EP2631881A1

EP2631881A1 - Banknote double-note detection method and device and automated terminal

Info

Publication number: EP2631881A1
Application number: EP11833831.8A
Authority: EP
Inventors: Peng Tao; Chunkai Xu; Chuntao Wang; Weiwei Xu
Original assignee: Shandong New Beiyang Information Technology Co Ltd
Current assignee: Shandong New Beiyang Information Technology Co Ltd
Priority date: 2010-10-19
Filing date: 2011-10-17
Publication date: 2013-08-28
Also published as: CN102456246B; EP2631881A4; WO2012051925A1; CN102456246A

Abstract

The invention provides a method and device for detecting overlapped banknotes and a self-service terminal. The method for detecting overlapped banknotes comprises: detecting a security thread on a banknote to be detected to obtain security thread characteristics data; determining whether the security thread characteristics data matches a first predetermined condition; and, in the condition that the security thread characteristics data does not match the first predetermined condition, determining that banknotes are overlapped. The detection method and device can easily detect and determine whether banknotes are overlapped and thus improve the accuracy of detection.

Description

Field of the Invention

The invention relates to the field of banknotes detection, and in particular to a method and device for detecting overlapped banknotes and a self-service terminal.

Background of the Invention

Cash transaction device (self-service terminal) receives banknotes continuously, particularly the Automatic Teller Machine (ATM) used for bank services and the Ticket Vending Machine (TVM) used in a railway system need to identify each kind of banknotes. Due to different surface conditions of banknotes and the impact of climate conditions, it is common that two or more banknotes stick together; if it can not be identified accurately whether banknotes are overlapped, a serious error would be caused.
A common method to identify whether banknotes are overlapped is to detect overlapped banknotes by using the thickness of banknotes, for example, detect the thickness of the banknotes with a Hall element or an ultrasonic sensor. However, the method that identify whether banknotes are overlapped by detecting only the thickness of banknotes has a detection error, for example, the contaminated degree of banknotes such as dust sticking to the banknote surfaces, and the usage condition of banknotes such as the wearing out degree of banknotes would affect the accuracy of the detection on overlapped banknotes with the thickness of banknotes detection method.
Another common method to identify overlapped banknotes is to detect whether banknotes are overlapped by detecting the intensity of transmitted light, such as a detection method provided by an American patent US6,082,732 , in which whether banknotes are overlapped is detected by comparing whether the intensity of transmitted light is greater than a threshold value. However, this method can only detect whether the banknotes are overlapped in medium; due to colour difference of different banknotes and usage conditions of different banknotes, accuracy of overlapped banknotes detection can not be ensured if only using the intensity of the light transmitted character in banknotes.

Summary of the Invention

The invention is provided in view of the problem in relevant art that accuracy can not be ensured during the detection on whether banknotes are overlapped; therefore, the main purpose of the invention is to provide a method and device for detecting overlapped banknotes and a self-service terminal to solve the above problem.
In order to achieve the purpose above, according to one aspect of the invention, a method for detecting overlapped banknotes is provided, which comprises: detecting a security thread on a banknote to be detected to obtain security thread characteristics data; determining whether the security thread characteristics data matches a first predetermined condition; and, determining that the banknotes are overlapped in the condition that the security thread characteristics data does not match the first predetermined condition.
In order to achieve the purpose above, according to another aspect of the invention, a device for detecting overlapped banknotes is provided, which comprises: a security thread detector configured to detect a security thread on a banknote to be detected to obtain security thread characteristics data; a memory configured to store reference data of the banknote to be detected; and a controller configured to determine whether the security thread characteristics data matches a first predetermined condition according to the reference data, and to determine that banknotes are overlapped in the condition that the security thread characteristics data does not match the first predetermined condition.
In order to achieve the purpose above, according to another aspect of the invention, a self-service terminal is provided, which comprises the device for detecting overlapped banknotes provided by the invention.
With the invention, by detecting the security thread on the banknote to be detected to obtain security thread characteristics data, and by determining whether the security thread characteristics data matches the first predetermined condition, it is determined that banknotes are overlapped in the condition that the security thread characteristics data does not match the first predetermined conditions. Since the detection on whether banknotes are overlapped using the security thread on the banknotes would not be impacted by the color and the wearing out degree of the banknotes, the problem in relevant art that accuracy can not be ensured during the detection on whether banknotes are overlapped is solved. Thus, the detection on whether banknotes are overlapped can be conveniently performed and the accuracy of banknote detection is improved.

