EP2892835A1

EP2892835A1 - Device and method for controlling the tracking of a value document stack

Info

Publication number: EP2892835A1
Application number: EP13759983.3A
Authority: EP
Inventors: Thomas Hildebrandt
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient Currency Technology GmbH
Priority date: 2012-09-07
Filing date: 2013-09-06
Publication date: 2015-07-15
Anticipated expiration: 2033-09-06
Also published as: EP2892835B1; DE102012017770A1; WO2014037119A1; US20150274467A1; IN2014KN02742A; CN104487368B; US9216869B2; RU2632323C2; RU2015101157A; CN104487368A

Abstract

In order to continuously separate value documents from a value document stack (10), the value document stack is lifted and tracked to the separator (30). In order to control the tracking of the value document stack, an image of one side of the value document stack is taken and evaluated in order to recognize the edges of the individual value documents. The tracking of the value document stack is controlled on the basis of the number of value document edges which are detected in the image taken. If, however, the number of value document edges cannot be detected or can be detected only insufficiently, a brightness of the image in this image portion is also determined. When separating the value documents shown in this image portion, the tracking of the value document stack is controlled on the basis of the brightness detected in this image portion.

Description

DEVICE AND METHOD FOR CONTROLLING THE ADDITION OF ANOTHER

VALUE DOCUMENT STACK

The invention relates to a device and a method for processing value documents, in particular for controlling the tracking of a value document stack.

From EP0865398 Bl a Vereinzeier for value documents is known to be deducted by the value documents individually from a value document stack. In this case, a value-document stack lying on a movable pressure plate is fed to the separating animal by raising the pressure plate. The Vereinzeier has a feed device, a separating roller and a retaining device. In order to separate the sheet material, the pressure plate is moved in the direction of the singler until the value-document stack is pressed against the feed device with slight pressure. Thereafter, the respective highest value document of the stack is moved by means of the feed device in the direction of the separating roller, which then separates the uppermost value document. Since the number of value documents in the value document stack decreases as the singulation progresses, the pressure plate is continuously adjusted upward in order to raise the value document stack further so that the top value document can be detected by the advancing device of the singler.

In order to track the value-document stack appropriately, the density of the value documents in the stack is determined continuously during singulation. Thus, the stack can be pressed during the entire separation with a suitable pressure to the feed device of the singler. To determine the density of the document of value stack, for example, a camera is used, which is directed to the side of the document of value document in order to capture an image of the value document edges. By means of an image processing, the value document edges are recognized and from this the Density of the value document stack, ie the number of value documents determined in a particular section of the value document stack. Depending on the determined number of value documents, the distance between the pressure plate and the Vereinzeier is controlled.

With the previously known image processing methods, however, recognition of the value document edges is not always possible. Therefore, image processing techniques have been proposed that allow for improved edge detection, e.g. in WO2011161642 Al. Furthermore, in EP1576552 B1 it has been proposed to increase the recorded image of the value document edges in the direction along the stack and to increase the number of pixels along the stack direction in order to achieve a more accurate edge detection. In the case of heavily used value documents, where the edge detection does not work, it was proposed in EP1576552 Bl to mechanically cut the value document stack, so that the used value documents receive a new clean cut edge, and then perform the edge detection on the basis of the obtained clean cut edges. The object of the present invention is to find an alternative solution for those cases in which the value document edges can not yet be recognized or only insufficiently recognized.

This object is solved by the features of the independent claims. Further advantages of the present invention will become apparent from the dependent claims.

While the state of the art is aimed at improving the edge recognition of the value document edges even further, in order to make it difficult to recognize recognizing bare value document edges, the invention moves away from this approach. Because the invention makes it possible to control the tracking of a value document stack even in the case when the recognition of value document edges does not work.

To control the tracking of the value document stack, an image of one page of the value document stack is taken. The captured image of the value document stack page is evaluated to recognize the edges of the individual value documents and to determine a number of value document edges in the image. The tracking of the value document stack is controlled as a function of the number of value document edges that are determined in the recorded image.

