Birefringence Authentication Using Multi-Wavelength Light Sources
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Solution Overview
Problem
Existing birefringence measurement systems for polymer films in banknote authentication are limited by their inability to differentiate between various films due to the integration of white-light spectra, resulting in similar measurements for films with different properties, which reduces the accuracy and range of authenticity determination.
Innovation Solution
The use of multiple wavelength light sources, such as red, green, and blue, to measure and compare birefringence effects, allowing for a more precise differentiation between film types by analyzing the retardation of light transmitted and reflected at different wavelengths, and employing neural networks for improved data processing to enhance authenticity determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If white-light light source is used with integrated spectrum measurement, then the measurement system is simple, but the ability to differentiate between various film types is reduced
Solution Approach 1:
The patent divides the continuous white-light spectrum into multiple discrete wavelength bands using filters. Each wavelength band is measured separately, allowing the system to capture spectral information at specific wavelengths rather than integrating the entire spectrum. This segmentation enables differentiation between film types that appear similar under integrated white-light measurement.
2Measurement precision
If multiple wavelength light sources and separate measurements are used, then film type differentiation accuracy is improved, but the measurement system complexity increases
Solution Approach 1:
The patent combines multiple wavelength-specific measurements into a single integrated authentication decision. By measuring birefringence effects at multiple discrete wavelengths and processing these measurements together, the system achieves superior film type differentiation while managing complexity through unified data processing rather than physically separate measurement systems.
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 significantly expands the range and accuracy of authenticity determination, enabling the differentiation between films made by different processes and improving the reliability of birefringence-based authentication systems, particularly in banknote sorting machines.
Implementation Method 1
an optically-based birefringence measuring arrangement operative to measure a first effect influenced by a birefringence characteristic of said film
Implementation Method 2
an optically-based birefringence measuring arrangement operative to measure a first effect influenced by a birefringence characteristic of said film
Implementation Method 3
measuring a first effect influenced by a birefringence characteristic of said film from a first angle comprising a non-normal angle to a plane of said film
Data Source
Figure 1~2
Figure 3~4a
Figure 4b~4c
AI summary
An authentication apparatus operative to determine the authenticity of a polymer film, comprising an optically-based birefringence measuring apparatus operative to: •expose the film to a first light source of a first wavelength or range of wavelengths; • expose the film to a second light source of a second wavelength or range of wavelengths, the first wavelength or range of wavelengths being different from the second wavelength or range of wavelengths; • measure a first effect influenced by a birefringence characteristic of the film responsive to said first light source; • measure a second effect influenced by a birefringence characteristic of the film responsive to said second light source; • compare a value or range of values representative of a comparison between the first and second effects with a value or range of values representative of a comparison between a specified first effect and a specified second effect corresponding to a predetermined birefringence characteristic of an authentic polymer film responsive to the first and second light sources; and • output an authenticity signal indicative of authenticity or otherwise of the film based upon one or more of the comparisons.