WO2018202676A1

WO2018202676A1 - Method and device for verifying an electroluminescent security feature in a value or security document

Info

Publication number: WO2018202676A1
Application number: PCT/EP2018/061138
Authority: WO
Inventors: Florian Peters
Original assignee: Bundesdruckerei Gmbh
Priority date: 2017-05-02
Filing date: 2018-05-02
Publication date: 2018-11-08
Also published as: DE102017207367B3; EP3619691B1; EP3619691A1

Abstract

The invention relates to a method for verifying an electroluminescent security feature (2) in a value or security document (3), comprising the following steps: exciting the electroluminescent security feature (2) by a predetermined input signal (8) using an electric field by an excitation device (4), detecting a luminescence (9) emitted by the electroluminescent security feature (2) and converting the detected luminescence (9) into an output signal (11) by a detection device (5), transforming the output signal (11) by means of a provided characteristic function (12) by an evaluation device (6), evaluating the transformed output signal (14) while taking into account at least one input signal information (16) of the input signal (8) for deriving a verification decision (18) by the evaluation device (6), outputting the verification decision (18) by the evaluation device (6). The invention further relates to an associated device (19).

Description

Method and device for verifying an electroluminescent security feature in a value or security document

The invention relates to a method and an apparatus for verifying an electroluminescent security feature in a value or security document.

Background of the invention

In the field of value and security documents, electroluminescent security features are used. In this case, for example, printing inks and preparations with electroluminescent pigments are used, which exhibit a luminescence in the visible and / or non-visible spectral range when excited in a static or dynamic electric field.

Such security features are known, for example, from WO 98/39163 and WO 2004/108426 A2.

If a dynamic excitation of such an electroluminescent pigment takes place, for example by means of an electric field modulated by a harmonic excitation, then the electroluminescent pigment exhibits a characteristic

Luminescence. However, only in very few cases is such a luminescence response a signal that can be described as a harmonic wave alone. Rather, analyzes of the luminescence response increasing after the start of an excitation have shown that there is an exponential dependence of the peak value of the luminescence on the electric field component (D. Curie, Sur le mecanisme de l'electroluminescence - II. Applications aux faits experimentaux, J. Phys , 1953, 14 (12), pp- 672-686). In the literature, an exponential function is set up for the increase. By contrast, the luminescence response decaying after switching off the excitation is usually described only qualitatively, for example as hyperbolic. As a rule, this has very strong nonlinear courses with secondary maxima.

The evaluation of such a luminescence response, that is to say the intensity of a luminescence over time, takes place in the prior art via a temporal detection of the luminescence and a spectral decomposition of the luminescence response in the frequency space instead.

Subsequently, exactly the harmonic component is evaluated, which usually corresponds to the exponential dependence of the slope and of the e.g. hyperbolic decay because of the luminescent response most characterized. This creates a conditional link with the properties of the color of the used

electroluminescent pigment, which can be exploited to identify the electroluminescent pigment used and in this way the authenticity of a provided with this electroluminescent pigment

Security feature.

The recognition of the properties of the luminescence response and thus of the

However, electroluminescent pigment in this case are very inaccurate, since several influencing factors can change the components of the frequency spectrum, without modifying the basic property of the electroluminescent pigment in this case. When external conditions change, this can lead to significant difficulties in verifying the security feature. Verifying should mean checking the authenticity of such a security feature.

The reproducibility of measurements on the same pigment is limited.

This may also lead to unsafe detection of true versus counterfeit (non-genuine) electroluminescent pigments. For example, the detection of true pigments may lead to a misinterpretation, ie a true pigment is erroneously classified as not true ("false reject").

In addition, a selectivity is limited, so that a distinction and

Recognition of other electroluminescent pigments which are very similar in their properties are very difficult or almost impossible with the conventional method.

Object of the invention

The invention is based on the technical problem, a method and a

To provide an apparatus for verifying an electroluminescent security feature in a security or valuable document in which the verification of the authenticity of the electroluminescent security feature is improved. The technical problem is solved by a method with the features of claim 1 and a device having the features of claim 16. Advantageous embodiments of the invention will become apparent from the

Dependent claims.