Brief Description of the Drawings

For a better understanding of the invention, accompanying drawings described hereinafter are provided to constitute one part of the application; the schematic embodiments of the invention and the description thereof are used to illustrate the invention but to limit the invention improperly. In the accompanying drawings:

Fig. 1 shows a schematic diagram of a device for detecting overlapped banknotes according to the embodiment of the invention;
Fig. 2 shows a flowchart of a method for detecting overlapped banknotes according to the embodiment of the invention;
Fig. 3 shows a flowchart of a preferred embodiment of the method for detecting overlapped banknotes according to the invention;
Fig. 4 shows a flowchart of a detection step about image size consistency detection of the method for detecting overlapped banknotes according to the invention;
Fig. 5 shows a flowchart of a detection step about security thread characteristics consistency detection of the method for detecting overlapped banknotes according to the invention;
Fig. 6 shows a flowchart of a detection step about transmitted light intensity consistency detection of the method for detecting overlapped banknotes according to the invention;
Fig. 7a shows a diagram of the signal wave of a double-security-thread detection according to the invention;
Fig. 7b shows a diagram of the signal wave of security threads when banknotes are totally overlapped according to the invention;
Fig. 8a shows a diagram of a banknote in the invention; and
Fig. 8b shows a diagram of a transmitted light wave of the banknote shown in Fig. 8a.

Detailed Description of the Embodiments

It should be noted that the embodiments in the application and the characteristics of the embodiments can be combined if no conflict is caused. The invention is described below in detail by reference to the accompanying drawings in conjunction with embodiments.
Fig. 1 shows a schematic diagram of a device for detecting overlapped banknotes according to the embodiment of the invention. Description is provided below in conjunction with Fig. 1.
As shown in Fig. 1, an overlapped banknotes detection device 10 comprises: a controller 12, a security thread detector 16, and a memory 20 for storing various data.
The security thread detector 16 is configured to detect the security thread on a banknote, to output a security thread detection signal of the banknote and to determine the number of security threads according to the security thread signal of the banknote. The common security detector is a magnetic detection device, such as magneto-sensitive head, magneto-resistive head and the like. The security thread detector 16 detects the security thread on the banknote to be detected to obtain security thread characteristics data.
The memory 20 may comprise a RAM memory, a FLASH memory and the like, wherein the RAM memory is configured to temporarily store various data processed in the overlapped banknotes detection device, such as type of the banknote to be detected, size of a scanned image, number of security threads, transmitted light data and so on; the FLASH memory is configured to store reference data of the banknote to be detected, for example, to store reference size of each kind of banknotes, security thread number of each kind of banknotes, threshold value of transmitted light intensity of each kind of banknotes and the like.
The controller 12 is configured to control the security thread detector 16 to detect the security thread on the banknote to be detected, and to process relevant data. The controller 12 can determine whether the security thread characteristics data matches a first predetermined condition according to the reference data, and determine that the banknotes are overlapped in the condition that the security thread characteristics data does not match the first predetermined condition.
The overlapped banknotes detection device 10 further comprises an acquisition mechanism which is configured to acquire size of the banknote to be detected. The acquisition mechanism can further comprise an image scanner 14which is configured to scan the banknote to be detected to acquire scanned image data of the banknote and to determine the size of the scanned image according to the scanned image data. The common image scanner is a Charge Coupled Device (CCD), a Contact Image Sensor (CIS) or a CMOS image sensor. Preferably, the image scanner 14 scans the banknote to be detected before the security thread detector 16 detects the security thread on the banknote to be detected, so that the controller determines whether the size of the banknote to be detected matches a second predetermined condition. In the condition that the size of the banknote to be detected does not match the second predetermined condition, it is directly determined that banknotes are overlapped, and no further detection is needed, and thus the operation process is simplified. In the condition that the size of the banknote to be detected matches the predetermined condition, the security thread detector is controlled to detect the security thread on the banknote to be detected.
The overlapped banknotes detection device 10 may also comprise a transmitted light detector 18, which comprises a light emitter, a light receiver and the like. The light emitter is configured to irradiate the banknote, and the light receiver is configured to receive the light transmitted through the banknote and to output transmitted light data. The common light emitter is an infrared light emitter, and the common light receiver is an infrared light receiver.
Hereinafter, an overlapped banknotes detection method provided by the embodiment of the invention is described. The detection method provided by the embodiment of the invention can be implemented by, but not limited to, the overlapped banknotes detection device provided above.
Fig. 2 shows a flowchart of an overlapped banknotes detection method according to the embodiment of the invention. As shown in Fig. 2, the method comprises the following steps:

Step S102: detecting a security thread on a banknote to be detected to obtain security thread characteristics data.

