Fast phase-measuring profilometry through composite color-coding method

Abstract

Phase-measuring profilometry (PMP) has become one of the most effective means of three-dimensional (3D) shape measurement. Owing to the low robustness of the phase-unwrapping algorithm and the large number of projection patterns, the off-the-shelf PMP methods have a limited speed and accuracy for the measurement of discontinuous objects. To improve the measurement speed and accuracy, a composite color-coding method is presented in this paper. The main idea of the coding is embedding sinusoidal stripes, phase-coding stripes, and Gray code into the red, blue, and green channels of a color pattern, respectively. The Gray code is used for identifying the order of the sub-stair phase, which is quantized into m levels with a stair height of 2π/m. Each stair corresponds to the 2π phase-changed period of the sinusoidal fringes. The complexity of the phase unwrapping is low, and the proposed method needs fewer patterns for measurement than conventional methods. The experimental results indicate that the proposed method can achieve more accurate and efficient 3D shape measurement than the traditional phase-coding methods and is suitable for measuring discontinuous objects with complex shapes.