A value or security document will be referred to below as a document with at least one security feature. This security feature makes it difficult or impossible to forge or copy the value or security document. In particular, such a value or security document should have an electroluminescent security feature. Such a value or security document may, for example, a banknote, a security, a

Token, a ticket, a ticket, a certificate, a seal, a

Identification document, such as a passport, ID card, driver's license or any other trained for individual identification document, be. In addition to the electroluminescent security feature, the security or security document may additionally have further security features.

In the following, a symbol is intended to designate a single character unit for transmitting an information content. A symbol has a certain symbol shape. In particular, a symbol is to be understood here in the sense of communication technology, wherein a transmission unit for transmitting data sends symbols with a known symbol transmission rate over a transmission channel and a receiving unit recognizes these symbols and reconstructs the transmitted data.

Core idea of the invention

The core idea of the invention is the electroluminescent pigment of the

Security feature to describe communications technology. A message-technical description should mean that the luminescence response or the measured

Luminescence signal is understood as a signal chain of individual members described by means of telecommunications modeling methods. The measuring chain here consists of the excitation elements, an element describing the behavior of the electroluminescent pigment and a transmission channel. Of the

Transmission channel reproduces the disturbing influences in the measuring chain. The transmission channel comprises all the influences of the transmission path of the signal. This can For example, be disturbances, which are caused by a sampling frequency, an A D conversion or a light detector used.

The measured luminescence signal is then modeled as a convolution of a provided characteristic function of the electroluminescent pigment with excitation and with a transmission channel. Excitation describes the actual electric field used to excite the electroluminescent pigment. The characteristic function provided describes the behavior of the electroluminescent pigment after or during a specific excitation and may correspond, for example, to a classical impulse response, a step response or a sinusoidal response. Sinusoid is a waveform that starts over time with a zero signal, followed by a sine half-wave followed and then again consists of a zero signal.

The provided characteristic function is determined for this purpose by means of numerical methods. If the provided characteristic function is known, following the excitation, a demodulation of the luminescence signal by means of known

message technology methods, for example, using a matched filter (English Matched filter), in which the symbol shape used in the excitation flows.

In terms of telecommunications, verification of the electroluminescent pigment or of the security feature can thus be understood as a measuring chain consisting of the individual steps: excitation of the electroluminescent pigment by a specific symbol sequence, change of the excitation signal by the signal

electroluminescent pigment according to the characteristic function, transmission over a transmission channel which mimics all disturbances, demodulating the detected luminescence response by transforming it by means of a

Reference pigment known characteristic function, checking the demodulated result with the symbol sequence of the excitation. For example, the verification occurs such that the measured luminescence signal matches that provided

characteristic function for the real electroluminescent reference pigment or its inverted Fourier transform is unfolded, the result is demodulated and the demodulated result is evaluated. The authenticity of the security feature is determined on the basis of the evaluation result. On the basis of the telecommunications description it is possible, for example, to obtain an optimum signal-to-noise ratio and high interference immunity, so that it can be determined with optimum certainty during verification whether or not there is a specific electroluminescent pigment - and thus whether the

Security feature is real or not.

Special embodiments

In particular, a method for verifying an electroluminescent

Security feature provided in a value or security document, comprising the following steps: exciting the electroluminescent

Security feature by a predetermined input signal by means of an electric field by an excitation device, detecting one of the

electroluminescent security feature emitted luminescence and converting the detected luminescence into an output signal by a detection device, transforming the output signal by means of a provided characteristic function by an evaluation device, evaluating the transformed

Output signal in consideration of at least one input signal information of the input signal for deriving a verification decision by the

Evaluation device, issuing the verification decision by the

Evaluation. The input signal information may be the symbol form or the symbol itself.

Further, an apparatus for verifying an electroluminescent

Security feature created in a value or security document, comprising an excitation device for exciting the electroluminescent

Security feature by means of an electric field by a predetermined

Input signal, a detection device which is designed so as to detect a luminescence emitted by the electroluminescent security feature and to form an output signal, an evaluation device which is designed to transform the output signal by means of a provided characteristic function, the transformed output signal taking into account at least evaluate input signal information of the input signal, derive therefrom a verification decision and output the derived verification decision. For example, access barriers, such as a lock, a barrier, etc., or a sorting machine, in which banknotes are selected for destruction, can be controlled via the evaluation device.

To encode the input signal, for example, a rectangular pulse as

Symbol shape, which is multiplied by a sinusoidal carrier. Also possible is a half-wave of a sine function. The input signal can therefore only consist of the symbol form.