The security thread characteristics data may comprise the number of security threads and the signal intensity of the security thread.
Step S104: determining whether the security thread characteristics data matches a first predetermined condition.
In step S104, determining whether the security thread characteristics data matches the first predetermined condition may be achieved by determining whether the number of security threads or the signal intensity of the security thread meets the predetermined condition, wherein the first predetermined condition is set according to the number of security threads on a single banknote or the signal intensity of the security thread on a single banknote.
Preferably, when the security thread characteristics data comprises the number of security threads and the signal intensity of the security thread, step S104 comprises: determining whether the number of security threads is equal to a preset number, wherein the preset number is set according to the security thread data of a single banknote; if the number of security threads is equal to the preset number, determining whether the signal intensity of the security thread is consistent with a preset signal intensity of the security thread, wherein the preset signal intensity of the security thread is set according to the signal intensity of the security thread on a single banknote; if the signal intensity of the security thread is consistent with the preset signal intensity of the security thread, it is determined that the security thread characteristics data matches the first predetermined condition. Through the detection on the number of security threads and the signal intensity of the security thread, that is, taking the number of security threads and the signal intensity of the security thread as the security thread characteristics data to compare with the first predetermined condition, not only the operation is simplified, but also the accuracy of detection can be improved.
It should be noted that the order of determining whether the number of security threads is equal to the preset number and determining whether the signal intensity of the security thread is consistent with the preset signal intensity of the security thread could be arbitrary.
Step S106: in the condition that the security thread characteristics data does not match the first predetermined condition, it is determined that the banknote to be detected has a banknote overlapped thereon.
If the detected security thread characteristics data does not match the preset condition, it is indicated that the banknotes are overlapped.
Preferably, before detecting the security thread on the banknote to be detected, the method further comprises: acquiring size of the banknote to be detected; determining whether the size of the banknote to be detected matches a second predetermined condition according to the size of the banknote to be detected, wherein the second predetermined condition is set according to the size of a single banknote; and, in the condition that the size of the banknote to be detected does not match the second predetermined condition, it is determined that banknotes are overlapped; wherein, in the condition that the size of the banknote to be detected matches the second predetermined condition, the security thread on the banknote to be detected can be detected sequentially. In this embodiment, it is determined whether banknotes are overlapped through determining the size of the banknote to be detected first; and the security thread on the banknote to be detected is detected only when it can not be determined whether banknotes are overlapped through determining the size of the banknote to be detected. Thus, detection efficiency is improved and unnecessary detection steps are avoided.
Acquiring the size of the banknote to be detected mentioned above comprises: scanning the banknote to be detected to acquire a scanned image of the banknote to be detected; and processing the scanned image to obtain the size of the banknote to be detected. Determining whether the size of the banknote to be detected matches the second predetermined condition according to the size of the banknote to be detected comprises: obtaining the type of the banknote to be detected according to the scanned image; looking up a reference size corresponding to the type of the banknote, wherein the reference size comprises reference length and reference width; when the size of the scanned image is not greater than the reference size, it is determined that the size of the banknote to be detected matches the second predetermined condition; when the size of the scanned image is greater than the reference size, it is determined that the size of the banknote to be detected does not match the second predetermined condition. Preferably, in the condition that the security thread characteristics data matches the first predetermined condition, the above method can further comprise: irradiating the banknote to be detected to acquire transmitted light data of the banknote to be detected; determining whether the transmitted light data matches a third predetermined condition, wherein the third predetermined condition is set according to the transmitted light data of a single banknote; and, in the condition that the transmitted light data does not match the third predetermined condition, it is determined that banknotes are overlapped. In this embodiment, the size of the banknote, the security thread on the banknote and the transmitted light through the banknote to be detected are detected in order, if any one of the three does not match the condition, it is determined that banknotes are overlapped; therefore, detection accuracy on whether the banknote to be detected has a banknote overlapped is greatly improved.
In the above, irradiating the banknote to be detected to acquire the transmitted light data of the banknote to be detected comprises: irradiating different areas on the banknote to be detected to acquire the transmitted light data of different areas on the banknote to be detected; and weighted-averaging the transmitted light data of different areas on the banknote to be detected to obtain a weighted average of the transmitted light data. Determining whether the transmitted light data matches the third predetermined condition comprises: determining whether the weighted average of the transmitted light data matches the third predetermined condition. Through the calculation of weighted average, detection accuracy is further improved.
Fig. 3 shows a flowchart of a preferred embodiment of the method for detecting overlapped banknotes according to the invention, and the detailed process is as follows:

