EP3443542B1 - Device and method for checking value documents, in particular banknotes, and value document processing system - Google Patents

Description

The invention relates to a device and a method for checking documents of value, in particular banknotes, and a system of document of value processing.

In certain cases, banknotes are subsequently provided with a marking color. For example, in national financial institutions, certain areas of banknotes that are to be withdrawn from cash transactions are marked with marking color, in particular blackened. Marking ink is also used as an anti-theft device in that the marking ink is released in the event of an unauthorized opening of a transport container for banknotes that is equipped with a so-called ink bomb system, so that the banknotes are wetted with the ink.

Out of DE 10 2009 057 348 A1 a device for the automatic detection of banknotes marked with marking color is known, with at least one sensor detecting at least one of the surfaces of the banknote to be checked and the presence of marking color being checked using the data obtained from an edge area of the surface of the banknote.

With the known methods for checking banknotes, it can happen that areas of a banknote provided with marking color cannot be distinguished with sufficient reliability from areas that are folded over or dog-eared, so that these banknotes are incorrectly classified as marked with a marking color and thus unintentionally removed from cash transactions, although they could have been put back into circulation.

It is the object of the present invention to specify a device, a method and a value-document processing system which enables identification of value documents, in particular banknotes, with a marking color to be identified as reliably as possible.

This object is achieved by the device, the method and the value-document processing system according to the independent claims.

The device according to the invention for checking documents of value, in particular banknotes, has at least one first sensor and at least one second sensor. The at least one first sensor is preferably designed as an optical sensor and set up to detect electromagnetic radiation reflected and/or transmitted by a document of value and to convert it into corresponding first sensor signals. The at least one second sensor is preferably designed as an ultrasonic sensor and set up to detect sound waves, in particular ultrasonic waves, reflected and/or transmitted by the document of value and to convert them into corresponding second sensor signals. The device also has an evaluation device which is designed to use the first sensor signals to determine a first area value characterizing a first area of the value document, to use the second sensor signals to determine a second area value characterizing a second area of the value document and when a predetermined value is exceeded Value for an area difference between the first and second area value to conclude a possible identification of the document of value with a marking color.

The document-of-value processing system according to the invention has at least one device for processing, in particular for conveying and/or counting and/or sorting, of documents of value, in particular banknotes, and a device according to the invention.

In the method according to the invention for checking documents of value, in particular banknotes, electromagnetic radiation which is reflected and/or transmitted by a document of value is detected and converted into corresponding first sensor signals. Furthermore, sound waves, in particular ultrasonic waves, which are reflected and/or transmitted by the document of value, are detected and converted into corresponding second sensor signals. A first area value, which characterizes a first area of the document of value, is determined on the basis of the first sensor signals. A second area value, which characterizes a second area of the document of value, is determined on the basis of the second sensor signals. Finally, based on a predetermined value for an area difference between the first and second area value being exceeded, it is determined whether the document of value is possibly marked with a marking color.

The invention is based on the approach of determining the area of the document of value to be checked using an optical sensor and an acoustic sensor, in particular an ultrasonic sensor, and in the event of a difference between the areas determined in each case, to conclude that the document of value may have been marked with marking color. For this purpose, a first area value is determined on the basis of first sensor signals from an optical sensor, which detects the electromagnetic radiation reflected and/or transmitted by the document of value. Furthermore, based on second sensor signals of an ultrasonic sensor, which detects the ultrasonic waves reflected and/or transmitted by the document of value, a second Area value determined. The area values determined in each case characterize, for example, the size and/or the format of the area of the document of value. The ultrasonic sensor reliably detects the ultrasonic waves reflected and/or transmitted by the entire surface of the value document, regardless of any coloring of the value document with marking color, since the reflectance or transmissivity of the value document for ultrasonic waves is not or only slightly influenced by the marking color becomes. The second area value determined using the second sensor signals therefore corresponds to the actual area of the document of value. For the optical sensor, on the other hand, partial areas of the document of value colored with marking color are not visible or cannot be distinguished from the dark background of the document of value, since the reflection or transmissivity of the document of value for electromagnetic radiation is generally strongly influenced by the marking color, in particular prevented or at least diminished, will. In the case of edge areas of the document of value that are colored with marking color, in particular blackened, the first area value determined using the first sensor signals is therefore smaller than the actual size of the area of security.