If, when evaluating the image in an image section of the image, the number of value document edges can be determined, the tracking of the value document stack is controlled as a function of the number of value document edges determined for this image section when the value documents mapped in the image section are separated. However, if the number of value document edges can not or only insufficiently be determined when evaluating the image in an image section of the image, the tracking of the value document stack can not be controlled on the basis of the number of value document edges present in this image section. Instead, a brightness of the image in this image section is additionally determined. And when the value documents mapped in this image section are singulated, the tracking of the value-document stack is controlled as a function of the brightness determined in this image section. If a high brightness is determined in the image section in which the number of value document edges could not or only insufficiently be determined, it is assumed that value documents with very good condition are present in the relevant section of the value document stack. Since such value documents in a stack are usually close to one another and thus form a value document stack of greater density than heavily used value documents, a low tracking speed is selected for such value documents. Therefore, if the value documents mapped in the image portion are singulated, if the number of value document edges in the image portion can not be determined insufficiently and if a large brightness is detected in the image portion, the tracking is temporarily stopped or a low tracking speed is selected. For example, a lower tracking speed is selected than in the case when a low brightness is determined in this image section in which the number of document edges can not or only insufficiently be determined.

The invention ensures that the tracking is braked in the case of dense documents of value whose edges are not recognized. This avoids that tight document of value stack are pressed by the tracking too much to the Vereinzeier or the feed device and that the value-document stack is clamped between the pressure plate and the Vereinzeier. If, however, a low brightness is determined in the image section in which the number of value document edges could not or only insufficiently be determined, it is assumed that there are value documents in the relevant section of the value document stack which are less close to one another, eg value documents with a worse state , In one In such a case, the tracking can remain unchanged during the separation of the value documents mapped in the image section, for example. For example, the tracking rate will be maintained as it was previously selected, ie, as selected for the value documents for which a number of value document edges were last identified.

The tracking speed is e.g. maintained as selected on the basis of an earlier determined number of value document edges determined in a previously evaluated image portion of the same value document stack. Or the tracking will stop if it was stopped earlier. Alternatively, the tracking speed is set to a value that has been predefined for less dense value documents. Alternatively, the tracking and possibly also the separation of the value documents can be stopped. The stoppage of the singler can be useful if there is a suspicion that there are defective value documents or folded value documents or foreign objects in the relevant image section in which no value document edges and low brightness have been detected.

For example, the tracking of the value-document stack, in the case of the value documents mapped in this image section, is controlled as a function of the brightness determined in this image section in such a way that the tracking speed is reduced stepwise or continuously as the brightness of the image section increases. Reducing the tracking speed may also include temporarily stopping the tracking. For example, different levels for the tracking speeds can be selected as a function of the ascertained brightness, for example a high tracking speed for a low brightness, a medium tracking speed for a medium brightness and at a high brightness, a low tracking speed or even stopping the tracking.

In addition, the separation rate with which the value documents are singled is also controlled as a function of the brightness determined in the relevant image section. For example, a decreasing brightness of the image portion will be used as an indication of a worse condition of the value documents. The dicing rate is then reduced as the brightness of the image portion decreases, to avoid dysfunctions in singulating value documents having a bad condition. For example, when falling below a brightness threshold, a somewhat low singulation rate is selected. This brightness threshold is i.a. different from the brightness threshold relevant for the tracking. The image section in which the number of value document edges is determined may be the entire recorded image or only part of the captured image. The image portion is e.g. chosen such that the next of the value documents of the document of value document to be separated are mapped therein. The image section preferably lies in that section of the document of value document which faces the separator animal. The image section to be evaluated can also be subdivided into several image sections, in each of which a number of the document value edges is determined. These image sections may be e.g. be offset from each other along the stacking direction and adjoin one another.

The image portion of the image in which the edge detection is performed and the number of edges is detected may be a continuous two-dimensional image portion. Alternatively, the image portion may also consist of several image strips which are parallel to each other and run perpendicular to the stacking direction of the value document stack that the same value documents of the document of value stack are shown in this image strip. The edge detection is then performed correspondingly for the two-dimensional image portion or for these image stripes.

