Three-Dimensional CT Gauge Calibration for Steep-Angle Accuracy
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Solution Overview
Problem
Existing x-ray computed tomography (CT) systems lack a reliable and efficient method for calibrating and verifying their accuracy, particularly at steep angles, which is critical for precise metrology applications.
Innovation Solution
A calibration/verification gauge with a first and second base supporting a plurality of objects, such as spheres, positioned orthogonally to form a perpendicular configuration, allowing for accurate measurement of center distances to ensure precise calibration and verification of CT systems, even at steep angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional coordinate measuring machines are used for calibration, then measurement accuracy can be maintained, but the ability to measure internal dimensions and combine dimensional quality control with material quality control is limited
Solution Approach 1:
The patent replaces traditional mechanical coordinate measuring machines with x-ray computed tomography technology. The CT system uses non-contact x-ray imaging to capture three-dimensional data of the gauge and workpieces, eliminating the need for mechanical probe contact. This substitution enables internal dimension measurement through x-ray penetration while maintaining measurement accuracy through advanced image reconstruction algorithms.
2Adaptability or versatility
If x-ray CT systems are used for measurement, then internal dimensions can be measured, but reliable calibration and verification methods particularly at steep angles are lacking
Solution Approach 1:
The patent implements preliminary calibration actions by using a specialized gauge with known dimensional characteristics before actual workpiece measurement. The gauge contains reference features with precisely known positions and dimensions that serve as a baseline for verifying CT system accuracy. This preliminary calibration establishes traceability to the unit of length and enables uncertainty calculations for subsequent measurements.
Solution Approach 2:
The patent employs parameter changes by varying the rotation angle of the gauge during calibration to include steep angles. The CT system acquires images at multiple angular positions, and the calibration process evaluates measurement accuracy across different orientations. This approach verifies system reliability under diverse geometric conditions, particularly at steep angles where calibration is most challenging.
3Ease of operation
If conventional calibration methods are used, then simple procedures can be followed, but accurate verification at steep angles and combined dimensional and material quality control cannot be achieved
Solution Approach 1:
The patent merges dimensional quality control with material quality control into a single integrated CT measurement process. The calibration gauge contains both geometric reference features for dimensional verification and material regions for density and composition analysis. This combination allows simultaneous verification of spatial accuracy and material characterization capabilities, eliminating the need for separate calibration procedures while maintaining operational efficiency.
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 highly accurate measurements of small dimensions, down to the micrometer or nanometer level, ensuring compliance with verification standards and preventing catastrophic measurement errors in critical applications like aircraft components and medical devices.
Implementation Method 1
x-ray computed tomography machine
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A method of calibrating an x-ray computed tomography machine provides an x-ray computed tomography machine having calibration settings, and uses the x-ray computed tomography machine to produce a gauge reconstruction. The gauge has a first base (20) supporting two or more objects (22), and a second base (21) supporting two or more objects (22). The first base and the second base form a perpendicular configuration, and each of the plurality of objects is secured on at least one of the first base and the second base. Each of the objects has a center, and the distance between the centers of each object is known. The method then measures the distance between at least two objects to produce measured center distance values, compares the measured center distance values against the known center distance values, and uses the comparison to determine if there is a distance error in the gauge reconstruction.