If the determined first and second area values do not match or if a predefined value for an area difference is exceeded, a possible identification of the value document with marking color can be concluded, with the value document being classified as a value document marked with marking color or provisionally as a value document possibly marked with marking color can. In the latter case, provision can be made for the definitive classification as a document of value marked with a marking color to be subjected to one or more further tests and dependent A final classification is only made based on the result of the tests.

The approach according to the invention can be used to prevent documents of value with folded areas or dog-ears, which the optical sensor usually also cannot distinguish from the dark background, from being incorrectly classified as value documents marked with a marking color, since a folded area or dog-ear both the first area value and the second area value are reduced in the same way, so that no appreciable difference between the first and second area value can be determined.

Overall, the invention thus allows reliable identification of documents of value marked with a marking color.

The at least one first sensor is preferably designed as a spatially resolving sensor, for example as an area camera or line scan camera, with electromagnetic radiation that is reflected and/or transmitted at different points on the security being converted into corresponding first sensor signals. Preferably, the second sensor is also designed as a spatially resolving sensor that detects the ultrasonic waves reflected and/or transmitted by the document of value in a spatially resolved manner.

In a preferred embodiment, the evaluation device is designed to conclude that the document of value has been marked with a marking color if the difference between the second area value and the first area value exceeds a predetermined first value. This is a particularly simple way of using the first and second area value to identify the document of value with a close highlight color. The predetermined first value is preferably greater than, in particular at least twice as great as, the accuracy, for example the standard deviation or the variance, with which the first and/or second area value can be determined from the first and/or second sensor signals. This ensures that a possible marking of a document of value with marking color is reliably recognized.

In a further preferred embodiment, the evaluation device is designed to conclude that the document of value has been marked with a marking color if the quotient of the second area value and the first area value exceeds a predetermined second value. When selecting the predetermined second value, the accuracy, e.g. the variance or standard deviation, can also be taken into account when determining the first and/or second area value, analogously to the embodiment described above. This also ensures that a possible marking of a document of value with marking color is reliably recognized.

In a further preferred embodiment, the evaluation device is designed to conclude that the document of value has been marked with a marking color if a relative deviation of the second area value from the first area value exceeds a predetermined third value. When choosing the predetermined third value, measurement inaccuracies can preferably also be taken into account when determining the first and/or second area value. It is particularly preferred that the predetermined third value is greater than or equal to 4%. In this case, the document of value is therefore classified as possibly marked with a marking color if the second area value is around is at least 4% larger than the first area value. As a result, the checking of a document of value with regard to a possible marking with marking color is particularly reliable.

In a further preferred embodiment, the evaluation device is designed to specify the first, second or third value depending on the denomination, i.e. the nominal value, of the document of value. As a result, when documents of value are checked with regard to marking with marking color, it is taken into account that the absolute and/or relative size of the areas of the documents of value marked with marking color can depend on the respective denomination. This further increases the reliability of checking a document of value with regard to a possible marking with marking ink.

In a further preferred embodiment, the evaluation device is designed to use first sensor signals, which are obtained from the electromagnetic radiation reflected and/or transmitted in at least one edge region of the value document, to infer a possible identification of the value document with marking color. This check is preferably carried out when the identification of the document of value with marking ink cannot be inferred, or not sufficiently reliably, on the basis of the first and second area value alone. By restricting the test to at least one edge area, the effort involved in evaluating the corresponding sensor signals is reduced. At the same time, the restriction to the at least one edge area is usually sufficient, since the marking color is usually located at the edges of the documents of value, particularly in the case of marking using a so-called color bomb system.

