JP3736028B2 - Bill discrimination device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a banknote discriminating apparatus, and more particularly, to a banknote discriminating apparatus that identifies the authenticity of a counterfeit ticket or a counterfeit ticket by color copy inserted in a vending machine or a change machine.
[0002]
[Prior art]
In recent years, as color copiers, color printers, and scanners have become more sophisticated, there are cases in which color copying of banknotes using these devices is used as a tendency of counterfeit tickets, or some of them are used by cutting them into genuine banknotes. Many. These counterfeit tickets are hereinafter collectively referred to as color copy counterfeit tickets. In color copying, contrast and hue can be finely adjusted by functions such as density adjustment and color correction, so it is difficult to identify authenticity of color copy counterfeits.
[0003]
Conventional bill discriminating apparatuses generally use a magnetic sensor or an optical sensor such as a magnetic head or a magnetoresistive element as a sensor unit for authenticating authenticity.
9A and 9B are diagrams showing a configuration example of a sensor unit of a conventional banknote discriminating apparatus, in which FIG. 9A is a plan view of a banknote, and FIG. 9B is a side view. Here, for explanation, three types of sensors are shown simultaneously. That is, the bill 1 is sandwiched between a magnetic sensor 2, a light source 3 such as an LED (light emitting diode), and a light receiver 4 such as a PD (photodiode), which are fixedly provided to the bill 1 moving in the transport direction. And a photosensor in which the light source 3a and the light receiver 4a are arranged in pairs on the one surface side of the banknote 1. A scanning area 1 a extending in the transport direction shown in the banknote 1 is an area in which the magnetic sensor 2 detects magnetism, and a scanning area 1 b is an area in which the light from the light source 3 that has passed through the banknote 1 is detected by the light receiver 4. The scanning region 1c is a region where the light from the light source 3a that has reflected the banknote 1 is detected by the light receiver 4a. Since either the magnetic sensor 2 or the optical sensor scans one point of the banknote 1 in the transport direction and determines the authenticity of the banknote 1 from the magnetic information or shading pattern information obtained therefrom, This is called a point scanning type.
[0004]
Although color copy counterfeits depend on the printing method, that is, the ink material used, such as dyes and pigments, and the fixing method on the paper surface, since the ink generally does not contain a magnetic component, False identification is possible. On the other hand, the optical sensor simply illuminates the banknote with a monochromatic light source, receives the reflected or transmitted light, measures the pattern and contrast (shading) of the pattern, and uses this as identification data.
[0005]
10A and 10B are diagrams showing another configuration example of the sensor unit of the conventional bill discriminating device, in which FIG. 10A is a view seen from a direction orthogonal to the bill transport direction, and FIG. It is a figure. The optical sensor includes a light source 5 such as an LED array in which a plurality of LEDs are arranged in a row over almost the entire width of the banknote 1 in a direction orthogonal to the conveyance direction of the banknote 1, and a linear CCD that receives the transmitted light of the banknote 1. And a light receiving device 6 such as a PD array, and an imaging lens 7 that forms an image of the transmitted light of the banknote 1 on the light receiving device 6. When the light source 5 irradiates the lower surface of the banknote 1, the light transmitted through the banknote 1 is imaged on the light receiving surface of the light receiver 6 by the imaging lens 7, and the pattern of the banknote 1 is detected. Since the pattern information is detected along the conveyance direction of the banknote 1, this is called a surface scanning type. In addition, in this surface scanning type, there is a case where a light receiver is brought into close contact with a banknote to read a pattern of the banknote.
[0006]
[Problems to be solved by the invention]
However, since color copy counterfeits can be used to finely adjust contrast and hue using functions such as density adjustment and color correction at the time of color copy, it is difficult to distinguish them from genuine banknotes. Therefore, there is a problem that identification by a conventional surface scanning optical sensor is becoming difficult.
