EP2278558B1 - Apparatus and method for examining value documents - Google Patents

Description

The invention relates to a device and a method for checking, in particular, luminescent documents of value, the document of value being irradiated with light and the luminescent radiation emanating from the document of value being detected in a spectrally resolved manner.

Such luminescent documents of value can be, for example, banknotes, cheques, coupons or chip cards. Although not limited thereto, the present invention is primarily concerned with the validation of banknotes. These typically contain a feature substance or a mixture of several feature substances in the paper or in the printing ink that exhibit luminescent behavior, such as fluorescence or phosphorescence.

There are a number of known systems for checking the authenticity of such documents of value. A system is, for example, from the DE 23 66 274 C2 known. In this system, to check the authenticity of a bank note, ie in particular to check whether a fluorescent feature substance is actually present in a bank note to be checked, the bank note is irradiated obliquely and the vertically reflected fluorescence radiation is detected spectrally resolved using 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 that has an even more compact design and can still test sufficiently reliably even at very low intensities of the luminescence radiation to be detected.

In EP 1158 459 A1 describes a method and a device for detecting the authenticity of a feature. In this case, a luminescence feature is excited with at least one excitation pulse of at least one excitation source, and emission intensity values of the emission radiation emitted by it as a response to the excitation pulse are measured at time intervals. An intensity-time emission function of the emission intensity values is then formed. This function is compared to at least one reference intensity-time emission function, with the two emission functions being normalized before they are compared.

Proceeding from this, an object of the present invention is a device and a method for checking luminescent documents of value provide, which allow a safe test with a compact luminescence sensor.

This object is achieved by the independent claims. The dependent claims and the following description explain preferred configurations.

Since the document of value to be checked that is transported past the luminescence sensor in a transport direction is illuminated with an illumination surface that extends in the transport direction, it is also possible to effectively measure documents of value that emit only very little luminescence radiation. This significantly improves the measurement of phosphorescence radiation in particular

It should be particularly emphasized that the features of the dependent claims and the exemplary embodiments mentioned in the following description in combination or independently of one another and of the subject matter of the main claims, i.e. e.g. also in devices that do not generate an illumination surface extending in the transport direction or a measurement of other radiation perform as luminescent radiation, can be used advantageously.

Fig. 1

eine schematische Ansicht einer Banknotensortiervorrichtung;

Fig. 2

eine schematische Ansicht von der Seite auf das Innere eines erfindungsgemäßen Lumineszenzsensors, der in der Banknotensortiervorrichtung 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 alternativen erfindungsgemäßen Lumineszenzsensors, der in der Banknotensortiervorrichtung nach Fig. 1 eingesetzt werden kann;

Fig. 5

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

Fig. 6

eine Ansicht von oben auf ein Beispiel einer Detektorzeile zur Verwendung 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 Detektorzeile des Lumineszenzsensors der Fig. 2oder Fig. 4;

Fig. 10

eine schematische Ansicht von der Seite auf das Innere eines nicht erfindungsgemäßen Lumineszenzsensors;

Fig. 11

eine schematische Ansicht auf einen nicht erfindungsgemäßen Lumineszenzsensor mit externer Lichtquelle;

Fig. 12

eine schematische Ansicht auf einen Teil eines weiteren nicht erfindungsgemäßen Lumineszenzsensors und

Fig. 13

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

Further advantages of the present invention are explained in more detail below by way of example with reference to the accompanying drawings

1

a schematic view of a bank note sorting device;

2

a schematic view from the side of the interior of a luminescence sensor according to the invention in the bank note sorting device 1 can be used;

3

Luminescence sensor components 2 in supervision;

4

a schematic view from the side of the interior of an alternative luminescence sensor according to the invention, which is used in the bank note sorting device 1 can be used;

figure 5

a schematic view of a banknote to explain the use of the luminescence sensor 2 and 3 ;

6

a view from above of an example of a detector array for use in the luminescence sensor of FIG 2 ;

7

a top view of another example of a detector array for use in the luminescence sensor of FIG 2 ;

8

a cross-sectional view along the line II in 7 ;

9

a schematic representation for reading out the data from a detector line of the luminescence sensor 2 or 4 ;

10

a schematic view from the side of the interior of a luminescence sensor not according to the invention;

11

a schematic view of a non-inventive luminescence sensor with an external light source;

12

a schematic view of part of a further luminescence sensor not according to the invention and

13

a schematic view of a detector part of yet another luminescence sensor not according to the invention.

