Classifications

• • G—PHYSICS
  • G07—CHECKING-DEVICES
  • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
  • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
  • G07D7/06—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using wave or particle radiation
  • G07D7/12—Visible light, infrared or ultraviolet radiation
  • G07D7/1205—Testing spectral properties
• • G—PHYSICS
  • G07—CHECKING-DEVICES
  • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
  • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
  • G07D7/003—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using security elements
  • G07D7/0034—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using security elements using watermarks

Definitions

• the invention relates to a method and a device for checking documents of value with an authenticity feature in the form of at least one luminescent substance, the document of value being irradiated with light and the luminescence radiation emanating from the document of value being detected spectrally resolved in order to determine whether this Authenticity feature is actually present in the checked value document.
• a luminescent e.g. a fluorescent or phosphorescent authenticity feature is understood to mean a single substance or a mixture of several substances which show a luminescence behavior.
• a system for example from the applicant's DE 23 66 274 C2.
• this system to check the authenticity of a banknote, i.e. H. in particular, checking whether a fluorescent authenticity feature is actually present in a banknote to be checked, irradiated it and recorded the remitted fluorescence radiation in a spectrally resolved manner. The evaluation is carried out by comparing the signals from different photocells of the spectrometer.
• the present invention is therefore based on the knowledge that a simple and reliable distinction between different authenticity features can best be obtained if a measurement vector is formed from the measurement values which correspond to different frequencies and / or frequency ranges of the luminescence radiation, and one Class assignment of the measurement vector to one of several predefined reference vectors which correspond to different authenticity features is achieved by assigning at least one class assignment area to each of the reference vectors and checking in which class assignment area the measurement vector is located.
• the measurement vector can consist of the measurement values themselves and / or quantities derived therefrom.
• the class assignment areas and thus the class assignment from the measurement vector to one of the reference vectors can preferably be determined by comparing the measurement vector with a plurality of reference vectors or with at least one variable which depends on at least two reference vectors.
• a particularly preferred example of the first-mentioned variant can be that the authenticity feature, the reference vector of which has the smallest difference, such as the smallest distance from the measurement vector, is determined or can be determined as being present in the value document to be checked.
• This procedure has become particularly important with authenticity features very similar spectral curve has proven to be much more suitable than a procedure in which it is checked whether the intensity and / or the curve of a measured luminescent radiation differs from the intensity or the curve of a reference radiation only by a maximum of a predetermined value.
• the second variant in which the measurement vector is not compared with each individual reference vector itself, but with at least one variable derived from at least two reference vectors, significantly reduces the computational effort and is therefore particularly advantageous when high test speeds are important.
• the size which depends on at least two reference vectors, acts as a separating surface between the two reference vectors, e.g. an (n-1) dimensional hyperplane is formed between the two n-dimensional reference vectors, the separating surface separating the class assignment areas of the two reference vectors from one another. In this case e.g. determines the position of the measurement vector in relation to the interface.
• the test system according to the invention can preferably be expanded to include a further step in which it is checked whether or not the magnitude of the measurement vector is greater than a predetermined reference value.
• This step will be carried out particularly preferably before the step of assigning the class assignment areas and / or the step of checking in which of these areas the measurement vector is located. This can result in significant time savings in the evaluation, since the subsequent, more time-consuming evaluation steps for checking the class assignment areas are no longer necessary if the simple amount check already delivers a negative result.
• This procedure proves to be particularly useful when checking authenticity features whose luminescence radiation lies to a significant extent in the non-visible, such as, for example, ultraviolet or in particular in the infrared spectral range.
• the measurement vector is thus preferably formed from measurement values in the infrared spectral range.
• Measurement vector and the reference vectors can be standardized in the same way.
• this can be done, for example, by normalizing to an n-1 dimensional unit sphere, so that the magnitude of all standardized vectors is the same, i.e. specifically has the value 1.
• the measurements have a background signal, which does not result from the luminescent radiation and is superimposed on the luminescent radiation.
• This background signal interferes with the evaluation, since the ratios of the measurement vectors to the reference vectors change significantly as a result of the normalization, depending on the level of the background signals, and can therefore lead to less precise results of the evaluation.
• a background signal which does not result from the luminescence radiation is therefore preferably taken into account when evaluating the measured values.
• an amount can be subtracted from the measurement values that depends on the size of the background signal.
• the amount can vary from measured value to measured value of the measurement vector, i.e. a background vector generated by the background signal can also be used.
