Bill handling device, foreign matter detection method, and foreign matter detection program

Abstract

Provided is a bill handling device, a foreign matter detection method, and a foreign matter detection program for improving the accuracy of foreign matter detection. A light source (103) emits light onto a bill (B). A camera (105) captures a surface image of the bill (B) on the basis of reflection of the light emitted from the light source (103). A data conversion unit converts the surface image captured by the camera (105) into gradation data. A measurement unit (121) measures a thickness of the bill (B). A determination region specifying unit specifies a determination region including regions having different thicknesses in the bill (B) on the basis of a measurement result from the measurement unit (121). A foreign matter detection unit detects foreign matter by comparing the gradation data for the determination region in the bill (B) with gradation data for a determination region in a reference bill.

Description

Banknote handling device, foreign object detection method, and foreign object detection program

[0001] The present invention relates to a banknote handling machine, a foreign object detection method, and a foreign object detection program.

[0002] Many banknote handling machines that automatically process banknote deposits and withdrawals through customer operation are installed in financial institutions, etc. Banknote handling machines have a banknote validation unit that determines the denomination and authenticity of banknotes and detects foreign matter attached to banknotes, etc. Banknotes that are determined to be defective or damaged by the banknote validation unit are excluded from further processing or are returned, etc.

[0003] The banknote validator generally uses one or a combination of a thickness sensor, an optical sensor (contact image sensor (CIS)), and a magnetic sensor to determine the authenticity of banknotes and detect foreign objects. In particular, thickness sensors and optical sensors are often used to detect tape attached to banknotes.

[0004] When a thickness sensor is used, the banknote handling system determines that a banknote has a foreign object attached when an output from the thickness sensor exceeds a threshold value. When an optical sensor is used, the banknote handling system determines whether a foreign object is attached to the banknote using the ratio of light transmitted through the banknote.

[0005] Another proposed technology detects foreign objects by irradiating a banknote with terahertz light and determining its thickness from the phase difference between the waves reflected from the front and back. Another proposed technology involves irradiating a banknote with infrared light, receiving the distribution of reflected light using a photodiode element, and identifying foreign objects based on the ratio of the amount of light received by the element with the greatest amount of light to that of the adjacent element. Another proposed technology involves irradiating a piece of paper with light, detecting the reflected light with a photoreceiver, and determining whether it is good or bad based on its glossiness.

[0006] JP 2009-300279, JP 11-173997, JP 3-102491

[0007] However, when detecting foreign objects using a thickness sensor, the change in thickness is small even when a thinner tape is attached compared to conventional methods, making it difficult to distinguish it from wrinkles or folds in the banknote, and setting a strict threshold can lead to incorrect detection. Therefore, it is difficult to detect thin tape using foreign object detection technology using a thickness sensor.

[0008] When detecting foreign objects using optical sensors, the reflectance and transmittance of a banknote covered with transparent cellophane tape are nearly the same as when no transparent tape is applied, and the changes are included in the dirt and other factors that occur during the banknote's circulation, making detection difficult. Furthermore, detecting transparent tape requires various light sources. For example, if sensors are arranged in a row to inspect the entire banknote, the number of sensors increases, making it difficult to secure the space for placement.

[0009] Furthermore, even with technology that detects foreign objects by determining thickness from the phase difference of reflected waves, it is difficult to detect foreign objects when the change in thickness is small. Furthermore, with technology that distinguishes foreign objects based on the ratio of the amount of light received by the element with the largest amount of light in the distribution of reflected infrared light to the amount of light received by the adjacent element, thin transparent tape, etc., does not provide adequate reflected light, which can make it difficult to detect foreign objects. The same is true for technology that judges quality based on gloss.

[0010] The disclosed technology has been made in view of the above, and aims to provide a banknote handling device, a foreign object detection method, and a foreign object detection program that improve the accuracy of foreign object detection.

[0011] In one aspect of the banknote handling device, foreign object detection method, and foreign object detection program disclosed herein, a light source irradiates light onto a medium. A camera captures a surface image of the medium based on reflected light from the light source. A data conversion unit converts the surface image captured by the camera into grayscale data. A measurement unit measures the thickness of the medium. A determination target area determination unit determines a determination target area including areas of different thicknesses on the medium based on the measurement results by the measurement unit. A foreign object detection unit detects foreign objects by comparing the grayscale data of the determination target area on the medium with the grayscale data of the determination target area on a reference medium.

[0012] In one aspect, the present invention can improve the accuracy of foreign object detection.

[0013] FIG. 1 is a schematic diagram showing the configuration of a banknote handling apparatus according to an embodiment. FIG. 2 is a diagram showing an overview of thickness detection by a thickness sensor. FIG. 3 is a diagram showing thickness detection by a displacement roller. FIG. 4 is a diagram showing details of the banknote validator and foreign object detector. FIG. 5 is a diagram showing the dependency of glass surface reflectance on the angle of incidence. FIG. 6 is a block diagram of the control unit. FIG. 7 is a diagram showing an overview of photographing the surface of a banknote by a camera. FIG. 8 is a diagram showing an example of gradation values ​​calculated by the data converter. FIG. 9 is a diagram showing an example of gradation values ​​of a judgment target area on a banknote with foreign matter attached and a judgment target area on a reference banknote. FIG. 10 is a diagram showing an example of foreign object detection using a foreign object judgment threshold. FIG. 11 is a diagram showing an example of a similarity calculation result. FIG. 12 is a flowchart of photographing both sides of a banknote by a banknote handling apparatus according to an embodiment. FIG. 13 is a flowchart of foreign object judgment processing by a banknote handling apparatus according to an embodiment. FIG. 14 is a hardware configuration diagram of the control unit.