Step S10: performing image size detection to acquire size of the banknote to be detected.

For example, an image scanner 14 scans the banknote to be detected to acquire scanned image data of the banknote; a controller 12 processes the scanned image data to obtain size of the scanned image, such as image length, image width and the like. Besides the image scanning method, other ways also can be adopted to perform the size detection.
Step S20: determining whether the size meets a banknote size requirement.
It is determined whether the size of the banknote to be detected matches the second predetermined condition mentioned above.
For example, the controller 12 compares the image size (such as image length and width) of the banknote to be detected obtained by the image scanner 14 in Step S10 with the size (that is, length and width of a single banknote) of the same type of banknote stored in the memory 20, to determine whether the image size of the banknote to be detected meets the banknote size requirement. If the image size of the banknote to be detected does not meet the banknote size requirement, go to Step S74; if the image size of the banknote to be detected meets the banknote size requirement, go to Step S30 to perform the following process.
Step S30: detecting a security thread.
A security thread detector 16, such as magneto-sensitive head, magneto-resistive head and the like, detects the security thread on the banknote to be detected and outputs a security thread signal. The controller 12 processes the security thread signal to determine the security thread characteristics data of the banknote to be detected, such as number of security threads, intensity of the security thread signal and the like.
Step S40: determining whether the security thread meets a security thread characteristics requirement.
It is determined whether the security thread characteristics data of the banknotes to be detected matches the first predetermined condition mentioned above.
The controller 12 compares the security thread characteristics data (such as the number of security threads and intensity of a security thread signal) of the banknotes to be detected obtained by the security thread detector 16 in Step S30 with the preset security thread characteristics data (that is, security thread number and security thread signal intensity of a single banknote) stored in the memory 20, to determine whether the banknote to be detected meets the security thread characteristics requirement. If the banknote to be detected does not meet the security thread characteristics requirement, go to Step S74; if the banknote to be detected meets the security thread characteristics requirement, go to Step S50 to perform the following process.
Step S50: detecting transmitted light.
A light emitter in a transmitted light detector 18 irradiates partial area on the banknote; a light receiver receives the light transmitted through the banknote and outputs transmitted light data of the banknote. The common light emitter and light receiver are an infrared light emitter and an infrared light receiver respectively.
Step S60: determining whether the transmitted light meets a light intensity requirement.
It is determined whether the transmitted light data of the banknote to be detected matches the third predetermined condition mentioned above.
The controller 12 analyzes the transmitted light data acquired in Step S50 and calculates a weighed average of the transmitted light data (called weighed average hereinafter), wherein the weighed average reduces the impact on the light transmission of the banknote from areas on the banknote such as watermarks, stripes, patterns and security threads, and can better reflect the inversely proportional relationship between the light transmission and the thickness of the banknote. Since the transmitted light data is larger when the transmitted light has a higher intensity and the transmitted light data is smaller when the transmitted light has a lower intensity, a weighted average used for representing transmitted light data size can be used to represent the transmitted light intensity of the banknote (called light intensity hereinafter). If the transmitted light meets the light intensity requirement, go to Step S72; if the transmitted light does not meet the light intensity requirement, go to Step S74.
Step S72: it is determined that banknotes are not overlapped.
When the image size, the security thread characteristics and the transmitted light intensity of the banknote to be detected all meet the requirement, it is indicated that the banknote to be detected is a single banknote.
Step S74: it is determined that banknotes are overlapped.
When any one of the image size, the security thread characteristics and the transmitted light intensity of the banknote to be detected does not meet the requirement, it is indicated that banknotes are overlapped.
In this embodiment, by detecting the size of the scanned image, banknotes overlapping phenomenon when banknotes are not directly aligned can be detected out; by detecting the security thread consistency of the banknote, the banknotes overlapping phenomenon can be detected out except the security thread aligned directly; by detecting the thickness change of banknote through determining the transmitted light intensity of the banknote, the banknotes overlapping phenomenon can be detected out. By detecting multiple characteristics of the banknote, the problem that the accuracy of single characteristic detection is low and the detection result is instable is solved, and the reliability of the detection result is guaranteed.
The method for determining whether the image size of the banknote to be detected meets a banknote size requirement is illustrated below in conjunction with Fig. 4; and the method comprises:

Step S22: reading the banknote size of a single banknote stored in a memory.

A controller identifies the type of the banknote to be detected by processing detected data such as scanned image data, wherein the specific process of banknote identification does not belong to this invention and no further description is provided here. According to the identified type, the controller reads the size of a single banknote of this type stored in the memory 20, including a preset length and a preset width of a single banknote.
After this step, it is determined whether the size of the banknote to be detected matches the second predetermined condition mentioned above according to the size of the banknote to be detected; for example, it can be implemented by executing the following Step S24 and Step S26.
Step S24: determining whether the image length of the banknote to be detected is greater than the preset length of a single banknote.
The controller 12 processes the scanned image of the banknote to be detected, for example, the controller 12 determines image edge using the gray difference of image edge to obtain the image size of the banknote to be detected, such as image length and image width; then the controller 12 compares the image length of the banknote to be detected with the preset length of a single banknote; if the image length of the banknote to be detected is greater than the preset length of a single banknote, it is indicated that the image size of the banknote to be detected does not meet the size requirement of a single banknote, then go to Step S74 in the above embodiment; otherwise, execute Step S26 to perform the following process.
Step S26: determining whether the image width of the banknote to be detected is greater than the preset width of a single banknote.
The controller 12 compares the image width of the banknote to be detected with the preset width of a single banknote; if the image width of the banknote to be detected is greater than the preset width of a single banknote, it is indicated that the image size of the banknote to be detected does not meet the size requirement of a single banknote, then go to Step S74 in the above embodiment; otherwise, go to Step S30 in the above embodiment.
The execution order of Step S24 and Step S26 can be adjusted as needed, for example, Step S26 can be executed before Step S24, or Step S24 and Step S26 can be executed simultaneously; no matter in which order the two steps are executed, the purpose for detecting whether the image size of the banknote to be detected meets the size requirement of a single banknote can be achieved.
When two or more banknotes are overlapped, since it is difficult for the overlapped banknotes align in length and/or width, after acquiring the image size, which includes image length and width, of the banknote to be detected, by comparing the image length and/or image width of the banknote to be detected with the preset length and/or preset width of a single banknote of the same type, it can be determined whether banknotes are overlapped according to the outline size.
The method for determining whether the security thread characteristic of the banknote to be detected meets a requirement is illustrated below in conjunction with Fig. 5; and the method comprises:

Step S42: determining whether the number of security threads on the banknote to be detected is equal to a preset number.