In a further preferred embodiment, the evaluation device is designed to use first sensor signals, which are obtained from the electromagnetic radiation reflected and/or transmitted in at least one predetermined area of the document of value, to conclude that the document of value has been marked with a marking color. The at least one predetermined area is in particular selected in such a way that it does not contain any areas of the document of value in which certain security elements, in particular holographic security elements, for example patches or LEAD strips, are present.

Preferably, the above-described check of the document of value is carried out when the first and second area values and/or the evaluation of the at least one edge region of the document of value described above cannot be used to identify the document of value with marking ink, or not with sufficient reliability.

In a further preferred embodiment, the evaluation device is designed to specify the at least one predefined area depending on the denomination of the document of value. This ensures that regions which are not suitable for marking with marking color when the document of value is checked are not taken into account when evaluating the first sensor signals. This further increases the reliability of checking documents of value with regard to marking with marking ink.

In a further preferred embodiment, the device has one or more transport elements, in particular transport belts, which are designed to transport the document of value relative to the second sensor. In this case, the transport elements can cover one or more first areas of the document of value. The evaluation device is preferably designed to determine the second area value by estimation using second sensor signals which are obtained from the sound waves reflected and/or transmitted in one or more second areas of the document of value that are not covered by the transport elements. The area of the covered first areas is estimated on the basis of the image information from the second areas that are not covered by the transport elements, and the second area value of the document of value is finally determined therefrom. Reliable checking of the value documents using the first and second area value is thus also possible if parts of the value document are covered by transport elements when capturing an image of the value document using ultrasound.

In a further preferred embodiment, the at least one first sensor is designed to detect electromagnetic radiation in the infrared range of the spectrum and to convert it into corresponding first sensor signals.

In a further preferred embodiment, the evaluation device is set up to combine, for example to average, the first area values determined independently of one another on the basis of first sensor signals from more than one first sensor.

In a further preferred embodiment, the evaluation device is set up to use the first and/or second sensor signals to determine whether in the measurement window, ie in the area from which the first and/or second sensor signals are detected, for example a field of view of a camera, if there is a document of value to be checked at all. The first and/or second area value is preferably used for this purpose, with an empty measurement window being indicated in particular by a first and/or second area value of 0 or almost 0 or a first and/or second area value which is smaller than a fourth predefined value .

In a further preferred embodiment, the evaluation device is set up to use the first and/or second sensor signals to determine whether there may be shingled prints of value documents, i.e. overlapping value documents or layers of value documents, in particular whether parts of the value documents, in particular corners, are present , protrude from the measuring window. For this purpose, the y-coordinates of the corner points of the documents of value in the coordinate system of the at least one first and/or second sensor, i.e. the corresponding measurement window, are preferably determined by means of image processing methods.

Furthermore, the evaluation device is preferably set up to determine whether shingled prints that do not protrude from the measurement window and/or folded banknotes are present. Second sensor signals are preferably used for this purpose, which were obtained by detecting transmitted sound waves, in particular ultrasonic waves, since the second sensor signals are in particular a measure of the thickness of the document or documents of value present. A shingled deduction is present, for example, if more than four corners were determined and at least a first thickness and a second thickness were determined based on the second sensor signals, with the second thickness in particular being twice as large is like the first thickness. In this case, the second thickness characterizes the area in which the documents of value overlap.

Fig. 1

ein Beispiel eines Aufbaus eines Wertdokumentbearbeitungs-systems in einer schematischen Darstellung;

Fig. 2

a) ein erstes Beispiel und b) ein zweites Beispiel eines zu prüfenden Wertdokuments in Form einer Banknote;

Fig. 3

ein erstes Beispiel eines von einer Banknote erfassten Bildes;

Fig. 4

ein zweites Beispiel eines von einer Banknote erfassten Bildes; und

Fig. 5

ein Beispiel einer in einer Sensoreinrichtung befindlichen Banknote.