[0014] The following describes in detail exemplary embodiments of a banknote handling system, a foreign object detection method, and a foreign object detection program disclosed herein with reference to the accompanying drawings. Note that the banknote handling system, the foreign object detection method, and the foreign object detection program disclosed herein are not limited to the following exemplary embodiments.

[0015] 1 is a schematic diagram showing the configuration of a banknote handling device according to an embodiment. In this embodiment, banknotes B are used as an example of paper sheets, but the present invention is not limited to banknotes B. Paper sheets also include, for example, bills, checks, gift certificates, various securities, stock certificates, and other valuable securities.

[0016] As shown in Fig. 1, a banknote handling apparatus 1 according to this embodiment includes a deposit / withdrawal unit 2, a temporary storage unit 3, a plurality of storage units 4, and a reject unit 5. The banknote handling apparatus 1 also includes a foreign object detection unit 11 and a banknote discrimination unit 12. The banknote handling apparatus 1 also includes a transport path 13 for transporting banknotes B, and a control unit 20 that provides overall control of the operation of the banknote handling apparatus 1. Although Fig. 1 illustrates the control unit 20 as being separate from the housing in which the deposit / withdrawal unit 2, temporary storage unit 3, a plurality of storage units 4, and reject unit 5 are provided, it may also be housed within the same housing.

[0017] The deposit / withdrawal unit 2 deposits and withdraws banknotes B to and from users. The temporary storage unit 3 temporarily stores banknotes B deposited in the deposit / withdrawal unit 2. The storage unit 4 stores banknotes B and withdraws them, thereby circulating the banknotes B. The reject unit 5 stores banknotes B with abnormal thickness or length, or banknotes B that are deteriorated or damaged. The transport path 13 is a bidirectional transport path that can transport banknotes B in both directions, excluding the path portion for storing banknotes B in the reject unit 5.

[0018] The banknote validator 12 performs validation such as determining the denomination and authenticity of banknotes B transported from the deposit / withdrawal unit 2 or the temporary storage unit 3, and detecting foreign matter. The banknote validator 12 has a thickness sensor 121, an IN sensor 122, a magnetic sensor 123, a CIS 124, and an OUT sensor 125.

[0019] The thickness sensor 121 measures the amount of displacement in the thickness of each region of the banknote B being transported along the transport path 13. This thickness sensor 121 is an example of a "measuring unit." Since the thickness is determined from the amount of displacement from a reference position, it can be said that the thickness sensor 121 measures the thickness of the banknote B.

[0020] 2 is a diagram showing an overview of measurement of the displacement amount by the thickness sensor. The upper part of the drawing in FIG. 2 shows the displacement roller 130 of the thickness sensor 121 and the banknote B, and the lower part shows the detection result of the thickness sensor 121 for the banknote B.

[0021] In this embodiment, the length of the banknote B in the short-edge direction is 7 cm and the length in the long-edge direction is 16 cm. The thickness sensor 121 according to this embodiment divides the surface of the banknote B into 16 longitudinal sections and 7 transverse sections, each measuring the amount of displacement for each 1 cm square section. Here, the divided sections in Fig. 2 are represented by numbers 1 to 16 assigned along the long-edge direction of the banknote B and numbers 1 to 7 assigned along the short-edge direction.

[0022] The thickness sensor 121 has a plurality of displacement rollers 130 that are arranged in a line perpendicular to the traveling direction D of the banknotes B and across the conveyance path 13. In this embodiment, seven displacement rollers 130 are arranged. That is, each of the seven displacement rollers 130 detects the amount of displacement in a different area with a width of 1 cm in the short side direction. The seven displacement rollers 130 detect the amount of displacement at positions corresponding to numbers 1 to 7 in the short side direction.

[0023] FIG. 3 is a diagram showing thickness detection by the displacement roller. In the graph of FIG. 3, the vertical axis represents the displacement amount detected by the displacement roller 130, and the horizontal axis represents the movement distance of banknote B on the conveyance path 13 based on a specific point in time before it reaches the displacement roller 130. A section 201 before movement distance L1 and a section 204 after movement distance L4 represent a state in which banknote B is not present at the displacement roller 130. In other words, if banknote B is not present, the displacement roller 130 outputs the displacement amounts for sections 201 and 204. Banknote B reaches the position of the displacement roller 130 at the time of movement distance L1 and passes through the position of the displacement roller 130 at the time of movement distance L4. In other words, in section 202, banknote B is present at the measurement position of the displacement roller 130. The displacement amount between movement distance L2 and movement distance L3 is larger than in the other sections of section 202. That is, the range of section 202 other than section 203 has the normal thickness of banknote B, but section 203 is thicker than normal banknote B.