• the amount will particularly preferably depend on the size of a minimum and / or maximum of the measured values and / or a ratio of several measured values to one another. If the emission spectrum of the background signal is known, then by measuring the background signal for a single or e.g. a few frequencies the background vector can be calculated. If the background vector is known, it can e.g. stored in the sensor and can be deducted from the measured values even without measurement.
• Figure 1 is a schematic view of a test device according to a first embodiment; the FIG. 2 shows a two-dimensional representation to illustrate the method according to the invention; the
• FIG. 3 shows a two-dimensional representation to illustrate the method of class assignment according to the invention
• FIG. 4 shows a schematic view of a spectral curve L 1 measured from a bank note and a portion L 2 of the spectral curve L 1 that is based only on the luminescent radiation.
• test system according to the invention can be used in all devices which test luminescent authenticity features.
• checking bank notes in bank note processing devices is described below, which can be used, for example, for counting, sorting, depositing and / or paying out bank notes.
• the test device 4 has a light source 5, a spectral sensor 6 and an evaluation device 7, which is at least connected to the spectral sensor 6 via a signal line 8.
• the light source 5 serves for irradiating the bank note 3 with light rays 9 at an oblique angle to the bank note surface and the spectral sensor 6 for detecting and spectrally decomposing the radiation 10 reflected by the bank note surface.
• the spectral sensor 6 preferably detects luminescent radiation 10 im using a spectrometer 6 in- infrared spectral range.
• the signals detected by the spectral sensor 6 are transmitted via the signal line 8 to the computer-based evaluation device 7, which uses the measured signals to check whether a certain authenticity feature is present in the bank note 3.
• the device 1 is distinguished in particular by the type of evaluation of the measurement signals in the evaluation device 7. According to one embodiment of the method according to the invention, this can be done in the following way:
• the measurement vector X (x ⁇ , ..., x n ) is, for example, a measure of the spectral curve of the recorded luminescence radiation 10 of the bank note 3, where xi to x n are values which are based on the measurement signals from n different photo cells of the Spectral sensor 6 are formed.
• the spectral values xi to x n can preferably correspond to the measured luminescence intensity at different frequencies or frequency ranges in an invisible to the eye, such as, for example, ultraviolet or particularly preferably infrared spectral range.
• the measurement vector X thus represents a measure of the shape, ie the course of the measured spectral curve, at least for the case n> 1, preferably of n> 5 or n>10>.
• the banknote In order to decide whether one of the two permitted authenticity features is present in or on the banknote, it can first be checked whether the amount of the measurement vector X, i.e. ] X
• the threshold can be 0, but is preferably chosen so that counterfeits without authenticity can already be distinguished here. In the exemplary case of FIGS. 2 and 3, this reference value R has, for example, an amount
• this criterion is that the amount
• R particularly preferably used for the pre-evaluation of the measurement values.
• This can mean, for example, that this minimum value comparison of the amount
• This variant of the upstream amount check can significantly increase the speed of the bank note check.
• Reference vectors (Ai, ..., Ak) are assigned.
• these areas are half-planes GA, GB, as illustrated in FIG. 3.
• the class assignment areas are averages of finitely many half-levels.
• the class assignment areas can now be defined either via the reference vectors A, B (in the general case Ai, ..., Ak) or via a description of the hyperplanes delimiting them.
• That reference vector A, B is determined which has the smallest difference from the measurement vector X.
• the distance of the measurement vector X to all possible authenticity features, in the case specifically described, to the two reference vectors A, B can be calculated.
• the distance can be defined as the Euclidean distance between the relevant vectors, i.e. d (X, A) and d (X, B) are calculated in the example.
• any function d (X, A) can be used with the following property: For any measurement vectors X and reference vectors A, B, d (X, A)> d (X, B) applies if
• the class assignment areas are defined by a separating surface T which delimits the two reference vectors A, B (in the general case Ai, ..., Ak) .
• This variant has the advantage, in particular in real-time environments, that the computing effort is reduced.
• the measurement vector X is only assigned to one of the reference vectors A, B when their mutual distance d (X, A) or d (X, B ) does not exceed a predetermined threshold.
• the class assignment areas GA, GB SO are limited, that the class assignment areas do not touch anymore.
• "no man's land” is created between the class assignment areas GA, GB, ie areas that are not assigned to a class and thus not to a reference vector Ai, ..., Ak.
• Banknotes 3 the measurement vector of which lie in these areas, can, for example, be provided with a warning after the check in the test device 4 or be placed in a special storage.
• the probability that a measurement vector X corresponds to one of at least two reference vectors A, B is not equally distributed, but e.g. has a correlation.
• the distance of the measurement vector X from the reference vectors A, B increases with its intensity and the intensity of the individual reference curves A, B. This means that if one of the two possible authenticity features is introduced into the checked banknote 3 in a significantly higher quantity and concentration, the distance between its reference vector A or B and the measurement vector X can also be correspondingly larger.
• both the reference vectors A, B, and the measurement vector X is also standardized.
• normalization to the unit circle E is carried out, for example. This means that the normalized vectors A /
• k reference vectors Ai, ..., Ak which each have n components owning the projection onto the n-dimensional unit sphere E.
• calculated.