Furthermore, it can be provided in particular that the input signal information is a symbol form which is used to encode information in the input signal. Knowledge of the symbol shape then allows demodulation of the transformed output signal and reconstruction of the encoded information.

It is important to note that the information encoded with the transmitted symbol or symbols does not necessarily have to be determined and evaluated. In some embodiments, it is sufficient to use knowledge of the symbol shape to determine that the symbol transfer by the measured pigment corresponds to transmission by a true reference pigment.

For example, a verification decision can then be derived by determining the signal-to-noise ratio in the transformed output signal. For example, the security feature is found to be true when a certain threshold signal-to-noise ratio is reached or exceeded.

Another alternative method for demodulation is, for example, the use of an "integrate and dump" filter, in which a discrete input signal is accumulated cumulatively for a certain number of samples or for a given time window for each step. After the certain number of samples have been counted, the sum is reset to zero ("dump") and the cumulative summation is started again, and then, for example, threshold information can be used to recover the information encoded in the excitation, which method can generally be used if a symbol form of the excitation has a simple rectangular pulse shape. Another alternative method uses a Kalman filter, which determines the system response at each time of the sampled luminescence signal and then determines the system response despite noise. Preferably, a so-called Extended Kalman filter is used, ie a non-linear Kalman filter. Here it is very important to completely grasp the above-mentioned measuring chain, since the actual input function of the Kalman filter is the excitation signal of the luminescent substance. Only with correct knowledge of the excitation signal is the system response to be recorded.

It can therefore be provided to measure the actual excitation signal given by the input signal by means of a sample. With such a sample, which measures as possible under the environmental conditions, under which the

Lumineszenzpigmente are integrated in a real security document, a so-called feedback circuit can be realized, which adapts the input signal, so that the actual excitation of the desired excitation (a desired

Symbol shape or the desired symbol of the input signal).

The advantage of the method and the device is that small non-linearities due to the integration and longer time recording, especially when using the Kalman filter, the evaluation hardly affect and spectral shifts in

Frequency range of the output signal in contrast to the prior art no longer lead to a large error in the evaluation and verification. Furthermore, the DC component of the output signal does not need to be considered separately. Another advantage is that the phase position no longer necessarily needs to be recognized (a so-called phase recovery is not necessary) and the maximum possible signal-to-noise ratio is achieved.

In particular, it is provided in a particularly advantageous embodiment that the luminescent effect of the security feature is modeled as a short-term linear time-invariant system (LTI). That is, it is assumed in a first approximation that the behavior of the electroluminescent effect has both the property of linearity and independent of temporal

Shifts is. This simplifies the transformation equations and thus enables particularly efficient further processing of the output signal. In particular, it is provided in an advantageous embodiment that the

To derive the verification decision in the evaluation device, a correlation of the transformed output signal with at least one part of the

Input signal is performed, wherein the electroluminescent

Security feature is found to be true when a correlation function at a given time or in a predetermined time range reaches or exceeds a predetermined threshold. Thus, a cross-correlation of the transformed output signal with at least a part of the input signal is performed. This part of the input signal may in particular be one in the

Input signal used be symbol shape.

Furthermore, it can also be provided that the threshold value must be exceeded for a plurality of predetermined times or a plurality of predetermined time ranges, so that the security feature is found to be genuine. If the predetermined threshold or the predetermined thresholds are not exceeded, the

Security feature not found to be genuine.

The characteristic function can in particular consist of a

Reference security feature, which is known as genuine derived. Therefore, it is provided in a particularly advantageous embodiment that the characteristic function is determined by means of a calibration measurement, wherein a

electroluminescent reference security feature is excited and its

Luminescence is detected and evaluated as a reference output signal. To the

deriving characteristic function, a calibration measurement is thus carried out, which (like the verification method itself) stimulates the

Reference security feature by a predetermined input signal by means of an electric field by an exciter, detecting one of the

Reference security feature emitted luminescence and converting the detected luminescence into a reference output signal by a detection means comprises. The characteristic function is then derived from the reference output signal and the predetermined input signal.

In particular, for this purpose, it is provided in a further advantageous embodiment that the characteristic function is the inverse of a transfer function of the

electroluminescent reference security feature, wherein the electroluminescent effect of the security feature and the

Reference security feature is understood as a linear time-invariant system.