In order to evaluate the brightness of the image section in which the number of value document edges could not or only insufficiently be determined, this can be compared with a brightness threshold. However, several brightness thresholds can be used to evaluate the brightness. If the number of value document edges in the image section can not or only insufficiently be determined and the brightness in the image section exceeds the brightness threshold, the tracking is temporarily stopped or the tracking speed is reduced. For example, a smaller tracking speed is selected when separating the value documents mapped in this image section than in the case when a brightness is determined in this image section that does not exceed the brightness threshold. For example, when the brightness threshold is exceeded, a tracking speed may be selected which is lower than the tracking speed in the case when value document edges are detected in the image section.

The tracking speed, which was reduced on the basis of the ascertained brightness, remains reduced until a number of value document edges can be determined again in a later recorded image section, for example in the next evaluated image section of the following value documents of the same value document stack. As soon as a number of value document edges can be determined again in a later recorded image section, the tracking speed for the value documents which are depicted in the later recorded image section can be determined. be selected again depending on the number of value document edges.

If, when evaluating the image in an image portion of the image, the number of value document edges can be determined, the brightness of the image in the relevant image portion need not be determined, but the tracking speed can - regardless of the brightness - only depending on the number of in the value document edges recognized in the relevant image section are selected. Optionally, however, in the case of recognition of the value document edges, the brightness of the image can be determined, evaluated and used in addition to controlling the tracking.

The captured image is eg a grayscale image. The brightness of the image results from the pixel intensities of the image, eg in the visible and / or in the infrared spectral range. As a measure of the brightness of the image in the image section, an average of the pixel intensity is formed over the image section, for example. In order to determine the brightness in the image section, the frequency distribution of the pixel intensities in the image section can be determined. The tracking is controlled, for example, as a function of the position of the mean value of the frequency distribution and / or as a function of the width (eg, half-width or standard deviation) of the frequency distribution. For example, a small width (narrow frequency distribution) can be used as an indication of the presence of a homogeneous stack of value documents. With a high brightness mean and a small width of the frequency distribution, the conclusion is made of the existence of documents of value with a very good condition. For large width is used on the presence of Value documents or an inhomogeneous stack of value documents closed.

The invention also relates to a device for controlling the detection of a value-document stack from which the value documents are to be separated. The device has an image sensor, an evaluation device for evaluating the image recorded by the image sensor, and a control device for controlling the tracking of the value document stack.

The image sensor is arranged in the vicinity of the singulator so that it can take an image of one side of the document of value-value stack. Of the

Image sensor captures the image from one side of the value document stack, i. from a direction that is perpendicular to the stacking direction of the value document stack. The image sensor is preferably a two-dimensional one

Image sensor. The value-document stack, from which the value documents are to be singled out by means of the singler, is tracked in order to bring in each case the uppermost value document of the value-document stack into the coverage area of a feed device of the singler. The value document stack is based on e.g. a pressure plate, which is moved toward the Vereinzeier to track the value document stack to the Vereinzeier.

The evaluation device is connected to the image sensor and receives from this image data of the recorded image. The evaluation device is designed to evaluate the image of the page of value document stack recorded by the image sensor in order to recognize the edges of the individual value documents in an image section of the image and to display in the image section a number of document edges and possibly the brightness of the document To determine image. The evaluation device has, for example, corresponding hardware circuits and / or a corresponding software program for edge detection. The evaluation device checks whether it can determine the number of value document edges when evaluating the image in a designated image section of the image. If it can not or only insufficiently determine the number of value document edges, the evaluation device additionally determines a brightness of the image in this image section. The evaluation device is connected to a control device which is designed to control the tracking of the document of value document as a function of the number of value document edges which the evaluation device has determined in the recorded image. For example, two or more tracking modes are provided for this purpose in the control device, which can be implemented by appropriate hardware and / or software of the control device. The evaluation device sends the information about whether the recognition of the value document edges was successful, as well as possibly the number of value document edges and possibly the brightness of the image section to the control device. The control device controls the tracking of the value document stack when separating the in this

Image portion illustrated value documents, depending on the determined number of value document edges and in dependence of the brightness, which has determined the evaluation in the image section of these value documents. The control device selects the tracking mode as a function of the number of value document edges and, if this is not possible, as a function of the brightness of the image section. In the follow-up mode, it is determined whether the value-document stack is updated and, if so, with which speed the value-document stack is tracked. For tracking the control device initiates a corresponding movement of the pressure plate which feeds the value-document stack to the separator.

