EP2278556A2 - Apparatus and method for examining value documents - Google Patents

Abstract

A document/bank note (BN) to be verified is irradiated to excite luminescent radiation that is detected through resolution in a spectrum. To measure such documents effectively that emit very little luminescent radiation, the BN to be verified passes a luminescence sensor (12) to be illuminated with an illumination area (35) extending in a direction (T) for conveying the BN. An independent claim is also included for a method for checking luminescent documents of value, such as bank notes, with a luminescence sensor.

Description

The invention relates to a device and a method for testing, in particular, luminescent value documents, wherein the value document is irradiated with light and the luminescence radiation emanating from the value document is detected spectrally resolved.

Such luminescent value documents may e.g. Banknotes, checks, coupons or chip cards. Although not limited thereto, the present invention is primarily concerned with the validation of banknotes. These typically contain in the paper or in the ink a feature substance or a mixture of several feature substances which exhibit a luminescent behavior, such as e.g. fluoresce or phosphoresce.

There are a number of known systems for checking the authenticity of such value documents. A system is for example from the DE 23 66 274 C2 known. In this system, to check the authenticity of a banknote, ie in particular the test, whether a fluorescent feature substance is actually present in a banknote to be tested, obliquely irradiated and detected the vertically remitted fluorescence spectrally resolved by means of an interference filter. The evaluation is carried out by comparing the signals from different photocells of the spectrometer.

This system works very reliably in most cases. However, there is a need for a luminescence sensor which is even more compact in design and can still test sufficiently reliably even at very low intensities of the luminescence radiation to be detected.

On this basis, an object of the present invention, an apparatus and a method for testing luminescent value documents to provide a safe test with a compact luminescence sensor.

This object is solved by the independent claims. The dependent claims and the following description illustrate preferred embodiments.

By illuminating the document of value to be checked, which is transported past in a transport direction on the luminescence sensor, with an illumination surface which extends in the transport direction, an effective measurement of documents of value which emit only very little luminescence radiation is possible. As a result, in particular the measurement of phosphorescence radiation is substantially improved.

It should be particularly emphasized that the features of the dependent claims and the embodiments mentioned in the following description, taken in combination or independently of one another and the subject of the main claims, i. e.g. Even with devices that produce no in the transport direction extending illumination surface or perform a measurement of radiation other than luminescence, can be used advantageously.

Fig.

1 eine schematische Ansicht einer Banknotensortiervorrichtung;

Fig. 2

eine schematische Ansicht von der Seite auf das Innere eines erfin- dungsgemäßen Lumineszenzsensors, der in der Banknotensortiervor- richtung nach Fig.1 eingesetzt werden kann;

Fig. 3

Bauteile des Lumineszenzsensors der Fig. 2 in Aufsicht;

Fig. 4

eine schematische Ansicht von der Seite auf das Innere eines alterna- tiven erfindungsgemäßen Lumineszenzsensors, der in der Banknoten- sortiervorrichtung nach Fig. 1 eingesetzt werden kann;

Fig. 5

eine schematische Ansicht einer Banknote zur Erläuterung der Ver- wendung des Lumineszenzsensors der Fig. 2 und 3;

Fig. 6

eine Ansicht von oben auf ein Beispiel einer Detektorzeile zur Ver- wendung im Lumineszenzsensor der Fig. 2;

Fig. 7

eine Ansicht von oben auf ein weiteres Beispiel einer Detektorzeile zur Verwendung im Lumineszenzsensor der Fig. 2;

Fig. 8

eine Querschnittsansicht entlang der Linie I-I in Fig. 7;

Fig. 9

eine schematische Darstellung zur Auslesung der Daten aus einer De- tektorzeile des Lumineszenzsensors der Fig. 20 der Fig. 4;

Fig. 10

eine schematische Ansicht von der Seite auf das Innere eines alterna- tiven erfindungsgemäßen Lumineszenzsensors;

Fig. 11

eine schematische Ansicht auf einen erfindungsgemäßen Lumines- zenzsensor mit externer Lichtquelle;

Fig. 12

eine schematische Ansicht auf einen Teil eines weiteren erfindungs- gemäßen Lumineszenzsensors und

Fig. 13

eine schematische Ansicht auf einen Detektorteil noch eines weiteren erfindungsgemäßen Lumineszenzsensors.

Further advantages of the present invention will be explained in more detail by way of example with reference to the accompanying drawings. It shows

FIG.