[0024] 2, when the transparent tape 210 is attached to the banknote B, the measurement result of the thickness sensor 121 based on the displacement amounts of the seven displacement rollers 130 shows that the displacement amounts of the divided areas included in the hatched area 212 are large. In other words, the displacement amounts of the divided areas (1,1), (1,2), (1,3), (2,1), (2,2), (2,3), (2,4), (2,5), (3,2), (3,3), (3,4), (3,5), (3,6), (4,4), (4,5), and (4,6) are measured to be large.

[0025] Continuing the explanation, returning to FIG. 1 , the IN sensor 122 detects that the banknote B has passed through a predetermined position on the transport path 13, and detects that the banknote B has entered the banknote validation unit 12. The magnetic sensor 123 detects electromagnetic changes caused by magnetic ink printed on the banknote B. The CIS 124 reads the image of the banknote B using one or more of visible light, ultraviolet light, infrared light, etc. The OUT sensor 125 detects that the banknote B has passed through a predetermined position on the transport path 13, and detects that the banknote B has passed through the banknote validation unit 12.

[0026] When the thickness sensor 121 measures a displacement of a banknote B that is equal to or greater than a predetermined value, the banknote validation unit 12 detects deterioration or damage to the banknote B. The banknote validation unit 12 also determines the authenticity of the banknote B based on the electromagnetic change in the magnetic ink detected by the magnetic sensor 123 and the image detected by the CIS 124. Banknotes B that have been detected as deteriorated or damaged by the banknote validation unit 12 are sent to the reject unit 5. Banknotes B that have been determined to be counterfeit by the banknote validation unit 12 are sent to the deposit / withdrawal unit 2 and returned to the user.

[0027] 4 is a diagram showing the details of the banknote validation unit and foreign object detection unit. The foreign object detection unit 11 is arranged near the banknote validation unit 12. In this embodiment, the foreign object detection unit 11 is arranged behind the banknote validation unit 12, facing the direction in which banknotes B transported from the deposit / withdrawal unit 2 or temporary storage unit 3 enter the banknote validation unit 12. By arranging the foreign object detection unit 11 near the banknote validation unit 12, the banknote handling device 1 can detect foreign objects using the foreign object detection unit 11 almost simultaneously with the validation of banknotes B by the banknote validation unit 12, making it possible to collectively determine whether banknotes B are defective or damaged, and allowing for smooth banknote handling processing.

[0028] The foreign object detection unit 11 includes a pair of conveyance rollers 101, an IN sensor 102, a first LED (Light Emitting Diode) 103 serving as a light source, a first lens 104, a first camera 105, an OUT sensor 106, and a transparent conveyance guide 107. The foreign object detection unit 11 further includes a pair of conveyance rollers 111, an IN sensor 112, a second LED 113 serving as a light source, a second lens 114, a second camera 115, an OUT sensor 116, a transparent conveyance guide 117, and a pair of conveyance rollers 118.

[0029] Conveying rollers 101, 111, and 118 convey banknotes B in traveling direction D. Transparent conveying guides 107 and 117 have two opposing surfaces made of a transparent material, and a space is defined between the two surfaces through which banknotes B pass. Banknotes B move through the space defined by transparent conveying guides 107 and 117 between conveying roller 101 and conveying roller 111, and between conveying roller 111 and conveying roller 118.

[0030] The IN sensor 102, the OUT sensor 106, the IN sensor 112, and the OUT sensor 116 detect the presence of the banknote B at each position. When the banknote B moves in the moving direction D, the leading edge and the trailing edge of the banknote B are detected in order by the IN sensor 102, the OUT sensor 106, the IN sensor 112, and the OUT sensor 116.

[0031] The first LED 103 emits light toward a predetermined position on the transparent conveying guide 107. This first LED 103 is an example of a "first light source." The light emitted from the first LED 103 passes through the transparent conveying guide 107, is reflected by the banknote B, passes through the transparent conveying guide 107 and the first lens 104, and is incident on the first camera 105. The first camera 105 captures an image of a predetermined position on the transparent conveying guide 107. Using the light emitted from the first LED 103, the first camera 105 captures an image of a partial area of ​​the banknote B using the light reflected by the banknote B, for example, when the banknote B is present at the light irradiation position.

[0032] FIG. 5 is a diagram showing the incidence angle dependence of glass surface reflectance. In FIG. 5, the horizontal axis represents the incidence angle, and the vertical axis represents the glass surface reflectance. Graph 251 represents S-polarized light, and graph 252 represents P-polarized light. As shown in FIG. 5, when the incidence angle of light reflected from the glass surface is less than the Preuster's angle of 250, the reflected wave is small, making it difficult to detect transparent foreign objects such as glass. In contrast, when the incidence angle is equal to or greater than the Preuster's angle of 250, sufficient reflected wave is obtained, making it possible to detect transparent foreign objects such as glass. When irradiating light onto a thin, transparent tape, the Preuster's angle 250 can be set to approximately 55 degrees.

[0033] Therefore, in this embodiment, the incident angle θ of the first LED 103 is set to 55 degrees or more. As a result, even if a thin transparent tape is attached to the banknote B, the reflected wave from the tape can be obtained, and the first camera 105 can capture an image of the thin transparent tape.

