EP3400583A1

EP3400583A1 - Checking the authenticity of value documents

Info

Publication number: EP3400583A1
Application number: EP16819439.7A
Authority: EP
Inventors: Erich KERST; Thomas Happ
Original assignee: Giesecke and Devrient Currency Technology GmbH
Current assignee: Giesecke and Devrient Currency Technology GmbH
Priority date: 2016-01-05
Filing date: 2016-12-21
Publication date: 2018-11-14
Anticipated expiration: 2036-12-21
Also published as: WO2017118466A1; EP3400583B1; RU2710766C1; US11830329B2; DE102016000012A1; US20210019976A1

Abstract

The aim of the invention is to test a value document (1) which is guided past a test sensor (10) in a transport direction T and in which a luminescent feature (3) is provided in a substantially homogeneously distributed manner in a security region (2) extending over the value document (1) in the transport direction (T). This is achieved in that a sampling sequence (A) is repeated multiple times (S1-S4), and a subsequent authenticity test (S5) is carried out. The sampling sequence A has the following steps: (1.) irradiating (S1) a test region (4) of a test sensor (10) which at least partly overlaps the security region (2) with an excitation radiation beam (L) and a test radiation beam (P) in a first irradiation phase (A1), wherein the test radiation beam (P) is designed to be at least partly remitted by the value document (1) in a detection spectral range of the test sensor (10), and the excitation radiation beam (L) is designed to cause radiation to be emitted by the luminescent feature (3) in the detection spectral range; (2.) sampling (S2) at least one location-dependent remission spectral value (R) in the test region (P) in the first irradiation phase (A1); (3.) irradiating (S3) the test region (4) solely with the excitation radiation beam (L) in a second irradiation phase (A2); and (4.) sampling (S4) at least one location-dependent emission spectral value (E) in the test region (4) after the first irradiation phase (A1). In the authenticity test (S5), the value document (1) is finally classified as authentic or inauthentic on the basis of the at least one location-dependent remission spectral value (R) which is sampled multiple times in a spatially resolved manner and on the basis of the at least one location-dependent emission spectral value (E) which is sampled multiple times in a spatially resolved manner.

Description

Authenticity check of value documents

The present invention relates to a method and a test sensor and a test device for checking a value document for authenticity.

In the authentication of value documents, such as banknotes, identity documents, securities or the like, it is particularly important to also check their integrity or completeness in order to exclude so-called "snippet forgeries" or composed counterfeits. Such counterfeit checks, which are often based on the evaluation of emission radiation of a luminescence feature present in or on the document of value, are realized by combined test methods or probing sensors, which are used in addition to counterfeit parts the actual luminescence also make a remission or reflection measurement.

Such a test sensor, in which a spectrally resolving luminescence sensor comprises a spectral detector with diffraction grating, for example, describes the DE 10 2004035 494 AI. For remission measurement, a separate detector is used there, whereby the test sensor has a high space requirement and its production requires a high design effort.

In addition, DE 10 2008 028 689 A1 and DE 10 2008 028 690 A1 disclose a spectrally resolving luminescence sensor which can be used for calibration In addition, a reference radiation source and a light scanner used to determine the position of a value document to be tested. The reference radiation is designed so that it lies within the spectral range of the luminescence sensor, so that no separate detector is needed as a light scanner. In order to determine the spectral properties of a value document to be checked without interference, the reference radiation is switched off as soon as an edge of the value document is detected. However, this has the disadvantage that either no remission measurement can take place within the value document or only a small spatial resolution of the luminescence measurement is achieved at the usual transport speeds of the value documents to be tested.

In this respect, it is the object of the present invention to propose a method for testing documents of value, on the one hand allows the use of a test sensor with a small footprint and design effort and on the other hand, a sufficiently high spatial resolution offers.

This object is achieved by a method and a test sensor and a test device having the features of the independent claims. In the dependent claims advantageous refinements and developments of the invention are given.

For checking a value document, in particular for its integrity or completeness, the value document is guided past the inventive inspection sensor in a transport direction. The value document to be checked here has a security area which extends over the entire extent of the value document to be checked in the transport direction and in which or on which a substantially homogeneous shared luminescence feature is present. The luminescent feature here is introduced into the volume of the value document as homogeneously as possible or evenly distributed in the security area, or it is applied in the security area as a coating or coating of the value document, for example in the form of a luminescent color or lacquer. Preferably, the security area extends over the entire value document, so that the luminescence feature is substantially uniformly distributed in or on the entire value document. The luminescence feature present in or on the security area can here be excited by means of an excitation radiation for luminescence, ie for phosphorescence and / or fluorescence.

According to the invention, the value document is checked by a scanning sequence which repeatedly repeats itself on the test sensor during the transport of the value document, in the context of which the value document is irradiated and scanned. The repeatability scan sequence is then preferably followed by the actual check for integrity and / or authenticity, in which the previously scanned spectral values are suitably evaluated.

The repetitive sampling sequence here comprises a first irradiation phase and an adjoining second irradiation phase. In the first irradiation phase, the security area of the value document is irradiated with a test radiation and an excitation radiation in a detection or test area of the test sensor. In this case, the test radiation is designed in such a way that the proportion of the test radiation remitted by the safety area lies at least partially in a detection spectral range of the test sensor. Accordingly, the excitation radiation is designed, an emission radiation of the luminescence feature which also at least partially emits in the detection spectral range of the test sensor.

During the first irradiation phase in which the security area is irradiated simultaneously with the test radiation and the excitation radiation, preferably towards the end of the first irradiation phase, a spatially resolved reflectance spectral value is sampled, which on the one hand shares the remitted test radiation and on the other hand shares the emission radiation of the emission radiation emitted by the excitation radiation Luminescence feature comprises. After the first irradiation phase, the security area in a second irradiation phase in the test area of the test sensor is only irradiated with the excitation radiation and, preferably at the end of the second irradiation phase, at least one spatially dependent emission spectral value is scanned spectrally resolved.