1 is a schematic view of a banknote sorting apparatus;

Fig. 2

a schematic view from the side of the interior of a luminescence according to the invention, in the Banknotensortiervor- direction according to Fig.1 can be used;

Fig. 3

Components of the luminescence sensor of Fig. 2 in supervision;

Fig. 4

a schematic view from the side of the interior of an alternative luminescence according to the invention, in the banknote sorting apparatus according to Fig. 1 can be used;

Fig. 5

a schematic view of a banknote for explaining the use of the luminescence of the Fig. 2 and 3 ;

Fig. 6

a top view of an example of a detector array for use in the luminescence of the Fig. 2 ;

Fig. 7

a top view of another example of a detector line for use in the luminescence of the Fig. 2 ;

Fig. 8

a cross-sectional view taken along the line II in FIG Fig. 7 ;

Fig. 9

a schematic representation for reading the data from a detector tektorzeile the luminescence sensor of Fig. 20 of Fig. 4 ;

Fig. 10

a schematic view from the side of the interior of an alternative inventive luminescence sensor;

Fig. 11

a schematic view of a luminescence sensor according to the invention with external light source;

Fig. 12

a schematic view of a part of another inventive luminescence and

Fig. 13

a schematic view of a detector part of yet another inventive luminescence sensor.

The devices according to the invention can be used in all types of devices in which optical radiation, in particular luminescence radiation, is tested. Although not limited thereto, the following describes as a preferred variant the checking of banknotes in banknote processing devices, which can serve, for example, for counting and / or sorting and / or depositing and / or paying out banknotes.

In the Fig.1 For example, such a banknote sorting apparatus 1 is shown. The banknote sorting device 1 in this case has an input compartment 3 for banknotes BN in a housing 2, into which banknotes to be processed BN can either be input manually from the outside or banknotes bundles can be fed automatically, if necessary after a preceding debrapping. The banknotes BN entered into the input compartment 3 are separated from the stack by a singler 4 and transported through a sensor device 6 by means of a transport device 5. The sensor device 6 can have one or more sensor modules integrated in a common housing or mounted in separate housings. The sensor modules can serve, for example, to check the authenticity and / or the state and / or the nominal value of the banknotes BN being tested. After passing through the sensor device 6, the checked banknotes BN are then output sorted into output pockets 9 as a function of the test results of the sensor device 6 and of predetermined sorting criteria via switches 7 and associated spiral stackers 8, from which they are optionally manually removed after previous banding or packaging or can be removed automatically. It can also be a shredder 10 may be provided in order to destroy bills classified as genuine and no longer fit for circulation BN. The control of the banknote sorting device 1 takes place by means of a computer-assisted control unit 11.

As already mentioned, the sensor device 6 can have different sensor modules. The sensor device 6 is distinguished in particular by a sensor module 12 for testing luminescence radiation, which is referred to below as the luminescence sensor 12 for short. Fig. 2 FIG. 4 illustrates, in a schematic cross-sectional view, the internal structure and arrangement of the optical components of a particularly compact luminescence sensor 12 according to an embodiment of the present invention. Fig. 3 also shows a top view of a part of these located inside the luminescence sensor 12 components. This luminescence sensor 12 is designed to be particularly compact and optimized with regard to high signal-to-noise ratios.

The luminescence sensor 12 has in particular in a common housing 13 both one or more light sources 14 for exciting luminescence radiation, as well as a detector 30, preferably a spectrometer 30 for the spectrally dispersed detection of the luminescent light. The housing 13 is closed so that unauthorized access to the components contained therein is not possible without damaging the housing 13.

The light source 14 may, for. B. an LED, but preferably be a laser light source such as a laser diode 14. The laser diode 14 may emit one or more different wavelengths or wavelength ranges. If you work with several different wavelengths or wavelength ranges, can also be provided that in the same light source housing or in separate light source housings, ie separate light source modules, multiple light sources 14 for different wavelengths or wavelength ranges, for example, are arranged side by side and preferably emit parallel light that can be projected onto the same location or adjacent locations of the banknote BN.

If the light sources 14 can emit light of a plurality of different wavelengths or wavelength ranges, it can be provided that the individual wavelengths or wavelength ranges can be selectively activated.

Another variant is described below with reference to Fig. 4 to be discribed.

The light emanating from the laser diode 14 is irradiated by means of an imaging optical system 15, 16, 17 onto a banknote to be tested. The imaging optics include a collimator lens 15, a deflection mirror as a beam splitter 16, in particular a dichroic beam splitter 16, which deflects the emanating from the laser diode 14 and formed by the collimator lens 15 laser beam by 90 °, and a condenser lens 17 with a large opening angle, which the deflected laser beam through a front glass 18 preferably perpendicular to the transported by means of the transport system 5 in the direction T transports to be examined banknote BN and thus the banknote BN to emit emission of luminescent radiation.

With the aid of the spectrometer 30, the luminescence radiation emanating from the illuminated banknote BN is then preferably likewise detected in the vertical direction, ie coaxially with the excitation light. This leads to a lower susceptibility due to positional tolerances of the transported banknotes BN on the measurements as in the oblique illumination, for example DE 23 66 274 C2 ,

The optics for imaging the luminescence radiation onto a photosensitive detector unit 21 likewise comprises the front glass 18, the condenser lens 17 and the mirror 16 at least partially transparent to the luminescence radiation to be measured. In addition, the optic subsequently has another condenser lens 19 with a large opening, followed by a filter 20, which is designed to block the illumination wavelength of the light source 14 and other wavelengths not to be measured, and a deflection mirror 23. The deflecting mirror 23 serves to fold the beam path and to redirect the luminescence radiation to be measured to an imaging grating 24 or another device for spectral decomposition 24. The deflection mirror is advantageously mounted parallel or nearly parallel to the image plane of the spectrometer for an extremely compact design (angle < 15 degrees). The imaging grating 24 in this case has a wavelength-dispersing element with a concave mirror 26 which preferably images the luminescence radiation of the first order or minus the first order onto the detector unit 21. However, higher orders can also be mapped. The detector unit 21 preferably has a detector row 22 of a plurality of photosensitive pixels arranged in series, ie pixels, as they are z. B. in relation to the FIGS. 6 or 7 will be described below by way of example.