• the classification is in turn carried out for the authenticity feature, the reference vector A, B of which has the smallest distance d (X, A) d (X, B) from the measurement vector X, in the case shown the authenticity feature A.
• the distance d (X, A) of two vectors can be, for example, the Euclidean distance of the standardized vectors X, A
• d (X, A) can be used with the following property: For any measurement vector X and reference vector A, B, d (X, A)> d (X, B) applies if
• the distance d (X, A) of the vectors X and A can be the angle between straight lines of origin defined by them.
• d (X, A) X - (X, A) • Al ⁇ A ⁇ Der
• Distance d (X, A) corresponds to the length of the plumb line from X to the straight line of origin defined by A.
• This expression is particularly preferred when the distance has to be calculated in a time-critical manner, since this saves the time-consuming calculation of the root in the second example.
• the banknotes 3 are preferably irradiated intermittently by the light source 5 in order, for example, to be able to measure the decay behavior of the luminescent radiation 10 in a temporally resolved manner.
• a time-dependent representation of the measurement vectors X and / or the reference vectors A, B can also be selected with particular preference and the distance formation can be carried out as a function of time.
• the luminescence radiation is measured only on predetermined subregions of the banknote area, which are selected in a particularly preferred manner to be nominal value-specific. This can take place, for example, in that the light source 5 illuminates only one or more special partial areas of the bank note 3 as it is transported past a test device 3, or information about the position of the respectively illuminated partial areas of the bank note 3 during the evaluation in the evaluation device 7 taken into account.
• This location-dependent measurement of the luminescent radiation 10 can be used, for example, in order to be able to distinguish spatially coded authenticity features that are not homogeneously incorporated in the banknote paper.
• the luminescent radiation 10 does not necessarily have to be in reflection, but it can alternatively or additionally also be measured and evaluated in transmission. As mentioned, it can be disruptive in the evaluation if the measurement signals have a background signal which does not originate from the luminescent radiation and is superimposed on the luminescent radiation 10. These disturbing background signals falsify the ratios of the individual measurement vectors to the reference vectors during normalization.
• the spectral sensor 6 shows the spectral course of the measurement signals of an illuminated bank note 3, i.e. the dependence of the measurement signal intensity I (f) on the measurement signal frequency f is shown.
• the portion of the measurement curve L1 that actually only originates from the luminescent radiation 10, corresponding to the curve L2 drawn in dashed lines, is, however, lower in magnitude and is overlaid by a disruptive background signal which is not due to the luminescent radiation 10.
• a reference measurement can be carried out in a banknote gap. Measured values are recorded using the spectral sensor 6 when there is no banknote 3 in the detection range of the spectral sensor 6. The signals obtained in this way then represent a measure of the strength of the background signal and can be taken into account in the subsequent formation or evaluation of the measurement vectors, e.g. be subtracted from the measured values when measuring the following bank note 3.
• spectral sensors 6 in which the measurement ratios in the measurement with bank note 3 are so clearly differentiated from the measurement without bank note 3 that the background signals measured in the case without bank note are not representative of the background signals measured with bank note.
• the size of a relative, preferably the absolute minimum and / or maximum of the measurement signals can therefore be determined in a spectral range used for further evaluation. This can be, for example, a point in the spectrum at which the luminescent substances to be tested usually do not emit. In the spectrum of FIG. 4, this minimum is exemplarily at the frequency f ini and has an intensity iMini.
• the ratio of the intensity of the luminescent radiation at two different frequencies has a constant known value.
• the two frequencies can preferably be chosen such that they correspond to a maximum and a minimum of the spectral curve.
• the intensity ratio I (fMa ⁇ ) / I (fMin2) of the luminescent radiation 10, corresponding to curve L2 is equal to a constant value ko.
• a linear offset i.e. a deduction of a constant value I ÜÜ or Io from the measurement intensity I (f) of the measurement curve L2
• another non-linear offset can also be deducted, in which the deducted value varies with the frequency f.
• the amount can differ from the measured value to the measured value of the measurement vector, i.e. a background vector generated by the background signal can also be used.
• the background vector can be calculated by measuring the background signal at one or more frequencies. If the background vector is known, it can e.g. stored in the sensor and subtracted from the measured values even without measurement.
• the procedure according to the invention consequently enables simple and reliable checking and differentiation of authenticity features, in particular with a very similar spectral profile, which may be contained in documents of value.

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• Physics & Mathematics (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Computer Security & Cryptography (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Engineering & Computer Science (AREA)
• Inspection Of Paper Currency And Valuable Securities (AREA)
• Document Processing Apparatus (AREA)
• Peptides Or Proteins (AREA)
• Financial Or Insurance-Related Operations Such As Payment And Settlement (AREA)
• Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)

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• 2002
  • 2002-11-29 DE DE10256114A patent/DE10256114A1/de not_active Withdrawn
• 2003
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  • 2003-11-28 DE DE50303063T patent/DE50303063D1/de not_active Expired - Lifetime
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