A controller compares the number of security threads on the banknote to be detected with the preset number of security threads on the same type of banknote stored in a memory 20; if the two numbers are equal, it is indicated that the banknote to be detected meets the number requirement of security thread on a single banknote, then go to Step S44; otherwise, it is indicated that the banknote to be detected does not meet the number requirement of security thread on a single banknote, then go to Step S74 in the above embodiment.
Step S44: determining whether the signal intensity of the security thread on the banknote to be detected is consistent with a preset signal intensity of the security thread.
The controller compares the signal intensity of the security thread on the banknote to be detected with the signal intensity of the security thread on the same type of banknote preset in the memory 20; if the signal intensity is consistent, it is indicated that the banknote to be detected meets the requirement of security thread signal intensity of a single banknote, then go to Step S50 in the above embodiment; if the signal intensity is inconsistent, it is indicated that the banknote to be detected does not meet the requirement of security thread signal intensity of a single banknote, then go to Step S74 in the above embodiment.
It should be noted that only one or both of Step S42 and Step S44 may be executed ; when both Step S42 and Step S44 are executed, the execution order is changeable.
Since the position of security thread is changeable within a range on each banknote, when two or more banknotes are overlapped, it is difficult for the security threads of each banknote to overlap totally. Therefore, by acquiring the security thread characteristic of the banknote to be detected and comparing the security thread characteristic of the banknote to be detected with the security thread characteristic of a single banknote of the same type, it can be determined whether banknotes are overlapped.
In the embodiment of the invention, the number of security threads can be determined through the number of security thread signals detected by the security thread detector 16. For example, if the number of security threads on a single banknote of a certain type is one, when multiple security thread signals are detected out, it is indicated that banknotes are overlapped. For example, when the security thread detector 16 detects two security thread signals 30, 32 as shown in Fig. 7a, it can be determined that the banknote to be detected has at least two security threads 34, 36, that is, at least two banknotes are overlapped. However, if only one security thread signal is detected for the banknote to be detected, for example, the signal 40 shown in Fig. 7b detected by the security thread detector 16, it can not be determined that the banknote is a single banknote, because when two or more banknotes are overlapped, the respective security thread might be totally overlapped in extreme conditions. Therefore, the number of security threads needs to be further determined according to the intensity of the security thread signal. Only when both number and intensity of security thread signal detected for the banknote to be detected are consistent with preset values, it can be determined that the number of security threads on the banknote to be detected is consistent with the preset value. Due to the impact caused by the difference of the wearing out degree and version of banknotes, there is a considerable difference between the signal intensity of the security threads on the same type of banknote; therefore, according to the detection based on signal intensity a relatively bigger deviation can be caused. Generally, only the security thread signal number of the banknote to be detected is adopted to determine whether the security thread characteristic meets the requirement of a single banknote; meanwhile, other characteristics of the banknote to be detected are detected to exclude the condition that the security threads of two or more banknotes are totally overlapped.
The method for determining whether the transmitted light intensity of the banknote to be detected meets a light intensity requirement is illustrated below in conjunction with Fig. 6; and the method comprises:

Step S52: calculating a weighted average.