[0034] The second LED 113, the second lens 114, and the second camera 115 are installed on the opposite side of the transparent transport guide 107 from the first LED 103, the first lens 104, and the first camera 105. This second LED 113 is an example of a "second light source." Furthermore, to avoid interference of light during photography, the first LED 103, the first lens 104, and the first camera 105 are positioned at offset positions on the transport path 13 from the second LED 113, the second lens 114, and the second camera 115. In other words, the first LED 103 and the first camera 105 and the second LED 113 and the second camera 115 are positioned on opposite sides of the banknote B, and are positioned so that the light used for photography does not interfere with each other.

[0035] The second LED 113 emits light toward a predetermined position on the transparent conveyance guide 117. The light emitted from the second LED 113 passes through the transparent conveyance guide 117 and is reflected by the banknote B, and then passes through the transparent conveyance guide 117 and the second lens 114 to enter the second camera 115. The second camera 115 captures an image of the predetermined position on the transparent conveyance guide 117. Using the light emitted from the second LED 113, the second camera 115 captures an image of a partial area of ​​the banknote B using the light reflected by the banknote B, for example, when the banknote B is present at the light irradiation position.

[0036] The second camera 115 captures an image of the surface of the banknote B opposite to the surface captured by the first camera 105. For example, when the first camera 105 captures an image of the surface of the banknote B, the second camera 115 captures an image of the back side of the banknote B. In this way, the first camera 105 and the second camera 115 acquire images of the surfaces of both sides of the banknote B. Here, an image of either the front or back side is referred to as a "front image," and the respective images are referred to as a "front image" and a "back image."

[0037] 6 is a block diagram of the control unit. The control unit 20 controls the lighting of the first LED 103 and the second LED 113 and the photographing by the first camera 105 and the second camera 115. The control unit 20 then determines whether or not a foreign object is attached to the banknote B using the surface images of the banknote B photographed by the first camera 105 and the second camera 115. The operation of the control unit 20 will be described in detail below. As shown in FIG. 6 , the control unit 20 includes a photographing control unit 21, an image generation unit 22, a data conversion unit 23, a database 24, a determination target area determination unit 25, a foreign object detection unit 26, and a post-processing unit 27.

[0038] When the IN sensor 102 detects the arrival of banknote B, the photography control unit 21 turns on the first LED 103. Next, the photography control unit 21 waits for a predetermined time T1. The time T1 is the time it takes for banknote B to travel from the detection position of the IN sensor 102 to the point irradiated with light from the first LED 103, and is determined based on prior operation checks and the specifications of the banknote handling apparatus 1. For example, if the distance from the detection position of the IN sensor 102 to the point irradiated with light from the first LED 103 is 20 mm and the transport speed of banknote B is 1600 mm / s, the time T1 is 20 / 1600 = 0.0125 seconds.

[0039] After the time T1 has elapsed, the photographing control unit 21 causes the first camera 105 to photograph multiple times. Since the photographing range of the first camera 105 in one photographing operation covers only a portion of the front surface of the banknote B, the entire front surface is photographed multiple times. After that, when the OUT sensor 106 detects that the banknote B has passed through, the photographing control unit 21 turns off the first LED 103.

[0040] When the IN sensor 112 detects the arrival of banknote B, the photography control unit 21 turns on the second LED 113. Next, the photography control unit 21 waits for a predetermined time T2. The time T2 is the time it takes for banknote B to move from the detection position of the IN sensor 112 to the point where light from the second LED 113 is irradiated, and is determined by prior operation checks, etc.

[0041] After the time T2 has elapsed, the photography control unit 21 causes the second camera 115 to take multiple photographs. Since the photography range of each photograph taken by the second camera 115 also covers part of the front surface of the banknote B, the entire front surface is photographed multiple times. After that, when the OUT sensor 116 detects that the banknote B has passed through, the photography control unit 21 turns off the second LED 113.

[0042] 7 is a diagram showing an overview of photographing the surface of a banknote by a camera. Here, the explanation will be given assuming that the surface of the banknote B is divided into 1 cm square regions 310, similar to the division when measuring the amount of displacement by the thickness sensor 121. For example, as shown in FIG. 7, the first camera 105 sequentially photographs regions 301 to 304, each 7 cm wide in the short direction of the banknote B and 4 cm wide in the long direction. In this way, the photographing control unit 21 causes the first camera 105 to photograph the entire surface of the banknote B. The photographing control unit 21 also causes the second camera 115 to photograph in a similar manner.

[0043] 6 , the image generation unit 22 acquires photographed images of a plurality of partial areas on the front surface of the banknote B from the first camera 105 and the second camera 115. The image generation unit 22 then synthesizes the photographed images of the acquired partial areas to generate an image of the entire front surface of the banknote B.

[0044] For example, the image generation unit 22 acquires four captured images, each capturing an image of the areas 301 to 304 in Fig. 7, from the first camera 105. Then, the image generation unit 22 combines the four captured images, each capturing an image of the areas 301 to 304, to generate a single image capturing the entire surface of the banknote B.

[0045] The image generation unit 22 generates front images of the entire front and back surfaces of the banknote B from the images acquired from the first camera 105 and the second camera 115. The image generation unit 22 then outputs the front image and the back image of the banknote B to the data conversion unit 23.

