Three-dimensional precision measurement and calibration method for industrial CT (computed tomography)

Abstract

The invention discloses a three-dimensional precision measurement and calibration method for industrial CT (computed tomography). The three-dimensional precision measurement and calibration method comprises two parts, namely industrial CT scanning parameter optimization and three-dimensional precision industrial CT measurement and calibration. According to the method, the conventional technology is innovatively optimized on the basis of a large quantity of laboratory researches and industrial applications aiming at three important processes, including setting of main scanning parameters, correction of a ray beam hardening phenomenon in a three-dimensional reconstruction process and voxel dimension and boundary definition calibration in a three-dimensional modeling and precision measurement process, which affect the three-dimensional industrial CT measurement quality. According to the method, the precision and the stability of the three-dimensional industrial CT measurement can be greatly improved, so that the applications of the three-dimensional industrial CT measurement in the fields of precision measurement and control, three-dimensional modeling, quantitative and qualitative analysis of internal and external structures of complicated machinery, reverse engineering and the like can be greatly expanded.

Description

technical field [0001] The invention relates to an industrial CT three-dimensional precision measurement and calibration method, belonging to the fields of industrial CT measurement and control and quality inspection. Background technique [0002] CT technology has been widely used in medical diagnosis, material analysis, and non-destructive testing since the 1970s. It is recognized as one of the greatest scientific and technological achievements in the late 20th century and is known as the best non-destructive testing technology. The world's first industrial CT equipment with relatively precise measurement accuracy appeared at the German Industrial Exhibition in 2005. Since then, the application of industrial CT in the field of three-dimensional precision measurement has received extensive attention and has gradually been recognized by the industry. [0003] Industrial CT detection technology is extremely complex, from X-ray scanning to 3D modeling requires experience: [...

AI Technical Summary

Problems solved by technology

[0028] (1) Gray value comparison table: extremely unstable and with large errors, suitable for the medical field but far from meeting the requirements of three-dimensional precision measurement;

[0029] (2) Accurate reconstruction method: time-consuming and demanding on computer performance, and difficult to apply to objects with complex structures;

[0030] (3) Predefined polynomial correction: The predefined polynomial coefficients are only based on the operator's personal experience, which is prone to large deviations and poor reliability;

[0031] (4) Using mid-level slices to optimize polynomials: to a certain extent, the aforementioned "predefined polynomial correction method" is optimized, but this method requires that mid-level slices must contain the maximum penetration length of the scanned object, which is often difficult to achieve in practical applications

Moreover, this method will produce large errors when processing cylindrical parts;

[0032] (5) No-reference back-projection method: This method relies too much on the definition of the material boundary before measurement, and this boundary definition often contains large errors, so it is difficult to meet the accuracy requirements of three-dimensional measurement

[0034] The voxel size calibration using the distance between the centers of the two spheres is often mixed with the inherent error of the traditional contact three-coordinate measurement method, thus increasing the error of the calibration coefficient

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