Further advantages, features and application possibilities of the present invention result from the following description in connection with the figures. Show it:

1

an example of a structure of a value document processing system in a schematic representation;

2

a) a first example and b) a second example of a document of value to be checked in the form of a bank note;

3

a first example of an image captured from a bill;

4

a second example of an image captured from a bill; and

figure 5

an example of a bank note located in a sensor device.

figure 1 shows an example of a schematic structure of a value document processing system 1 with an input compartment 2, in which a stack of value documents to be processed, in particular banknotes 3, is made available, and a separator 8, by which the bottom banknote of the input stack is picked up and sent to a - in transport device 10, which is reproduced only schematically in the selected illustration, is transferred, which transports the bank note in the transport direction T to a sensor device 20.

In the example shown, the sensor device 20 comprises a first sensor 21 and a further first sensor 22, each of which is preferably designed as a so-called line scan camera or area scan camera and detects light emanating from the banknote, in particular in the visible and/or infrared and/or ultraviolet spectral range, by means of sensor elements arranged along a line or area and convert them into corresponding sensor signals.

In the example shown, the first sensor 21 detects the light emitted by a radiation source (not shown) that hits the bank note and is remitted by it, i.e. reflected diffusely and/or directed, and converts this into corresponding first sensor signals. Accordingly, the further first sensor 22 detects the light remitted from the back of the bank note, i.e. reflected diffusely and/or in a directed manner, and converts this into corresponding further first sensor signals.

The sensor device 20 also includes a second sensor 24, which is preferably designed as an ultrasonic sensor and which, emanating from an ultrasonic source 25, detects ultrasonic waves which pass through the bank note, ie are transmitted, and converts them into corresponding second sensor signals. The second sensor 24 and/or the ultrasonic source 25 preferably have piezoelectric elements which are designed to convert incident ultrasonic waves into an AC voltage or an applied AC voltage into ultrasonic waves. Instead of a conversion into an AC voltage, basically any signal that is suitable for the qualitative and/or quantitative description of the sensor signal can be selected, for example a mixed voltage, a digital signal, a frequency modulated signal or an analog DC voltage.

The second sensor 24 particularly preferably has a large number of sensor elements, in particular piezoelectric elements, arranged in a row or area, by means of which the ultrasonic waves passing through the banknote can be detected in a spatially resolved manner.

The row with the sensor elements of the respective sensor 21, 22 or 24 preferably runs essentially perpendicularly to the transport direction T of the banknotes, so that a first or second sensor signal curve along the sensor row is obtained with each readout process in the respective sensor 21, 22 or 24 , which corresponds to an intensity profile of the light or of the ultrasonic waves, which is or are remitted or transmitted by the bank note in a direction running perpendicularly to the transport direction T.

The first and second sensor signals generated by the sensors 21, 22 and 24 of the sensor device 20, in particular the corresponding first and second sensor signal curves, are forwarded to a control device 50 and an evaluation device 51. The evaluation device 51 can be contained in the control device 50 or can also form a unit that is separate from the control device 50 .

In evaluation device 51, the sensor signals are used, possibly after pre-processing, to check the respective bank note, with statements about various properties of the bank note being derived from the respective sensor signals, such as denomination, authenticity, degree of soiling, wear and tear, defects, the presence of Foreign objects, such as adhesive tape, other stickers, paper clips and staples, and in particular the presence of an identification or coloring of the banknote with marking ink.

Depending on the properties of the respective bank note determined in the evaluation device 51, the transport device 10 and the switches 11 and 12 along the transport route are controlled by the control device 50 in such a way that the bank note is fed to one of several output compartments 30 and 31 and deposited there. For example, in a first output compartment 30 banknotes are deposited that have been recognized as not being marked with a marking color and possibly also meet other criteria, e.g .

The reference number 13 at the end of the illustrated transport path is intended to indicate that further output compartments and/or other devices, for example for storing banknotes classified as counterfeit, can be provided.

Alternatively, it can be provided that a banknote marked with a marking color, in particular in the form of a blackening of larger and/or certain surface areas of the banknote, is sent directly to a shredder (not shown) for destruction instead of to the second output compartment 31 or to a manual processing compartment for banknotes suspected of being counterfeit is transferred.