[0046] The data conversion unit 23 receives input of the front and back surface images of the banknote B from the image generation unit 22. Next, the data conversion unit 23 converts the front surface image of the banknote B into grayscale data with 0 to 255 gradations, and calculates a grayscale value as the pixel value of each pixel of the front surface image of the banknote B. The size of the pixel is determined depending on the analytical capability of the data conversion unit 23. Thereafter, the data conversion unit 23 outputs the grayscale value of each pixel of the entire image of the front and back surfaces of the banknote B to the foreign object detection unit 26. In this way, the data conversion unit 23 converts the front surface images captured by the first camera 105 and the second camera 115 into grayscale data.

[0047] Fig. 8 is a diagram showing an example of gradation values ​​calculated by the data conversion unit. The data conversion unit 23 converts the data of each pixel included in each region of the image of one of the 1 cm square divided regions 310 in Fig. 7, for example, to obtain gradation values ​​represented as values ​​shown in each rectangle shown in Fig. 8. Each rectangle in Fig. 8 corresponds to one pixel. In other words, the data conversion unit 23 calculates a gradation value for each pixel corresponding to a region obtained by dividing the 1 cm square divided region 310 into 10 equal parts vertically and horizontally.

[0048] Continuing the explanation by returning to Fig. 6, the database 24 stores information on the gradation values ​​of each pixel on the surface of reference banknotes that are free of dirt or attachments, for various denominations handled by the banknote handling apparatus 1. However, the gradation values ​​of these reference banknotes are gradation values ​​when the reference banknote is photographed while sandwiched between the transparent conveyance guides 107 or 117. For example, the reference banknote may be fed through the conveyance path 13, and the surface images photographed by the first camera 105 and the second camera 115 may be converted into gradation values ​​by the data conversion unit 23, and the converted information may be stored in the database 24.

[0049] The judgment target area determination unit 25 acquires the measurement results of the amount of displacement for each divided area of ​​the banknote B from the thickness sensor 121. Next, the judgment target area determination unit 25 detects divided areas of different thicknesses on the banknote B from the measurement results of the amount of displacement acquired from the thickness sensor 121. Then, the judgment target area determination unit 25 determines a rectangular area including divided areas of different thicknesses as the judgment target area. For example, the judgment target area determination unit 25 determines the judgment target area so as to include continuous divided areas of different thicknesses. Here, in this embodiment, the judgment target area determination unit 25 determines the judgment target area to be rectangular, but the shape is not limited to this.

[0050] The determination target area determination unit 25 obtains, for example, the measurement result shown in the detection result 211 in FIG. 2 from the thickness sensor 121. Here, the determination target area determination unit 25 obtains the amount of displacement for each 1 cm square divided area on the surface of the banknote B from the thickness sensor 121. Next, when transparent tape 210 is attached to the banknote B as shown in FIG. 2, the determination target area determination unit 25 detects the portion corresponding to the hatched area 212 as a divided area with a different thickness based on the amount of displacement in each divided area. The determination target area determination unit 25 detects the divided areas (1,1), (1,2), (1,3), (2,1), (2,2), (2,3), (2,4), (2,5), (3,2), (3,3), (3,4), (3,5), (3,6), (4,4), (4,5), and (4,6) as divided areas with different thicknesses.

[0051] 9 is a diagram showing an example of the gradation values ​​of the determination target area in a banknote with a foreign object attached and the gradation values ​​of the determination target area in a reference banknote. The determination target area determiner 25 determines the range surrounded by columns numbered 1 to 5 in the longitudinal direction and rows numbered 1 to 7 in the lateral direction shown in FIG. 9 as the determination target area 311, which includes an area 212 corresponding to the portion where the transparent tape 210 is attached.

[0052] The foreign object detection unit 26 receives input of the gradation values ​​of each pixel of the image of the entire front and back surfaces of the banknote B from the data conversion unit 23. The foreign object detection unit 26 also acquires information on the determination target area of ​​the banknote B from the determination target area determination unit 25. Next, the foreign object detection unit 26 calculates the average value of the gradation values ​​of each pixel for each divided area included in the determination target area.

[0053] The foreign object detection unit 26 also acquires from the database 24 the gradation values ​​of each pixel in the image of the entire front and back surfaces of a reference banknote of the same denomination as banknote B. The foreign object detection unit 26 then calculates the average value of the gradation values ​​of each pixel for each divided area included in the determination target area of ​​the reference banknote.

[0054] 9 , the foreign object detection unit 26 calculates the average value of the gradation values ​​of each pixel for each divided area of ​​the judgment target area 311 to obtain a calculation result 312 of the average gradation values ​​of banknote B. The foreign object detection unit 26 also obtains the gradation values ​​of each pixel of the judgment target area 313 in the reference banknote that corresponds to the judgment target area 311 of banknote B from the gradation values ​​of each pixel of the image of the entire surface obtained from the database 24. The foreign object detection unit 26 then calculates the average value of the gradation values ​​of each pixel for each divided area of ​​the judgment target area 313 in the reference banknote to obtain a calculation result 314 of the average gradation value of the reference banknote.

[0055] Returning to FIG. 6 , the explanation continues. Next, the foreign object detection unit 26 calculates the similarity for each divided area from the ratio between the average value of the gradation values ​​of each pixel included in the judgment target area on banknote B and the average value of the gradation values ​​of each pixel included in the judgment target area on the reference banknote. Next, the foreign object detection unit 26 determines whether the similarity for each divided area exceeds a predetermined foreign object determination threshold. If the similarity exceeds the foreign object determination threshold, the foreign object detection unit 26 detects a foreign object in that divided area. Thereafter, the foreign object detection unit 26 outputs the detection result of the foreign object on banknote B to the post-processing unit 27.