The examination of the value document preferably takes place on its authenticity. In this case, a classification takes place as genuine or spurious on the basis of the spatially resolved multiple sampled, in particular at different locations, at least one location-dependent reflectance spectral value and the spatially resolved multiple scanned, in particular at different locations, at least one location-dependent emission spectral values.

It should be noted here that an intensity of the reflectance spectral value comprises, on the one hand, intensity components of the reflected test radiation and, on the other hand, also intensity components of an emission radiation of the luminescence feature excited by the excitation radiation, since the safety region during the first irradiation phase coincides both with the

Test radiation is irradiated as well as with the excitation radiation. In one embodiment, a spatially resolved remission curve is formed for checking, in particular, the authenticity of the value document from the location-dependent reflectance spectral values acquired in the course of the plurality of scanning sequences, which reproduces the remission spectral values sampled along the safety area in the transport direction. Accordingly, a spatially resolved emission curve is formed from the spatially dependent emission spectral values acquired in the course of the plurality of scanning sequences, which reflects the emission spectral values sampled along the safety zone in the transport direction. Each remission / emission spectral value of the remission / emission curve thus reflects the remitted / emitted radiation intensity at a dedicated position of the security area of the value document caused by the first or second irradiation phase. The remission curve represents the extent of the value document in the transport direction, while the emission curve represents that area of the value document in the transport direction in which the luminescence feature could be detected. In one embodiment, the value document, after it has passed completely past the test sensor, is finally classified as complete and / or genuine if the remission curve and the emission curve have a qualitatively comparable curve, since this means that the luminescence feature is along the entire extension the value document is present in the transport direction. If the two curves have gradients that are qualitatively not comparable, a forgery can be assumed, since the luminescence feature is not present in a forgery area of the value document which results from the emission curve. For carrying out the method according to the invention, a corresponding test sensor according to the invention is used. This comprises a test radiation source which generates a test radiation which is at least partially remitted from the value document in the detection spectral range of the test sensor, and an excitation radiation source which generates an excitation radiation which excites the luminescence feature to emission radiation which also at least partially in the detection spectral range of the test sensor emitted. Furthermore, the test sensor comprises a scanning unit which scans test radiation remitted from the value document and emission radiation emitted by the luminescence feature as location-dependent reflectance spectral values and location-dependent emission spectral values in the detection spectral range. The detection of the emission spectral values and the reflectance spectral values takes place spectrally resolved with preferably more than two spectral channels, in particular more than eight spectral channels and particularly preferably with more than sixteen spectral channels. A control unit of the inspection sensor coordinates the radiation sources and the scanning unit such that the scanning sequence is continuously repeated as the value document passes the inspection sensor. An evaluation unit of

Finally, the test sensor forms the remission curve and the emission curve in the manner described above and qualitatively compares their curves. On the one hand, the invention offers the advantage that no additional scanning or detection channel is required for the acquisition of the reflectance spectral values, since both the emission spectral values and the reflectance spectral values are at least partially in the same detection spectral range of the test sensor lie. This allows a comparatively compact test sensor with reduced constructive Her position effort.

Furthermore, the invention enables a maximum spatial resolution and intensity of the emission curve, since the luminescence feature is already excited to emit during the irradiation of the value document with the test radiation in the first irradiation phase, and not only after switching off the test radiation with the onset of the second irradiation phase. The spatial / temporal spacing of successive emission spectral values is thereby reduced by the length of the first irradiation phase compared to conventional solutions. Since, according to the invention, the first irradiation phase is also used for excitation of the luminescence feature, the intensities or amplitudes of the emission spectral values also fall more clearly since the luminescence feature can be optically pumped over the maximum time available.

In the evaluation, the emission and remission curves are checked for qualitative comparability. This means in particular that no quantitative comparison or a signal-theoretical correlation of the curves is made, but that the two curves are compared only in terms of their local / temporal widths, which in a genuine value document in each case substantially its extension along the transport direction or the duration of Pre-transport on the test sensor correspond. For example, the two curves can be subjected to edge detection, for example by edge or high-pass filtering, if appropriate after suitable noise correction or local / temporal low-pass filtering. Before that, the two curves can be processed by means of suitable intensity threshold values in order to obtain significant or suprathreshold remission / emission spectral values of noise-abatement. separate spectral values which are not due to a remission of the test radiation or an emission of the luminescence feature.

The evaluation unit preferably determines the number of significant or suprathreshold remission / emission spectral values or the corresponding pixels under the preferably smoothed remission / emission curve. The emission curve and the remission curve are considered qualitatively comparable if the emission curve has significant intensities essentially at those position / time positions or pixels at which the remission curve also forms significant intensities.

In this case, the quotient of the pixels with significant intensities can be formed in the remission curve and in the emission curve, so that a qualitative comparability of the two curves can be assumed if this quotient is approximately one. In order to compensate for measurement errors caused by noise or detection, a suitable interval can be selected for the quotient, depending on the spatial resolution of the two curves, for example an interval between 0.9 and 1.1 or, preferably, an interval between 0.95 and 1.05 ,

Alternatively, the evaluation unit determines the number of pixels in which, although the reflectance curve has significant intensities, the emission curve has subliminal values. Here then the value document is classified as spurious if this number of fake suspect pixels exceeds a certain threshold value of eg 0, 1, 2, etc. Preferably, the time period of the first irradiation phase is set between 0.5 and 500 μβ, more preferably between Ιμβ and 50 μβ. The ratio between the duration of the first irradiation phase and the duration of the entire scanning sequence is preferably between 1: 1000 and 1: 4, more preferably between 1: 100 and 1: 5. This means that the proportion of the first irradiation phase, in which the value document is irradiated both with the test radiation and with the excitation radiation, in the entire duration of the scanning sequence, ie the total duration of the irradiation with the excitation radiation, between about 0.1% and 25 % is and is preferably between about 1% and 20%. The transport speed with which a value document to be tested is guided past the test sensor is between 1 m / s and 13 m / s, preferably in the range of 4-12 m / s. Preferably, the scanning sequence is configured in such a way that the excitation irradiation can take place interruption-free by the first irradiation phase of a scanning sequence directly following the second irradiation phase of the preceding scanning sequence. The irradiation with the test radiation then takes place in pulses during the first irradiation phase, in each case interrupted by the second irradiation phase.

