Label Inspection Using Infrared Illumination for High-Contrast Defect Detection
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Solution Overview
Problem
Existing methods for inspecting labeled vessels, particularly those with labels that have colors similar to the filling material, face challenges in reliably detecting holes and tears due to weak contrast, leading to reduced detection reliability and the need for frequent reference image updates and calibrations.
Innovation Solution
A device that uses selective illumination with visible and invisible light, including infrared, to enhance contrast, combined with angled camera views and polarization filters to suppress reflections, allowing for improved detection of label defects by capturing images in both visible and infrared light and processing them for high-contrast display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If visible light illumination is used to inspect labels with colors similar to filling material, then the inspection can be performed with standard equipment, but the contrast between holes/tears and surrounding label is weak leading to reduced detection reliability
Solution Approach 1:
The patent changes the spectral parameter of illumination from visible light to infrared light. The lighting device is configured to illuminate the label with infrared light, and the camera is sensitive to infrared radiation. This parameter change exploits the fact that label prints typically absorb less infrared light than visible light, creating higher contrast between defective areas (holes/tears) and the surrounding label when the label color is similar to the filling material color.
Solution Approach 2:
The patent combines multiple illumination approaches by providing both a first lighting device for visible light and a second lighting device for infrared light. The system can selectively use either illumination type or combine them based on the inspection requirements, merging the advantages of both approaches to improve overall detection reliability across different label and product combinations.
2Ease of operation
If reference images are used to compensate for label position variations, then detection can be performed, but large tolerance ranges must be allowed which reduces detection reliability
Solution Approach 1:
The patent changes the spectral parameter to infrared illumination, which fundamentally alters how the label and filling material interact with light. This parameter change inherently improves contrast for detecting holes and tears regardless of label position or print variations, eliminating the need for large tolerance ranges in reference image comparisons while maintaining high detection reliability.
3Adaptability or versatility
If frequent label changes or imprint changes occur, then product variety is increased, but many reference shots and additional calibrations are necessary which are difficult to handle
Solution Approach 1:
The patent changes from visible to infrared illumination, which fundamentally alters the interaction between light and the label-print-filling material system. This parameter change creates inherently higher contrast for defect detection that is less sensitive to variations in label prints and colors, thereby reducing the need for frequent recalibrations and reference shot updates when product variety changes.
Solution Approach 2:
The infrared illumination system provides universal applicability across different label types, colors, and products. Since infrared light interacts differently with most materials compared to visible light, the system achieves broad versatility without requiring specific calibration for each label design, making it universally effective for detecting holes and tears across diverse packaging applications.
4Object-affected harmful factors
If the camera looks at the label at a steep angle, then reflections on the bottle surface are reduced, but the labeling area to be inspected may be limited
Solution Approach 1:
The patent changes the spectral parameter of illumination to infrared light. This parameter change alters the reflection characteristics of the bottle surface and label, allowing for reduced reflections even at steeper camera angles. The infrared illumination combined with the specific camera angle of at least 75° to the vertical axis minimizes reflections while the infrared sensitivity of the camera maintains adequate image quality across the label surface.
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
The solution significantly increases the reliability of label inspection by providing high-contrast images of defects, reducing the need for frequent calibrations and improving detection accuracy, especially in cases where label colors match the filling material.
Implementation Method 1
the lighting device (10) is set up in such a way that it can selectively irradiate the label (4) with visible light and with invisible light, in particular infrared light
Implementation Method 2
the label print absorbs less light in the infrared range than the contents of the bottle and therefore appears lighter in the image
Implementation Method 3
linear polarization filters with mutually crossed planes of polarization being provided in the illumination and imaging beam paths in order to suppress disruptive reflections
Data Source
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AI summary
The invention relates to a device and a method for inspecting labeled containers (3). The detection of holes (4a) in the label (4) is made possible with a high success rate, even with a label color similar to the filled product, by illuminating the label with visible and invisible light, e.g. by means of the fluorescent screens (12), and/or by imaging it in reflected and transmitted light, e.g. by means of the lenses (6) and the camera.