The approach with an active laser beam for triangulation measurement is outlined for modeling and calibration 20. The approach is based on a flexible 2D calibration target, composed of a photo-electrical aiming device, a 3D translation platform and an improved algorithm of back propagation neural network. A novel approach is proposed to generate the sufficient calibration points with high accuracy for structured light 3D vision 19. ![]() The nonlinear model reduces the errors in the generated 3D data by a precise camera model. The way in which laser lines are extracted from the camera images is a natural formulation of the calibration problem as a nonlinear least squares problem. As the measurement precision relies on the calibration result of the laser plane, determining the accurate equation of a laser plane in the world coordinate system is meaningful to the vision measurement system adopting structured light.Ī nonlinear measurement model is developed to the laser line image considering the radial distortion of the camera lens 18. Therefore, it is the key point to precisely calibrate laser plane equation in the whole measurement task 16, 17. ![]() ![]() The 2D coordinates of the laser line centers in the image are extracted and then transformed to 3D coordinates according to the calibration data of the laser plane. A typical measurement system mainly includes a laser projector providing a laser plane on the object and a camera capturing the image with the bended laser line on the object 13, 14, 15. Capitalizing on these capabilities, structured-light-based applications are being explored in measurement fields, such as inspection of mechanical parts, reconstruction of vehicle surface and medical CAD/CAM 7, 8, 9, 10, 11, 12. Vision measurement based on structured light is one of the most important methods to reconstruct the surfaces of 3D objects, which improves 3D shape measurement with non-contact process, moderate speed, high reliability and informative data 1, 2, 3, 4, 5, 6. The experiments show that the method of the distance optimal object from the feature point to the origin point provides an accurate and robust calibration for the laser plane in structured light measurement. Finally, the comparison work about the influences of the non-Gaussian noise and point number is investigated experimentally. The projective lines of the optimized laser plane on the 3D calibration board overlap the real intersection lines in the experimental images. The objective function is constructed to optimize the coefficients of the laser plane by minimizing the difference between the distance from the feature point to the the origin point and the length of the 1D target. ![]() A group of 2D coordinates of the intersection points are extracted from the images with the 1D target at different positions. Here we create a simple 1D target with a cone at the bottom and a checkered pattern on the top to calibrate the equation of the laser plane in the view field of a camera. Equation construction of a laser plane demonstrates a remarkable importance for vision measurement systems based on the structured light.
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