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 to this, the checking of banknotes in banknote processing devices, which can be used, for example, for counting and/or sorting and/or depositing and/or paying out banknotes, is described below as a preferred variant.

In the 1 such a bank note sorting device 1 is shown in an exemplary manner. The banknote sorting device 1 has an input compartment 3 for banknotes BN in a housing 2, into which banknotes BN to be processed can either be input manually from the outside or bundles of banknotes can be fed automatically, optionally after a previous debanding. The banknotes BN fed into the input pocket 3 are individually withdrawn 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 be used, for example, to check the authenticity and/or the condition and/or the denomination of the checked banknotes BN. After passing through the sensor device 6, the checked banknotes BN are then output sorted, depending on the test results of the sensor device 6 and predetermined sorting criteria, via switches 7 and associated spiral compartment stackers 8 into output compartments 9, from which they are either removed manually, if necessary after prior banding or packaging or can be transported away automatically. It can also be a shredder 10 may be provided in order to destroy banknotes BN classified as genuine and no longer fit for circulation. The banknote sorting device 1 is controlled by means of an EDP-supported control unit 11.

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

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

The light source 14 can, for. B. an LED, but preferably a laser light source such as a laser diode 14 be. The laser diode 14 can emit one or more different wavelengths or wavelength ranges. If several different wavelengths or wavelength ranges are used, provision can also be made for several light sources 14 for different wavelengths to be used in the same light source housing or in separate light source housings, ie separate light source modules or wavelength ranges, which are arranged next to each other, for example, and preferably emit parallel light that can be projected onto the same point or adjacent points on the bank note BN.

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

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

The light emanating from the laser diode 14 is radiated onto a banknote to be checked by means of imaging optics 15,16,17 the collimator lens 15 deflects the laser beam formed by 90°, as well as a condenser lens 17 with a large opening angle, which images the deflected laser beam through a front glass 18, preferably perpendicularly, onto the bank note BN to be checked, which is transported past by means of the transport system 5 in direction T, and thus the bank note BN for emission stimulated by luminescent radiation.

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

The optics for imaging the luminescence radiation on a photosensitive detector unit 21 also includes the front glass 18, the condenser lens 17 and the mirror 16, which is at least partially transparent for the luminescence radiation to be measured. In addition, the optics have a further condenser lens 19 with a large opening, a subsequent 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 deflection mirror 23 serves to fold the beam path and deflect the luminescence radiation to be measured onto an imaging grating 24 or another device for spectral decomposition 24. For the most compact construction possible, the deflection mirror is advantageously mounted parallel or almost parallel to the image plane of the spectrometer (angle < 15 degrees). The imaging grating 24 has a wavelength-dispersing element with a concave mirror 26 which preferably images the first-order or minus-first-order luminescence radiation onto the detector unit 21 . However, higher orders can also be mapped. The detector unit 21 preferably has a detector line 22 composed of a plurality of photosensitive pixels, ie picture elements, arranged in a row, as is the case, for. B. in relation to the Figures 6 or 7 are described below as an example.

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

In a further embodiment, the deflection mirror 23 is positioned in relation to the imaging grating 24 in such a way that the entrance slit AS falls on the area of the deflection mirror 23 . Since this means that 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 deflection mirror 23 is part of the detector unit 21, the deflection mirror 23 can thereby not only according to figure 2 above but also next to the photosensitive areas of the detector unit 21.

A special embodiment 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 bank note BN to be checked.

