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Research Papers

Evaluation of Scanning Parameters Based on Image Entropy for Dimensional Computed Tomography Metrology

[+] Author and Article Information
Lin Xue

RCAST,
The University of Tokyo,
7-3-1, Hongo, Bunkyo,
Tokyo 1538904, Japan
e-mail: mechanicalautomaticxue@gmail.com

Hiromasa Suzuki

RCAST,
The University of Tokyo,
7-3-1, Hongo, Bunkyo,
Tokyo 1538904, Japan

Manuscript received March 16, 2016; final manuscript received December 29, 2016; published online March 6, 2017. Assoc. Editor: Laine Mears.

J. Manuf. Sci. Eng 139(7), 071001 (Mar 06, 2017) (24 pages) Paper No: MANU-16-1166; doi: 10.1115/1.4035676 History: Received March 16, 2016; Revised December 29, 2016

Many types of artifacts appear in X-ray computed tomography (CT) volume data, which influence measurement quality of industrial cone beam X-ray CT. Most of those artifacts are associated to CT scanning parameters; therefore, a good scanning parameter setting can weaken the influence to improve measurement accuracy. This paper presents a simulation method for evaluating CT scanning parameters for dimensional metrology. The method can aid CT metrology to achieve high measurement accuracy. In the method, image entropy is used as a criterion to evaluate the quality of CT volume data. For entropy calculation of CT volume data, a detailed description about bin width and entropy zone is given. The relationship between entropy values of CT volume data and error parameters of CT metrology is shown and discussed. By use of this method, mainly we focus on specimen orientation evaluation, and some other typical scanning parameters are used to evaluate the proposed method. Two typical specimens are used to evaluate the performance of the proposed method.

Copyright © 2017 by ASME
Topics: Entropy , Errors , Metrology
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References

Figures

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Fig. 1

Workflow for dimensional metrology

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Fig. 2

Example of bad orientation (more serious cone beam artifact on the left): (a) reconstructed slice of a cube and (b) reconstructed slice of stepped cylinders

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Fig. 3

CT volume data with high entropy value and low entropy value, reconstructed slice of stepped cylinders

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Fig. 4

Relationship between blurring area and CT measurement accuracy (a cylinder as example): (a) CT volume data with less blurring area and (b) CT volume data with more blurring area

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Fig. 5

Histogram of CT value of voxels

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Fig. 6

Entropy zone definition for a local geometric feature: (a) cylindrical surface and (b) plane

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Fig. 7

Example of entropy zone contour for plane with standard geometric contour

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Fig. 8

Example of geometric feature perpendicular to the rotation axis: (a) cylindrical surface and (b) plane

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Fig. 9

Parameters definition for geometric feature perpendicular to the rotation axis (the worst case): (a) plane and (b) cylindrical surface

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Fig. 10

Calculation of the blurring area size in the worst case: (a) blurring area range, (b) minimum cross section of a cube in the xz plane for all rotation angles, and (c) maximum cross section of a cube in the xz plane for all rotation angles

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Fig. 12

Entropy zone size for a local geometric feature: (a) cylindrical surface and (b) plane

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Fig. 13

Scale coefficient effects (a cylindrical surface with small cone angle at different orientations around the y-axis)

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Fig. 14

A realistic specimen with cylindrical surfaces R1, R2, R3, R4, R5, R6, and plane P

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Fig. 15

Orientation evaluation for cylindrical surface R1, curves of entropy, radius error, cylindricity, and sigma

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Fig. 16

Orientation evaluation for cylindrical surface R2, curves of entropy, radius error, cylindricity, and sigma

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Fig. 17

Orientation evaluation for cylindrical surface R3, curves of entropy, radius error, cylindricity, and sigma

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Fig. 18

Orientation evaluation for cylindrical surface R4, curves of entropy, radius error, cylindricity, and sigma

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Fig. 19

Orientation evaluation for cylindrical surface R5, curves of entropy, radius error, cylindricity, and sigma

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Fig. 20

Orientation evaluation for cylindrical surface R6, curves of entropy, radius error, cylindricity, and sigma

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Fig. 21

Orientation evaluation for plane P, curves of entropy, flatness, and sigma

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Fig. 22

Blurring area of CT volume data for cylindrical surface R1

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Fig. 23

Orientation evaluation, relationship between entropy and error parameters: (a), (b), and (c) show graphs for R1, R5, and P, respectively, all other graphs are given in Fig. 41 of the Appendix

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Fig. 24

Cases evaluation for cylindrical surface R1, curves of entropy, radius error, cylindricity, and sigma

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Fig. 25

Cases of evaluation for cylindrical surface R2, curves of entropy, radius error, cylindricity, and sigma

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Fig. 26

Cases of evaluation for cylindrical surface R3, curves of entropy, radius error, cylindricity, and sigma

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Fig. 27

Cases of evaluation for cylindrical surface R4, curves of entropy, radius error, cylindricity, and sigma

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Fig. 28

Cases of evaluation for cylindrical surface R5, curves of entropy, radius error, cylindricity, and sigma

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Fig. 29

Cases of evaluation for cylindrical surface R6, curves of entropy, radius error, cylindricity, and sigma

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Fig. 30

Cases of evaluation for plane P, curves of entropy, flatness, and sigma

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Fig. 31

Cases of evaluation, relationship between entropy and error parameters: (a), (b), and (c) show graphs for R1, R2, and P, respectively, all other graphs are given in Fig. 42 of the Appendix

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Fig. 32

Stepped cylinders used in this paper

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Fig. 33

Orientation evaluation for cylindrical surface R1, curves of entropy, radius error, cylindricity, and sigma

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Fig. 34

Orientation evaluation for cylindrical surface R2, curves of entropy, radius error, cylindricity, and sigma

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Fig. 35

Orientation evaluation for cylindrical surface R3, curves of entropy, radius error, cylindricity, and sigma

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Fig. 36

Orientation evaluation for cylindrical surface R4, curves of entropy, radius error, cylindricity, and sigma

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Fig. 37

Orientation evaluation for cylindrical surface R5, curves of entropy, radius error, cylindricity, and sigma

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Fig. 38

Orientation evaluation for plane P, curves of entropy, flatness, and sigma

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Fig. 39

Blurring area of CT volume data for plane P

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Fig. 40

Orientation evaluation, relationship between entropy and error parameters: (a), (b), and (c) show graphs for R1, R5, and P, respectively, all other graphs are given in Fig. 43 of the Appendix

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Fig. 41

Orientation evaluation, relationship between entropy and error parameters (simulation data)

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Fig. 42

Cases evaluation, relationship between entropy and error parameters (simulation data)

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Fig. 43

Orientation evaluation, relationship between entropy and error parameters (actual data)

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