The entrance slit of the spectrometer 30 is in the Fig. 2 denoted by the reference symbol AS. The entrance slit AS can be present in the housing 13 in the form of a diaphragm AS in the beam path. However, it is also possible that at this point no aperture is present, but only a "virtual" entrance gap AS is present, which is given by the illumination track of the light source 14 on the banknote BN. The latter variant leads to higher light intensities, but can also lead to an undesirable greater sensitivity to ambient light or stray light.

In a further embodiment, the deflecting mirror 23 is positioned with respect to the imaging grating 24 so that the entrance slit AS falls onto the region of the deflecting mirror 23. Since in this way the beam cross section of the radiation to be deflected on the deflection mirror 23 is particularly small, the deflection mirror 23 itself can also have particularly small dimensions. If the deflecting mirror 23 is a component of the detector unit 21, the deflecting mirror 23 can thereby not only according to FIG FIG. 2 above, but also adjacent to the photosensitive areas of the detector unit 21 are attached.

A particular idea of the present invention is that the light source 14 for the excitation of luminescence radiation generates an elongated illumination surface 35 extending in the transport direction T on the banknote BN to be tested.

This variant has the advantage that the luminescent, in particular phosphorescent feature substances present in the banknotes BN are usually pumped up longer by the illumination surface extending in the transport direction during the onward transport at the luminescence sensor 12 and, in particular, the radiation intensity of the luminescent phosphorescent feature substances is thereby increased ,

Fig. 5 illustrates a related snapshot. An elongated illumination surface 35 extending in the transport direction T can be understood to mean that the illumination radiation at any given time irradiates an arbitrarily shaped surface, in particular a rectangular track on the banknote, which is significantly larger in the transport direction T than perpendicular to the transport direction T. the extent of the illumination surface 35 in the transport direction T at least twice, especially preferably be at least three times, four times or five times as long as the extension perpendicular to the transport direction T.

In Fig. 5 With another hatching also the image surface 36, ie the entrance hatch 36 of the spectrometer 30 is illustrated, ie that region of the banknote BN which is imaged on the spectrometer 30 at the given time in accordance with the dimensions of the entry slit AS. It can be seen that the length and width of the entrance hatch 36 of the spectrometer 30 are preferably smaller than the corresponding dimensions of the illumination surface 35 of the laser diode 14. This allows greater adjustment tolerances for the individual sensor components.

Furthermore, in the snapshot of the Fig. 5 illustrated the case that the illumination surface 35 extends substantially further in the transport direction T as compared to the transport direction T compared to the image surface 36. This is particularly advantageous for exploiting the increased inflation effect. Alternatively, however, it may also be provided that the illumination surface 35 and the image surface 36 overlap only partially in the transport direction T. However, if the image surface 36 is arranged symmetrically, ie centrally in the illumination surface 35, the luminescence sensor 6 can be used both in devices 1 in which the banknotes BN are transported in the illustrated transport direction T and in devices 1 in which the banknotes BN be transported in opposite direction -T.

According to a further particular idea of the present invention, different detector units 21, 27 are used for detecting the luminescence radiation, in particular the luminescence radiation emanating from the device for spectral decomposition 24, ie, for example, the imaging grating 24. Thus, on or before the further detector unit 27 z. B. a filter may be provided to only one or more given wavelengths or regions to be measured, wherein the measurable spectral regions of the different detector units 21, 27 are preferably different and, for example, only partially or not overlap. It should be emphasized that a plurality of further detector units 27 may be present, which measure in different wavelengths or ranges. The plurality of further detector units 27 may be spaced apart from each other or may be in a sandwich structure, as shown in FIG DE 1 0127 837 A1 is described by way of example.

While one detector unit 21, i. H. In particular, the detector line 22 is designed for spectrally resolved measurement of the luminescence of the banknote BN, by means of the at least one further detector unit 27 thus at least one other measurement of the luminescence, such as additionally or alternatively also a measurement of the broadband non-spectrally resolved zeroth order of the spectrometer 30 and / or the decay behavior of the luminescence radiation are performed.

