Bank Note Authentication Using Restricted Luminescence Wavelengths
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Solution Overview
Problem
The existing luminescent substances used in bank notes are being successfully imitated by forgers, leading to difficulties in distinguishing authentic from forged notes, as the excitation and emission behaviors of the imitated substances overlap with those of the originals, rendering them unsuitable as a reliable authenticity feature.
Innovation Solution
A method and apparatus that utilize a restricted excitation wavelength range (600-640 nm) to differentiate between original and forged bank notes by detecting luminescence radiation in the 640-700 nm range, using a long-pass filter to block excitation radiation and ensure detection of emitted luminescence only in this range, allowing for reliable visual or sensor-based authentication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If luminescent substances are used in bank notes to prevent forgery, then authenticity protection is improved, but forgeries can be created with similar luminescent properties making detection difficult
Solution Approach 1:
The patent applies parameter changes by restricting the excitation wavelength to a specific range (600-640 nm) and detection wavelength range (640-700 nm). This narrows the spectral parameters used for luminescence verification, creating a detection window that authentic luminescent substances occupy but forged substances do not, thereby resolving the contradiction between maintaining reliability and improving detection precision
Solution Approach 2:
The patent implements local quality by focusing detection on a specific spectral region (red luminescence at 640-700 nm excited by 600-640 nm radiation). Instead of examining the entire luminescence spectrum, the system concentrates verification on the characteristic red emission band that distinguishes authentic bank notes from forgeries, enhancing detection accuracy while maintaining reliability
2Measurement precision
If the excitation wavelength range is restricted to 600-640 nm and detection to 640-700 nm, then detection accuracy is improved, but the complexity of the checking apparatus increases
Solution Approach 1:
The patent uses a long-pass filter as an intermediary component that automatically blocks excitation radiation (600-640 nm) and transmits only luminescence radiation (640-700 nm). This passive optical element simplifies the apparatus by eliminating the need for complex active filtering systems or multiple detectors, achieving high detection accuracy through a single strategic component
Solution Approach 2:
The patent extracts and isolates the specific detection task to a dedicated wavelength range (640-700 nm) using spectral filtering. By separating the detection function into a specific spectral band and removing irrelevant excitation wavelengths through the long-pass filter, the system achieves precise detection without requiring complex multi-wavelength analysis equipment
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
Enables reliable differentiation between authentic and forged bank notes by ensuring that only original notes emit red luminescence radiation in the specified wavelength range, effectively addressing the issue of forgery by altering the detection criteria to account for imitated substances.
Implementation Method 1
a radiation source for emitting radiation from the wave range from 600 to 640 nm to thereby excite the bank note to emit the luminescence radiation
Implementation Method 2
The luminescent substances can be added to the bank note paper and/or the bank note print. Frequently, the luminescent substance is also contained in colored or colorless fibers distributed within the substrate material
Implementation Method 3
Depending on the type of luminescent substance—they include both fluorescent and phosphorescent substances—the substance emits in a defined spectral range when it is irradiated by means of radiation
Implementation Method 4
a long-pass filter for blocking radiation from the excitation radiation range, wherein the long-pass filter is arranged relative to the excitation radiation source such that luminescence radiation emitted by the bank note is detectable through the long-pass filter
Data Source
AI summary
Forged bank notes are no longer reliably distinguishable from bank note originals (BN) on the basis of their luminescent fibers. According to the invention, the excitation of the fibers to luminescence is effected by means of excitation radiation (S) from the restricted wavelength range from 600 to 640 nm or from 520 to 550 nm, since the forgeries do not luminescence in this range but the originals luminescence red. Detection is therefore effected in the wavelength range from 640 to 700 nm.