Value Document Crease Detection Using Multi-Wavelength Illumination
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Solution Overview
Problem
Existing methods for checking the usage status of value documents, such as banknotes, face difficulties in accurately detecting stains on documents with dark or patterned backgrounds, and in assessing the fitness of documents due to issues like creases, which can be masked by reflective security elements.
Innovation Solution
A method involving illumination with light of multiple wavelength ranges and using an image sensor to detect and evaluate light intensities in selected image sections of value documents, particularly focusing on opaque, reflective areas to determine crease extent, which helps assess the document's state of use by excluding edge areas and accounting for holographic structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional light detection methods are used to check value documents, then the checking process is simple, but the detection precision is insufficient for stains on dark or patterned backgrounds
Solution Approach 1:
The patent divides the document surface into multiple regions of interest (ROIs) with different characteristics. Different wavelength ranges are assigned to different ROIs based on their optical properties - for example, visible light for light-colored areas and infrared for dark or patterned areas. This segmentation allows precise stain detection in each region while maintaining overall system efficiency.
Solution Approach 2:
The patent changes the wavelength parameter of the illuminating light based on the background characteristics of different document regions. By selecting appropriate wavelength ranges (visible or infrared) for different ROIs, the system optimizes contrast between stains and background, thereby improving detection precision without requiring a single complex detection system.
2Reliability
If reflective security elements are present on the document, then the document's security is enhanced, but the detection of creases in these areas becomes difficult
Solution Approach 1:
The patent dynamically adjusts the evaluation criteria for crease detection based on the presence of reflective security elements. In regions with security elements, the system uses different evaluation parameters compared to ordinary document areas, allowing accurate crease detection despite the masking effect of reflective surfaces.
Solution Approach 2:
The patent applies different detection and evaluation methods to different local regions of the document. For areas with reflective security elements, specialized image processing and evaluation criteria are used that account for the unique optical properties of these elements, enabling accurate crease detection locally while preserving the security features.
3Reliability
If the entire document is examined for usage status, then the assessment is comprehensive, but the checking time increases
Solution Approach 1:
The patent divides the document into multiple regions of interest and processes them in parallel. By segmenting the examination task across different wavelength ranges and processing channels, the system maintains comprehensive assessment coverage while reducing the time required for each individual region's analysis.
Solution Approach 2:
The patent focuses detection resources on critical regions of the document that most significantly indicate usage status. Rather than uniformly examining every area with equal detail, the system applies partial action by concentrating analysis on high-priority regions, thereby achieving reliable assessment with reduced checking time.
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
This approach allows for a more reliable assessment of document fitness by accurately detecting creases and stains, even on documents with complex backgrounds, enhancing the ability to determine the usability of value documents.
Implementation Method 1
the light intensity of the light reflected by the value document is detected in order to record an image of the illuminated value document
Data Source
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Figure 3
AI summary
The invention relates to a device and to a method for examining the physical condition of a value document. The value document is illuminated with illumination light and the intensity of the light reflected from the value document is detected using an image sensor so that an image of the value document can be recorded. An image section of the recorded image, said section depicting an opaque, reflecting section of the value document, is selected. The selected image section is examined for indications of creases which could possibly be present in the opaque, reflecting section of the value document. The results of the investigation for creases are used to evaluate the physical condition of the value document.