Banknote Authentication Using Phosphorescence Decay Rate Analysis
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Solution Overview
Problem
Current paper-sheet authentication methods are complex and costly due to the need for separate sensors to measure fluorescence and phosphorescence intensities, and determining authentication based on emission wavelengths requires specific filters, making it difficult to detect counterfeit banknotes effectively.
Innovation Solution
A paper-sheet authentication apparatus that uses a transport unit, excitation-light irradiating unit, phosphorescence-intensity acquiring unit, and phosphorescence decay-rate calculating unit to generate a phosphorescence decay-rate pattern, allowing for authentication by comparing the pattern of a genuine paper sheet with the target paper sheet, thereby simplifying the sensor structure and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate sensors are used to measure fluorescence and phosphorescence intensities, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines fluorescence and phosphorescence measurement functions into a single sensor system. The sensor captures both fluorescence intensity (during excitation light irradiation) and phosphorescence intensity (after excitation light is turned off) using one detector, thereby reducing device complexity while maintaining measurement precision through temporal separation of measurements.
Solution Approach 2:
The measurement process uses periodic excitation light irradiation followed by cessation, creating distinct measurement phases. During the irradiation phase, fluorescence intensity is measured; during the cessation phase, phosphorescence intensity is measured. This periodic action allows a single sensor to capture both phenomena sequentially without interference.
2Measurement precision
If filters with different transmitting wavelength ranges are used to acquire fluorescence and phosphorescence information, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent employs a single sensor that performs multiple functions: measuring both fluorescence and phosphorescence intensities, and detecting emission wavelength characteristics. By making the sensor universal rather than specialized for each measurement type, the system reduces component count while maintaining the ability to detect different wavelength characteristics through software-based spectral analysis.
Solution Approach 2:
The system changes the temporal parameter of measurement (during vs. after excitation) and analyzes spectral parameter variations to distinguish fluorescence from phosphorescence. Instead of using physical filters for each wavelength range, the patent uses digital signal processing to separate and analyze different wavelength characteristics from the sensor output, reducing hardware complexity.
3Ease of operation
If authentication is based on fluorescence and phosphorescence intensities only, then ease of operation is improved, but reliability decreases due to counterfeit detection limitations
Solution Approach 1:
The patent pre-stores authentication data (fluorescence intensity, phosphorescence intensity, and emission wavelength characteristics) from genuine paper sheets in a database. During authentication, the measured values from the target paper sheet are compared against these pre-established reference values, enabling automated and reliable counterfeit detection while maintaining ease of operation through database-driven decision making.
Solution Approach 2:
The system incorporates feedback by comparing measured fluorescence and phosphorescence characteristics against stored reference data from genuine paper sheets. The authentication result is determined based on the degree of match between measured and reference values, providing a feedback mechanism that enhances reliability by continuously validating against known genuine characteristics rather than relying on simple threshold comparisons.
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 enables a stricter authentication of banknotes while reducing the complexity and cost of the sensor structure by using a single system to measure and compare phosphorescence decay rates, effectively detecting counterfeit banknotes.
Implementation Method 1
a paper sheet having a characteristic to emit phosphorescence when irradiated with excitation light
Implementation Method 2
calculates a decay rate indicating a decrease rate of the phosphorescence intensity
Data Source
Figure 1A~1D
Figure 2A~2B
Figure 3
AI summary
An object is to realize a stricter authentication of a banknote while reducing the cost by making a sensor structure simpler. An excitation light is irradiated on a banknote having a characteristic to emit phosphorescence when irradiated with the excitation light, and a transmitted light passing through the banknote and an afterglow of the phosphorescence emitted by the banknote are detected with a line sensor (120). Authentication of the banknote is determined by evaluating the similarity between each of light-on image data (132) acquired while the excitation light is being irradiated, afterglow-intensity image data (134) generated from an afterglow intensity after the excitation light is turned off, and afterglow decay-rate image data (135) generated from a decay rate of the afterglow intensity after the excitation light is turned off, and a light-on reference image, an afterglow-intensity reference image, and an afterglow decay-rate reference image corresponding to a genuine banknote and stored previously.