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Method and apparatus for verifying the authenticity of an item by detecting encoded luminescent security markers

A security marking and authenticity technology, which can be used in the verification of the authenticity of banknotes, fluorescence/phosphorescence, material excitation analysis, etc., and can solve problems such as impracticality and complexity.

Inactive Publication Date: 2008-03-12
EI DU PONT DE NEMOURS & CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This system is inherently complex and impractical in uncontrolled environments such as those with ambient lighting

Method used

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  • Method and apparatus for verifying the authenticity of an item by detecting encoded luminescent security markers
  • Method and apparatus for verifying the authenticity of an item by detecting encoded luminescent security markers
  • Method and apparatus for verifying the authenticity of an item by detecting encoded luminescent security markers

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0080] Example 1 The luminescent material has a spectrum containing 3 peaks (Fig. 1A)

[0081] Apparatus 10 having four photodetector assemblies according to the configuration of Figure 2 can be used to determine the authenticity of articles bearing luminescent security markings having an emission spectrum similar to that shown in Figure 1A. In this arrangement, the bandpass filter 54 of the photodetector assembly 50 is centered at 589 nanometers and has a full width at half maximum (FWHM) transmission of 10 nanometers in order to pass the wavelength band of 584-594 nanometers, the photodetector Bandpass filter 64 of assembly 60 passes a wavelength band of 605-615 nanometers, and bandpass filter 74 of photodetector assembly 70 passes a wavelength band of 689-699 nanometers. Also for this spectrum, light detector assembly 80 with bandpass filter 88 can pass light between 540 and 570 nanometers to verify the absence of significant light energy in this wavelength range.

example 2

[0082] Example 2 Security marking with two luminescent materials to illustrate separation of Eu using specific wavelength beam splitters (48, 58) 3+ and Tb 3+ the glow

[0083] By combining Kasei Optonix(Y, Gd)BO excited by 394 nm light 3 : The first spectrum of Eu (sold as KX-504A) (Fig. 1A) with GTE Sylvania Gd excited by 377 nm light 2 o 2 The second spectrum (Fig. 1B) of S:Tb (type 2611) is mathematically added and "synthesized" to obtain a set of "Tb 3+ +Eu 3+ "Emission spectra, each multiplied by a variable factor to simulate different mixing ratios (as listed in columns 2 and 3 of Table 1 below). Using SPEX with excitation and emission resolution set to 1 nm  Fluorolog-3  The spectrometer measures two starting spectra. The resulting synthetic emission spectrum of this hypothetical mixture (shown in Figure 1C) was convolved with the reflectance spectral responses of the two filters chosen to separate the green Tb emission from the red Eu emission. The green f...

example 3

[0118] Example 3 sync detection

[0119] A commercial single-phase lock-in amplifier (EG&G Princeton Applied Research Model 5209) was used to analyze the output signal from the silicon photodiode circuit. The LEDs were electronically modulated by a Stanford Research DG535 pulse generator. The modulated excitation waveform is a square wave with independently variable pulse width and pulse frequency. Due to the use of a lock-in amplifier with an electronic bandpass filter centered at the LED modulation frequency, only the fundamental cos(ωt) component of the Fourier series expansion of the signal produced by the square wave excitation is detected. It should be appreciated that a slightly larger signal can be obtained by modulating the LED output sinusoidally such that the entire signal occurs at a single modulation frequency. The displayed data was acquired with a lock time constant of 1 second (chosen to conform to the criteria of a 1 second read time), which corresponds to...

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PUM

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Abstract

An apparatus for verifying, under ambient lighting conditions, the authenticity of an optical security mark on an item, the mark comprising a luminescent material which absorbs light within a first predetermined range of wavelengths and emits luminescence within a plurality of other predetermined wavelength ranges with a predetermined characteristic time response. The apparatus distinguishes the luminescence of the mark from fluorescence the item may have by distinguishing the slower luminescence decay rate of the security mark from the faster decay rate of the inherent fluorescence. The apparatus comprises an optical arrangement, having an illumination assembly and a luminescence detector assembly, and a signal processor assembly, all contained in a single housing. The illumination assembly and the luminescence detector assembly have a common focusing lens and are arranged along a common axis to illuminate the security mark and to detect emitted light from the security mark in a retro-reflective manner.

Description

[0001] This application claims priority to US Provisional Application 60 / 839648, filed August 23,2006. technical field [0002] The invention relates to a device for verifying the authenticity of an optical security mark comprising a luminescent material which absorbs light in a first predetermined wavelength range and emits light in a plurality of predetermined wavelength ranges. Background technique [0003] Various materials and systems have been proposed to provide materials and methods for encoding fluorescent material in security documents such as banknotes, on labels or directly on items requiring authenticity. Each of these previous attempts has certain disadvantages or deficiencies. [0004] Typical prior art is U.S. Published Patent Application 2003 / 0032192A1 ('192), which describes luminescent security marking materials and by comparing the emission at one or more expected peak emission wavelengths with nearby wavelengths where low or no emission is expected to be...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G07D7/12G01N21/64
CPCG07D7/121G07D7/122G06K7/12G07D7/1205
Inventor E·N·布兰查德M·K·克劳福德P·A·埃姆斯M·R·麦夸德R·佩奇R·J·斯马利
Owner EI DU PONT DE NEMOURS & CO
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