Furthermore, the further detector unit 27 can also be designed to check another optical property of the at least one feature substance of the banknote BN. This can be done, for example, by the measurements mentioned at other wavelengths or wavelength ranges. Preferably, the further detector unit 27 can also be designed to check another feature substance of the banknote BN. So z. B. the detector line 22 for measuring the optical properties of a first feature substance of the banknote BN and the further detector unit 27 for measuring another feature substance of the banknote BN, in particular in a different spectral range than the detector line 22, be designed. The detectors 22, 27 will preferably have filters to suppress unwanted scattered light or higher order light in the measurement.

As in the supervision of Fig. 3 can be seen, this further detector unit 27, in particular when it is designed for measuring zeroth order of the spectrometer 30, tilted with respect to the imaging grating 24 and the detector line 22 may be arranged to avoid a disturbing back reflection on the concave mirror 26 , In this case, in addition, a radiation-absorbing light trap, such as a black-colored surface at the end of the beam path of the outgoing radiation from the further detector unit 27 may be present.

For calibration and functional testing of the luminescence sensor 12, it is further possible to provide a reference sample 32 with one or more luminescent feature substances which may have an identical or different chemical composition to the luminescent feature substances to be tested in the banknotes BN. Like in the Fig. 2 is shown, this reference sample 32 may be integrated in the housing 13 itself and be applied, for example, as a film 32 on a further light source (LED 31), which is arranged opposite to the laser diode 14 with respect to the beam splitter 16. The reference sample 32 may instead be, for example, a separate component between the LED 31 and the angle mirror 16. For calibration, for example in the intervals between two banknote measuring cycles of the luminescence sensor 12, the reference sample 32 can then be excited by irradiation by means of the LED 31 to a defined luminescence, which is mapped by parasitic reflection on the dichroic beam splitter 16 on the detector line 22 and evaluated.

For intensity calibration of the spectrometer 30, the luminescent feature substances of the reference sample 32 can preferably emit broadband, for example over the entire spectral range detectable by the spectrometer 30. However, the luminescent feature substances of the reference sample 32 may alternatively or additionally also have a specific characteristic emit spectral signature with narrowband peaks to perform wavelength calibration. However, it is also possible that only the further light source 31 without reference sample 32 is used to adjust the spectrometer 30.

Alternatively or additionally, the reference sample 32 can therefore also be mounted outside of the housing 13, in particular on the side opposite to the banknote BN to be measured, and e.g. be integrated in a counter element, such as a plate 28.

Outside the housing 13, an additional detector unit 33 may be present as a separate component or integrated in the plate 28. The additional detector unit 33 may be e.g. one or more photocells for measuring the radiation of the laser diode 14 and / or the luminescence radiation of the banknote BN which has passed through the front glass 18 and possibly through the banknote BN. In this case, the plate 28 may be slidably mounted in a guide in the direction P, so that either either the reference sample 32 or the photocell 33 can be brought into alignment with the illumination radiation of the laser diode 14.

The plate 28 is preferably connected to the housing 13 via a dotted connection element 55, which lies outside the transport plane of the banknotes BN. In an in Fig.2 horizontally extending cross-sectional plane is then in an approximately U-shaped form of housing 13, connecting surface 55 and plate 28 before. This attachment of the plate 28, also in an alternative variant without reference sample 32 and photocell 33, has the advantage that a light protection against unwanted leakage of the laser radiation of the laser diode 14 is given. If the plate 28 for maintenance purposes or for removing jams releasably on the housing 13th is fixed, it can be provided that when dissolved or removed plate 28, the laser diode 14 is deactivated.

FIG. 4 shows a schematic cross-sectional view of an alternative and very compact luminescence sensor 6, which in the banknote sorting device according to Fig.1 can be used. Same components are given the same reference numerals as in Fig. 2 characterized.

The arrangement of the optical components in the luminescence sensor 6 according to Fig. 4 differs from the luminescence sensor 6 after Fig. 2 in particular the fact that it is possible to dispense with the deflecting mirror 23. It should be noted that the luminescence sensor 6 after Fig. 4 also has no further detector units 31, 33, although this would also be possible. The dichroic beam splitter 16 does not deflect the illumination radiation but the luminescence radiation in a mirrored manner.

Furthermore, the light source 14 has two laser diodes 51, 52 arranged perpendicular to one another which emit at different wavelengths, the radiation of the individual laser diodes 51, 52 being e.g. can be coupled by a further dichroic beam splitter 53, so that the same illumination surface 35 or overlapping or spaced illumination surfaces 35 can be irradiated on the banknote BN. Depending on the bill to be checked, it is preferably possible to activate either one or the other laser diode 51, 52 or both laser diodes 51, 52 at the same time or alternately to emit radiation.

The elevationally visible photosensitive detector elements, ie, the detector row 22, are asymmetrically mounted on the carrier as described with respect to FIG FIG. 7 will be explained in more detail.

Moreover, the luminescence sensor 6 preferably has in the housing 13 itself a control unit 50 which serves for signal processing of the measured values of the spectrometer 30 and / or for power control of the individual components of the luminescence sensor 6.