[0007]
In addition, in the case of the one-point scanning type of the magnetic sensor, it is impossible to discriminate a forged ticket in which a genuine bill is cut into the scanning portion, and in order to avoid this, a large number of magnetic sensors may be arranged in an array, Since the magnetic sensor is relatively expensive, the cost greatly increases when the necessary amount is provided. There is a problem that a forged ticket in which a genuine bill is cut into a scanning portion cannot be discriminated even by a one-point scanning optical sensor.
[0008]
The present invention has been made in view of the above points, and an object thereof is to provide a banknote discriminating apparatus capable of identifying a color copy counterfeit with higher accuracy without increasing cost.
[0009]
[Means for Solving the Problems]
In the present invention, in order to solve the above problem, a sensor means including a light source for illuminating a bill and a linear image sensor arranged in a direction perpendicular to the bill conveyance direction, and the transmitted light from the bill for the sensor portion. Banknote discriminating apparatus comprising: authenticity identification processing means for identifying authenticity of a banknote based on grayscale data of images detected intermittently at predetermined intervals as the banknote is conveyed. There is provided a bill discriminating apparatus which is constituted by two types of light emitting elements having different emission wavelengths, and wherein the light receiving unit alternately reads the grayscale data of the image by the transmitted light of the two types of wavelengths.
[0010]
According to such a bill discriminating apparatus, the authenticity of the bill and the color copy counterfeit is determined based on the difference in transmittance ratio due to the difference in the wavelength of the light transmitted therethrough. In other words, authentic bills have very different transmittances for light with different wavelengths, but color copy counters made with the most common toner-based color copies, for example, have no significant difference in transmittance for light with different wavelengths. Similarly, in color copy counterfeit bills using other methods, the transmittance of light having different wavelengths with respect to patterns at almost the same detection position is utilized by utilizing the fact that the transmittance of light having different wavelengths is different from that of genuine bills. Authenticity is determined by evaluating the ratio. Thereby, it is possible to accurately identify a color copy counterfeit or the like without significantly increasing the cost.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a bill validating device according to the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a basic configuration of a banknote discrimination device. According to the present invention, the banknote discrimination device performs a banknote authenticity discrimination process that performs a color copy counterfeit discriminating process from a sensor unit that reads a pattern of a banknote 11 being conveyed and a pattern of the banknote 11 detected by the sensor unit. And a processing unit 15. The sensor unit includes two types of light sources having different emission wavelengths for illuminating the banknote 11 and a light receiving unit 12 that detects transmitted light from the banknote 11.
[0012]
The light receiving unit 12 includes a linear image sensor arranged in a direction perpendicular to the conveyance direction of the banknote 11 and an imaging lens that forms an image of the pattern of the banknote 11 on the linear image sensor, and uses the imaging lens. This is a surface scanning type sensor that forms an image on a light receiver and reads it. Of course, the light receiving unit 12 may be a contact type linear image sensor.
[0013]
The light source is disposed on the side opposite to the side on which the light receiving unit 12 of the banknote 11 is disposed, and includes a red LED array 13a composed of a plurality of red LEDs that emit light having a wavelength in the red light region, and a wavelength in the infrared light region. And an infrared LED array 13b composed of a plurality of infrared LEDs that emit light. The red LED array 13a emits red light 14a having an emission wavelength of λ1 = 660 nm, and the infrared LED array 13b emits infrared light 14b having an emission wavelength of λ2 = 940 nm. The red LED array 13 a and the infrared LED array 13 b are alternately controlled to light as the banknote 11 is conveyed, and the red light 14 a and the infrared light 14 b radiated alternately are read alternately by one light receiving unit 12. become.
[0014]
Here, the optical characteristics of the genuine bill and the color copy counterfeit will be described. The color copy counterfeit has its production method, that is, a method using toner, a method using an ink jet printer, a method using a thermal transfer printer, etc., but here, it is based on a method using the most common toner as a color copy method. Pick up a color copy counterfeit ticket.