This variant has the advantage that the luminescent, in particular phosphorescent, feature substances present in the banknotes BN, usually only in very low concentrations, are pumped up longer by the illumination surface extending in the transport direction when the luminescence sensor 12 is transported past, and the radiation intensity of the afterglow, phosphorescent feature substances in particular is thereby increased .

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

In figure 5 the image area 36, ie the entrance hatch 36 of the spectrometer 30, is also illustrated with a different hatching, ie that area of the banknote BN which is imaged on the spectrometer 30 at the given point in time according to the dimensions of the entrance slit AS. It can be seen that the length and width of the entrance port 36 of the spectrometer 30 are preferably smaller than the corresponding dimensions of the illumination area 35 of the laser diode 14 . This allows greater adjustment tolerances for the individual sensor components.

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

According to a further special idea of the present invention, different detector units 21, 27 are used to detect the luminescence radiation, in particular the luminescence radiation emanating from the device for spectral decomposition 24, ie the imaging grating 24. Thus, on or in front of the further detector unit 27 z. B. a filter can be provided to only in one or more given wavelengths or ranges to measure, the measurable spectral ranges of the different detector units 21, 27 preferably differ and, for example, only partially or not overlap. It should be emphasized that there can also be several further detector units 27 which measure in different wavelengths or ranges. The several other detector units 27 can be spatially spaced from each other or in a sandwich structure, as shown in FIG DE 1 0127 837 A1 is described as an example.

While one detector unit 21, i. H. in particular the detector row 22 is designed for the spectrally resolved measurement of the luminescence radiation of the banknote BN, the at least one further detector unit 27 can thus also be used to measure the broadband, non-spectrally resolved zeroth order of the spectrometer 30 and, if appropriate, the decay behavior of the luminescence radiation.

Furthermore, the further detector unit 27 can also be designed to check a different optical property of the at least one feature substance of the bank note BN. This can be done, for example, by the measurements mentioned at other wavelengths or wavelength ranges. The further detector unit 27 can preferably also be designed to check another feature substance of the bank note BN. So e.g. 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 in order to suppress undesired scattered light or higher-order light during the measurement.

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

A reference sample 32 with one or more luminescent feature substances can also be provided for calibrating and functional testing of the luminescence sensor 12, which can have an identical or different chemical composition to the luminescent feature substances to be tested in the banknotes BN. Like in the 2 is shown, this reference sample 32 can be integrated in the housing 13 itself and applied, for example, as a film 32 to another light source (LED 31), which is arranged opposite the laser diode 14 with respect to the beam splitter 16. The reference sample 32 can instead, for example, also be a be a separate component between LED 31 and corner mirror 16. For calibration, e.g. in the pauses between two banknote measurement cycles of the luminescence sensor 12, the reference sample 32 can then be excited by irradiation using the LED 31 to form a defined luminescence radiation, which is imaged on the detector line 22 and evaluated by parasitic reflection at the dichroic beam splitter 16.

In order to calibrate the intensity of the spectrometer 30, the luminescent feature substances of the reference sample 32 can preferably emit broadband, for example over the entire spectral range that can be detected by the spectrometer 30. However, the luminescent feature substances of the reference sample 32 can alternatively or additionally also have a specific characteristic emit a spectral signature with narrow-band peaks to perform wavelength calibration. However, it is also possible for only the additional light source 31 without reference sample 32 to be used to adjust the spectrometer 30 .

As an alternative or in addition, the reference sample 32 can therefore also be attached outside the housing 13, in particular on the opposite side in relation to the bank note BN to be measured, and e.g. integrated in a counter-element such as a plate 28.