In the example shown, the value document processing system 1 also includes an input/output device 40 for inputting data and/or Control commands by an operator, for example by means of a keyboard or a touchscreen, and output or display of data and/or information on the processing process, in particular on the banknotes processed in each case.

The value-document processing system 1 shown as an example is particularly suitable for checking value documents for the presence of an identification by marking color, which is explained in more detail below.

Figure 2a ) shows a first example of a document of value in the form of a banknote 3--in the present case shown only highly schematically--which has been colored, in particular blackened, in an area 4 at the upper edge of the banknote 3. In the present example, the blackened area 4 extends over the entire width of the banknote 3. However, the following explanations also apply to markings of any size and position on the banknote 3.

If electromagnetic radiation, in particular infrared radiation and/or visible light, strikes the bank note 3, this is remitted depending on the optical properties, such as absorption and scattering, of the bank note and detected by the first sensors 21 or 22 (see figure 1 ) is detected and converted into corresponding first sensor signals. In this case, electromagnetic radiation that impinges on the area 4 of the banknote 3 inked with marking color is not remitted or only slightly remitted, since the marking color strongly absorbs the impinging radiation. A first area value calculated using the corresponding first sensor signals, such as the size and/or shape of the captured image of the bank note 3, therefore characterizes a first area in the present example, which is the actual corresponds to the area of the bank note 3 minus the area 4 colored with the marking color.

Ultrasonic waves generated by the ultrasonic source 25 (see figure 1 ) are emitted are, on the other hand, transmitted in the same way by the entire surface of the banknote 3, i.e. in particular also by the area 4 colored with marking color, so that a second surface value determined using the second sensor signals, such as the size and/or shape of the captured image of the bank note 3, the actual surface of the bank note 3 characterizes.

In the present case, the second area value determined using the ultrasonic sensor signals is greater than the first area value determined using the optical sensor signals.

If a difference between the second and first area value is found and/or the difference exceeds a specific predetermined threshold value, then it can be concluded that the bank note 3 may be marked with a marking color. A difference between the second and first area value can be determined, for example, by comparing the determined area values and/or by forming a difference or a quotient from the second and first area value. The difference between the second and the first area value relative to the second area value, i.e. a relative deviation of the two area values from one another, is preferably determined as a measure for the difference.

For example, provision can be made for a bank note 3 to be classified as a bank note 3 possibly marked with a marking color, if the relative deviation of the area values is greater than a predetermined threshold. Preferred thresholds are between about 2 and 8%. The threshold value is particularly preferably about 4%.

At the in Figure 2b ) shown second example, the banknote 3 is bent in such a way that an area 5 (dashed) of the banknote 3 is not visible. In this example, a first area value ascertained using the first sensor signals characterizes an area which is exactly as large as the area which is characterized by the second area value which is obtained from the second sensor signals. In this case, the first and second area values are essentially identical, so that the banknote 3 is not mistakenly identified as a banknote colored with a marking color, such as the banknote 3 in the first example of FIG Figure 2a ), is classified.

In this case, the banknote 3 is preferably only provisionally classified as a banknote marked with a marking color, with the banknote 3 initially only being classified as possibly marked with a marking color on the basis of the first and second area value and being subjected to one or more further tests in which the banknote 3 otherwise checked for the presence of marking paint and, depending on the result of the check, then finally classified accordingly. This is preferably done by checking edge areas of the banknote 3 and/or by so-called template matching, in which specific areas of the banknote 3 are subjected to an examination. This is explained below using the Figures 3 and 4 explained in more detail.

figure 3 shows a first example with one of the first sensors 21, 22 (see figure 1 ) captured image of a banknote 3, which in the area 4 with marked with a marking colour. In the reproduced image of the banknote 3, a number of edge areas 6 are drawn in, which are checked for the presence of marking color.