The at least one remission spectral value is scanned towards the end of the first irradiation phase, preferably at the end of the first irradiation phase, during which the at least one emission spectral value is scanned toward the end of the second irradiation phase, preferably at the end of the second irradiation phase. On the one hand, this embodiment of the sampling sequence ensures maximum spatial resolution of the emission curve and, on the other hand, achieves maximum intensity of the emission spectral values. In a preferred embodiment of the scanning sequence, a rest phase immediately follows the second irradiation phase, in which neither irradiation by the test radiation nor by excitation radiation takes place. In this embodiment, therefore, the irradiation by the excitation radiation pulsed, in each case during the first and second irradiation phase and interrupted by the resting phase. The first irradiation phase of a scanning sequence then immediately follows the quiescent phase of the preceding scanning sequence. In this case, emission spectral values can also be detected during the idle phase, preferably towards the end of the idle phase, so that a maximum intensity of the emission spectral values can be ensured if the luminescent marker still emits after the excitation radiation has been switched off.

The pulsed irradiation with the excitation radiation allows the multiple sampling of emission spectral values within a scanning sequence during and / or after the excitation radiation pulse so that the temporal decay / decay behavior of the luminescence feature can also be determined as a function of location by comparing the emission spectra scanned within a scanning sequence. This location-dependent attack / decay behavior can then be taken into account in the authenticity check, since the time profile of the emission spectral values within a scanning sequence provides information about the emission properties and the exact nature of the tested luminescence feature. For example, the multi-sampled emission spectral values may be compared to corresponding location-dependent reference spectral values previously determined for the particular value document. Preferably, the value document is irradiated with a spectrally narrow-band test radiation, so that it is detected only in one or a few spectral channels of the detector. The test radiation is preferably not suitable to stimulate appreciable Lur incarnation in the document of value.

Furthermore, the value document is irradiated with preferably narrow-band excitation radiation, wherein the excitation radiation takes place in the ultraviolet (UV), in the visible (VIS) and / or in the infrared spectral range (IR). This can also include several different wavelength ranges. This ensures that the test radiation causes no or only a small emission radiation of the luminescence feature in the detection spectral range, so that the sampled emission spectral values are exclusively due to the excitation radiation and as little as possible to the test irradiation.

Preferably, the test radiation source comprises an LED or semiconductor laser radiation source, e.g. an edge emitter laser diode. Particularly preferably, the test radiation source comprises a narrow-band VCSEL or surface emitter radiation source. Accordingly, the excitation radiation source preferably comprises an LED or semiconductor laser radiation source, more preferably a narrowband VCSEL or surface emitter radiation source.

In order to allow the best possible evaluation of the reflectance and emission values, the reflectance spectral values and / or emission spectral values are preferably corrected with regard to noise and interference influences. Thus, scattered radiation components or electronic or electromagnetic interference radiation components can be eliminated by offset correction from the reflectance spectral values and / or emission spectral values The corresponding correction parameters are determined either beforehand by scanning a reference substrate with the test sensor or, preferably, by sampling during the authenticity check at times when no value document is passed past the test sensor (dark measurement), for example before the beginning of the test

Authenticity check or between two successive value documents to be checked.

The remission spectral values are preferably further corrected in such a way that they only include those sampled spectral components which are actually due to the test irradiation and their remission by the value document. Accordingly, those sampled spectral components and / or intensity components or intensities are filtered out or eliminated from the scanned remission spectral values, which are due to emission radiation of the luminescence feature as a consequence of the excitation radiation. For efficient differentiation between the respective spectral components of the remitted remission radiation and the emission radiation emitted by the luminescence feature, a narrow-band test radiation is particularly suitable, so that the spectrally resolved scanned remission / emission spectral values can be effectively filtered.

Instead of spectral components, it is also possible to determine intensity components or intensities for the remitted radiation. Alternatively, each of the emission spectral values measured at a later point in time and its time course can be interpolated for the contribution expected at the earlier time of the scanning of the remission spectral value and thus be subtracted to a good approximation. A non-negligible local or temporal offset can form between the reflectance curve and the emission curve at higher transport speeds, since the value document to be tested is moved between the scanning of the reflectance spectral values and the scanning of the emission spectral values. This offset can be compensated as part of the authenticity check by shifting the emission curve by exactly that time interval relative to the remission curve, which lies between the scanning of the reflectance spectral values and the scanning of the emission spectral values.

The test sensor according to the invention, together with the transport device, which guides the value document past the test sensor during the authenticity check in such a way that the test area of the test sensor continuously travels over the security area of the value document, forms a test device according to the invention. In this case, the transport speed of the document of value and the duration of a scanning sequence are preferably matched to one another in such a way that the resulting spatial resolution of the remission curve and / or emission curve is sufficiently high in order to enable a reliable authenticity check. A sufficient spatial resolution exists, for example, if the boundaries of the value document or the security area can be detected accurately or if the spatial resolution is sufficient to map important details of the appearance or an imprint of the value document.

Further features and advantages of the invention will become apparent from the present description of embodiments according to the invention and further alternative embodiments in conjunction with the following drawings, which show: FIG. 1 shows the steps of the method sequence of the test method according to the invention;

FIG. 2 shows an illustration of a true value document (FIG. 2 a) and of a forged value document (FIG. 2 b);

3 shows two embodiments of a sampling sequence with continuous

Excitation radiation (Figure 3a) and pulsed excitation radiation (Figure 3b);

4 shows quantitative representations of the emission and remission curves for the real value document according to FIG. 2a (FIG. 4a) and the forged value document according to FIG. 2b (FIG. 4b); and FIG. 5 shows two preferred embodiments of the invention

Prüfsehsors with separate irradiation paths (Fig. 5a) and a common irradiation path (Fig. 5b).

