Dual-frequency structured light coding and decoding method for real-time three-dimension reconstruction

In order to realize real-time three-dimensional (3D) reconstruction, this paper proposes a novel dual-frequency method for measuring the 3D surface geometry of objects. First, a group of unit-frequency sinusoidal wave patterns and a group of high-frequency sinusoidal wave patterns are combines. Then the generated patterns are projected onto the object surface and the reflected patterns distorted by the object are captured by a camera simultaneously. Second, the unit-frequency phase and high-frequency phase can be derived through the captured unit-frequency patterns and high-frequency patterns respectively. The unwrapped phase can be obtained by unwrapping the high-frequency phase by means of the unit-frequency phase which represents the correspondences between the projector and the camera, i.e., the high-frequency patterns guarantee high-quality phase and the unit-frequency patterns help to conveniently unwrap the wrapped phase generated from the high-frequency patterns. Finally, the high-quality 3D point clouds of the object can be computed using the unwrapped phase through triangulation. To confirm the validity of the proposed method, a statue is scanned and the results indicate that the variance of the phase error is 5.559 110-6 rad2 and the sweep time is 0.156 3 s. Compared with the data of the traditional methods, the proposed method reduces the number of projected patterns and keeps the accuracy of reconstructed results.