Abstract
Large-scale triangulation scanning measurement systems are widely used to measure the three-dimensional profile of large-scale components and parts. The accuracy and speed of the laser stripe center extraction are essential for guaranteeing the accuracy and efficiency of the measuring system. However, in the process of large-scale measurement, multiple factors can cause deviation of the laser stripe center, including the spatial light intensity distribution, material reflectivity characteristics, and spatial transmission characteristics. A center extraction method is proposed for improving the accuracy of the laser stripe center extraction based on image evaluation of Gaussian fitting structural similarity and analysis of the multiple source factors. First, according to the features of the gray distribution of the laser stripe, evaluation of the Gaussian fitting structural similarity is estimated to provide a threshold value for center compensation. Then using the relationships between the gray distribution of the laser stripe and the multiple source factors, a compensation method of center extraction is presented. Finally, measurement experiments for a large-scale aviation composite component are carried out. The experimental results for this specific implementation verify the feasibility of the proposed center extraction method and the improved accuracy for large-scale triangulation scanning measurements.
Highlights
Geometric accuracies of large-scale aircraft components or parts, including tail and wings, are the essential specifications for determining the airworthiness of the major subassemblies or subsystems of an aircraft.[1,2,3] Geometrical measurements in large-scale aircraft components are fundamental for both aircraft assembly and aircraft reliability testing.[4]
Because the gray distribution of a laser stripe is asymmetric and a significant deviation in the laser stripe center could occur, we propose an image evaluation method for the laser stripe extraction to determine the degree of deviation between the center of the captured laser stripe and the geometric center
We propose a laser stripe center extraction method based on the analysis of multiple source factors
Summary
Geometric accuracies of large-scale aircraft components or parts, including tail and wings, are the essential specifications for determining the airworthiness of the major subassemblies or subsystems of an aircraft.[1,2,3] Geometrical measurements in large-scale aircraft components are fundamental for both aircraft assembly and aircraft reliability testing.[4]. To improve the accuracy of laser stripe extraction, conventional center extraction methods, such as geometric center extraction, barycenter extraction, and Gaussian fitting extraction, are enhanced. The laser stripe center was extracted using the Gaussian fitting method at the range of 5 pixels around the initial center. Zhang et al.: Accuracy improvement in laser stripe extraction for large-scale triangulation scanning measurement system a Hessian matrix. After analyzing the Gaussian fitting structural similarity and image features of laser stripes, the deviation in the laser stripe extraction can be corrected, improving the measurement accuracy of a large-scale triangulation scanning system.
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