The image sensor can also be designed to check for dirt on its own, preferably at a time when there is no value-document stack in its field of view. If then a too low brightness is detected, it is concluded that contamination of the image sensor. As a result of contamination, automatic cleaning of the image sensor or any lens or window upstream therefrom (e.g., by blowing) may or may not occur

Message may be output from the value-document processing device, for example, to prompt an operator to clean the image sensor, the lens or the window. Advantageously, on the side of the document of value document which lies opposite the image sensor, a reference surface may be applied, so that at times when no document of value is in the field of vision of the image sensor, the brightness of the image captured by the image sensor is determined by the reference surface. This ensures that the recorded image of the document of value stack has a defined background brightness. The reference surface makes it possible to detect a reference brightness from time to time, which is included in the image analysis. By way of example, the brightness threshold with which the detected brightness of the image section is compared is selected as a function of the reference brightness which the image sensor detects from the reference surface (without existing value-document stack). The reference surface may be designed to be pivotable or permanently installed. Preferably, the reference surface - as far as it is in the field of view of the image sensor - a uniform brightness. The invention also relates to a separating device having a device for controlling the tracking and a value document processing device having such a separating device. The separating device contains, for example, a feed device, a separating element (for example a roller) and a retaining device and optionally the pressure plate for receiving and for tracking the value-document stack. The device for value document processing furthermore has a transport system for transporting the value documents, sensors for checking the value documents and optionally one or more output compartments and / or storage containers for the value documents.

The invention will be described with reference to figures. Show it:

1a view of a device for value document processing from above,

1b is a side view of the separator of the device,

FIGS. 2a-d are side views of a value document stack and image section, in FIG

Four examples of the frequency distribution of the pixel intensities in an image section in which the number of value document edges could not be determined.

FIG. 1 a shows by way of example a section of a device 100 for value document processing in a bird's eye view from above (z-direction) onto the area of the separator 30 of the device 100. From the operator side B of the device 100, a value-document stack 10 has been inserted into the singler compartment 6 of the device 100. The value-document stack 10 rests on a movable pressure plate 20, which can be moved up and down (z-direction) in order to feed the stack 10 to the separator 30 of the device 100. With the aid of the separating roller 33, the uppermost value document along the x-direction is deducted from the value-document stack 10 in each case. For better illustration, the other components of the singler 30 and of the device 100, which are located between the observer in a bird's-eye view and the value document stack 10, are omitted in FIG.

The device 100 has a camera module 3, which is arranged in the interior of the device, on that side of the singulator 30, which faces away from the operator side B of the device 100. The camera module 3 is directed from the interior of the device 100 into the singulator compartment 6 in order to record an image of the document of value document 10 from the side of the document of value document stack. The value-document stack 10 is viewed in the y-direction. The image sensor 1 of the camera module 3 is arranged so that it can receive an image of the interior of the device 100 facing side of the value document stack 10. To illuminate the value document stack 10, two light sources 2 are provided on the camera module 3, which emit flash light synchronously to each other. The image recorded by the image sensor 1 is evaluated by means of an evaluation device 4, which performs image processing in order to recognize the edges of the individual value documents and to determine the number of value document edges or the density of the value documents from the recorded image. For this purpose, the image section is subjected to an edge detection process, for example with the aid of edge operators, as are known from the prior art. The evaluation device 4 is connected to the control unit. 21 of the pressure plate 20, which controls the movement of the pressure plate 20 along the z-direction.

FIG. 1b shows a side view of the separator 30, viewed from the side of the cavity module 3. The singler 30 has in this example a feed device 31, a retaining device 32, a separating roller 33 and a retaining roller 34. The feed device is designed here as an air guide plate, which sucks the top value document and moves in the x direction, but can also be realized differently, e.g. by feed rollers etc.