FIG. 1 shows the steps of a method for checking the authenticity of a value document 1 with one of the test sensors 10 shown in FIG. 5, comprising a sampling sequence A repeating steps S1 to S4 and a concluding evaluation step S5. The sampling sequence A is illustrated in FIG. 3, while FIG. 4 illustrates the evaluation. A document of value 1 which can be checked by this method is shown in FIG. 2.

FIG. 2 a illustrates a genuine value document 1 with a security area 2, in which or on which one or more luminescent features 3 are present, which are illuminated by a suitable excitation radiation L for fluorescence or fluorescence be excited to phosphorescence. In particular, the luminescent feature 3 with longer wavelengths (Stokes luminescence) or shorter wavelengths (anti-Stokes luminescence or upconverter) can be excited to emit in a certain emission spectral range. The luminescence feature 3 is in this case as homogeneously or evenly distributed over preferably as wide as possible areas of the volume of the document of value 1 introduced, which may consist of paper or plastic (polymer), or, alternatively, printed over the entire area on the security area 2 or painted.

In this case, the security area 2 is preferably equipped along the complete extent of the value document 1 in a transport direction T with the luminescence feature 3. Notwithstanding Figure 2a, the security area 2 may extend over the entire surface of the value document 1 or assume almost any contiguous geometric shapes. These preferably extend over the entire extent of the value document 1 in the transport direction.

In contrast, FIG. 2b illustrates a forged value document 1 in which there is a so-called "snapping forgery" in a counterfeit area F, which affects the security area 2 in relation to that of FIG. 2a such that the luminescence feature 3 no longer extends over the entire extent of the value document 1 in the transport direction T is detectable.

The inventive method according to FIG. 1 is based, on the one hand, on the consideration that a remission caused by a test radiation P on the value document 1 is significantly faster for detection or scanning and can be evaluated than a On the other hand, the method according to the invention is based on the knowledge that irradiation of the value document 1 by the test radiation P can also be realized in parallel with the irradiation of the value document 1 by the excitation radiation L in a time-parallel manner. to optically inflate the luminescence feature 3 significantly more effective and to stimulate luminescence emission, as in a sequential irradiation with the test radiation P and the excitation radiation L. The optical inflation of the luminescence feature 3 already during the irradiation of the value document 1 with the test radiation P is useful in particular with phosphorescence features since their excitation or decay times can range from a few microseconds to a few milliseconds. While the value document 1 is guided past the inspection sensor 10 along the transport direction T and over a time axis t, the steps S1 to S4 of the scanning sequence A are repeated several times. In a first step S1, the value document 1 is first irradiated in the course of a first irradiation phase AI with both the test radiation P and the excitation radiation L. A correspondingly arranged scanning unit 14 of the test sensor 10 then scans spectral components of both the remitted test radiation P and the emission radiation emitted by the luminescence feature 3, which result from the first irradiation phase AI in step S2. Instead of spectral components, spectrally superimposed intensity components can be scanned by the scanning unit 14.

This situation is also illustrated in FIG. 3, which illustrates two different variants of a scanning sequence A according to the invention in the respective dashed area. There it is shown that the value document 1 is irradiated with both the test radiation P and with the excitation radiation L during the first irradiation phase AI, while at the end of the first irradiation phase AI the reflection of reflectance spectral values R according to step S2 takes place, which both remitted intensity components of the test radiation P and emitted intensity components of the emission radiation of the Luminescence feature 3 include. The test radiation P is remitted directly from the value document 1, so that in addition to the pure time of light no waiting or integration times are needed, but the sampling of the remission spectral R in step S2 can take place directly against or at the end of the first irradiation phase AI.

Preferably, the reflectance spectral values R are sampled synchronously and very rapidly, so that the intensities attributable to the individual spectral channels of the scanning unit 14 can be evaluated in parallel. The fast scan prevents a restriction of the relevant spectral channels while the value document 1 moves in the transport direction T. The sampling step S2 can be carried out here by means of photodiodes and suitable sample-and-hold circuits or by CCD or CMOS detectors with charge accumulation and a suitable array architecture with synchronous displacement of the charges of a whole spectral line in a darkened memory area of the test sensor 10.

At the transition between the first irradiation phase AI and the second irradiation phase A2, ie immediately after the scanning step S2, the test radiation P is switched off while the irradiation with the excitation radiation L is continued and continues throughout the second irradiation phase A2 (step S3). Finally, in step S4, the sampling unit 14 is read again to acquire emission spectral values E. determine that due to the optical pumping of the luminescence feature 3 already during the first irradiation phase AI sufficiently strong emission intensities. The separate sampling of the emission spectral values E without superimposed spectral components of the remitted test radiation P in step S4 allows a particularly accurate and reliable testing of the luminescence feature 3, since otherwise erroneous or deviating emission radiations, which are caused for example by fake luminescence features, may not be reliably detected, when the emission spectral values E are not sampled with sufficient intensity or by the

Test radiation P are covered.

As shown in FIG. 3 a, the scanning sequence A is continuously and continuously repeated at least until the document of value 1 has been completely guided past the test sensor 10, so that for the

Authenticity check in step S5 reflectance spectral values R and emission spectral values E along the entire extent of the document of value 1 in the transport direction T in a spatial resolution, which depends on the one hand on the total duration of the sampling sequence A and on the other hand on the transport speed of the value document 1.