Based on 6 and 7 Two different variants of the detector lines 22 that can be used in the luminescence sensor 12 will now be described. Fig. 6 In this case, a conventional detector line 22 is shown in sections, which usually has more than 100 juxtaposed photosensitive picture elements (referred to as pixels 40 for short) (of which FIG Fig. 6 only the first seven left pixels 40 are shown) which are of equal size and spaced apart on or in a substrate 41 which is approximately equal to the width of the pixels 40.

In contrast, however, preferably a modified detector line 22 is used with a significantly smaller number of pixels 40, with a larger pixel area and a reduced proportion of non-photosensitive areas, as shown by way of example in US Pat Fig. 7 is illustrated. Such a modified detector row 22 has the advantage of a significantly greater signal-to-noise ratio than the conventional detector row 22 of FIG Fig. 6 exhibit. Preferably, the modified detector rows 22 are constructed to have only between 10 and 32, more preferably between 10 and 20, individual pixels 40 in or on a substrate 41. The individual pixels 40 may have dimensions of at least 0.5 mm × 0.5 mm, preferably 0.5 mm × 1 mm, particularly preferably 1 mm × 1 mm. After the design of the Fig. 7 For example, the detector array 22 has twelve pixels 40 of 2 mm height and 1 mm width, the non-photosensitive area 41 between adjacent pixels 40 having an extension of about 50 μm.

Furthermore, it can also be provided that individual pixels 40 have different dimensions, in particular in the direction of dispersion of the luminescence radiation to be measured, as described in US Pat Fig. 7 is shown. Since usually not all wavelengths of the spectrum, but specifically only individual wavelengths or wavelength ranges are evaluated, the pixels 40 can be constructed adapted to the respective wavelengths (ranges) to be evaluated.

Depending on the wavelength range to be detected spectrally, the detector line 22 may consist of a different material in the cases mentioned. For luminescence measurements in the ultraviolet or visible spectral range, detectors made of silicon, which are sensitive below about 1100 nm, and particularly suitable for measurement in the infrared spectral range detector array 22 of InGaAs, which are sensitive above 900 nm. Preferably, such an InGaAs detector array 22 will be deposited directly on a silicon substrate 42, most preferably comprising an amplifier stage made in silicon technology for amplifying the analog signals of the pixels 40 of the InGaAs detector array 22. This also provides a particularly compact design with short signal paths and increased signal / noise ratio.

By the detector line 22 with a few pixels 40 (eg after Fig. 7 ), preferably only a relatively small spectral range of less than 500 nm, more preferably less than or of about 300 nm is detected. It can also be provided that the detector line 22 has at least one pixel 40 which is photosensitive outside the luminescence spectrum of the banknotes BN to be measured in order to carry out normalizations such as baseline determination in the evaluation of the measured luminescence spectrum.

The imaging grating 24 is preferably more than about 300, more preferably more than about 500 lines / mm, i. Have diffraction elements in order to still allow a sufficient dispersion of the luminescence radiation on the detector element 21 despite the compact construction of the luminescence sensors 6 according to the invention. In this case, the distance between the imaging grating 24 and the detector element 21 may preferably be less than approximately 70 mm, particularly preferably less than approximately 50 mm.

A readout of the individual pixels 40 of the detector line 22 may be z. B. using a shift register serial. Preferably, however, a parallel readout of individual pixels 40 and / or pixel groups of the detector row 22 will take place. After the example of Fig. 9 For example, the three left-hand pixels 40 are read out one at a time by the measuring signals of these pixels 40 by means of an amplifier stage 45 which, for example, is part of the silicon substrate 42 Fig. 7 can be amplified and each supplied to an analog / digital converter 46. The two right-hand pixels in the schematic representation of Fig. 9 in turn, first amplified by separate amplifier stages 45, then a common multiplexing unit 47, which may optionally include a sample & hold circuit, and then a common analog / digital converter 46 is supplied, which is connected to the multiplexing unit 47.

The parallel readout of a plurality of pixels 40 or pixel groups thereby made possible short integration times and a synchronized measurement of the banknote BN. This measure also contributes to an increase in the signal-to-noise ratio.

According to a further independent idea of the present invention, integration of components of the imaging optics for the luminescence radiation with components of the detector 30 takes place Deflection mirror 23 for deflecting the luminescence radiation to be detected on the spectrometer 30 may be connected directly to the detector unit 21, as for example in Fig. 2 is shown.

Fig. 7 shows a modified variant in which the deflection mirror 23 is applied directly on a common carrier with the detector line 22, that is, in particular on the silicon substrate 42. Alternatively, the deflection mirror 23 may be applied, for example, on a cover glass of the detector unit 21.

Furthermore, below the deflecting mirror 23, a photodetector, such as a photocell 56, may be present. This preferred variant is exemplary in the FIG. 8 pictured, which is a cross section along the line II of FIG. 7 shows. In this case, the deflecting mirror 23 applied to the photocell 56 is at least partially transparent to the wavelengths to be measured by the photocell 56. The photocell 56 can in turn be used for calibration purposes and / or for evaluating other properties of the luminescence radiation.

