Three-image composite encoding method for fast fringe projection profilometry with enhanced efficiency and accuracy

Fringe projection profilometry (FPP) is generally used to measure the 3D shape of an object because of the advantages of noncontact operation, full-field acquisition, and high resolution based on phase-shifted demodulation and multifrequency unwrapping technology. However, this technique requires at least nine images, which increases the time cost and is not conducive to fast measurements. We propose a composite encoding method that combined 2 Gray code images and a fringe image into a color image, which aims to reduce the time cost of acquiring images and then improves the efficiency of the traditional three-step phase shift demodulation and multifrequency unwrapping method. The proposed method can achieve phase reconstruction by acquiring only three color images, which lowers the influence of object motion on the measurement results and is more favorable for fast measurements. However, due to the ambient light, different surface reflectance, the projector’s defocusing, and color coupling of the color channels, the edge of the Gray code image becomes smooth, leading to a fringe order jump error. Hence, a fringe order region matching the correct algorithm is also proposed to overcome the error. Theoretical analysis and experimental results show that the proposed approach can effectively eliminate jump errors, reliably perform Gray code unwrapping, and improve measurement efficiency and accuracy of FPP.