FIG. 3 a further illustrates that the first irradiation phase AI is of considerably shorter duration than the second irradiation phase A 2. The test radiation P is directed to the value document 1 with very short pulse lengths so that the emission spectral values E decisive for the authenticity check are disturbed as little as possible by remitted test radiation P and also the highest possible spatial resolution is achieved. The temporal portion of the first illumination phase AI on the entire scanning sequence A is therefore between 0.1% and 25%, and preferably between 1% and 20%. Preferably, the duration of the entire sampling sequence A is formed here by the sum of the durations of the first illumination phase AI and the second illumination phase A2. The absolute time duration of the first irradiation phase AI, that is to say the pulse length of the test irradiation P, is in the range from 0.5 to 500 μβ, preferably in the range from 1 μβ to 50 μs.

With such short pulse lengths of the test radiation P, depending on the specific design of the scanning unit 14 and an evaluation unit 17 of the test sensor 10, it may be necessary to perform the sampling of the reflectance spectral values R (step S2) only after completion of the first irradiation phase AI, by the time constant an account either parasitically occurring or deliberately built low-pass filtering of the scanning unit 14, because then a certain time has to wait until the caused by the short pulse length of the test radiation P remission spectral R also have formed electronically and can be effectively scanned.

After the test radiation P has been switched off in the second irradiation phase A2 (step S3), the value document 1 is continuously irradiated further with the excitation radiation L in order to further optically pump up the luminescence feature 3. At or before the end of this phase of the optical pumping on, that is to say at the end of the second irradiation phase A2, emission spectral values E can then be sampled (step S4) which are essentially exclusively due to the emission radiation of the optically excited or maximally excited luminescence feature 3.

Immediately following the sampling of the emission spectral values E in step S4, the sampling sequence A then starts again with the first irradiation tion phase AI, by a further pulsed irradiation with the test radiation P takes place (step Sl), as shown in Figure 3a.

Although FIG. 3 a provides only one sampling of emission spectral values E per sampling sequence (step 4), a plurality of emission spectral values E can also be scanned offset in time (step S 4 ') in the course of the second irradiation phase A 2, in order thereby also to image the on / off behavior of the luminescence feature 3 and to be usable for a location-dependent authenticity check. This is shown, for example, by the alternative embodiment of the sampling sequence A according to FIG. 3b, in which a rest phase A3 follows the second irradiation phase A2 before another sampling sequence A begins again with the first irradiation phase AI.

In the sampling sequence A according to FIG. 3b, not only the test radiation P is pulsed, but also the excitation radiation L, albeit with a substantially longer pulse length. Irradiation with pulsed excitation radiation L allows a simple (step S4) or multiple (steps S4 ', S4) sampling of emission spectral values E during and / or after the pulsed irradiation with the excitation radiation L, ie within the second irradiation phase A2 and / or the rest phase A3 ,, so for example once within and once at the end of the second irradiation phase A2 (step S4 ') and finally towards or at the end of the rest phase (step S4), just before the first irradiation phase AI of the next sample sequence A begins. Here, too, a location-dependent evaluation of the arrival / decay behavior of the luminescence feature 3 can be carried out and thus lead to an improved authenticity check, which takes into account not only the mere presence of a luminescence feature 3 over the entire extent of the value document along the transport direction T, but also the time behavior depending on location the issue In a preferred embodiment, sampling of emission spectral values E occurs relatively shortly after the end of the first irradiation phase AI or the scanning of the reflectance spectral values R, so that the contribution to the reflectance spectral values R can be estimated more accurately.

The temporal portion of the first illumination phase AI on the entire scanning sequence A is therefore between 0.1% and 25%, and preferably between 1% and 20%. The absolute time duration of the first irradiation phase AI, that is to say the pulse length of the test irradiation P, is in the range from 0.5 μβ to 500 μβ, preferably in the range from 1 to 50 μβ. Preferably, the duration of the entire sampling sequence A is determined by the sum of the durations of the phases A1 + A2 + A3, thereby being dominated by the duration of the second illumination phase A2, i. also the duration of the resting phase A3 is relatively short. The absolute duration of the resting phase A3 is preferably in the range of 0.1 to 500 μβ, in particular in the range of ΙΟμβ to 100 μβ. This allows a particularly good inflation of relatively slow luminescence features 3 with good spatial resolution.

In contrast to FIG. 3 b, the scanning of the reflectance spectral values R, as already described in connection with FIG. 3 a, can also take place only after termination of the irradiation by the test radiation P, ie only within the irradiation phase A 2, in order to compensate for any electronics run times of the scanning unit 14. To evaluate the measured reflectance R and emission spectral values E in step S5, first correction and compensation methods are used. For this purpose, the two spectral values R, E are subjected to an offset or background correction, in the event of any effects caused by scattered radiation or by electronic / electromagnetic radiation Spectral components are eliminated. The correction parameters used in this case can either be permanently predefined in the evaluation unit 17, or can only be determined during the course of the test method according to the invention, for example by dark measurements without test irradiation P and excitation irradiation L at times at which no value document 1 is present. Alternatively or additionally, it is also possible to normalize the sampled reflectance / emission spectral values R, E to predetermined or currently detected intensities or to reference spectral values measured on the basis of a calibration substrate.

In the case of the remission spectral values R, only one spectral channel of the scanning unit 14 is read out in the case of narrow-band test irradiation P, and in the case of a broader spectrum of the remitted test irradiation P, several spectral channels are read out at the same time. In this case, only those spectral channels of the scanning unit 14 are evaluated which correspond to the spectrum of the remitted test irradiation P by eliminating spectral components from the reflectance spectral values R resulting from the emission radiation excited during the first irradiation phase AI. The respective parameters of this spectral filtering can in turn either be predefined in the evaluation unit 17 or determined in the course of the test procedure. Similarly, in the case of spectral overlap between the emission radiation and the

Test radiation of the intensity contribution of the emission radiation to the corresponding spectral channels of the reflectance R values are corrected. In this case, estimated values for the time profile of the intensity of the emission radiation are determined on the basis of a linear or exponential model, which model the temporal emission behavior of the luminescence feature 3. In this way, from the sampled reflectance spectral values R, noise components are eliminated which result from / Abklingeffekten the emission radiation during the first irradiation phase AI result.