As a rule, the inverse of the transfer functions can not be determined analytically. In a further advantageous embodiment, it is therefore provided that the inverse of the transfer function is calculated by means of numerical methods. This can be done, for example, by means of the Matlab function "fmincon ()" (for example in Matlab® Version 2016a, a software of The MathWorks, Inc. in Natick, Massachusetts, USA).

In carrying out the process, it may happen that the experimental

Conditions on or in the device are not constant over time and thus vary from measurement to measurement. Also, a non-optimal or different than individual measurements operation by a user may lead to a variance of conditions on the device. It has therefore proved to be advantageous if changes in the conditions on or in the device are taken into account in the evaluation. In a further advantageous embodiment, it is therefore provided that the transformation of the output signal comprises a deconvolution with an adaptation function. The adaptation function forms the influences of the device and the conditions during a measurement (excitation and detection of the device)

Electroluminescence). In particular, these conditions may be, for example, an actual voltage applied to the excitation of the electroluminescence or an actual distance of the electrodes of the excitation device.

In some situations these are in particular parameterizable

Deviations that are estimable and / or measurable. In a particularly advantageous embodiment it is provided that the adaptation function is estimated on the basis of measurable parameters by an estimating device. So can

for example, an actual electrodes (capacitor plates) of the

Exciting means present electrical voltage can be determined. An actual distance of the electrodes of the excitation means can also be determined by suitable means. In this way, for example, a caused by vibration of the device harmonic excitation, which by a vibration following change of the plate spacing in the electric field

is taken into account. From the measurable or determinable Parameters, the adaptation function is then estimated by the estimator, for example, by estimating a harmonic in the electric field caused by a vibration. Furthermore, a mechanical plate spacing at

different similar devices may be different and the present electrical voltage may differ from the nominal voltage, so that for each device, the adjustment function must be determined or estimated individually. A temperature and general environmental conditions can also be taken into account when estimating.

In one embodiment, it is provided that the deployment is carried out by means of a Kalman filter. In this case, for example, a so-called amplifier matrix can be calculated.

In particular, it can be provided in an advantageous embodiment that an output signal is transformed by at least one further characteristic function and then evaluated. In the case of several security features, each with different electroluminescent pigments, it is possible in this way, in addition to the pure verification of an expected security feature, to determine which security feature or which electroluminescent pigment is present. In this way, security features can be tested for the presence and the authenticity of certain electroluminescent pigments. In particular, it can be provided that a security feature with a plurality of

characteristic functions is checked. The characteristic functions may for example be stored in a memory and, if necessary, provided by the latter individually. The characteristic function to be used is then selected either automatically, for example by the evaluation device or manually by a user of the device. In the automatic selection, for example, before the verification of the security feature, a type of

Security document or a security feature can be detected and detected, for example by means of an additional optical detection device, etc., so that the evaluation subsequently based on the recognized type of

Security document or security feature can select an associated characteristic function from the memory. Furthermore, all the characteristic functions stored in the memory can also be successively checked. Furthermore, it is possible to use different suggestions in verifying the security feature. The basic procedure of the method remains the same, only the predetermined input signal is changed. It should be noted here that a characteristic function is used for the transformation, which is optimal in nature for the selected input signal.

In particular, it is provided in a further embodiment that the

Input signal is composed of a sequence of symbols. Such a sequence can for example consist of symbols which have a rectangular pulse as a symbol form. Furthermore, but also a half-wave (half-wave) of a

Sinusoidal function or completely different symbols formed as a symbol shape possible.

Furthermore, it can be provided in a further embodiment that the sequence is composed at least partially of at least one sequence of identical symbols.

In a further embodiment, it is provided that the sequence is composed at least partially of different symbols.

In an advantageous embodiment, it is provided that the output signal is filtered before and / or after the transformation. This allows, for example, a noise suppression and / or a time saving in a numerical calculation, since only a smaller frequency range must be processed. Suitable filters for this purpose may be, for example, a bandpass filter, a low-pass filter or a high-pass filter, the filter ideally being adapted to a frequency spectrum of the excitation or the individual symbol form. For example, if a symbol used for coding and excitation contains only certain portions of the frequency spectrum, then the filter is chosen such that those not present in the symbol or symbol form

Frequency components are filtered out. In this way, disturbances (noise) in these frequency ranges in the overall signal can be suppressed without affecting the proportion of the frequency spectrum necessary for the formation of the symbol. A limitation to a frequency band with the goal of a

Of course, noise cancellation also limits the electroluminescent response to this frequency range. High-frequency noise can be filtered by evaluating only one frequency range. For a comparison of Electroluminescent response with literature values or other measurement methods, however, a consideration of this restriction is necessary.

