Bi-cell photodetector decay time ratio for moving value document authentication
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Solution Overview
Problem
Existing validation systems for value documents, such as bank notes, fail to accurately authenticate moving documents due to unpredictable deterioration of covert features and increased sophistication of counterfeiters, and lack the ability to differentiate between authentic and counterfeit documents when the emitted radiation parameters are similar.
Innovation Solution
An apparatus and method that utilize a pre-selected covert composition absorbing exciting light and emitting optical radiation at a specific wavelength, with a bi-cell photodetector capturing images at different times to measure the decay time intensity of the emission, allowing for accurate authentication of moving value documents by comparing the output electronic signal ratio to determine authenticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If covert features are incorporated in value documents for authentication, then authentication capability is improved, but the features are easily identified by forgers and counterfeitters
Solution Approach 1:
The patent employs fluorescent materials that change their optical properties (from invisible to visible emission) when exposed to specific wavelengths of light. The covert features remain invisible under normal viewing conditions but emit fluorescent radiation when excited by ultraviolet or blue light, making them undetectable to forgers who cannot provide the appropriate light source
Solution Approach 2:
The patent introduces a fluorescent material as an intermediary between the hidden authentication feature and the detection system. The fluorescent material absorbs ultraviolet or blue light and converts it to visible emission, serving as a mediator that enables authentication without directly exposing the covert feature to the human eye or simple detection devices
2Ease of operation
If emission spectra detection is used to authenticate value documents, then authentication is simplified, but unpredictable deterioration of emission spectra amplitude occurs
Solution Approach 1:
The patent employs time-resolved fluorescence measurement where the fluorescent material is excited by periodic or pulsed light sources. The emission is measured at multiple time points during the decay period, creating a temporal profile that is characteristic of the fluorescent material. This periodic excitation and time-resolved measurement approach provides stable, reproducible authentication data that is not affected by unpredictable deterioration of the fluorescent material over time
3Ease of operation
If validation systems detect only emission spectra, then authentication process is simplified, but counterfeit documents with similar emitted radiation parameters cannot be differentiated
Solution Approach 1:
The patent employs time-resolved fluorescence measurement where the fluorescent material is excited by periodic or pulsed light sources. The emission is measured at multiple time points during the decay period, creating a temporal profile that is characteristic of the fluorescent material. This periodic excitation and time-resolved measurement approach provides stable, reproducible authentication data that is not affected by unpredictable deterioration of the fluorescent material over time
Solution Approach 2:
The patent measures multiple parameters of the fluorescent emission including emission wavelength, decay time constant, and intensity ratios at different time points. By analyzing the temporal decay profile and comparing multiple parameters rather than relying on a single emission spectrum measurement, the system achieves high precision differentiation between authentic and counterfeit documents, even when basic emission characteristics are similar
4Reliability
If covert features are used in value documents, then authentication security is improved, but counterfeiters with access to scientific apparatus can detect and replicate these features
Solution Approach 1:
The patent employs fluorescent materials that change their optical properties (from invisible to visible emission) when exposed to specific wavelengths of light. The covert features remain invisible under normal viewing conditions but emit fluorescent radiation when excited by ultraviolet or blue light, making them undetectable to forgers who cannot provide the appropriate light source
Solution Approach 2:
The patent employs time-resolved fluorescence measurement where the fluorescent material is excited by periodic or pulsed light sources. The emission is measured at multiple time points during the decay period, creating a temporal profile that is characteristic of the fluorescent material. This periodic excitation and time-resolved measurement approach provides stable, reproducible authentication data that is not affected by unpredictable deterioration of the fluorescent material over 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
The system effectively authenticates moving value documents with high accuracy and security by combining emission wavelength detection with decay time characteristics, preventing misidentification and counterfeiting, even at high speeds.
Implementation Method 1
a pre-selected covert composition that absorbs exciting incident light and emits optical radiation having a pre-selected emission wavelength
Implementation Method 2
a first detector element and a second detector element housed in at least one photodetector, wherein the first detector element receives a first image of an area of the value document at a first time and outputs electronic signal data for the first image
Data Source
AI summary
An authentication apparatus used to authenticate a moving value document with uniform or non-uniform distribution of a pre-selected covert composition that includes an active ion that emits optical radiation at a pre-selected wavelength when excited by exciting incident light. The optical radiation is imaged onto at least one photodetector having first and second detector elements. The imaged intensities are captured at pre-determined times relating to the velocity of the value document. The ratio between the second detector element and the first detector element measured at the same image location or different image locations represents the characteristic decay time intensity data of the pre-selected wavelength emission. The authenticity of the value document is rejected when the pre-selected wavelength emission is not received by the at least one photodetector or when the output electronic signal ratio does not meet expected value.