If a luminescence feature 3 is tested with a short on / off time compared to the duration of the first irradiation time AI, those spectral components which are due to emission radiation of the luminescence feature 3 during the first irradiation phase AI can be at least approximately directly eliminated, ie without a temporal modeling of the arrival / decay behavior of the luminescence feature 3.

The remission spectral values R corrected in this way are then stored in a memory of the test sensor 10 for evaluation by the evaluation unit 17 together with the associated measurement positions in the value document 1. Likewise, the corrected emission spectral values E are stored together with the associated measurement positions. The location-dependent, optionally corrected reflectance spectral values R or emission spectral values E are then combined in each case to form a spatially resolved remission curve RC or emission curve EC over the time axis t.

Subsequently, one or both curves RC, EC are smoothed, for example by calculating a moving average, a moving median or a sliding percentile from a plurality of adjacent spectral values R, E of the respective curve RC, EC. Optionally, the curves RC, EC can be normalized in addition to a suitable intensity value, for example, to the respective intensity maximum or the respective intensity median, but in particular in the case of the emission curve EC an additional test for exceeding a absolute lower intensity threshold, in order to be able to reliably identify any counterfeits with too low feature intensity.

Depending on the spatial resolution of the scanning sensor 19 and the transport speed of the document of value 1 along the transport direction T, motion compensation can additionally be carried out. For this purpose, the two curves EC, RC are shifted from one another within the scope of the time interval between the scanning of the reflectance spectral values R (step S2) and the sampling of the emission spectral values E (step S4). In particular, in the case of a high spatial resolution, a local / temporal offset between the reflectance spectral values R recorded somewhat earlier in time and the emission spectral values E recorded somewhat later can be corrected with regard to the qualitative comparison of the curves RC, EC.

Subsequently, the actual local dimension of the value document 1 along the transport direction T is determined by an edge detection of the remission curve RC, for example by digital edge or high-pass filtering. In the simplest case, it is possible to determine those extreme positions of the remission curve RC at which the reflectance spectral values R rise above the intensity median or again fall below the intensity median. However, it is less susceptible to linear interpolation between a suitable intensity quantum (eg 75%, which is almost white) and a minimum of the remission curve RC or an intensity quantile of about 5%, and from that to determine those (two) positions of the remission curve RC at which the remission curve RC intersects the intensity quantiles of 50% (or alternatively the average of 5% and 75% quantiles). The difference between the two positions then results in the extension of the value document 1 along the trans- Portion direction T. The intensity quantiles are in this case determined as a function of the respective appearance or the expected, remitted intensity distribution of the value document 1 to be tested. The authenticity of the tested value document 1 or its integrity or completeness is finally determined to exclude snippet counterfeiting when the width of the corrected remission curve RC is qualitatively comparable to the width of the corrected emission curve EC. A measure of the completeness of the value document 1 is the quotient of the number of curve points (or pixels) with significant or suprathreshold emission spectral values E and the number of curve points (or pixels) with significant or suprathreshold reflectance spectral values R, which are essentially correspond to the extent of the value document 1 along the transport path T. The significant emission spectral values E are then those whose intensity lies between predefined or lower and upper threshold values determined during the test.

Based on the curves of Figure 4 results in this way a measure (quotient) of about 1 for the real banknote according to Figure 2a (see Fig. 4a) and a measure (quotient) of about 0.82 for the forged value document according to FIG 2b (see Fig. 4b).

The inventive method according to Figure 1 is realized by using a test sensor 10 according to the invention. Figures 5a and 5b show two preferred embodiments of such a test sensor 10, the scanning unit 14 is designed with the scanning sensor 19, the test area 4, under which the value document to be tested 1 in the transport direction T with a transport speed between 1 m / s and 13 m / s, before- is passed between 4m / s and 11 m / s, is passed, spectrally resolved scan.

The scanning unit 14 detects an emission radiation emitted by the luminescence feature 3 in a specific detection spectral range of the scanning sensor 19 and supplies emission spectral values E which reproduce spectral properties of the sampled emission radiation. To excite the luminescence feature 3, an excitation radiation source 13 irradiates the test area 4 with the excitation radiation L. The excitation radiation L is tuned to the luminescence feature 3 such that emission radiation is effected in the optical range, for example in the ultraviolet (UV), visible (VIS) or infrared Spectral range (IR). In this case, the excitation radiation L is preferably spectrally narrow band, but may also be broadband or comprise a superposition of different narrowband and / or broadband radiation components.

The test area 4 is also irradiated by an irradiation source 12 with the test radiation P in order to determine the presence of a value document 1 in the test area 4 at the time of scanning on the basis of the remitted remission spectral values R or to determine its extent in the transport direction T by evaluating the resulting remission curve RC ,

In this case, the test radiation source 12 generates a test radiation P with a spectral distribution which partially or completely overlaps the detection spectral range of the scanning unit 14 or of the scanning sensor 19. Particularly preferably, the test radiation P is spectrally narrow-band, and is detectable only in one or in a few spectral channels of the scanning sensor 19. The generated test radiation P is preferably spectrally designed so that it does not stimulate the luminescence feature 3 to a significant emission radiation. The proportion of emission radiation caused by the luminescence feature 3 is preferably less than 10% of the intensity of the scanned remission spectral values R.