To separate the value-document stack 10, the uppermost value document 5 is transported by the feed device 31 in the direction of the separating roller 33 (x-direction). This then takes the top value document and subtracts it from the stack 10. The value documents of the stack 10 following the highest value document are retained by the retention device 32. In the event that several value documents are transported by the feed device 31 in the direction of the separating roller 33, the restraining roller 34 is additionally provided, which then transports the following value documents back into the stack 10. The item of value isolated by the separating device 30 will then be transferred to a transport system 40. This includes e.g. Transport rollers 41, by means of which transport belt 42 are moved. For transport, the respective value document is clamped between the transport belt 42.

Since the number of value documents in the value document stack 10 decreases as the separation of the value documents progresses, the pressure plate 20 is tracked along the z direction with the aid of a motor, to further increase the value document stack. As a result, the highest value document 5 in each case comes into the detection range of the feed device 31 and can be singulated. However, the tracking speed with which the pressure plate 20 is moved upward is selected to be different depending on the density of the value-document stack 10. With loosely stacked value documents (low stack density), the stack 10 is tracked at a relatively high speed in order to achieve a high singulation rate. In the case of a dense document of value stack 10, the tracking is slowed down or temporarily stopped, so that there is no disruption of the separation. In order to adjust the distance D between the pressure plate 20 and the feed device 31 during singulation to the density of the value documents to be singled in each case, the movement of the pressure plate 20 along the z direction is controlled by means of the control device 21. The control device 21 controls the setting device 25, which is mechanically connected to the pressure plate 20.

The density of the value document stack is determined from the number K of value document edges that are recognized in a picture section 8. In FIG. 2 a, an image section 8 suitable for this purpose is sketched, which the image sensor 1 records from the side of the value-document stack 10. If the edge detection in the image section 8 is successful, the control device 21 receives from the evaluation device 4 information about the currently present number K of value document edges detected in the image section 8. The number K of value document edges is, for example, determined continuously during the separation of the value documents. The control device 21 controls the tracking of the pressure plate 20 as a function of this number K of value document edges. For example, the distance D between the pressure plate 20 and the separator 30 is dependent on gigkeit of the determined number K to value document edges adapted so that the stack 10 is easily pressed against the feed device 31.

The image section 8 is preferably accommodated in that side section of the valuable document stack which is located in the vicinity of the singulator 30 (in FIG. 2a, top right). The image section 8 preferably comprises those value documents which are separated next, immediately before they are separated. The respectively determined from the image portion number K of value documents then directly, virtually without delay, are used to control the movement of the pressure plate 20. However, the respective number K of value document edges and / or the image data can also be stored permanently or temporarily. By storing the number K, the number K determined in the respective image section can already be determined before the value documents are separated and only then retrieved and used for control, if the respective value documents are actually separated. Therefore, the storage of the number K allows the image sensor 3 to be arranged along the z-direction also at some distance from the separating animal 30. In the example from FIG. 2a, the value-document stack 10 lying on the pressure plate 20 consists of an upper stack section 10a and a lower stack section 10b. In the upper stack section 10a are used value documents which have a certain waviness and therefore lie on one another with a relatively low density. The lower stack section 10b contains documents of value with vanishing waviness, which are very close to each other, eg value documents that are hardly used or new documents of value. In the example of FIG. 2a, ten value document edges are recognized in the image section 8 in which the used value documents of the upper stacking section 10a are depicted. FIG. 2b shows the value-document stack from FIG. 2a after a part of the upper stacking section 10a has already been singled. The image section 8 of FIG. 2b therefore only includes the lower value documents of the upper value-document stack 10a. It shows fourteen value document edges. The ten value document edges of the image section 8 from FIG. 2a and the fourteen value document edges of the image section 8 from FIG. 2b can be identified by means of conventional image processing methods for edge detection.