An additional detector unit 33 can also be present outside of the housing 13 as a separate component or integrated in the plate 28 . The additional detector unit 33 can be, for example, one or more photocells for measuring the radiation from the laser diode 14 that has passed through the front glass 18 and possibly through the bank note BN and/or the luminescence radiation from the bank note BN. In this case, the plate 28 can be slidably mounted in a guide in the direction P, so that 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 connecting element 55, shown in dotted lines, which lies outside the plane of transport of the banknotes BN. in a Fig.2 The housing 13, connecting surface 55 and plate 28 are then approximately U-shaped in the horizontal cross-sectional plane. This attachment of plate 28, also in an alternative variant without reference sample 32 and photocell 33, has the advantage that light protection is provided against unwanted escape of the laser radiation from laser diode 14 if plate 28 is detachably attached to housing 13 for maintenance purposes or to clear jams is fixed, it can be provided that when the plate 28 is loosened or removed, the laser diode 14 is deactivated.

figure 4 shows a schematic cross-sectional view of an alternative and very compact luminescence sensor 6, which is used in the banknote sorting device according to FIG 1 can be used. The same components have the same reference numbers as in 2 marked.

The arrangement of the optical components in the luminescence sensor 6 4 differs from the luminescence sensor 6 according to 2 in particular in that the deflection mirror 23 can be dispensed with. It should be noted that the luminescence sensor 6 after 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 rather the luminescence radiation in a mirrored manner

Furthermore, the light source 14 has two laser diodes 51, 52 arranged perpendicularly to one another, which emit at different wavelengths, the radiation of the individual laser diodes 51, 52 being able to be coupled in, e.g. by a further dichroic beam splitter 53, so that the same illumination area 35 or overlapping or spaced illumination areas 35 can be irradiated on the bank note BN. Preferably, depending on the bank note to be checked, either one or the other laser diode 51, 52 or both laser diodes 51, 52 can be activated simultaneously or alternately to emit radiation.

The recognizable in an elevation photosensitive detector elements, ie the detector line 22 is mounted asymmetrically on the carrier, as in relation to figure 7 will be explained in more detail.

In addition, the luminescence sensor 6 preferably has a control unit 50 in the housing 13 itself, which is used 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 Figures 6 and 7 two different variants of the detector rows 22 that can be used in the luminescence sensor 12 will now be described. 6 shows a section of a conventional detector line 22, which usually has more than 100 photosensitive picture elements, called pixels 40 for short, arranged next to one another (of which 6 only the first seven left pixels 40 are shown), which are of the same size and are mounted at a distance from one another on or in a substrate 41 which corresponds approximately to the width of the pixels 40

In contrast to this, however, a modified detector line 22 is preferably used with a significantly lower number of pixels 40, with a larger pixel area and a reduced proportion of non-photosensitive areas, as is the case in FIG 7 is illustrated. Such a modified detector line 22 has the advantage of a significantly greater signal-to-noise ratio than the conventional detector line 22 of 6 to exhibit. The modified detector rows 22 are preferably constructed in such a way that they have only between 10 and 32, particularly preferably between 10 and 20, individual pixels 40 in or on a substrate 41. The individual pixels 40 can have dimensions of at least 0.5 mm×0.5 mm, preferably 0.5 mm×1 mm, particularly preferably 1 mm×1 mm. After designing the 7 For example, the detector line 22 has twelve pixels 40 with a height of 2 mm and a width of 1 mm, with the non-photosensitive area 41 between adjacent pixels 40 having an extent of approximately 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 is shown in FIG 7 is shown Since not all wavelengths of the spectrum are usually evaluated, but rather only individual wavelengths or wavelength ranges, the pixels 40 can be designed to be adapted to the wavelengths (ranges) to be evaluated.

Depending on the wavelength range to be spectrally recorded, the detector line 22 can 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 detector line 22 made of InGaAs, which are sensitive above 900 nm, are particularly suitable for measurements in the infrared spectral range. Such an InGaAs detector line 22 is preferably applied directly to a silicon substrate 42, which particularly preferably has an amplifier stage produced using silicon technology for amplifying the analog signals of the pixels 40 of the InGaAs detector line 22. This also results in a particularly compact structure with short signal paths and increased given signal/noise ratio.

Through the detector line 22 with a few pixels 40 (e.g. after 7 ) preferably only a relatively small spectral range of less than 500 nm, particularly preferably less than or of about 300 nm is detected. Provision can also be made for the detector line 22 to have at least one pixel 40 which is outside the luminescence spectrum of the banknotes to be measured BN is photosensitive in order to carry out normalizations such as finding a baseline when evaluating the measured luminescence spectrum.