The test radiation source 12 generates the test radiation P with a suitable light source, for example a light-emitting diode or laser diode, particularly preferably with an edge emitter or a VCSEL or a VCSEL array. If required, additional optical units, filters or phosphor converters are introduced into the beam path of the test sensor 10 in order to ensure a desired, optionally narrowband spectrum of the test radiation P with a corresponding spectral overlap with the spectrum of the emission radiation emanating from the luminescence feature 3 in the detection spectral range of the scanning sensor 19. Here, the optics of the test sensor 10 is designed so that the test radiation P is coupled by remission or scattering on the surface of a value document 1 in a beam path to the scanning unit 14 as soon as the document of value 1 moves into the test area 4. Furthermore, the test sensor 10 comprises a control / evaluation unit 17, which controls the test radiation source 12 and the excitation radiation source 13 in such a way that a scanning sequence A according to FIG. 3a or 3b is realized. The control / evaluation unit 17 also checks the value document 1 on the basis of the determined remission curve RC and emission curve EC for authenticity or completeness.

The test sensor 10 according to FIG. 5a directs the test radiation P directly onto the test area 4, and thus onto the document of value 1, wherein additionally diaphragms or illumination optics may also be used. By doing Test area 4 locally overlapping with the test radiation P, the excitation radiation L is coupled from the excitation radiation source 13 via a dichroic tables radiator divider 16 and directed with the optics 15 to the transported past value document 1. In this case, the excitation radiation source 13 comprises, for example, a light-emitting diode or a semiconductor laser, in particular a VCSEL or VCSEL array. Both the test radiation P remitted by the value document 1 and the emission radiation emitted by the luminescence feature 3 are coupled into the scanning unit 14 via the optics 15 and detected there by the scanning sensor 19 in a spectrally resolved manner. For this purpose, the scanning unit 14 comprises a spectrographic device 18 and the scanning sensor 19, which detects the spectral components and spectrally resolved spectral components which are generated by the spectrographic unit 18.

In the test sensor 10 according to FIG. 5b, the irradiation of the document of value 1 can alternatively take place by means of a combined irradiation unit 11 which comprises suitable irradiation sources 12, 13 for generating the test radiation P and the excitation radiation L. In this embodiment of the test sensor 10, both radiations are coupled together via the dichroic radiation splitter 16 into the beam path of the test sensor 10 in the direction of the test area 4.

The typical polarization dependence in the spectral edge region of dielectric interference filters on dichroic mirrors can be exploited, for example by deflecting a linearly polarized radiation (in particular test radiation) at a dichroic mirror with high reflectivity (preferably greater than 80%), while the diffuse from the value document 1 remitted radiation and spectral components of to vertical polarization component, which are thus sufficiently well transmitted, for example in a range of greater than 40%.

Claims

Patent claims

1. A method for checking a value document (1) which is guided past a test sensor (10) in a transport direction (T), in or on a security area (2) extending over the value document (1) in the transport direction (T) Luminescence feature (3) is present substantially homogeneously distributed, characterized by a while repeating the value document (1) on the test sensor (10) repeatedly repeating scanning sequence (A), comprising the steps:

Irradiating (Sl) a test area (4) of the test sensor (10) at least partially overlapping the safety area (2) with an excitation radiation (L) and a test radiation (P) in a first irradiation phase (AI), the test radiation (P) being designed is to be remitted from the value document (1) at least partially in a detection spectral range of the test sensor (10), and the excitation radiation (L) is adapted to cause emission radiation of the luminescence feature (3) in the detection spectral range;

Sampling (S2) at least one location-dependent reflectance spectral value (R) in the test area (4) in the first irradiation phase (AI); Irradiating (S3) the test area (4) only with the excitation radiation (L) in a second irradiation phase (A2); and

Sampling (S4) at least one location-dependent emission spectral value (E) in the test area (4) after the first irradiation phase (AI).

2. The method according to claim 1, characterized by a step for authentication (S5), after which the value document (1) on the basis of spatially resolved repeatedly scanned, at least one location-dependent remission spectral value (R) and the spatially resolved scanned multiple times, 2 at least one location-dependent emission spectral value (E) is classified as true or spurious.

3. The method according to claim 1 or 2, characterized in that the dimension of the value document (1) in the transport direction (T) on the basis of the number of significant remission spectral values (R) is determined, eih emission spectral value (E) and / or a remission spectral value ( R) is considered significant if it is above a lower threshold and optionally below an upper threshold.

4. The method according to any one of claims 2 or 3, characterized in that the number of significant reflectance spectral values (R) to the number of significant emission spectral values (E) is checked for authenticity testing (S5).

5. The method according to any one of claims 2 to 4, characterized in that the value document (1) is classified as genuine, if one of the repeatedly sampled, at least one location-dependent remission spectral value (R) formed, spatially resolved remission curve (RC) and one of the repeatedly sampled, at least one location-dependent emission spectral value (E) formed, spatially resolved emission curve (EC) have a qualitatively comparable curve.

6. The method according to claim 5, characterized in that the dimension of the value document (1) in the transport direction (T) is determined on the basis of the number of significant remission spectral values (R) under the, preferably smoothed, remission curve (RC), and the remission curve (RC) and the emission curve (EC) are considered to be qualitatively comparable (S5) if the emission curve (EC) is substantially similar to that 3

Have significant emission spectral values (E) at which the remission curve (RC) also has significant reflectance spectral values (R),

7. The method according to any one of claims 1 to 6, marked thereby, that the time duration of the first irradiation phase (AI) is between 0.5 μβ and 500, preferably between 1 and 50 μβ, and the ratio between the duration of the first irradiation phase (AI) and the duration of the scanning sequence (A) between 1: 1000 and V. 4, preferably between 1: 100 and 1: 5, wherein the transport speed at which the value document (1) is passed to the test sensor (10) between 1 m / s and 13 m / s, preferably between 4 and 11 m / s.

