Banknote Color Fading Detection via Local Contrast Analysis
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Solution Overview
Problem
Current methods for detecting color wear on value documents, such as banknotes, are inefficient and unreliable, particularly when assessing local brightness and contrast, and require multiple reference documents and significant adaptation efforts.
Innovation Solution
A method and device that analyze pixel intensity values and contrast within a partial or entire image of a banknote, using a classification system based on local brightness and contrast, allowing for reliable detection of color wear without separate treatment of different areas and reducing the influence of quality fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current methods for detecting color wear are used, then detection can be performed, but the detection is inefficient and unreliable, requiring multiple reference documents and significant adaptation efforts
Solution Approach 1:
The evaluation unit automatically adapts to different document types by self-training on the captured image data without requiring manual intervention or multiple reference documents. The system performs unsupervised learning to identify ink wear patterns specific to each document type, eliminating the need for external reference materials and reducing adaptation complexity.
Solution Approach 2:
The system creates a digital model of the document's original appearance by analyzing the captured image and identifying regions with ink wear. This digital representation is then used to compare against the current state, enabling reliable detection without physical reference documents.
2Measurement precision
If current methods for detecting color wear are used, then detection can be performed, but computing time is excessive due to processing entire images with multiple reference comparisons
Solution Approach 1:
The evaluation unit divides the captured image into multiple regions of interest (ROIs) based on document features and ink distribution patterns. By processing only these segmented regions rather than the entire image, the system maintains detection precision while significantly reducing computing time and resource requirements.
Solution Approach 2:
The system applies different processing strategies to different regions of the image based on their characteristics. High-precision analysis is applied only to regions where ink wear is likely to occur, while other regions receive minimal or no processing, optimizing the balance between detection precision and computing time.
3Productivity
If current methods for detecting color wear are used, then detection can be performed, but the influence of quality fluctuations in value documents reduces reliability
Solution Approach 1:
The evaluation unit dynamically adjusts its analysis parameters and processing intensity based on the quality characteristics of the captured image. When quality fluctuations are detected, the system automatically adapts its algorithms to maintain reliable detection, allowing high productivity across varying document conditions.
Solution Approach 2:
The system changes processing parameters such as threshold values, region sizes, and analysis depth based on the quality of the input image. This dynamic parameter adjustment enables the system to maintain reliable detection results while adapting to different document qualities and processing speeds.
Data Source
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AI summary
The invention relates to a method for detecting color fading on a value document, in particular a banknote, on the basis of a captured image (4) of the value document, which image has a plurality of pixels, each pixel being assigned at least one intensity value (Pi), wherein the following steps are performed for each pixel of a selection of pixels of the image (4): determining an intensity value, in particular a mean, from intensity values (P0 - P8) assigned to the pixel and to pixels near the pixel; calculating a contrast value on the basis of intensity values (P0 - P8) assigned to the pixel and to pixels near the pixel; and classifying the pixel with respect to color fading of the value document (1) in accordance with the determined intensity value, in particular mean, and the calculated contrast value. The invention further relates to a corresponding device and to a value-document processing system.