In order to reduce the impact on the light transmission of the banknote to be detected from an abnormal light transmission area, in this step, the transmitted light data detected in Step S50 is further processed to obtain a weighted average of the transmitted light data, that is, the weighted average. The abnormal light transmission area includes an easily transmitted area (for example, area of the banknote without pattern or texture) and a difficultly transmitted area (for example, security thread, patterns with conspicuous color and the like), and the weight of the light data corresponding to the easily transmitted area and the difficultly area is relatively smaller.
Step S54: determining whether the weighted average is greater than a light intensity threshold value.
Since the thicker the banknote is, the worse the light transmission is, and the thinner the banknote is, the better the light transmission is, it can be determined whether the banknote to be detected meets the light intensity requirement through the weighted average that can represent the thickness of the banknote. If the weighted average is greater than the light intensity threshold value corresponding to the same type of banknote preset in the memory 20, it is indicated that the transmitted light intensity of the banknote to be detected meets the light intensity requirement of a single banknote, then go to Step S72 (refer to Fig. 3); if the weighted average is less than the light intensity threshold value, it is indicated that the transmitted light intensity of the banknote to be detected does not meet the light intensity requirement of a single banknote, then go to Step S74 (refer to Fig. 3).
The method for determining the light intensity threshold value is illustrated below in conjunction with Fig. 8a and Fig. 8b. Since the dust sticking to banknote surfaces reduces the light transmission performance of the banknote after the banknote is used for a period, the light transmission of an old banknote is worse than that of a new banknote; meanwhile, since the thicker the banknote is, the worse the light transmission is, and the thinner the banknote is, the better the light transmission is, the light transmission of a single banknote is higher than that of two banknotes. Based on the principle above, the light transmission performance goes in turn in an order from high to low: a single new banknote, a single old banknote, two new banknotes and two old banknotes. Therefore, if a preset light intensity threshold value can distinguish the light transmission difference of a single old banknote and two new banknotes, it can be determined whether the banknotes are overlapped with the light intensity threshold value as a reference.
An infrared light emitter in a transmission detector 18 is used to irradiate the area 52 of a banknote 50 to be detected along the direction 54 shown in Fig. 8a. An infrared light receiver is used to receive the light transmitted through the banknote and output the transmitted light data of the banknote. The curve of the infrared transmitted light data of a single old banknote is the curve 60 shown in Fig. 8b, while the curve of the infrared transmitted light data of two new banknotes is the curve 62 shown in Fig. 8b. In Fig. 8b, the horizontal axis represents the length of banknote, while the vertical axis represents the size of transmitted light data. From the wave of the curves 60, 62, it can be seen that most data on the curve 60 is bigger than the data on the curve 62 and there is an intersection between the two curves, thus, the two curves can not be distinguished from the size of the transmitted light data directly. Therefore, it is needed to calculate the weighted average of the transmitted light data through a formula $A = \sum_{i = 1}^{n} w_{i} x_{i}, \sum_{i = 1}^{n} w_{i} = 1,$
(w_i ≥ 0, i = 1, ..., n), where A represents the weighted average of the transmitted light data, x_i represents the transmitted light data and w_i represents the weight corresponding to the transmitted light data x_i, wherein the sum of all weights is equal to 1. By reducing the weight corresponding to the maximum data and the minimum data of the transmitted light data, the impact on the weighted average A from the maximum data and the minimum data is reduced. As shown in Fig. 8b, the weighted average of the curve 60 is straight line 64, while the weighted average of the curve 62 is straight line 66. As shown in Fig. 8b, it can be seen that there is a distance between the straight line 64 and the straight line 66. A straight line 68 between the straight line 64 and the straight line 66 can be used to distinguish the curve 60 and the curve 62, that is, the weighted average corresponding to the straight line 68 serves as the light intensity threshold value is used for determining whether the transmitted light intensity meets the requirement. If the weighted average of the banknote to be detected is above the straight line 68, it is indicated that the weighted average of the banknote to be detected is the weighted average of a single banknote, that is, the banknote to be detected is a single banknote; if the weighted average of the banknote to be detected is below the straight line 68, it is indicated that the weighted average of the banknote to be detected is the weighted average of two or more banknotes, that is, the banknote to be detected is multiple banknotes.
Since two or more banknotes are overlapped causes the increase in banknote thickness, by acquiring the weighted average of the banknote to be detected and comparing it with a reference threshold value, it can be determined whether banknotes are overlapped. By analyzing the transmitted light data of the banknote, instead of directly analyzing the thickness of the banknote, the impact on banknote thickness detection result caused by banknote medium wearing out and dust sticking to banknote surfaces can be avoided, and reliability of the detection result is guaranteed. By eliminating the scanned data corresponding to the easily transmitted area that is sensitive to transmitted light and the difficultly transmitted area that is insensitive to transmitted light, the average of the transmitted data can accurately reflect the thickness of the banknote, thus, accuracy of the detection result is guaranteed.
The execution order of the image size detection, the security thread characteristics detection and the transmitted light intensity detection of a banknote can be set as needed. When the detection result of any one of the above three does not meet a predetermined condition, it is indicated that banknotes are overlapped; when the detection results of all of the three meet predetermined conditions, it is indicated that the banknote to be detected is a single banknote. Since the probability of outline being not overlapped totally and security thread being not overlapped accurately is relatively higher when several banknotes are overlapped, thus, whether the banknotes are overlapped can be quickly determined by judging the size or security thread characteristics of banknote to be detected. Therefore, the detection order provided by the embodiment of the invention is a preferred detection order.
Through the combination of the detections on the image size, the security thread characteristics and the transmitted light intensity of the banknote to be detected, it can be accurately determined whether the banknotes are overlapped; thus, the impact on the detection result from the usage condition and the wearing out degree of the banknote is avoided, and the stability and reliability of detection are improved.
The embodiment of the invention also provides a self-service terminal, such as Automatic Teller Machine (ATM), Cash Deposit Machine (CDM) or Ticket Vending Machine (TVM), wherein this self-service terminal has the device for detecting overlapped banknotes provided in any embodiment above.
The above are only the preferred embodiments of the invention and not intended to limit the invention. For those skilled in the art, various modifications and changes can be made to the invention. Any modification, equivalent substitute and improvement made within the spirit and principle of the invention are deemed to be included within the scope of protection of the invention.

