While color-coding methods have improved the measuring efficiency of a structured light three-dimensional (3D) measurement system, they decreased the measuring accuracy significantly due to lateral chromatic aberration (LCA). In this study, the LCA in a structured light measurement system is analyzed, and a method is proposed to compensate the error caused by the LCA. Firstly, based on the projective transformation, a 3D error map of LCA is constructed in the projector images by using a flat board and comparing the image coordinates of red, green and blue circles with the coordinates of white circles at preselected sample points within the measurement volume. The 3D map consists of the errors, which are the equivalent errors caused by LCA of the camera and projector. Then in measurements, error values of LCA are calculated and compensated to correct the projector image coordinates through the 3D error map and a tri-linear interpolation method. Eventually, 3D coordinates with higher accuracy are re-calculated according to the compensated image coordinates. The effectiveness of the proposed method is verified in the following experiments.

Color-coding methods have significantly improved the measurement efficiency of structured light systems. However, some problems, such as color crosstalk and chromatic aberration, decrease the measurement accuracy of the system. A two-level space-time color-coding method is thus proposed in this paper. The method, which includes a space-code level and a time-code level, is shown to be reliable and efficient. The influence of chromatic aberration is completely mitigated when using this method. Additionally, a self-adaptive windowed Fourier transform is used to eliminate all color crosstalk components. Theoretical analyses and experiments have shown that the proposed coding method solves the problems of color crosstalk and chromatic aberration effectively. Additionally, the method guarantees high measurement accuracy which is very close to the measurement accuracy using monochromatic coded patterns.

In the calibration process of structured light three-dimensional (3D) measurement system, the accuracy of the calibration points' image coordinates directly influences the system's measurement accuracy. Based on the analysis of errors in calibration points' image coordinates, mathematical models are built. A solution to eliminate errors in those image coordinates is proposed according to the further analysis of the models, and calibration points are designed to be circle for high-precision and steady extraction. The solution contains procedures as following: 1) A novel and real-time algorithm is proposed, which is used for the correction of the non-uniform intensity in image caused by non-uniform illumination and the camera's parameters. Taking preliminary extracted elliptical center coordinates and average gray value of the ellipses as known information, the intensity distribution of calibration images can be obtained by interpolation. Then the non-uniform intensity of calibration images is corrected in accordance with the interpolation results. 2) High frequency noise in the images is filtered. 3) At last, error of asymmetric perspective projection is also compensated based on its model. Simulation and experiment results indicate that this solution can efficiently reduce the calibration errors.