8. The method according to any one of claims 1 to 7, characterized in that the sampling (S2) of the at least one reflectance spectral value (R) towards the end of the first irradiation phase (AI), wherein the second irradiation phase (A2) directly to the first irradiation phase (AI) and that the sampling (S4) of the at least one emission spectral value (E) takes place towards the end of the second irradiation phase (A2), the sampling sequence (A) starting again after the end of the second irradiation phase (A2),

9. The method according to any one of claims 1 to 8, characterized in that the Abtastsequenz (A) comprises a subsequent to the second irradiation phase (A2) resting phase (A3), in which the value document (1) not by the test sensor (10) is irradiated, the sampling sequence (A) after the end of the rest phase (A3) starts again and the sampling (S4) of the at least one location-dependent emission spectral value (E) in the rest phase (A3), preferably towards the end of the rest phase (A3). 4

10. The method according to any one of claims 1 to 9, characterized by repeated sampling (S4 ', S4) at least one location-dependent emission spectral value (E) within the sampling sequence (A), wherein based on the plurality of sampled, at least one emission spectral values (E) an An - / Abklingverhalten the Luminszenzmerkmals (3) is determined, which is taken into account in the test (S5).

11. Method according to claim 1, characterized in that a location-dependent authenticity check is carried out on the basis of sampled (S4; S4 '), at least one emission spectral values (E) within a single sampling sequence (S). at least one emission spectral values (E) are compared with reference spectral values and / or an analysis / decay behavior of the luminescence feature (3) is determined based on a plurality of sampled (S4, S4 '), at least one emission spectral values (E) - / decay behavior is compared.

12. The method according to any one of claims 1 to 11, characterized in that the value document (1) is irradiated with a narrow-band test radiation (P), which is designed, no or only a small emission radiation of the luminescence feature (3) in cause the detection spectral range, and is irradiated with a, preferably narrow-band, excitation radiation (L) in the ultraviolet, visible and / or infrared spectral range (S3).

13. The method according to any one of claims 1 to 12, characterized in that the test radiation (P) is generated by a Prüfstrahlungsquelle (12) comprising an LED or semiconductor laser radiation source, preferably a narrow-band VCSEL radiation source, and that the An - exciting radiation source (L) is generated by an excitation radiation source (13) comprising an LED or semiconductor laser radiation source, preferably a narrow-band VCSEL radiation source.

14. The method according to any one of claims 1 to 13, characterized in that the scanned remission spectral values (R) and / or emission spectral values (E) are corrected, in particular before the remission curve (RC) and / or emission curve (EC) are formed as far as provided (S5) by substantially eliminating scattered radiation components or electronic noise components by an offset correction from the reflectance spectral values (R) and / or the emission spectral values (E), offset correction correction parameters being obtained by scanning a reference substrate by the test sensor (10 ) or by a scanning by the test sensor (10) before a first scanning sequence (A) or between two documents of value (1) guided past the test sensor (10).

15. Method according to claim 1, characterized in that the scanned remission spectral values (R) are corrected, in particular before the remission curve (RC) is formed (S5), by extracting those spectral components of the remission spectral values (R), which result from remitted radiation components of the test radiation (P) and / or those spectral components from the reflectance spectral values (R) which result from the emission radiation of the luminescence feature (3) are eliminated.

16. The method according to claim 5 or 6, characterized in that a from the passing of the value document (1) on the test sensor (10) resulting offset between the remission curve (RC) and the emission on the curve (EC) is offset by the emission curve (EC) by the time period between the sampling (S2) of the at least one reflectance spectral value (R) and the sampling (S4) of the at least one emission spectral value (E) against the remission curve (RC) ,

17. The method according to claim 5 or 6, characterized in that the transport speed with which the value document (1) is guided past the test sensor (10), and the duration of the sampling sequence (A) are coordinated such that the remission curve (RC ) and / or the emission curve (EC) has a sufficient for a reliable authenticity check (S5) spatial resolution.

18. Test sensor (10) for testing a value document (1) for authenticity, comprising

a test radiation source (12) which is set up to generate a test radiation (P) which is at least partially remitted from the value document (1) in a detection spectral range of the test sensor (10);

an excitation radiation source configured to generate an excitation radiation that causes a luminescence feature present in or on the value document to emit emission radiation in the detection spectral range;

a scanning unit (14) arranged to scan test radiation (P) remitted from the value document (1) and emitted emission radiation in the detection spectral range;

wherein the test sensor (10) is set up while the document of value (1) is passed past the test sensor (10) to repeat a scanning sequence (A) several times, during which the document of value (1) in a first irradiation phase (AI) through the Test radiation source (12) and the excitation radiation source (13) is irradiated and in a second Bestrah- 7 scanning phase (A2) is irradiated only by the excitation beam source (13), wherein the scanning unit (14) scans at least one location-dependent reflectance spectral value (R) in the first irradiation phase (AI) and at least one location-dependent emission spectral value (E) after the first irradiation phase (AI ).

19. A test sensor (10) according to claim 18, further comprising an evaluation unit (17) which is adapted to the value document (1) on the basis of spatially resolved repeatedly scanned, at least one location-dependent reflectance spectral values (R) and the spatially resolved multiple scanned, at least classify a location-dependent emission spectral value (E) as true or spurious.

20. test sensor (10) according to claim 19, characterized in that the evaluation unit (17) the value document (1) classified as genuine if one of the repeatedly sampled, at least one location-dependent remission spectral value (R) formed, spatially resolved remission curve (RC) and a from the repeatedly sampled, at least one spatially resolved emission spectral value (E) formed emission curve (EC) have a qualitatively comparable curve.

21. A test sensor (10) according to any one of claims 18 to 20, characterized in that the test sensor (10) is configured and set up, on the test sensor (10) passing value document (1) according to a method according to one of claims 1 to 17 for authenticity and / or completeness.

22. Test device, comprising a test sensor (10) according to any one of claims 18 to 21 and a transport device (20) which is established is to pass a value document (1) in the transport direction (T) on the test sensor (10) such that the value document (1) according to a method of one of claims 1 to 17 can be checked for authenticity and / or completeness.

23. Use of a test sensor (10) according to claim 18 to 21 for testing a value document (1) according to a method according to one of claims 1 to 17 for authenticity and / or completeness.