Calibration Element With Support Foot For Camera Magnification
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Solution Overview
Problem
Existing calibration methods for camera magnification ratio, such as the DE 101 18 886 B4 calibration ruler, are inadequate for detecting objects with thickness, particularly in rubber webs, as they assume flat objects and do not account for object thickness, leading to calibration errors.
Innovation Solution
A calibration element with a calibration region containing perforations or indentations, a support foot, and indexing means, which allows for the determination of the magnification ratio as a function of object thickness and location, enabling accurate geometric measurements by varying the camera's field of view and correcting imaging errors like trapezoidal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a calibration ruler is used that assumes flat objects and invariable position, then the calibration is simple and works for thin product webs, but it fails to account for object thickness which leads to intolerable problems for rubber webs
Solution Approach 1:
The calibration element extends the traditional 2D calibration ruler into 3D by adding a support foot that creates a defined distance between the calibration region and the support surface. This third dimension (height/thickness) allows the calibration to account for object thickness, enabling accurate measurements for both thin and thick objects like rubber webs.
Solution Approach 2:
The support foot acts as an intermediary element that mediates between the calibration region and the support surface. By providing a known, fixed distance, it serves as a reference that allows the camera to calculate magnification ratios that compensate for varying object thicknesses, thus enabling accurate measurement of thick objects without requiring complex calibration procedures.
2Strength
If the calibration element has a thick calibration region, then it provides structural stability, but it causes unreliable detection of upper and lower edges leading to calibration errors
Solution Approach 1:
The calibration element is segmented into distinct functional regions: a thick support foot for structural stability and a thin calibration region for accurate edge detection. This segmentation allows each part to optimize its function - the support foot provides mechanical strength while the thin calibration region ensures reliable detection of upper and lower edges by the camera.
Solution Approach 2:
Different parts of the calibration element have different thicknesses optimized for their specific functions. The support foot is thick to provide structural stability, while the calibration region is thin to enable accurate edge detection. This local variation in quality (thickness) resolves the contradiction between structural stability and measurement precision.
3Measurement precision
If multiple perforations and indentations are provided in the calibration region, then the magnification ratio can be calculated as a function of location to correct imaging errors, but the device complexity increases
Solution Approach 1:
Multiple perforations and indentations are pre-positioned in the calibration region at known locations and dimensions. This preliminary arrangement of reference features allows the camera to calculate magnification ratios as a function of location across the field of view, correcting for optical distortions such as trapezoidal distortion without requiring complex real-time adjustments.
Data Source
AI summary
A calibration element (1) serves for calibrating the magnification ratio of a camera (3). The calibration element (1) has at least one calibration region (4) in which at least one perforation (5) or indentation is provided. The perforation (5) or indentation can be detected by the camera. The calibration element (1) is sufficiently slight in the calibration region (4) that the detection of an upper edge or lower edge of the perforation (5) or indentation produces only negligible differences. In order to determine the dependence of the magnification ratio on the thickness, the calibration element (1) additionally has at least one support foot (8), whose length (9) is selected in such a way as thereby to produce a variation in the measured magnification ratio of the camera image that can be evaluated.