[0056] For example, a case will be described in which a similarity is used in which the larger the value, the more similar the two are to each other. In this case, the foreign object detection unit 26 has a foreign object determination threshold of 0.9. In other words, the foreign object detection unit 26 determines that there is no foreign object when the average values ​​of the gradation values ​​of the divided regions are 90% or more similar. Specifically, the foreign object detection unit 26 calculates the similarity as (P-Q) / Q, where "P" is the average value of the gradation values ​​of a specific pixel in banknote B and "Q" is the average value of the gradation values ​​of the corresponding specific pixel in the reference banknote. The foreign object detection unit 26 determines whether the calculated similarity is below the foreign object determination threshold of 0.9, and detects a foreign object if it is below the threshold.

[0057] 10 is a diagram showing an example of foreign object detection using a foreign object determination threshold. The foreign object detection unit 26 detects a foreign object when the calculated similarity falls within a range 321 of 0.9 or less in FIG. 10. Conversely, when the calculated similarity falls within a range 322 of 0.9 or more, the foreign object detection unit 26 determines that no foreign object is present.

[0058] 11 is a diagram showing an example of a calculation result of similarity. For example, using the calculation result 312 of the average gradation value of banknote B and the calculation result 314 of the average gradation value of the reference banknote in FIG. 9 , the foreign object detection unit 26 obtains the calculation result 315 of similarity shown in FIG. 11 . The foreign object detection unit 26 then determines whether the similarity of each divided region shown in the calculation result 315 of similarity is below the foreign object determination threshold of 0.9, and detects foreign objects in divided regions with similarities below 0.9. In the case of FIG. 11 , the foreign object detection unit 26 detects foreign objects in the divided regions (1,1), (1,2), (1,3), (2,1), (2,2), (2,3), (2,4), (3,3), (3,4), (3,5), (3,6), (4,4), (4,5), and (4,6).

[0059] The post-processing unit 27 receives input of the foreign object detection result from the foreign object detection unit 26. If a foreign object such as tape is found attached to a banknote B, the post-processing unit 27 causes the banknote handling device 1 to post-process the banknote B as a defective or damaged note. The post-processing unit 27 has a template indicating whether a banknote B with thin tape attached should be treated as a defective or damaged note. Whether a banknote B with thin tape attached should be treated as a defective or damaged note is determined by the operating method of each country and the user's instructions. For example, a banknote B with thin tape attached is treated as a defective note in Japan or South Korea, but as a damaged note in the European Central Bank.

[0060] 12 is a flowchart showing the process of photographing both sides of a banknote by the banknote handling apparatus 1 according to the embodiment. Next, the flow of the process of photographing both sides of a banknote B by the banknote handling apparatus 1 according to the embodiment will be described with reference to FIG.

[0061] The thickness sensor 121 measures the displacement amount of each divided area of ​​the banknote B using the displacement roller 130 (step S101).

[0062] The photographing control unit 21 determines whether the IN sensor 102 has detected the arrival of banknote B (step S102). If the IN sensor 102 has not detected the arrival of banknote B (step S102: No), the photographing control unit 21 waits until the IN sensor 102 detects the arrival of banknote B.

[0063] On the other hand, if the IN sensor 102 detects the arrival of banknote B (step S102: Yes), the photography control unit 21 turns on the first LED 103 (step S103).

[0064] Next, the imaging control unit 21 determines whether or not the time T1 has elapsed (step S104). If the time T1 has not elapsed (step S104: No), the imaging control unit 21 waits until the time T1 has elapsed.

[0065] On the other hand, if the time T1 has elapsed (step S104: Yes), the photographing control unit 21 causes the first camera 105 to photograph multiple times (step S105).

[0066] Next, the image generation unit 22 acquires a plurality of captured images taken by the first camera 105. Then, the image generation unit 22 combines the acquired plurality of captured images to generate a single image showing the entire front surface of the banknote B (step S106). The image generation unit 22 outputs the generated image of the entire front surface of the banknote B to the data conversion unit 23.

[0067] Next, the photographing control unit 21 determines whether the OUT sensor 106 has detected the completion of the passage of the banknote B (step S107). If the OUT sensor 106 has not detected the completion of the passage of the banknote B (step S107: No), the photographing control unit 21 waits until the OUT sensor 106 detects the completion of the passage of the banknote B.

[0068] On the other hand, if the OUT sensor 106 detects that the banknote B has passed through (step S107: Yes), the photography control unit 21 turns off the first LED 103 (step S108).

[0069] Next, the photographing control unit 21 determines whether the IN sensor 112 has detected the arrival of banknote B (step S109). If the IN sensor 112 has not detected the arrival of banknote B (step S109: No), the photographing control unit 21 waits until the IN sensor 112 detects the arrival of banknote B.

[0070] On the other hand, if the IN sensor 112 detects the arrival of banknote B (step S109: Yes), the photography control unit 21 turns on the second LED 113 (step S110).

[0071] Next, the imaging control unit 21 determines whether or not the time T2 has elapsed (step S111). If the time T2 has not elapsed (step S111: No), the imaging control unit 21 waits until the time T2 has elapsed.

