Fringe-width encoded line-shifting method for complex 3D measurement

Complex 3D measurements, including reflective, dark, transparent, humid, and dynamic surfaces, pose challenges for existing fringe projection profilometry (FPP). Phase-shifting methods face difficulties in accurately measuring the surfaces of objects that are reflective, dark, transparent, or humid, due to its reliance on the surface light intensity. Thus, line-shifting methods emerge as a viable solution, leveraging binary patterns to enhance robustness. However, traditional line-shifting methods rely on extra Gray code patterns to determine the order of lines, resulting in decreased efficiency and the inability to measure dynamic objects accurately. To overcome these limitations, this research proposes a line-shifting method for complex 3D measurement, which allows for the simultaneous extraction of lines from the projected pattern along with their corresponding orders by encoding the information of fringe width. This method eliminates the requirement for additional patterns to discern line orders, thereby improving measurement efficiency and enabling more precise measurements of dynamic objects. Moreover, the use of binary images preserves the robustness of the conventional line-shifting method, enabling effective measurements of reflective, dark, transparent, and humid surfaces of objects. The experimental results verify the high-accuracy, high-robustness, and high-speed performance of the proposed method.