For example, the tracking of the pressure plate 20 is controlled as a function of the number K of value documents that were detected in the image section 8. Thus, e.g. in the case of the ten value document edges in FIG. 2a, a tracking speed G2 is chosen which is greater than a tracking speed G1 which is selected in the case of the fourteen document value edges from FIG. 2b.

Alternatively, however, the same Nachführge- speed of the pressure plate 20 can be selected in both cases. For example, a number Z of value document edges may be predetermined as a threshold, e.g. Z = 20, and in all cases where the number determined in the image section 8 is below the threshold Z, a predetermined tracking speed G is set. If Z or more than Z value document edges are detected in the image section 8, the tracking takes place more slowly or is temporarily stopped.

FIG. 2 c shows a case in which both a part of the upper value-document stack 10 a and a part of the lower-value document stack 10 a are displayed in the image section 8. ment stack 10b is shown. Since the edge detection is successful only in the upper part of the image section 8, a small number of K = 8 value document edges is detected in this case. The evaluation can again be carried out on the basis of the threshold comparison just mentioned. Since the number K = 8 value document edges is below the threshold Z = 20, the predetermined tracking speed G would then be selected again.

FIG. 2d shows the value-document stack 10 after all value documents of the upper stack section 10a have already been singulated, so that only the dense documents of value of the lower stack section 10b are contained in the image section 8. With such a large stack density, the number K of value document edges can not or only insufficiently be determined ("K =?"), Because the image processing detects too few or no value document edges, but not only the density, but also the color or the contamination of the value documents may impair the recognition of the value document edges, or also an incorrect position or a very large undulation of the value documents contained in the stack 10. In such cases, if the number of value document edges in the image section 8 can not or only insufficiently be determined, Therefore, the brightness of the image is additionally determined in the image section 8. And the tracking of the value-document stack 10 is then controlled as a function of the determined brightness of the image section 8.

For the image section 8 from FIG. 2d, the frequency distribution d of the brightness of the image section 8 is sketched in FIG. 3a, here schematically a histogram N (I) of the pixel intensities I of all image points of the image section 8. In the exemplary embodiment of FIG. 3a, the frequency distribution d in order to be able to control the tracking of the value documents on the basis of parameters of this frequency distribution d, even in the event that no number K of value document edges can be determined. For example, the position and / or the width S of the frequency distribution are used as parameters for controlling the tracking.

As a measure of the location of the frequency distribution, for example, the mean value M of the frequency distribution can be determined and compared with a threshold T, which was determined, for example, in advance of the value-document processing. If the mean value M exceeds the threshold T, as is the case with the frequency distribution d from FIG. 3 a, the image section 8 has a relatively high brightness. This is used as an indication that in the image section 8 value documents are shown, which are very close to each other and therefore appear bright. The tracking of the value document stack 10b by means of the pressure plate 20 is temporarily stopped in this case or a low tracking speed G0 is selected, which is lower than the above-mentioned tracking speeds G or G1 and G2. FIG. 3 b shows the case when no value documents are depicted in the image section 8 at all, eg when the singler box 6 is empty. Also in this case, the image processing in the image section can not detect value document edges. Since in this case only the dark background of the separator compartment 6 appears in the image section 8, the frequency distribution e lies at a substantially lower brightness or pixel intensity I and therefore significantly below the threshold T. The fact that the mean value M of the frequency distribution e - in contrast to the frequency distribution d - the threshold T falls below, is used as an indication that not because of a dense document of value, but from another reason no number of value document edges could be determined. If the average value M falls below the threshold T, the tracking speed is maintained or set to the above-mentioned tracking speed G or G2, for example, which is also used in the case where a small number K of value document edges is detected in the image portion.

The brightness threshold T can also be provided with a brightness interval Τ +/- Δ, cf. 3b, and the average M to the exceeding of the upper limit Τ + Δ of the brightness interval and the falling below the lower limit Τ-Δ of the brightness interval are checked.

As an alternative or in addition to the position M of the frequency distribution, the width S of the frequency distribution can also be taken into account, e.g. the half-width. As a measure of the width S, the standard deviation of the pixel intensity I in the image section 8 can also be used. For example, in addition to the position of the average M above the threshold T, a small width S is also used as an indication of the presence of a very dense stack (case of FIG. 3a).