Claims

A method for detecting overlapped banknotes, characterized by comprising:
detecting a security thread on a banknote to be detected to obtain security thread characteristics data;

determining whether the security thread characteristics data matches a first predetermined condition; and

determining that banknotes are overlapped in the condition that the security thread characteristics data does not match the first predetermined condition.
The method according to claim 1, characterized in that
before detecting the security thread on the banknote to be detected, the method further comprises:
acquiring size of the banknote to be detected; and

determining whether the size of the banknote to be detected matches a second predetermined condition according to the size of the banknote to be detected;

wherein, in the condition that the size of the banknote to be detected does not match the second predetermined condition, determining that banknotes are overlapped; in the condition that the size of the banknote to be detected matches the second predetermined condition, detecting the security thread on the banknote to be detected.
The method according to claim 2, characterized in that
acquiring the size of the banknote to be detected comprises: scanning the banknote to be detected to acquire a scanned image of the banknote to be detected; and processing the scanned image to obtain the size of the banknote to be detected;
determining whether the size of the banknote to be detected matches the second predetermined condition according to the size of the banknote to be detected comprises:
obtaining the type of the banknote to be detected according to the scanned image; looking up a reference size corresponding to the type of the banknote, wherein the reference size comprises reference length and reference width; and determining whether the size of the scanned image is greater than the reference size;
wherein, when the size of the scanned image is not greater than the reference size, it is determined that the size of the banknote to be detected matches the second predetermined condition; when the size of the scanned image is greater than the reference size, it is determined that the size of the banknote to be detected does not match the second predetermined condition.
The method according to claim 1, characterized in that the security thread characteristics data comprises the number of security threads; determining whether the security thread characteristics data matches the first predetermined condition comprises:
determining whether the number of security threads is equal to a preset number; and

in the condition that the number of security threads is equal to the preset number, determining that the security thread characteristics data matches the first predetermined condition.
The method according to claim 1, characterized in that the security thread characteristics data comprises a signal intensity of the security thread, determining whether the security thread characteristics data matches the first predetermined condition comprises:
determining whether the signal intensity of the security thread is consistent with a preset signal intensity of the security thread; and

in the condition that the signal intensity of the security thread is consistent with the preset signal intensity of the security thread, determining that the security thread characteristics data matches the first predetermined condition.
The method according to claim 1, characterized in that in the condition that the security thread characteristics data matches the first predetermined condition, the method further comprises:
irradiating the banknote to be detected to acquire transmitted light data of the banknote to be detected;

determining whether the transmitted light data matches a third predetermined condition;
and

determining that banknotes are overlapped in the condition that the transmitted light data does not match the third predetermined condition.
The method according to claim 6, characterized in that
irradiating the banknote to be detected to acquire the transmitted light data of the banknote to be detected comprises: irradiating different areas on the banknote to be detected to acquire the transmitted light data of the different areas on the banknote to be detected; weighted-averaging the transmitted light data of the different areas on the banknote to be detected to obtain a weighted average of the transmitted light data;
determining whether the transmitted light data matches the third predetermined condition comprises: determining whether the weighted average of the transmitted light data matches the third predetermined condition.
A device for detecting overlapped banknotes, characterized by comprising:
a security thread detector, configured to detect a security thread on a banknote to be detected to obtain security thread characteristics data;

a memory, configured to store reference data of the banknote to be detected; and

a controller, configured to determine whether the security thread characteristics data matches a first predetermined condition according to the reference data, and to determine that banknotes are overlapped in the condition that the security thread characteristics data does not match the first predetermined condition.
The device according to claim 8, characterized by further comprising:
an acquisition mechanism, configured to acquire size of the banknote to be detected;

wherein the controller is further configured to determine whether the size matches a second predetermined condition according to the reference data, to determine that banknotes are overlapped in the condition that the size of the banknote to be detected does not match the second predetermined condition, and to control the security thread detector to detect the security thread on the banknote to be detected in the condition that the size of the banknote to be detected matches the predetermined condition.
The device according to claim 8, characterized by further comprising a transmitted light detector, and the transmitted light detector comprises:
a light emitter, configured to emit light to irradiate the banknote to be detected; and

a light receiver, configured to receive the light transmitted through the banknote to be detected and to output transmitted light data;

wherein the controller is further configured to determine whether the transmitted light data matches a third predetermined condition, and to determine that banknotes are overlapped in the condition that the transmitted light data does not match the third predetermined condition.
A self-service terminal, characterized by comprising the device for detecting overlapped banknotes in any one of claims 8 to 10.
The self-service terminal according to claim 11, characterized in that the self-service terminal is an Automatic Teller Machine or a Ticket Vending Machine.