In a further advantageous embodiment, it is provided that, when evaluating in the evaluation device, a synchronous demodulation for recovering the phase of the input signal is carried out. This has the advantage that demodulation can be performed more reliably.

In particular, it may be provided that the method for verifying is performed several times and authenticity of the security feature is determined only if all verification decisions assess the security feature as genuine.

Furthermore, it can be provided in one embodiment that the predetermined

Input signal is provided or selected based on another in or on the security document trained security feature. In this way, it is possible, for example, that another security feature is checked before verification according to the method described, and a selection of the predetermined one based on the verification result of the other security feature or information formed in the other security feature

Input signal is hit. This has the advantage that the safety of the

Security feature can be further increased by an entanglement and / or plausibility of the security feature takes place with the other security feature. Furthermore, provision can also be made for a security feature to be based on the other security feature formed in or on the security document

characteristic function is selected for transforming.

Parts of the device can also be designed individually or combined as a combination of hardware and software, for example as program code that is executed on a microcontroller or microprocessor.

Generally it remains to be seen that a challenge in the analysis of

Luminescence signals is that on the one hand for a sufficient power of the luminescence signals a harmonic or repeatedly pulsed excitation are very beneficial, on the other hand, the pulse, jump, or sinusoidal response takes much longer in time than an excitation cycle. Thus arises in the luminescence signal in the language of Communications technology, a so-called intersymbol interference, which makes the luminescence signal look significantly different to an impulse response of a symbol. The characteristic actual entropy of the pigment, especially at

However, comparative measurements and comparisons with other pigments or literature must again be due to a standard or standard response to excitation, such as the impulse or step response or sinusoidal response. Based on this consideration, the solution described here was found.

The invention is based on preferred embodiments below

Referring to the figures explained in more detail. Hereby show:

Fig. 1 is a schematic representation of an embodiment of the device for

Verifying an electroluminescent security feature in a value or security document;

FIG. 2 shows a schematic illustration of a further embodiment of the device for verifying an electroluminescent security feature in a value or security document using an adaptation function; FIG.

Fig. 3 is a schematic flow diagram of an embodiment of the method for

4 is a schematic overview diagram of a calibration measurement;

5 is a schematic overview diagram of an embodiment of the method for verifying an electroluminescent security feature in a value or security document.

FIG. 1 shows a schematic illustration of an embodiment of the device 1 for verifying an electroluminescent security feature 2 in a value or security document 3. The device 1 comprises an excitation device 4, a detection device 5 and an evaluation device 6. The value or security document 3 is positioned between two electrodes 7 of the exciter 4. The electroluminescent security feature 2 located on the value or security document 3 is excited by means of an electric field by a predetermined input signal 8 for luminescence 9. The predetermined input signal 8 is provided, for example, by a modulation device 10 on the electrodes 7.

The luminescence 9 emitted by the excited electroluminescent security feature 2 is detected by the detection device 5. The detection device 5 can be, for example, a spectrometer with a downstream CCD line, which allows a time-resolved detection for a corresponding part of the electromagnetic spectrum. It is also possible to detect the luminescence by means of a photodiode time-resolved. The detection device 5 derives from the detected

Luminescence an output signal from 1 1 and forwards it to the evaluation device 6 on. Furthermore, another time-resolved measuring detector can also be used.

In particular, an analog-to-digital conversion can be provided after detection, so that the output signal can be provided in digital form, for example as a data stream or data record.

The evaluation device 6 transforms the output signal 1 1 in one

Transformation module 13 by means of a characteristic function 12. Such a transformation may be in particular a deployment of the output signal 1 1 with the characteristic function 12.

