A novel gray code assisted phase measuring profilometry for high-speed objects

Structured light imaging, particularly phase shifting methods, has become a research hotspot in the field of three-dimensional imaging due to its non-contact nature, high precision, and flexibility. Phase shifting methods require the use of gray codes to resolve phase order for 3D measurement. Given the low coding efficiency of binary images, this paper proposes a 3D imaging method that utilizes a quaternary gray code to assist three-step phase shifting, which has higher coding efficiency. This method requires fewer projection images compared to traditional binary gray code methods, making it more suitable for dynamic scene measurement. However, in actual measurement processes, noise and threshold segmentation operations can cause significant distortion at discontinuities between truncated phases, leading to errors in phase order and finally lead to the error of the measurement result. In this work, we utilize the method of quaternary complementary gray code to construct two complementary fringe order with half fringe period difference for unwrap the truncated phase. This approach is proven effective in addressing errors in the phase truncation regions.