Research On Geometric Dimensions And Area Measurement Method Of Industrial CT Image

In non-destructive conditions, Industrial CT can not only visually, clearly show thestructural relationship of the objects in the internal details and defect status, but also canbe used in high-precision measurements of the objects internal and external geometricdimensions. The transformation from the qualitative detect to the quantitativemeasurement is an inevitable trend of industrial CT. With the expansion of the scope ofpractical application of engineering, the requirements of the CT image measurementaccuracy is continuous improving. Therefore, to achieve high accuracy and automationof the CT images of geometric dimensions and three-dimensional surface measurementhas important engineering applications value. This is completed as follows:At first, the key of high-precision geometric parameters measurement of industrialCT images is high-precision industrial CT images edge location. In this present, thesub-pixel edge detection technology is studied, which focus on sub-pixel edge detectionalgorithm based on Zernike moment. The selection of Zernike moments algorithmtemplate, which has an essential effect on the edge location, was studied. The problemof slower speed and comparatively inaccurate result in Zernike moments edge detectionwas solved by improving the threshold principle and combining with the Sobel operator.It can quickly obtain the high-precision refinement edge.Then, A sub-pixel two-dimensional measurement method based on Zernikemoments is studied for improving the accuracy of two-dimensional dimensionmeasurement. At first, the algorithm base on improved Zernike moments is used todetect the precise sub-pixel edge positioning of the images; The method of edgeinterpolation fitting and the edge tracking algorithm based on the distance were appliedto solve problem of the sub-pixel edge is floating-point and discontinuous, which canform the closed edge curve; It is applied in the actual industrial CT images measurement,which respectively calculated the area, thickness and other parameters of the targetimage.Lastly, a three-dimensional surface area measurement method is studied to improvethe accuracy and speed of the three-dimensional surface measurement. The edge-fittinginterpolation method between layer is proposed to solve the problem of insufficientresolution of the CT images in the Z direction, the arc tangent extrapolation method isapplied to fill the missing data of the top image; Finally, the shortest diagonal method is used to reconstruct and calculate three-dimensional surface.In this present, Two-dimensional dimensions and three-dimensional surfacemeasurement of industrial CT images were researched systematically; the proposedmethod is designed and implemented in the actual CT image measurement. Theaccuracy, speed and scope of the proposed method were verified by the simulationimage and the actual work-piece measurement. The results show that the proposedmethod is effective, with some value of engineering applications.