The narrow edge areas 6 are preferably arranged in such a way that their long sides lie parallel to the edges of the bank note 3 . Typically, the edge areas 6 are between 1 and 4 mm from the edges and have a width of between about 1 and 3 mm. The edge areas 6 are also preferably arranged in such a way that certain areas of the bank note 3 are omitted, such as security features 7 in the form of holographic elements.

The evaluation device 51 (see figure 1 ) is preferably set up to count a number of first sensor signals in the edge regions 6, which are in a specific signal strength range, and to infer from this a possible marking of the bank note 3 with a marking color. For example, all image points (pixels) in the respective edge area 6 of the camera image whose brightness is between a first brightness value, eg 50, and a second brightness value, eg 800, are counted here. As a result, pixels from the dark background of the banknote, which typically have brightness values of less than 50, and pixels from the unblackened banknote, which typically have brightness values of more than 800, are masked out, and only pixels are counted that indicate a blackening of the banknote 3 have typical brightness.

The checking of the edge regions 6 of the bank note 3 described above is preferably carried out if a statement regarding an identification of the bank note 3 with marking color alone on the basis of the first and second area values is not possible or not possible with the required reliability.

Even if this test cannot be used to infer the presence of a colored marking, or cannot be reliably inferred, for example in the case of banknotes where an attempt was made to wash off the marking color, a further check of the banknote 3 can be provided. In this case, images recorded from the bank note 3 are preferably subjected to what is known as template matching, which is explained in more detail below.

figure 4 shows a second example with one of the first sensors 21, 22 (see figure 1 ) captured image of a banknote 3. In this example, a shaded area 9 indicates the area in which the electromagnetic radiation remitted by the banknote 3 and detected by the first sensors 21, 22 is evaluated to detect a color marking. Areas of the banknote 3 left out of the hatched area 9 (shown transparent) are not suitable for detecting a color marking, such as areas with a dark IR print and/or with a hologram foil (so-called patch, LEAD).

The hatched area 9, which is also referred to as a “mask” or “template”, is preferably chosen to be specific to the denomination, i.e. dependent on the determined denomination of the bank note 3, and/or specific to the location, i.e. corresponding to the orientation of the bank note 3.

In the present example, preferably all image points (pixels) in area 9 of the camera image are counted whose brightness exceeds a predetermined brightness value, such as 1500, for example. This ensures that normal soiling and watermarks are not misinterpreted as Labeling can be identified with marking color. The number of pixels determined in this way is compared with a predetermined number which depends on the size of the area of the region 9 . If the determined number is less than the specified number, it can be concluded that marking color is present in the area 9 examined.

A percentage match of the determined number with the predetermined number is preferably determined and, based on the result, an identification of the bank note 3 with marking color is concluded.

In order to save computing time, the evaluation device 51 is preferably set up to only evaluate a part of the first sensor signals or pixels in the shaded area 9 . In this case, preferably only every third pixel is checked with regard to its brightness value in relation to the predefined threshold value and counted accordingly.

figure 5 shows an example of a sensor device 20 (see figure 1 ) located bank note 3, which is partially covered by transport elements 10 ', such as transport belts, the transport device 10. This can be the case, for example, if the value-document processing system is designed as a so-called belt machine.

If the transport elements 10' are located, for example, between the second sensor 24 on the one hand and the banknote 3 or the ultrasound source 25 on the other hand, the image captured by the second sensor 24 in the areas of the transport elements 10' does not contain any image information about the banknote 3.

In this case, the size and/or shape of the missing image areas are preferably determined by estimation using the image information from the uncovered areas of the bank note 3 . This is achieved, for example, by multiplying second sensor signals or pixels from image areas 15 located above and/or below a transport element 10', which were preferably detected with a sensor line, and then replacing the missing image areas. The number of times this is multiplied depends on the width of the transport elements 10' or the areas covered by it. If the width of the covered areas corresponds, for example, to a width of two sensor lines, the image area 15 lying below a transport element 10' is doubled and inserted in the corrected image at the position of the respective transport element 10'. The second area value can be reliably estimated using an image corrected in this way.

