it. The proposed method requires only six images to achieve high-frequency absolute phase. Experimental results demonstrate that, compared to the popular three-frequency three-step phase-shifting method, the proposed method reduces the number of projection patterns by three while maintaining similar accuracy. Therefore, this method holds significant potential for high-speed 3D reconstruction applications.