As in FIG. 4 Not only for the sake of compact sensor design, as illustrated in FIG FIG. 4 is illustrated, but also for attaching further optical components 23, 56, the detector array 22 preferably asymmetrically on the support, that is applied to the silicon substrate 42.

As has been mentioned, calibration of the luminescence sensor 12 during operation, ie, in particular during breaks between two banknote measuring cycles of the luminescence sensor 12, will be necessary due to the only very low signal intensities of the luminescence radiation to be expected when checking banknotes BN. A already described possible measure is the use of the reference samples 32.

According to a further idea, this can also be done by an active mechanical adjustment of the optical components of the luminescence sensor 12, the adjustment depending on measured values of the luminescence sensor 12 e.g. by an external control unit 11 or preferably by an internal control unit 50 can be controlled.

For example, by an adjusting element 25, the component of the imaging grating 24 can be displaceably mounted in the direction S. Likewise, by other components, not shown, a mechanical adjustment of other optical components, such. B. the detector 21 can be achieved, the z. B. in the direction of arrow D in Fig. 2 actively controlled can be displaced. It is also possible to perform an adjustment of the optical components in more than one direction.

Thus, for example, during the ongoing operation of the luminescence sensor 12, an evaluation of the measured values of the luminescence sensor 12 is carried out and in the presence of deviations of the measured values (eg the detector row 22, the further detector unit 27 or the photocell 33) or of quantities derived therefrom Reference values or areas an active mechanical adjustment of one or more of the optical components of the luminescence sensor 12 are performed to achieve increased signal efficiency and compensation of undesirable changes, for example due to caused by the lighting or electronics temperature fluctuations or aging phenomena of optical components. This is particularly important for a detector unit 21 with few pixels 40.

To increase the life of the light sources of the luminescence sensor 12 may also be provided that, for example, the laser diode 14 is driven only with high power when a bill BN just in the field of the measuring window, d. H. of the front glass 18 is located.

Of course, other alternatives or additions are conceivable for the variants already described above.

While in terms of the Figures 2 and 4 Examples have been described in which the imaging grating 24 has a concavely curved surface, alternatively, a Plangitter can be used. The structure of such a luminescence sensor 12 is exemplary in the FIG. 10 illustrated. The radiation emitted by the banknote BN to be tested and detected by an entrance window 18 also falls in this case through a collimating lens 17 onto a beam splitter 16, from which the light is deflected by 90 °, via a lens 19 and a filter 20 for illumination suppression on a first spherical collimator mirror 70 falls. From this mirror 70, the radiation is deflected onto a screen grid 71. The spectrally dispersed light is then directed to a detector array 21 via a second spherical collimator mirror 72 and a cylindrical lens 73.

The luminescence sensor 12 of FIG. 10 is further characterized in that the illumination light is coupled by means of a fiber optic coupling. In particular, the light generated by a laser light source 68 is irradiated via a light guide 69, a beam shaping optics 66, the beam splitter 16, the collimating lens 17 and the entrance window 18 on the bill to be tested. Since light guides 69 are flexible and deformable and thus the illumination beam path can (largely) run as desired, it is only possible, for example, to fasten the light source in a particularly space-saving location in the housing 13.

In particular, when using such optical fiber, the light source may even be mounted outside of the housing 13 of the luminescence sensor 12. This spatial separation has the advantage that the heat generated by the light source 68 disturbs significantly less the operation and adjustment of the other in the housing 13 optical components and in particular the highly sensitive detectors 21. FIG. 11 shows an associated schematic example in which a light source 68 radiates into a light guide 69, which leads into the housing 13 of a luminescence sensor 12. The housing 13 may be constructed as an example of how the FIG. 10 with the only difference that the light source 68 is thus outside of the housing 13 and the light guide 69 thus also extends outside of the housing 13.

Another special feature of the light coupling, for example FIG. 11 it is that the light source 69 and the housing 13 connecting optical fiber 69 in a in the FIG. 11 schematically shown in a cross-sectional view middle portion 70 is spirally wound. When the light source 68 radiates into the light guide 69, a series of total reflections occurs in the light guide 69. In this way, the beam cross section of the coupled-in laser radiation of the light source 68 is spatially homogenized. This has the advantage that the illumination during the test fluctuates less and thus more reproducible test results can be achieved. However, the optical fiber does not necessarily have to be spirally wound in a plane for this purpose. Rather, it is only important that the light guide has a certain length. Thus, with a fiber cross-section of 50 μm to 200 μm, the light conductor 69 will preferably have a length of 1 m to 20 m.

Also, alternatively, it is conceivable that the irradiation of the banknote to be tested exclusively via outside of the housing 13 existing optical Components takes place and the luminescence sensor 12 inside the housing 13 includes only the optical components, which are used for the measurement of emanating from the illuminated banknote radiation.

To stabilize the illumination beam, e.g. also a so-called DFB laser, in which an additional grid is built into the resonator of the laser, or a so-called DFR laser can be used, in which an additional grid is installed outside the resonator of the laser.

