Banknote Soiling Detection Using Blue Light Illumination
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Solution Overview
Problem
Existing methods for checking the soiling of banknotes using optical density thresholds struggle to reliably identify heavily soiled banknotes across different denominations, as the optical density of soiled banknotes may fall below specified threshold values when exposed to light within specific wavelength ranges.
Innovation Solution
Illuminating banknotes with blue light (380-480 nm) and using optical sensors to detect the light reflected, transmitted, or emitted, allowing for the determination of optical density and reliable identification of soiling without specifying the denomination, utilizing a combination of stationary light sources and sensors with relative movement, and optionally combining with other wavelength ranges like infrared, red, and green for enhanced detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If banknotes are illuminated with light in specified wavelength ranges (500-560 nm, 410-450 nm, 590-650 nm) according to denomination, then optical density can be measured according to ECB thresholds, but heavily soiled banknotes may have optical density below threshold values and cannot be reliably identified
Solution Approach 1:
The patent changes the illumination wavelength parameter from denomination-specific ranges (500-560 nm, 410-450 nm, 590-650 nm) to a fixed blue wavelength range (380-480 nm). This parameter change ensures that soiled banknotes exhibit higher optical density values that consistently exceed threshold values, enabling reliable identification regardless of denomination. The blue light wavelength optimizes the contrast between clean and soiled banknotes.
Solution Approach 2:
The patent applies a universal illumination wavelength (blue light 380-480 nm) that works for all banknote denominations, replacing the previous denomination-specific wavelength ranges. This universal approach allows a single measurement system to reliably detect soiling across all denominations without requiring denomination identification first, making the system multi-functional and simplifying the detection process.
2Measurement precision
If different wavelength ranges are used for different banknote denominations, then optical density thresholds can be optimized for each denomination, but the system becomes complex and requires denomination specification
Solution Approach 1:
The patent employs a universal blue light wavelength range (380-480 nm) that functions for all banknote denominations, eliminating the need for denomination-specific wavelength configurations. This single wavelength range optimizes detection across all denominations, simplifying the device configuration and operation while maintaining measurement precision through the enhanced contrast blue light provides for soiling detection.
Solution Approach 2:
The patent standardizes the illumination wavelength parameter to a fixed blue range (380-480 nm) for all denominations, changing from a variable wavelength approach to a fixed parameter approach. This parameter standardization reduces device complexity by eliminating the need for wavelength selection mechanisms and simplifies operation by removing denomination-based configuration requirements.
3Measurement precision
If blue light (380-480 nm) is used for illumination, then greater differences in optical density and intensity between clean and soiled banknotes are achieved, but the system must accommodate a new wavelength range not previously specified for ECB thresholds
Solution Approach 1:
The patent introduces a new illumination wavelength parameter (blue light 380-480 nm) that maximizes the optical density difference between clean and soiled banknotes. This parameter change enhances measurement precision by creating greater contrast, allowing for more reliable soiling detection. The system establishes new threshold values appropriate for blue light wavelengths, adapting the measurement standard to the optimized wavelength range.
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 method enables reliable identification of soiled banknotes regardless of denomination, with increased differences in optical density and intensity between clean and soiled banknotes when using blue light, allowing for consistent threshold setting across all denominations and improved contamination detection.
Implementation Method 1
The light reflected and/or emitted by the banknotes and/or the transmission of the light through the banknotes is detected using optical sensors
Implementation Method 2
The light reflected and/or emitted by the banknotes and/or the transmission of the light through the banknotes is detected using optical sensors
Implementation Method 3
An interaction between the light and the bank note occurs in the form of reflection, transmission or emission due to luminescence
Data Source
AI summary
The invention relates to a method and device for checking the degree of soiling of bank notes. To this end, the bank notes are conveyed along a transport path and illuminated by at least one light source with visible light of the blue spectral range. The light reflected and/or emitted by the bank notes, and/or the light having penetrated the bank notes due to transmission, is detected by means of at least one sensor and evaluated.