The imaging grating 24 will preferably have more than about 300, particularly preferably more than about 500 lines/mm, i.e. have diffraction elements, in order to still allow sufficient dispersion of the luminescence radiation on the detector element 21 despite the compact design of the luminescence sensors 6 according to the invention. In this case, the distance between the imaging grating 24 and the detector element 21 can 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 can, for. B. done serially using a shift register. However, individual pixels 40 and/or pixel groups of detector line 22 are preferably read out in parallel. Following the example of 9 the three left pixels 40 are each read out individually by the measurement signals of these pixels 40 each with the aid of an amplifier stage 45 which, for example, is part of the silicon substrate 42 7 can be, amplified and fed to an analog/digital converter 46 each. The two right pixels in the schematic representation of the 9 are again amplified first by means of separate amplifier stages 45, then to a common multiplex unit 47, which can optionally also include a sample and hold circuit, and then to a common analog/digital converter 46, which is connected to the multiplex unit 47.

The parallel reading out of a plurality of pixels 40 or pixel groups made possible in this way enables short integration times and a synchronized measurement of the bank note BN. This measure also contributes to an increase in the signal-to-noise ratio.

According to a further embodiment of the present invention, components of the imaging optics for the luminescence radiation are integrated with components of the detector 30. In particular, the Deflection mirror 23 for deflecting the luminescence radiation to be detected onto the spectrometer 30 can be connected directly to the detector unit 21, as is the case, for example, in 2 is shown.

7 1 shows a modified variant in which the deflection mirror 23 is applied directly to a common carrier with the detector line 22, ie specifically to the silicon substrate 42. Alternatively, the deflection mirror 23 can also be applied, for example, to a cover glass of the detector unit 21 .

Furthermore, below the deflection mirror 23 there can also be a photodetector, such as a photocell 56 . This preferred variant is an example in the figure 8 pictured, showing a cross-section along line II of figure 7 indicates. In this case, the deflection mirror 23 mounted on the photocell 56 is at least partially transparent for 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 figure 4 illustrated, not only for reasons of compact sensor design, as it is in figure 4 is illustrated, but also for attaching further optical components 23, 56, the detector line 22 preferably asymmetrically on the carrier, ie the silicon substrate 42 may be applied.

As mentioned, due to the very low signal intensities of the luminescence radiation usually to be expected when checking banknotes BN, the luminescence sensor 12 needs to be calibrated during ongoing operation, ie specifically, for example, in the pauses between two banknote measurement cycles of the luminescence sensor 12. One The possible measure already described is the use of 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, with the adjustment depending on measured values of the luminescence sensor 12 being controlled, for example, by an external control unit 11 or preferably by an internal control unit 50.

For example, the component of the imaging grating 24 can be mounted displaceably in direction S by means of an actuating element 25 . A mechanical adjustment of other optical components, such as e.g. B. the detector 21 can be achieved, the z. B. in the direction of arrow D in 2 can be moved when actively driven. The optical components can also be adjusted in more than one direction.

Thus, for example, while the luminescence sensor 12 is in operation, the measured values of the luminescence sensor 12 can be evaluated and if there are deviations in the measured values (e.g. of the detector line 22, the further detector unit 27 or the photocell 33) or of variables derived therefrom from certain Reference values or ranges, an active mechanical adjustment of one or more of the optical components of the luminescence sensor 12 can be carried out in order to achieve an increased signal yield and compensation for undesirable changes, for example due to temperature fluctuations or signs of aging caused by the lighting or electronics of optical components. This is particularly important for a detector unit 21 with few pixels 40.

In order to increase the service life of the light sources of the luminescence sensor 12, it can also be provided that, for example, the laser diode 14 is only driven with high power when a bank note BN is just in the region of the measuring window, i. H. of the front glass 18 is located.