For example, while preferred variants of the test are described above using a grating spectrometer, i. a spectrometer 30 with imaging grating 24, it is possible to work without a grating spectrometer per se, e.g. a spectrometer 30 with prism for spectral dispersion can be used or a measurement with the aid of different filters for filtering out different wavelengths to be detected or wavelength ranges of the luminescence radiation can be carried out. This can be used in particular for a multi-track or a high-sensitivity measurement.

An example of a luminescence sensor 1 without a grating spectrometer is shown in FIG FIG. 12 illustrated. FIG. 12 shows in a schematic way only the detection part of a luminescence sensor. All other components such as the housing, the lighting and the imaging optics are omitted for the sake of clarity. After this example the FIG. 12 the outgoing from the banknote to be tested BN beam is deflected via a pivotable about a rotation axis 58 deflecting mirror 57 selectively to individual detectors 59, which are sensitive to different wavelengths or wavelength ranges. This can be done by the choice of photosensitive in different wavelength ranges Detector surfaces of the detectors 59 take place. However, as well as in FIG. 12 is indicated by way of example, filters 60 for different wavelength ranges upstream of the detectors 59 and preferably also be attached to these themselves.

It is also possible to use a so-called filter wheel with different filters. By turning the filter wheel, the individual different filters then successively intersect the light beam of the banknote BN to be tested which subsequently impinges on the detector.

In the FIG. 13 For example, a detector 61 is depicted in a very schematic manner according to yet another example. The detector has a row or an array of similar photosensitive pixels 63 on a substrate 62. On the detector 61, a filter 64 is mounted above the pixels 63, which has a direction indicated by the arrow gradient of the filter wavelength. This means that as seen in the direction of the arrow at different points of the filter 64 different wavelengths are filtered out. The use of such a filter with wavelength gradients filter 64 has the advantage that the light to be tested are irradiated directly to the detector 61 and on wavelength dispersing elements such as the grating 24 or the deflecting mirrors 23, 57 can be omitted. The structure of the luminescence sensor 1 can thereby be designed particularly simple and with fewer components.

In addition, for example, the active optical adjustment of individual components can be used not only in the particularly preferred example of a luminescence sensor, but also in other, in particular other optical sensors with advantage. In addition, for example, the special design of the spectrometer is also advantageous if the luminescence sensor itself has no light source for exciting luminescent radiation.

Furthermore, the system according to the invention can also be designed so that the measured values of the luminescence sensor 12 of a banknote BN are still evaluated, while at the same time measured values of a subsequent banknote BN are already recorded. However, the evaluation of the measured values of the preceding banknote BN must be carried out so quickly that the individual points 7 of the transport path 5 can still be switched sufficiently fast in order to divert the preceding banknote BN into the respectively assigned storage compartment 9.

Consequently, the devices and methods according to the invention enable a simple and reliable testing and differentiation of luminescent value documents. In this case, the test can be carried out, for example, by generating a light having a first wavelength with a predetermined intensity by means of the light source 14 for a specific time period 0-tp for the excitation of the feature substance. By the light of the light source 14, the feature substance of the banknote BN to be checked and which has been transported past the front glass 18 in the direction T is excited, whereupon the feature substance emits luminescent light of a second wavelength. The intensity of the emitted luminescent light increases during the time period 0-tp of the excitation according to a certain law. The manner of increase and decrease in the intensity of the emitted luminescent light depends on the feature substance used and on the exciting light source 14, ie its intensity and wavelength or wavelength distribution. After completion of the excitation at time tp, the intensity of the emitted luminescence light decreases according to a certain law.

With the aid of the spectrometer 30, the luminescent light emanating from the bank notes BN, ie, parallel to the excitation light, is detected and evaluated. By evaluating the signal of the detector unit 21 at one or more specific times t ₂ , t _{3, it} can be checked particularly reliably whether a genuine banknote BN is present, since only the feature substance used for the banknote BN or the combination of feature substances used has such a decay behavior , The verification of the decay behavior can take place by means of the above-described comparison of the intensity of the luminescence light at one or more specific times with given intensities for genuine banknotes BN. It can also be provided that the course of the intensity of the luminescence light is compared with predetermined progressions for known banknotes BN.

Claims (24)