The transformed output signal 14 is forwarded to a demodulator module 15 and demodulated there. Here, an input signal information 16 of the

Input signal 8 taken into account. Such input signal information is

For example, a symbol form of symbols used to generate the

Input signal 8 are used. The demodulation may be performed, for example, using a matched filter tuned to the symbol shape. Subsequently, in a verification module 17, a verification decision 18 is derived, which is then output. The verification decision can

For example, based on a predetermined signal-to-noise ratio are taken. If the signal-to-noise ratio exceeds a certain threshold, the security feature 2 is found to be true, but if the threshold is not exceeded, the security feature 2 is not found to be true.

It may be provided that before a check of the value or

Security document 3 a characteristic function 12 to a

Security feature 2 must be selected. In this case, it is both possible for the selection to be made manually by an operator, and for the selection to be made automatically on the basis of other criteria, for example because the type of the value or security document 3 is known and for this type

corresponding characteristic function 12 belongs. On the other hand, it is also possible to successively use a plurality of different characteristic functions 12 when verifying the security feature 2. Thus, both a type of security feature 2 or a type of value or security document 3, for example banknotes of different denominations, can be identified and their authenticity can be ascertained.

With a signal in which the verification decision is coded, other means, e.g. a sorting machine or access barriers, such as locks,

Barriers, security locks, etc., are controlled.

2, a further embodiment of the device 1 is shown. The device 1 corresponds to the device 1 shown in FIG. 1, wherein like reference numerals also designate like features. In addition, the evaluation device 6 in this embodiment has a deployment module 20, which transformed the

Output signal 14 unfolded by means of an adaptation function 21. These

Adaptation function 21 may be, for example, measurable or determinable

Parameters 22 are estimated and provided by an estimator 23. The adaptation function 21 in this case depicts the specific conditions under which the luminescence is excited and detected. These conditions may vary from measurement to measurement and may be due to both a current condition (eg, temperature, vibration, etc.) of the device 1 and a variance in the operation depend on different or the same operator. After deployment by means of the adaptation function 21, the unfolded transformed output signal 24 is forwarded to the demodulation module 15 and, as already described above (see FIG. 1), evaluated.

3, there is shown a schematic flow diagram of an embodiment of the method for verifying an electroluminescent security feature in a value or security document. The method is started, for example, by an operator, an automatic device or a provided start signal. After the start 100 of the method, the value or security document with the electroluminescent security feature is placed between the electrodes of the device (see schematic representation in FIG. 1).

In a first method step 101, the electroluminescent

Security feature then by means of an electric field through a

Excitation device excited. Here, the electric field is through a

modulated given input signal. The suggestion will do that

electroluminescent security feature in an excited state. When relaxing from this excited state emits the electroluminescent

Security feature electromagnetic radiation (luminescence).

In the next method step 102, the emitted luminescence is detected time-resolved by a detection device. The detection device may, for example, comprise a photodetector with or without a monochromator connected in front of it. Also, a photodiode or a Charged Coupled Devide (CCD) may be used as the photosensitive member. The detected luminescence becomes

subsequently converted into an output signal in the detection device 103.

In particular, an analog / digital conversion can be provided in this case, so that after the conversion, a digital signal in the form of a data stream or data set is available as an output signal.

In some embodiments, it can be provided that the output signal is filtered in an additional method step 104. Here, for example, a low-pass or a bandpass can ensure that a noise component is reduced or non-relevant frequency ranges are removed, for example in addition to one reduce numerical computational effort. The filtering is also possible both before and after an A / D conversion. A filter is then designed according to analog or digital.

The output signal is transformed in method step 105 by means of a characteristic function. In particular, the characteristic function is an inverse of the transfer function of a reference security feature that is known to be genuine. The transfer function or the inverse of the transfer function has previously been determined by means of a calibration measurement and numerical methods.

In particular, it may be provided that the transformation of the output signal takes place numerically by means of corresponding arithmetic operations, for example by executing a corresponding program code on a microcontroller or microprocessor designed for this purpose. All subsequent process steps in which the output signal is processed further, in particular, can be performed numerically.

In some embodiments of the method, it may be provided that the

Transforming the output signal, a deployment of the output signal or the transformed with the characteristic function output signal with a

Includes adjustment function. Ideally, the adaptation function is determined or calculated from measurable parameters of the device. These measurable parameters can be, for example, a temperature, an electrical voltage between the electrodes of the exciter or a distance of the electrodes of the

Be stimulator. By unfolding with the adaptation function, external influences caused by the measurement conditions at, near or in the

Device are eliminated in the output signal eliminated or at least reduced.

