Three-dimensional measurement method based on a three-step phase-shifting fringe and a binary fringe

Gray-code plus phase-shifting is currently a commonly used method for structured light three-dimensional (3D) measurement that is able to measure complex surfaces. However, the Gray-code fringe patterns tend to be complicated, making the measurement process time-consuming. To solve this problem and to obtain faster speed without sacrificing accuracy, a 3D measurement method based on three-step phase-shifting and a binary fringe is proposed; the method contains three phase-shifting fringe patterns and an additional binary fringe pattern. The period of the binary fringe is designed to be the same as the three-step phase-shifting fringe. Because of the specific pattern design strategy, the three-step phase-shifting algorithm is used to obtain the wrapped phase, and the connected region labeling theorem is used to calculate the fringe order. A theoretical analysis, simulation, and experiments validate the efficiency and robustness of the proposed method. It can achieve high-precision 3D measurement, which performs almost the same as the Gray-code plus phase-shifting method. Since only one additional binary fringe pattern is required, it has the potential to achieve higher measurement speed.