Device (1) for testing luminescent value documents (BN), comprising a light source (14, 51, 52, 68) for exciting luminescence radiation and a luminescence sensor (12) to detect the luminescence radiation emitted by the value document (BN) in a spectrally resolved manner,
characterized in that
the luminescence sensor (12) has one or more light sources (14, 51, 52, 68) which emit at different wavelengths, wherein preferably individual wavelengths are selectively activatable. Device (1) according to Claim 1, characterized in that the light source (14, 51, 52, 68) generates an illumination surface (35) on the value document (BN) transported past the luminescence sensor (12) in a transport direction (T) extends in the transport direction (T) and preferably the extent of the illumination surface (35) in the transport direction (T) at least twice, preferably at least three times, four times or more preferably at least five times as long as the extension perpendicular to the transport direction (T). Device (1) according to at least one of the preceding claims, characterized in that an image surface (36) of the luminescence sensor (12) extends in the transport direction (T) of the value document (BN) transported past the luminescence sensor (12). Device (1) according to at least one of the preceding claims, characterized in that the length and / or width of the image surface (36) are smaller than the corresponding dimensions of the illumination surface (35) of the light source (14, 51, 52, 68), and / or that at any given time the image surface (36) and the illumination surface (35) on the value document (BN ) are at least partially or completely overlapping. Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has at least one detector row (22) with a small number of pixels (40), preferably from 10 to 32 pixels (40), particularly preferably 10 to 20 pixels (40). Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has at least one detector element (40) in order to measure radiation outside the luminescence spectrum of the value documents (BN). Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has at least one detector row (22) with pixels (40) of different dimensions, in particular in the dispersion direction of the luminescence radiation of different dimensions to be measured. Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has an InGaAs detector line (22) on a silicon substrate (42), wherein the silicon substrate (42) preferably comprises one or more amplifier stages (45) for Amplification of the analog measurement signals from pixels (40) of the InGaAs detector line (22). Device (1) according to at least one of the preceding claims, characterized in that the detector unit (21) of the luminescence sensor (6) detects a spectral range of less than 500 nm, preferably less than or around 300 nm, and / or the imaging grating ( 24) of the luminescence sensor (6) has more than about 300, preferably more than about 500 lines / mm and / or the distance between the imaging grating (24) and detector unit (21) is less than about 70 mm, preferably less than about 50 mm , Device (1) according to at least one of the preceding claims, characterized in that the light source (14) and / or the luminescence sensor (12) and / or a control unit (50) for signal processing of the measured values of the luminescence sensor (6) and / or for power control of components of the luminescence sensor (6) in a common housing (13) and or in separate housings (13, 68) are integrated. Device (1) according to at least one of the preceding claims, characterized in that the light source (14) perpendicularly irradiates the value document (BN) to be tested and the luminescence sensor (12) detects luminescence radiation emanating vertically from the irradiated document of value (BN) and / or the radiation generated by the light source (68) is irradiated via a light guide (69) to the value document to be tested, and / or that the luminescence sensor (12) comprises a deflection mirror (23) for folding the beam path of the luminescence radiation to be measured and / or to a Deflection of the measured luminescence to another optical unit, such as on a device for Spektralzerlegung (24) down out. Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has a photodetector (56) with a deflection mirror (23) located on or above its surface, which is to be measured by the photodetector (56) Wavelengths is at least partially transparent, and that the luminescence sensor (12) preferably has a the photodetector (56, 59, 63) in the beam path of the radiation to be measured upstream filter (60, 64), in particular a filter (64) with filter wavelength gradients. Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has a component (21) which has both a photosensitive detector unit (22) for luminescence radiation and components (23) for imaging the luminescence radiation on the Photosensitive detector unit (22). Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has a detector line (22) which is asymmetrically applied to a substrate (42). Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has a plurality of detector units (21, 27) for detecting different properties of the luminescence radiation, which preferably measure in different spectral ranges and / or with different spectral resolutions. Device (1) according to at least one of the preceding claims, characterized in that different detector units (21, 27) are designed to test different feature substances of the value document (BN). Device (1) according to at least one of the preceding claims, characterized in that a detector unit (21) is designed for the spectrally resolved measurement of the luminescence radiation and another detector unit (27) for non-spectrally resolved measurement of the luminescence radiation Device (1) according to at least one of the preceding claims, characterized in that a detector unit (21) is designed for the time-integrated measurement of the luminescence radiation and another detector unit (27) for the time-resolved measurement of the luminescence radiation. Device (1) according to at least one of the preceding claims, characterized in that a detector unit (27) is designed for measuring the zeroth order of the spectrally dispersed luminescence radiation and another detector unit (21) for measuring a different order of the spectrally dispersed luminescence radiation. Device (1) according to at least one of the preceding claims, characterized in that a detector unit (27) is tilted with respect to a device (24) for spectral separation, in order to avoid a back reflection on the device (24). Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has a reference sample (32) with a luminescent feature substance and preferably a further light source (31) for irradiating the reference sample (32). Device (1) according to at least one of the preceding claims, characterized in that the luminescence sensor (12) has means (25) for the active mechanical adjustment of optical components (21, 24) of the luminescence sensor (12), and preferably an active mechanical adjustment of optical components (21, 24) of the luminescence sensor (12) in dependence on measured values of the luminescence sensor (12) by a control unit (11, 50) is controllable. Device (1) according to at least one of the preceding claims, characterized in that the measured values of the luminescence sensor (12) to a value document (BN) are still evaluated, while at the same time measured values of a subsequent value document (BN) are recorded. Device (1) according to at least one of the preceding claims, characterized in that individual pixels (40) and / or pixel groups of the detector row (22) are readable in parallel and / or individual pixels (40) and / or pixel groups of the detector row (22) respectively with its own amplifier stage (45) and a subsequent analog / digital converter (46) are connected.

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