Improved two-frequency temporal phase unwrapping method in fringe projection profilometry

Abstract In three-dimensional (3D) measurement using fringe projection profilometry (FPP), noise introduced by the camera during fringe capture can cause phase errors in the reconstructed results, affecting the accuracy of the 3D measurements. The two-frequency temporal phase unwrapping method is widely used due to its high efficiency. However, the use of only two fringe patterns in this method leads to reduced noise immunity and an increased phase error. Many researchers have focused on improving the two-frequency method, but little attention has been paid to enhancing its noise immunity. In this article, we propose a novel two-frequency phase unwrapping method. Firstly, we analyze the phase errors of the traditional 4fh + 4fl two-frequency method and our proposed method in detail. Then, the feasibility of our proposed method is demonstrated through multiple sets of experimental results. Finally, we provide solutions to the problems encountered in our proposed method. Through experiments, our proposed method reduces the phase error by 75.90% and 91.39% relative to the traditional 4fh + 4fl method, in metal object and gypsum board experiments, respectively. The experimental results show that our proposed method significantly improves the reliability of phase unwrapping and reduces phase errors, thus enhancing the accuracy of 3D reconstruction.