Of course, further alternatives or additions to the variants already described above are also conceivable.

While in terms of figures 2 and 4 Examples have been described in which the imaging grating 24 has a concavely curved surface, a plane grating can also be used as an alternative. The construction of such a luminescence sensor 12 not according to the invention is shown in FIG figure 10 illustrated. In this case, too, the radiation emitted by the bank note BN to be checked and detected through an entrance window 18 falls through a collimation lens 17 onto a beam splitter 16, from which the light is deflected by 90°, via a lens 19 and a filter 20 for suppressing illumination falls on a first spherical collimator mirror 70. The radiation is deflected onto a plane grating 71 by this mirror 70 . The light spectrally broken down by this is then directed onto a detector array 21 via a second spherical collimator mirror 72 and a cylindrical lens 73 .

The luminescence sensor 12 of figure 10 is further distinguished by the fact that the illumination light is coupled in by means of a light guide coupling. In particular, the light generated by a laser light source 68 is radiated onto the banknote to be checked via a light guide 69, beam shaping optics 66, the beam splitter 16, the collimation lens 17 and the entry window 18. Since light guides 69 are flexible and deformable and thus the illumination beam path can (largely) run arbitrarily, it is only possible, for example, to place the light source in a particularly space-saving location Housing 13 to attach.

In particular when using such light guides, the light source can even be fitted outside the housing 13 of the luminescence sensor 12 . This spatial separation has the advantage that the heat generated by the light source 68 significantly less disrupts the operation and the adjustment of the other optical components located in the housing 13 and in particular also the highly sensitive detectors 21 figure 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 can be constructed as an example like that of figure 10 with the only difference that the light source 68 is thus located outside of the housing 13 and the light guide 69 thus also runs outside of the housing 13

Another special feature of the light coupling, for example after figure 11 is that the light source 69 and the housing 13 connecting the light guide 69 in one in the figure 11 Central region 70 shown schematically in a cross-sectional view is spirally wound. When the light source 68 shines into the light guide 69, a series of total reflections occurs in the light guide 69. As a result, the beam cross-section of the coupled laser radiation from the light source 68 is spatially homogenized. This has the advantage that the illumination fluctuates less during the test and the test results are therefore more reproducible can be achieved. For this purpose, however, the light guide does not necessarily have to be spirally wound up in one plane. 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 guide 69 will preferably have a length of 1 m to 20 m.

It is also alternatively conceivable that the bank note to be checked is irradiated exclusively via optical devices outside the housing 13 Components takes place and the luminescence sensor 12 inside the housing 13 contains only the optical components which are used for measuring the radiation emitted by the illuminated bank note.

A so-called DFB laser, in which an additional grating is installed in the laser resonator, or a so-called DFR laser, in which an additional grating is installed outside the laser resonator, can also be used to stabilize the illumination beam.

Although preferred variants of the test using a grating spectrometer, i.e. a spectrometer 30 with an imaging grating 24, have been described above, it is also possible to work without a grating spectrometer and, for example, use a spectrometer 30 with a prism for spectral dispersion or a measurement using different ones Filtering to filter out different wavelengths to be detected or wavelength ranges of the luminescence radiation are carried out. In particular, this can also be used for a multi-track or a highly sensitive measurement.

An example of a luminescence sensor 1 not according to the invention without a grating spectrometer is shown in FIG figure 12 illustrated. figure 12 shows only the detection part of a luminescence sensor in a schematic manner. All other components such as the housing, the lighting and the imaging optics have been omitted for the sake of clarity. Following this example of figure 12 the beam emanating from the banknote BN to be checked is selectively deflected via a deflection mirror 57, which can be pivoted about an axis of rotation 58, onto individual detectors 59 which are sensitive to different wavelengths or wavelength ranges. On the one hand, this can be done by choosing photosensitive in different wavelength ranges Detector surfaces of the detectors 59 take place. However, as it is in figure 12 is indicated by way of example, filters 60 for different wavelength ranges can be arranged in front of the detectors 59 and preferably also attached to them 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 cross the light beam of the bank note BN to be checked, which subsequently impinges on the detector.