The transformed output signal is evaluated in the next method step 107. In particular, a demodulation takes place. Here is also a

Input signal information taken into account. Such input signal information may be, for example, a symbol form used in encoding the input signal. The evaluation may additionally comprise a further filtering, for example by means of an optimized filter (matched filter) which is tuned to the input signal or the symbol form used in the input signal.

When evaluating common methods of demodulation can be used, for example, a cross-correlation, "Integrate and Dump" or "Sample and Hold" etc.

In the "Integrate and Dump" filter, a discrete input signal is summed cumulatively for a certain number of samples or for a given time window for each step ("Integrate"). After the specified number of samples, the sum is reset to zero ("dump") and the cumulative summation is started again, and then, for example, the information coded in the excitation can be recovered by means of a threshold detection.

In a last method step 108, a verification decision is derived from the demodulated output signal. Here, for example, a signal-to-noise ratio can be determined and evaluated, wherein the signal-to-noise ratio must exceed a certain threshold, so that the to be verified

Security feature is found to be genuine.

Furthermore, the demodulated output signal can be compared with the input signal. In this case, correlations with the input signal or a part of the input signal can be performed, wherein the correlation result

(Correlation Factor) must exceed a certain threshold to make the security feature true.

The derived verification decision is subsequently output as an analog or digital signal, for example on an interface designed for this purpose or on a display device designed for this purpose. A signal generated on the basis of the derived verification decision can be used, for example, to control a further device, for example a sorting machine or

Access barriers, such as locks, barriers, security gates, etc.

Subsequently, the process is completed 109. In further developments of the method, moreover, it may be provided that the characteristic function to be used must be selected. The selection can be made both manually and automatically, for example, based on a type of security feature or the value or security document. Depending on the type of security feature, an associated characteristic function is then used. In this case, the various characteristic functions for different security features may for example be stored in a memory and, if necessary, retrieved therefrom and made available.

FIG. 4 shows a schematic overview diagram of a calibration measurement 40. In the calibration measurement 40, a reference security feature 42 is excited by means of a known input signal 41. The reference security feature 42 is known to be genuine. Its transfer function 43 is not known, however, it is believed that the electroluminescent pigment of the

Reference security feature 42 behaves as a linear time invariant (LTI) system. Thus, the transfer function 43 of the reference security feature 42 is also assumed to be linear.

The luminescence emitted by the reference security feature 42 is detected and converted into a digital reference output signal 44.

From the known input signal 41 of the excitation and the known (measured) reference output signal 44, the transfer function 43 can be calculated numerically. The inverse 45 of the transfer function 43, which is subsequently used in the method for verification as a characteristic function 12 during the transformation, can then be calculated from the calculated transfer function 43. The numerical calculation can be carried out, for example, by means of the Matlab function "fmincon ()" (eg in Matlab® Version 2016a, a software of The MathWorks, Inc. in Natick, Massachusetts, USA) The calculation of the characteristic function 12 for the reference security feature 42 may additionally under

Consideration of an adaptation function 21, which is estimated on the basis of measurable parameters of the device and / or the environment of the device. FIG. 5 shows a schematic overview diagram of an embodiment of the invention

A method of verifying 50 an electroluminescent security feature 2 in a value or security document. After being excited with a known input signal 51, the luminescence emitted by the electroluminescent security feature 2 is detected and converted into an output signal 54. Further, an adaptation function 21 for the device is estimated based on measurable parameters.

The output signal 54 is then transformed with the characteristic function 12 determined in the calibration (see FIG. 4). The transformation may include, for example, a deployment 25, 26 of the output signal 54. In this case, the output signal 54, for example, with the transfer function 43 of

Reference security feature unfolded. In addition, the transformation may additionally comprise a deconvolution 26 of the output signal 54 with the estimated adaptation function 21.

The transformed output signal is subsequently evaluated. This can

In particular, a demodulation with conventional methods include, so that a demodulated signal 55 is available for further evaluation. In this case, particular consideration is also given to input signal information, for example a symbol form of the symbols used for coding.

