Transparent Coating Defect Detection via Surface Structure Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods cannot automatically detect coating defects in thin, transparent layers applied to carrier materials, such as security documents, due to their transparency and application on colored or reflective surfaces, making direct photographic recognition impossible without using contrast agents.
Innovation Solution
A method and device that use an image acquisition device to detect and evaluate the surface structure of the layer on the application roller before it is transferred to the carrier material, allowing indirect determination of the layer's completeness and presence of defects, using a line camera and line illumination to generate contrast and evaluate shades of gray.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct photographic recognition is used to detect coating defects, then defect detection is possible, but it cannot be applied to transparent layers on colored or reflective surfaces
Solution Approach 1:
The invention introduces a preliminary action by applying a contrast agent to the carrier material before applying the transparent layer. This allows the underlying surface structure to be visible through the transparent layer during quality inspection, enabling defect detection without compromising the transparency requirement. The contrast agent is applied in advance, creating a visible reference pattern that persists through the subsequent transparent coating application.
2Measurement precision
If contrast agent is added to enable defect detection, then photographic recognition becomes possible, but the medium purity is compromised
Solution Approach 1:
The invention segments the contrast agent application from the transparent medium application. Instead of mixing the contrast agent with the transparent medium (which would compromise purity), the contrast agent is applied separately to the carrier material first. This segmentation allows both functions to be achieved: defect detection capability through the contrast agent and medium purity through separate application processes.
3Manufacturing precision
If transparent layer thickness is reduced for application quality, then coating precision is improved, but automatic defect detection becomes impossible
Solution Approach 1:
The invention introduces an intermediary element - the contrast agent pattern on the carrier material - that enables defect detection of thin transparent layers. The contrast agent acts as a mediator between the transparent layer and the inspection system, allowing optical detection methods to work effectively even with very thin coatings that would otherwise be invisible against the carrier material background.
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 automatic and efficient detection of coating defects, ensuring complete and uniform application of transparent layers without contrast media, suitable for thin layers on reflective or inhomogeneous surfaces, with high processing speeds and ability to monitor layers line by line.
Implementation Method 1
an illumination device, in particular a line illumination device, which are aligned towards the surface structure and controlled by a control device for illumination and image recording
Data Source
Figure 1~3
AI summary
The invention relates to a method and device for testing the integrity of an application of a transparent layer (14) of a medium on a carrier material (12), in which a layer (12) of the medium is applied to an application roller (21), the medium layer (14) is applied by the application roller (21) to the carrier material (12) which is to be coated. During or after the application of the medium layer (14) onto the application roller (21), a surface structure (30) is introduced into the medium layer (14) and prior to applying said medium layer (14) to the carrier material (12) by the application roller (21), the surface structure (30) of said layer (14) is detected by means of an image detection device (33) and is evaluated by means of an evaluation device (45).