Computer tomography-based precision inspection and shape extraction using facet model

Wenjian Wang; Xiaogu Wu; William G. Wee

doi:10.1117/1.602343

1 January 2000 Computer tomography-based precision inspection and shape extraction using facet model

Wenjian Wang, Xiaogu Wu, William G. Wee

Optical Engineering, Vol. 39, Issue 1, (January 2000). https://doi.org/10.1117/1.602343

We apply the facet model to extract edge and surface information from computed tomography (CT) images for precision inspection and shape extraction. First we explore the application of the facet model in a three-dimensional (3-D) filter design. A 3-D directional-derivative- based surface detector is developed to extract surface points from the CT images. Subpixel accuracy is achieved by locating the zeros of the 3-D second directional derivative along the estimated gradient direction. Then we develop a precision inspection system to take turbine blade wall width measurements from CT images and compare them to the corresponding optical measurements. Least mean squares (LMS) methods are used to enhance prediction accuracy with the adaptive property of increasing accuracy when additional verifiable data are available. The system accuracy is within 3 mil. Unverified measurements are adjusted based on the verified measurements, and experiments show increasing accuracy of the adjusted measurements as additional verified measurements are available. Also, quantitative analysis of a trapezoid-shaped workpiece is performed. The results indicate that the CT system performance is affected by the structure and size of a workpiece. We also present an algorithm to extract 3-D shapes from detected surface points interactively and use them for visual inspection.

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Wenjian Wang, Xiaogu Wu, and William G. Wee "Computer tomography-based precision inspection and shape extraction using facet model," Optical Engineering 39(1), (1 January 2000). https://doi.org/10.1117/1.602343

Published: 1 January 2000

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