Asymmetric 3D Reference Object for Position-Orientation Calibration
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Solution Overview
Problem
Existing 3D reference objects for calibration in computer vision systems either hide the target object or occupy a large area, leading to inaccurate recognition of their position and orientation, and may not allow for precise alignment of measurement viewpoints.
Innovation Solution
A calibration method using an asymmetric 3D reference object with predetermined dimensions, shaped by combining three cylinders with hemispherical ends, allowing accurate calculation of its position and orientation through 3D measurement data, and enabling the calculation of transformation matrices for precise calibration of the computer vision system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large 3D reference object is used, then recognition accuracy of position and orientation is improved, but the target object may be hidden or the imaging size is reduced
Solution Approach 1:
The patent applies asymmetry by designing a 3D reference object with three spheres of different diameters (first sphere: 50mm, second sphere: 30mm, third sphere: 20mm) positioned at non-symmetric locations. This asymmetric configuration allows the measurement system to accurately determine position and orientation without requiring a uniformly large object, thereby avoiding obstruction of the target object while maintaining sufficient recognition accuracy through the distinctive asymmetric pattern.
2Measurement precision
If multiple measurement points are used, then recognition accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies the principle of visual differentiation by equipping each of the three spheres with distinct surface properties: the first sphere has a reflective surface, the second sphere has a diffuse reflective surface, and the third sphere has a transparent surface. These distinct surface characteristics enable the measurement system to easily distinguish between the spheres and accurately identify their positions and orientations without requiring complex measurement procedures or additional devices, thereby achieving high recognition accuracy with simple implementation.
Data Source
Figure 1A~1B
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AI summary
A calibration method for performing calibration in a computer vision system using a three-dimensional reference object asymmetric as viewed in any direction and having predetermined dimensions includes calculating, based on three-dimensional shape data about the three-dimensional reference object and three-dimensional measurement data obtained through three-dimensional measurement of the three-dimensional reference object, a position and an orientation of the three-dimensional reference object relative to a measurement unit coordinate system defined for the three-dimensional measurement unit, and calculating a reference-measurement unit transformation matrix representing a coordinate transformation between the measurement unit coordinate system and a reference coordinate system defined for the three-dimensional reference object.