In the figure 13 a detector 61 according to yet another example is shown in a very schematic way. In this case, the detector has a row or an array of photosensitive pixels 63 of the same type on a substrate 62 . A filter 64 is mounted on the detector 61 above the pixels 63 and has a filter wavelength gradient indicated in the direction of the arrow. This means that, viewed in the direction of the arrow, different wavelengths are filtered out at different points of the filter 64 . The use of such a filter 64 with filter wavelength gradients has the advantage that the light to be tested is radiated directly onto the detector 61 and wavelength-dispersing elements such as the grating 24 or the deflection mirrors 23, 57 can be dispensed with. As a result, the structure of the luminescence sensor 1 can be designed in a particularly simple manner and with fewer components.

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

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

The devices and methods according to the invention consequently enable simple and reliable checking and differentiation of luminescent documents of value. The check can be carried out, for example, by using the light source 14 to generate a light with a first wavelength and a predetermined intensity for a specific period of time 0-t _P for the excitation of the feature substance. The feature substance of the bank note BN to be checked and transported past the front glass 18 in the direction T is excited by the light from the light source 14, whereupon the feature substance emits luminescent light of a second wavelength. The intensity of the emitted luminescence light increases according to a specific law during the period 0-tp of the excitation. The manner in which the intensity of the emitted luminescence light increases and decreases depends on the feature substance used and on the exciting light source 14, ie its intensity and wavelength or wavelength distribution. After the end of the excitation at time t _P , the intensity of the emitted luminescence light decreases according to a specific law.

With the aid of the spectrometer 30, the luminescence light emanating from the bank notes BN perpendicularly, ie parallel to the excitation light, is now detected and evaluated. By evaluating the signal from detector unit 21 at one or more specific points in time t ₂ , t ₃ , it is possible to check with particular certainty whether a genuine bank note BN is present, since only the feature substance used for bank note BN or the combination of feature substances used has such a decay behavior . The decay behavior can be checked by means of the above-described comparison of the intensity of the luminescence light at one or more specific points in time with specified intensities for genuine banknotes BN. Provision can also be made for the course of the intensity of the luminescence light to be compared with predetermined courses for known banknotes BN.

Claims (21)