On the other hand, if the width S is large, for example greater than a predetermined width limit S *, as is the case with the frequency distribution f of FIG. 3c, this is taken as an indication that the problems in edge detection are not due to the high density of the stack and not because of missing value documents, but for a different reason. The reason may be, for example, a large ripple of the value documents, cf. the image section 8 shown in FIG. 3c, or a misplacement of the value documents. A large width S may also be present if in the image section 8 a relative inhomogeneous value document stack from various value document types or qualities is mapped.

If the number K of the edges can not be determined, but neither the position M and the width S of the frequency distribution can be concluded in any of the above cases, the evaluation can be limited to a part of the image section 8. This can e.g. be helpful if in the image section 8 different qualities of value documents are included, as is the case in the example of Figure 3d. There, in the image section 8 above, a dense sub-stack of bright value documents and below a dense sub-stack of somewhat darker value documents shown. Since the position and standard deviation of the associated frequency distribution g do not permit a clear conclusion, the frequency distribution is evaluated only for the upper half of the image section 8. In the case of FIG. 3d, the frequency distribution of the upper half of the image section 8 would have only the right-hand of the two peaks P2 from FIG. 3d. The position and width of the peak P2 indicate the presence of a dense document of value stack (analogous to the case of FIG. 3a), which is to be tracked at low speed or in which the tracking should be stopped.

However, a more complex analysis of the frequency distribution can also be carried out, for example a compensation calculation for the identification of curve maxima. Through a more elaborate analysis, the two peaks PI, P2 of the frequency distribution g can be identified and their position and width used to control the tracking. The width of these two peaks PI, P2 is relatively small and suggests two homogeneous sub-stacks of dense documents of value. The position of the peaks on the intensity axis I indicates that one of the sub-stacks consists of bright value documents and the other sub-stacks consist of something darker value documents. Due to the high density of both value document stacks, the tracking should be slowed or stopped as they are being singulated. In those cases in which the evaluation of the image section 8 does not indicate any of the above-mentioned cases, the tracking speed can be maintained as selected on the basis of the number K 'of value document edges of an earlier evaluated image section 8' of the same value document stack 10 be set before defined tracking speed.

If despite the control of the tracking nevertheless problems occur in the separation of the value documents, the separation is stopped and the device 100 issues a corresponding message.

The images taken by the image sensor 1, on which the side of the document of value document stack 10 is to be imaged, can be displayed on a display device of the device 100, e.g. on a display. The images taken are preferably displayed in real time with the separation of the value documents, wherein the images can be shown to an operator or a service person of the device live or immediately after the images have been taken. The images include e.g. in each case the image section 8, on the basis of which the tracking of the stack is controlled and / or in each case the highest value document which is being singled out. Due to the pulsed illumination by means of the light sources, the fast sequence of the individual recorded images results in a kind of film which can be used to manually optimize the parameters for controlling the tracking and / or the singling parameters of the singler.

Claims

P a n t a n s p r e c h e

Method for controlling the tracking of a value document stack (10), from which value documents are separated, with the steps:

Taking a picture of one side of the document of value document (10),

Evaluating the recorded image of the page of the document of value document in order to recognize the edges of the individual documents of value in an image section (8) of the image and to determine a number (K) of document edges in the image section (8)

Controlling the tracking of the value-document stack as a function of the number (K) of the value-document edges determined in the image section (8),

characterized,

in addition, when evaluating the acquired image, if in the image section (8) the number (K) of value document edges can not or only insufficiently be determined, a brightness of the image in this image section (8) is determined, and

- That when singling the value documents mapped in this image section (8), the tracking of the document of value document (10) is controlled as a function of the brightness determined in this image section (8).

A method according to claim 1, characterized in that the tracking of the document of value document, when separating the value documents depicted in this image section (8), is controlled in dependence on the brightness determined in this image section (8) such that the tracking speed increases with increasing brightness of the image section (FIG. 8) is reduced.

3. The method according to any one of the preceding claims, characterized in that in the image portion (8) determined brightness with a brightness threshold (T) is compared.