[0072] On the other hand, if the time T2 has elapsed (step S111: Yes), the second camera 115 is caused to take images multiple times (step S112).

[0073] Next, the image generation unit 22 acquires a plurality of captured images taken by the second camera 115. Then, the image generation unit 22 combines the acquired plurality of captured images to generate a single image showing the entire surface of the banknote B opposite to the surface captured by the first camera 105 (step S113). The image generation unit 22 outputs the generated image of the entire surface of the banknote B to the data conversion unit 23.

[0074] Next, the photographing control unit 21 determines whether the OUT sensor 116 has detected the completion of the passage of the banknote B (step S114). If the OUT sensor 116 has not detected the completion of the passage of the banknote B (step S114: No), the photographing control unit 21 waits until the OUT sensor 116 detects the completion of the passage of the banknote B.

[0075] On the other hand, if the OUT sensor 116 detects that the banknote B has passed through (step S114: Yes), the photography control unit 21 turns off the second LED 113 (step S115).

[0076] 13 is a flowchart of the foreign object detection process performed by the banknote handling apparatus 1 according to the embodiment. Next, the flow of the foreign object detection process performed by the banknote handling apparatus 1 according to the embodiment will be described with reference to FIG.

[0077] The judgment target area determination unit 25 acquires the measurement results of the amount of displacement for each divided area of ​​the banknote B from the thickness sensor 121. Next, the judgment target area determination unit 25 detects divided areas of different thicknesses on the banknote B from the measurement results of the amount of displacement acquired from the thickness sensor 121. Then, the judgment target area determination unit 25 determines a rectangular area including the divided areas of different thicknesses as the judgment target area (step S201). The judgment target area determination unit 25 outputs information on the determined judgment target area to the foreign object detection unit 26. Here, a case will be described in which divided areas of different thicknesses exist on the banknote B.

[0078] The data conversion unit 23 receives an input of an image of the entire front and back surfaces of the banknote B from the image generation unit 22. Next, the data conversion unit 23 converts the image of the entire front surface of the banknote B into grayscale data with 0 to 255 gradations, and calculates a gradation value as the pixel value of each pixel in the image of the entire front surface of the banknote B (step S202). The data conversion unit 23 outputs the gradation value of each pixel in the image of the entire front and back surfaces of the banknote B to the foreign object detection unit 26.

[0079] The foreign object detection unit 26 receives an input of the gradation values ​​of each pixel in the image of the entire front and back surfaces of the banknote B from the data conversion unit 23. The foreign object detection unit 26 also receives an input of information on the determination target area of ​​the banknote B from the determination target area determination unit 25. Next, the foreign object detection unit 26 extracts the gradation values ​​of the determination target area from the gradation values ​​of each pixel in the image of the entire front and back surfaces of the banknote B, and calculates the average value of the gradation values ​​of each pixel for each divided area (step S203).

[0080] The foreign object detection unit 26 also acquires from the database 24 the gradation values ​​of each pixel of the image of the entire front and back surfaces of a reference banknote of the same denomination as banknote B (step S204).

[0081] Next, the foreign object detection unit 26 extracts the gradation values ​​of the judgment target area from the gradation values ​​of each pixel of the image of the entire front and back surfaces of the reference banknote, and calculates the average value of the gradation values ​​of each pixel for each divided area (step S205).

[0082] Next, the foreign object detection unit 26 calculates the similarity for each of the front and back sides from the ratio between the average value of the gradation value for each divided area of ​​the judgment target area on banknote B and the average value of the gradation value for each divided area of ​​the judgment target area on the reference banknote (step S206).

[0083] Next, the foreign object detector 26 determines whether the similarity in all divided regions is equal to or greater than the foreign object detection threshold (step S207). Here, a case will be described in which a similarity in which a larger value indicates greater similarity is used.

[0084] If the similarity in all divided regions is equal to or greater than the foreign object detection threshold (step S207: Yes), the foreign object detector 26 determines that no foreign object is present. The post-processing unit 27 receives the foreign object detection result for banknote B from the foreign object detector 26 and processes banknote B as a normal note (step S208).

[0085] On the other hand, if there is a divided area whose similarity is below the foreign object detection threshold (step S207: No), the foreign object detector 26 detects a foreign object on the banknote B (step S209).

[0086] The post-processing unit 27 receives the result of foreign object detection of banknote B by the foreign object detection unit 26 and processes banknote B as a defective or damaged note (step S210).

[0087] As explained above, the banknote handling system according to this embodiment irradiates the surface of a banknote with light at an incident angle equal to or greater than the Pruester angle and captures an image from the reflected waves. The banknote handling system then converts the captured image into grayscale data and calculates the gradation value of each pixel. Furthermore, the banknote handling system determines a target area including divided areas with different thicknesses, calculates the average gradation value for each divided area of ​​the target area, calculates the similarity between the average gradation value for each divided area of ​​the target area of ​​the reference banknote and the average gradation value for each divided area of ​​the target area of ​​the reference banknote, and uses the similarity to detect foreign objects.