1. An apparatus (1) for checking luminescent value documents (BN), having a light source (14, 51, 52, 68) for exciting luminescence radiation and a luminescence sensor (12) for detecting with spectral resolution the luminescence radiation emanating from the value document (BN), wherein the luminescence sensor (12) has an imaging grating (24) with a concave mirror (26) for spectral decomposition of the luminescence radiation and a detector unit (21) for measurement with spectral resolution of an order other than zero of the excited luminescence radiation spectrally decomposed by the imaging grating (24),
   characterized in that
   another detector unit (27) is designed for measurement with non-spectral resolution of the excited luminescence radiation and measurement of the zeroth order of the luminescence radiation coming from the imaging grating (24).
2. The apparatus (1) according to claim 1, characterized in that the light source (14, 51, 52, 68) produces on the value document (BN) transported in a transport direction (T) past the luminescence sensor (12) an illumination area (35) extending in the transport direction (T), and that preferably the extension of the illumination area (35) in the transport direction (T) is at least twice, preferably at least three times, four times or particularly preferably at least five times, as long as the extension perpendicular to the transport direction (T).
3. The apparatus (1) according to at least one of the previous claims, characterized in that an image area (36) of the luminescence sensor (12) extends in the transport direction (T) of the value document (BN) transported past the luminescence sensor (12).
4. The apparatus (1) according to at least one of the previous claims, characterized in that the length and/ or width of the image area (36) is smaller than the corresponding dimensions of the illumination area (35) of the light source (14, 51, 52, 68), and/or that the image area (36) and the illumination area (35) on the value document (BN) are at least partly or completely overlapping at a given time.
5. The apparatus (1) according to at least one of the previous claims, characterized in that the luminescence sensor (12) has one or more light sources (14, 51, 52, 68) which emit at different wavelengths, wherein preferably single wavelengths are selectively activatable.
6. The apparatus (1) according to at least one of the previous 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 from 10 to 20 pixels (40).
7. The apparatus (1) according to at least one of the previous claims, characterized in that the luminescence sensor (12) has at least one detector element (40) for measuring radiation outside the luminescence spectrum of the value documents (BN).
8. The apparatus (1) according to at least one of the previous 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 that is to be measured.
9. The apparatus (1) according to at least one of the previous claims, characterized in that the luminescence sensor (12) has an InGaAs detector row (22) on a silicon substrate (42), the silicon substrate (42) preferably having one or more amplifier stages (45) for amplifying the analog measuring signals of pixels (40) of the InGaAs detector row (22).
10. The apparatus (1) according to at least one of the previous claims, characterized in that the detector unit (21) of the luminescence sensor (6) detects a spectral range of less than 500 nm, preferably of less than or of about 300 nm, and/ or the imaging grating (24) of the luminescence sensor (6) has more than about 300 lines/mm, preferably more than about 500 lines/mm, and/or the distance between imaging grating (24) and detector unit (21) is less than about 70 mm, preferably less than about 50 mm.
11. The apparatus (1) according to at least one of the previous 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 measuring values of the luminescence sensor (6) and/or for power control of components of the luminescence sensor (6) are integrated in a common housing (13) and or in separate housings (13, 68).
12. The apparatus (1) according to at least one of the previous claims, characterized in that the light source (14) irradiates perpendicularly the value document (BN) to be checked, and the luminescence sensor (12) detects luminescence radiation emanating from the irradiated value document (BN) perpendicularly, and/or that the luminescence sensor (12) has a deflection mirror (23) for folding the beam path of the luminescence radiation to be measured and/ or for deflecting the luminescence radiation to be measured onto another optical unit, such as onto the imaging grating (24).
13. The apparatus (1) according to at least one of the previous claims, characterized in that the luminescence sensor (12) has a photodetector (56) with a deflection mirror (23) located on or above the surface thereof, which is at least partly transparent to the wavelengths to be measured by the photodetector (56).
14. The apparatus (1) according to at least one of the previous claims, characterized in that the luminescence sensor (12) has a structural part (21) having both a photosensitive detector unit (22) for luminescence radiation and components (23) for imaging the luminescence radiation onto the photosensitive detector unit (22).
15. The apparatus (1) according to at least one of the previous claims, characterized in that the luminescence sensor (12) has a detector row (22) which is applied to a substrate (42) asymmetrically.
16. The apparatus (1) according to at least one of the previous claims, characterized in that the one detector unit (21) is designed for time-integrated measurement of the luminescence radiation and the other detector unit (27) for time-resolved measurement of the luminescence radiation.
17. The apparatus (1) according to at least one of the previous claims, characterized in that the other detector unit (27) is disposed on a tilt with respect to the imaging grating (24) for spectral decomposition to avoid a re-reflection onto the imaging grating (24).
18. The apparatus (1) according to at least one of the previous 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).
19. The apparatus (1) according to at least one of the previous claims, characterized in that the luminescence sensor (12) has means (25) for active mechanical displacement of optical components (21, 24) of the luminescence sensor (12) and that preferably an active mechanical displacement of optical components (21, 24) of the luminescence sensor (12) is controllable by a control unit (11, 50) in dependence on measuring values of the luminescence sensor (12).
20. The apparatus (1) according to at least one of the previous claims, characterized in that the measuring values of the luminescence sensor (12) are still being evaluated for one value document (BN) while measuring values of a subsequent value document (BN) are already being sensed at the same time.
21. The apparatus (1) according to at least one of the previous claims, characterized in that single pixels (40) and/ or pixel groups of the detector row (22) are readable in parallel and/or single pixels (40) and/ or pixel groups of the detector row (22) are each connected to a separate amplifier stage (45) and a subsequent analog-to-digital converter (46).

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