A method according to claim 3, characterized in that in the case when the brightness determined in the image section (8) exceeds the brightness threshold (T), the tracking is temporarily stopped upon singulation of the value documents mapped in this image section (8) or during singulation the value documents mapped in this image section (8) are selected to have a lower tracking speed than in the case when the brightness determined in this image section does not exceed the brightness threshold (T).

A method according to claim 3, characterized in that in the case when the brightness determined in the image section (8) exceeds the brightness threshold (T), the tracking is temporarily stopped upon singulation of the value documents mapped in this image section (8) or during singulation the value documents depicted in this image section (8) are selected to have a lower tracking speed (G0) than in the case when value document edges are detected in the image section (8).

6. The method according to any one of claims 3 to 5, characterized in that in the case when the determined in this image portion (8) brightness in the image portion (8) does not exceed the brightness threshold (T), the tracking when singulating in the Image section (8) illustrated value documents remains unchanged or the tracking speed is set to a predefined for this case tracking speed (G).

7. The method according to any one of the preceding claims, characterized in that, in addition to the tracking of the value document stack (10), and the separation rate at which the documents of value are separated, is controlled in dependence on the brightness determined in the image section (8), wherein the separation rate is reduced in particular with decreasing brightness of the image section (8).

8. Method according to one of the preceding claims, characterized in that, when determining the brightness of the image in the image section (8), as a measure of the brightness of the image in the image section (8), an average value (M) of the pixel intensity ( I) is formed in the image section (8) and the tracking of the value document stack (10) is controlled in dependence on this mean value (M). 9. The method according to any one of the preceding claims, characterized in that when evaluating the recorded image, if in an image section (8) of the image, the number of value document edges (K) can not or insufficiently determined, to determine the brightness of the frequency distribution ( d, e, f, g) of the brightness in the image section (8) is determined and the tracking of the value-document stack

(10) is controlled as a function of the position (M) of the frequency distribution and / or as a function of the width (S) of the frequency distribution.

10. The method as claimed in claim 9, characterized in that the tracking of the value-document stack is stopped on the basis of the brightness determined in the image section under the condition or the tracking speed is reduced on the condition that the mean value (M) of the frequency distribution in the image section ( 8) exceeds a predetermined threshold (T).

A method according to claim 9 or 10, characterized in that the tracking of the value document stack is stopped on the basis of the brightness detected in the image section under the condition or its tracking speed is reduced under the condition that the width (S) of the frequency distribution in the image section ( 8) is below a predetermined width limit (S *).

12. The method according to any one of the preceding claims, characterized in that the tracking, which was stopped due to the determined brightness or whose speed was reduced due to the determined brightness remains unchanged until, in a later recorded image section (8) again a number (K) can be determined at value document edges.

13. Device for controlling the tracking of a value document stack (10) from which the value documents are to be separated, comprising:

an image sensor (1) for taking an image of one side of the document of value document (10),

- An evaluation device (4) for evaluating the recorded

Image which is designed to evaluate the image of the page of the document of value document in order to recognize the edges of the individual value documents in an image section (8) of the image and to determine a number (K) of value document edges in the image section (8),

- A control device (21) for controlling the tracking of the value document stack in dependence on the number (K) of the value document edges, which has determined the evaluation device (4) in the image section (8),

characterized in that - the evaluation device (4), if it can not or only insufficiently determine the number (K) of value document edges when evaluating the recorded image in the image section (8), additionally determines a brightness of the image in this image section (8), and

- That the control device (21) controls the tracking of the value document stack (10) for the value documents mapped in this image section (8) as a function of the brightness determined in this image section (8). 14. The device according to claim 13, characterized in that, the control device (21) is adapted to control the tracking of the value document stack (10) according to the method of any one of claims 1 to 12. 15. Separation device (30) for separating value documents from a value-document stack, which is designed to singulate the value documents from the value-document stack and which has a device for controlling the tracking of the value-document stack according to one of claims 13 to 14.

16. Device (100) for processing value documents, which has a separating device according to claim 15.