X-ray CT Tolerance Error Estimation via Centroid Analysis
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Solution Overview
Problem
Existing methods for correcting tolerance errors in X-ray CT apparatuses, such as image alignment and sensor-based corrections, are either time-consuming or increase manufacturing costs.
Innovation Solution
A tolerance error estimating apparatus that calculates the deviation of a rotation drive axis from a reference position over time using X-ray detection images, allowing for high-speed and cost-effective estimation and correction of tolerance errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image alignment method is used to correct tolerance error, then correction accuracy is improved, but processing time is increased due to required image reconstruction
Solution Approach 1:
The invention extracts only the necessary information (centroid position of absorption coefficient) from the projection images without requiring full image reconstruction. By calculating the centroid position directly from the acquired projection images, the method obtains correction data while avoiding the time-consuming reconstruction process, thus resolving the contradiction between accuracy and processing time.
2Productivity
If sensor-based correction method is used, then correction speed is improved, but manufacturing cost is increased due to sensor requirements
Solution Approach 1:
The invention replaces the mechanical sensor-based measurement system with an optical/image processing approach. By using the existing projection image acquisition system and calculating centroid positions from these images, the method achieves fast correction speeds comparable to sensor methods while avoiding the additional manufacturing costs of precision sensors and their installation infrastructure.
3Measurement precision
If reference sample is positioned at reference position with centroid coinciding with rotation drive shaft center, then measurement accuracy is improved, but device complexity is increased
Solution Approach 1:
The invention employs a self-aligning mechanism where the spherical reference sample automatically provides its centroid position information through its symmetric geometry. The spherical shape ensures that the centroid coincides with the geometric center, eliminating the need for complex alignment procedures or additional positioning devices, thus achieving high measurement accuracy without increasing device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables high-quality data acquisition at low cost and high speed by estimating deviations in real-time, reducing the burden on tolerance error correction and improving the accuracy of reconstructed images.
Implementation Method 1
rotating an X-ray source and a detector or the sample around the rotation drive axis to acquire an X-ray detection image as a projection image of the sample
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An estimation of the rotation axis jitter of a tomography system: a metal sphere (S) is aligned with the rotation axis and the shift of the projection of the sphere is measured as a function of the angle of rotation θ. A look-up table for correcting the movement of the rotation axis is calculated. The shift as a function of the angle of rotation may be approximated by a Fourier series.