[0088] In this way, by setting the incident angle to be equal to or greater than the Preuster's angle, reflected waves can be obtained from transparent tape or the like attached to the banknote, and a captured image of the surface of the banknote with the transparent tape reflected thereon can be obtained. Furthermore, by using a captured image that shows the transparent tape, it is possible to clearly distinguish the difference between the shading data of the transparent tape or the like and the shading data when the transparent tape or the like is not present. Therefore, foreign objects can be reliably detected even when transparent tape or the like is attached, thereby improving the accuracy of foreign object detection. Furthermore, by using a single light source to capture images of the surface of the banknote divided into multiple areas, the banknote handling device can be made compact and manufactured inexpensively. Furthermore, by limiting the area to be determined, the amount of processing required for foreign object detection can be reduced, thereby improving processing speed.

[0089] (Hardware Configuration) Fig. 14 is a diagram showing the hardware configuration of the control unit 20. Next, an example of the hardware configuration for realizing each function of the control unit 20 will be described with reference to Fig. 14.

[0090] 14, the control unit 20 can be realized by, for example, a CPU (Central Processing Unit) 91, a memory 92, a hard disk 93, and a network interface 94. The CPU 91 is connected to the memory 92, the hard disk 93, and the network interface 94 via a bus.

[0091] The network interface 94 is an interface for communication between the control unit 20 and an external device. The network interface 94 relays communication between the CPU 91 and an external user terminal device, for example.

[0092] The hard disk 93 is an auxiliary storage device and stores programs for implementing the functions of the imaging control unit 21, the image generation unit 22, the data conversion unit 23, the database 24, the determination target region determination unit 25, the foreign object detection unit 26, and the post-processing unit 27 illustrated in FIG.

[0093] The memory 92 is a main storage device, and may be, for example, a dynamic random access memory (DRAM).

[0094] The CPU 91 reads various programs from the hard disk 93, loads them into the memory 92, and executes them. As a result, the CPU 91 realizes the functions of the imaging control unit 21, image generation unit 22, data conversion unit 23, database 24, determination target region determination unit 25, foreign object detection unit 26, and post-processing unit 27 illustrated in FIG.

[0095] REFERENCE SIGNS LIST 1 Banknote handling device 2 Deposit / withdrawal unit 3 Temporary storage unit 4 Storage unit 5 Reject unit 11 Foreign object detection unit 12 Banknote validation unit 13 Conveyance path 20 Control unit 21 Photography control unit 22 Image generation unit 23 Data conversion unit 24 Database 25 Judgment target area determination unit 26 Foreign object detection unit 27 Post-processing unit 101, 111, 118 Conveyance roller 102, 112 IN sensor 103 First LED 104 First lens 105 First camera 106, 116 OUT sensor 107, 117 Transparent conveyance guide 113 Second LED 114 Second lens 115 Second camera 121 Thickness sensor 122 IN sensor 123 Magnetic sensor 124 CIS 125 OUT sensor B Banknote

Claims

1. A banknote handling device comprising: a light source that irradiates light onto a medium; a camera that captures a surface image of the medium based on reflected light of the light irradiated from the light source; a data conversion unit that converts the surface image captured by the camera into grayscale data; a measurement unit that measures the thickness of the medium; a determination target area determination unit that determines a determination target area including areas with different wall thicknesses in the medium based on the measurement result by the measurement unit; and a foreign object detection unit that compares the grayscale data of the determination target area in the medium with the grayscale data of the determination target area in a reference medium to detect foreign objects.

2. The banknote handling device according to claim 1, wherein the light source irradiates the light at an incident angle equal to or greater than the Brewster angle when irradiating light onto a transparent tape.

3. The banknote handling device according to claim 1, wherein the light source irradiates the light at an incident angle of 55 degrees or more.

4. The light source has a first light source and a second light source, the camera has a first camera that performs imaging using the light irradiated from the first light source and a second camera that performs imaging using the light irradiated from the second light source, and the first light source and the first camera, and the second light source and the second camera are arranged at opposite positions with respect to the medium and at positions where the light used for imaging does not interfere with each other. The banknote handling device according to claim 1.

5. The banknote handling device according to claim 1, wherein the foreign object detection unit detects the foreign object using the average value of the grayscale data.

6. The measurement unit performs the measurement for each divided area obtained by dividing the surface of the medium into a predetermined size, the determination target area determination unit determines a determination target area so as to include continuous divided areas with different wall thicknesses, and the foreign object detection unit detects the foreign object using the average value of the grayscale data for each divided area. The banknote handling device according to claim 4.

7. A banknote handling device comprising a light source for irradiating light onto a medium and a camera for photographing a surface image of the medium based on reflected light of the light irradiated from the light source, converts the surface image photographed by the camera into grayscale data, determines a determination target area including areas with different wall thicknesses in the medium based on a measurement result of measuring the thickness of the medium, and compares the grayscale data of the determination target area in the medium with the grayscale data of the determination target area in a reference medium to detect foreign matter. A foreign matter detection method characterized by executing the process.

8. A foreign matter detection program characterized by causing a computer to execute a process of irradiating light from a light source onto a medium, photographing a surface image of the medium with a camera based on the reflected light of the irradiated light, converting the surface image photographed by the camera into grayscale data, determining a determination target area including areas with different wall thicknesses in the medium based on a measurement result of measuring the thickness of the medium, and comparing the grayscale data of the determination target area in the medium with the grayscale data of the determination target area in a reference medium to detect foreign matter.

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