From the demodulated signal 55, a verification decision 18 is derived, for example by evaluating a signal-to-noise ratio, a

Correlation factor or a value of the demodulated signal at a given time. If these exceed a predetermined threshold, that is

electroluminescent security feature 2 genuinely, the threshold is not exceeded, the electroluminescent security feature 2 is not found to be true. LIST OF REFERENCE NUMBERS

contraption

electroluminescent security feature

Value or security document

exciter

detector

evaluation

electrode

input

Luminescence

modulation means

output

characteristic function

transformation module

transformed output signal

demodulator module

Input information

verification module

verification decision

deployment module

Customizer

measurable parameters

estimator

unfolded transformed output signal

development

calibration measurement

known input signal

Reference safety feature

transfer function

Reference output

Inverse of the transfer function

To verify

known input signal known output signal demodulated signal method steps

Claims

claims

1 . Method for verifying an electroluminescent security feature (2) in a value or security document (3), comprising the following steps: excitation of the electroluminescent security feature (2) by a predetermined input signal (8) by means of an electric field by an excitation device (4),

Detecting a luminescence (9) emitted by the electroluminescent security feature (2) and

Converting the detected luminescence (9) into an output signal (1 1) by a detection device (5),

Transform the output signal (1 1) by means of a provided

characteristic function (12) by an evaluation device (6),

Evaluating the transformed output signal (14) taking into account at least one input signal information (16) of the input signal (8) for deriving a verification decision (18) by the evaluation device (6), outputting the verification decision (18) by the evaluation device (6).

2. The method according to claim 1, characterized in that during evaluation for deriving the verification decision (18) in the evaluation device (6), a correlation of the transformed output signal (14) with at least a part of the input signal (8) is performed, wherein the electroluminescent

Security feature (2) is found to be true when a correlation function at a predetermined time or in a predetermined time range reaches or exceeds a predetermined threshold.

3. The method according to any one of the preceding claims, characterized in that the characteristic function (12) by means of a calibration measurement (40) is determined, wherein an electroluminescent reference security feature (42) is excited and its luminescence is detected and evaluated as a reference output signal (44).

4. The method according to claim 3, characterized in that the characteristic function (12) the inverse (45) of a transfer function (43) of the

electroluminescent reference security feature (42), wherein the electroluminescent effect of the security feature and the reference security feature (42) is considered as a linear time-invariant system.

5. The method according to claim 4, characterized in that the inverse (45) of the transfer function (43) is calculated by means of numerical methods.

6. The method according to any one of the preceding claims, characterized in that the transformation of the output signal (1 1) comprises a deployment with an adjustment function (21).

7. The method according to claim 6, characterized in that the deployment is carried out by means of a Kalman filter.

8. The method according to claim 6 or 7, characterized in that the

Adjustment function (21) on the basis of measurable parameters (22) is estimated by an estimator (23).

9. The method according to any one of the preceding claims, characterized in that the input signal (8) is composed of a sequence of symbols.

10. The method according to claim 9, characterized in that the sequence itself

at least partially from at least one sequence of identical symbols

composed.

1 1. A method according to claim 9 or 10, characterized in that the sequence is composed at least partially of different symbols.

12. The method according to any one of the preceding claims, characterized in that the output signal (1 1) is filtered before and / or after the transformation.

13. The method according to any one of the preceding claims, characterized in that when evaluating in the evaluation device (6) a synchronous demodulation for recovering the phase of the input signal (8) is performed.

14. Method according to one of the preceding claims, characterized in that at least one characteristic function (12) is provided, wherein the characteristic function (12) used for the transformation is automatically preceded by a user or on the basis of predetermined criteria

Verify is selected.

15. The method according to any one of the preceding claims, characterized in that the transforming comprises an unfolding of the output signal (1 1) with the provided characteristic function (12).

16. Apparatus for verifying an electroluminescent

Security feature (2) in a value or security document (3), comprising: an excitation device (4) for exciting the electroluminescent

Security feature (2) by means of an electric field by a predetermined input signal (8),

a detection device (5) which is designed to detect a luminescence (9) emitted by the electroluminescent security feature (2) and to form an output signal (1 1) therefrom,

an evaluation device (6), which is designed such that

To transform the output signal (1 1) by means of a provided characteristic function (12), to evaluate the transformed output signal (14) taking into account at least one input signal information (16) of the input signal (8), to derive therefrom a verification decision (18) and to derive the derived verification decision (18 ).