Alternatively, however, it can also be preferred to arrange the at least one ultrasonic sensor at a point at which the banknotes are not covered by transport elements.

Claims (12)

1. An apparatus for checking value documents (3), in particular banknotes, having

   - at least one first sensor (21, 22), which is configured to detect electromagnetic radiation reflected and/or transmitted by a value document (3) and to convert said radiation into corresponding first sensor signals, and

   - at least one second sensor (24), which is configured to detect sound waves, in particular ultrasonic waves, reflected and/or transmitted by the value document (3) and to convert said waves into corresponding second sensor signals,

   and an evaluation device (51), which is configured to determine a first area value characterizing a first area of the value document (3) on the basis of the first sensor signals, to determine a second area value characterizing a second area of the value document (3) on the basis of the second sensor signals, and

   to infer a possible identification marking of the value document (3) with a marking ink in the event that a predetermined value for an area difference between the first and the second area value is exceeded.
2. The apparatus according to claim 1, wherein the evaluation device (51) is configured to infer an identification marking of the value document (3) with a marking ink when the difference between the second area value and the first area value exceeds a predetermined first value.
3. The apparatus according to claim 1 or 2, wherein the evaluation device (51) is configured to infer an identification marking of the value document (3) with a marking ink when the quotient of the second area value and the first area value exceeds a predetermined second value.
4. The apparatus according to any of the preceding claims, wherein the evaluation device (51) is configured to infer an identification marking of the value document (3) with a marking ink when a relative deviation of the second area value from the first area value exceeds a predetermined third value.
5. The apparatus according to any of claims 2 to 4, wherein the evaluation device (51) is configured to predetermine the first, second or third value in dependence on the denomination of the value document (3).
6. The apparatus according to any of the preceding claims, wherein the evaluation device (51) is configured to infer an identification marking of the value document (3) with marking ink on the basis of the first sensor signals which are obtained from the electromagnetic radiation reflected and/or transmitted in at least one edge region (6) of the value document (3).
7. The apparatus according to any of the preceding claims, wherein the evaluation device (51) is configured to infer an identification marking of the value document (3) with marking ink on the basis of the first sensor signals which are obtained from the electromagnetic radiation reflected and/or transmitted in at least one predetermined region (9) of the value document (3).
8. The apparatus according to claim 7, wherein the evaluation device (51) is configured to predetermine the at least one predetermined region (9) in dependence on the denomination of the value document.
9. The apparatus according to any of the preceding claims, having one or several transport elements (10'), in particular transport belts, which are configured to transport the value document (3) relative to the second sensor (24), wherein the transport elements (10') cover one or several first regions of the value document, and wherein the evaluation device (51) is configured to determine by estimation the second area value on the basis of second sensor signals which are obtained from the sound waves reflected and/or transmitted from the one or several second regions (15) of the value document (3) which are not covered by the transport elements (10').
10. The apparatus according to any of the preceding claims, wherein the at least one first sensor (21, 22) is configured to detect electromagnetic radiation in the infrared range of the spectrum and to convert said radiation into corresponding first sensor signals.
11. A value document processing system (1), having at least one apparatus (2, 8, 10 - 13, 30, 31, 50) for processing, in particular for conveying and/or counting and/or sorting, of value documents (3), in particular banknotes, and an apparatus according to any of the preceding claims.
12. A method for checking value documents (3), in particular banknotes, having the following steps of:

    - detecting electromagnetic radiation reflected and/or transmitted by a value document (3), and converting the detected electromagnetic radiation into corresponding first sensor signals and

    - detecting sound waves, in particular ultrasonic waves, reflected and/or transmitted by the value document (3), and converting the detected sound waves into corresponding second sensor signals,

    - determining a first area value characterizing a first area of the value document (3) on the basis of the first sensor signals,

    - determining a second area value characterizing a second area of the value document (3) on the basis of the second sensor signals and

    - determining whether the value document (3) is possibly marked with a marking ink on the basis of an exceedance of a predetermined value for an area difference between the first and the second area value.

Images