[0015]
FIG. 2 is a schematic diagram of the results of transmitted light spectroscopic analysis of a bill and a color copy counterfeit note. As a result of the transmitted light spectroscopic analysis, spectral characteristics of a certain printed portion in the banknote and a corresponding portion of the color copy counterfeit were examined. In FIG. 2, the horizontal axis indicates the wavelength λ and the vertical axis indicates the transmittance. Further, a curve 21 represented by a thick solid line shows a change in transmittance in a printed portion with a genuine banknote, and a thin solid line curve 22 shows a change in transmittance in a corresponding portion color-copied by increasing the copy density. A thin broken line curve 23 shows a change in the transmittance of the corresponding portion color-copied with a light copy density.
[0016]
For the genuine banknote indicated by the curve 21, the transmittance in the red light region (λ = 620 to 720 nm) is significantly lower than the transmittance in the infrared light region (λ = 820 nm or more). In the case of a copy counterfeit note, there is no significant difference between the transmittance in the red light region and the transmittance in the infrared light region for both the dark color copy and the light color copy. That is, even if the density of the color copy is adjusted and the transmittance of one wavelength region is made closer to the banknote, the transmittance of the other wavelength region is changed in the same manner. Therefore, the color copy counterfeit ticket can be identified by evaluating the transmittance ratio in the two-wavelength region. The transmittance ratio is
[0017]
[Expression 1]
Ratio of transmittance = τ1 / τ2 (1)
Where τ1 is the transmittance for the infrared light region and τ2 is the transmittance for the red light region. The transmittance ratio is large for genuine banknotes, and even with color copy counterfeits, even if the density of color copies is adjusted, it does not change much. Therefore, the banknotes and their color copy counterfeits are identified by evaluating according to equation (1). be able to.
[0018]
Next, sensor output when the linear image sensor of the light receiving unit 12 reads a portion of a bill and its color copy counterfeit printed with, for example, a light and shade pattern at equal intervals will be described.
[0019]
FIGS. 3A and 3B are diagrams showing an output example of banknote image data with two different wavelengths. FIG. 3A shows a case of scanning with red light, and FIG. 3B shows a case of scanning with infrared light. Here, the horizontal axis indicates the position of the detection pixel of the linear image sensor, and the vertical axis indicates the sensor output. As shown in FIG. 3 (A), for the wavelength λ1 of red light, the transmittance of the pattern printed portion of the banknote is low, so the contrast with the unprinted portion becomes very large, and the image density The amplitude of the detected waveform increases. Further, as shown in FIG. 3B, for the wavelength λ2 of the infrared light, since the transmittance of the pattern portion of the banknote is high, the contrast with the unprinted portion is reduced, and the image density is reduced. The amplitude of the detected waveform is reduced.
[0020]
FIGS. 4A and 4B are diagrams showing output examples of image data of a color copy counterfeit ticket with two different wavelengths, where FIG. 4A shows a case where scanning is performed with red light, and FIG. 4B illustrates a case where scanning is performed with infrared light. Yes. The magnitudes of the amplitudes of these image shading detection waveforms are related to the transmittance in FIG. That is, in the case of color copy, when the density is adjusted, the image density for each wavelength also changes, but the transmittance of the red light of wavelength λ1 and the infrared light of wavelength λ2 changes at substantially the same ratio. The magnitude of the amplitude of the light and shade detection waveform also changes at almost the same ratio. As a result, the sensor output by the red light with the wavelength λ1 is slightly smaller than the case of the genuine banknote, and the sensor output by the infrared light with the wavelength λ2 is The amplitude is slightly larger than that of a genuine bill. Therefore, by comparing the amplitudes of the detected waveforms of the image shading with the wavelengths λ1 and λ2, that is, by evaluating the amplitude ratio, it is possible to identify the bill and its color copy counterfeit.
[0021]
As described above, there are several methods for the bill authenticity discrimination processing unit 15 to actually identify authenticity, and examples of the processing are sequentially shown below.
FIG. 5 is a diagram for explaining the banknote identification process in the banknote authenticity determination processing unit. When a banknote in which patterns and characters are arranged in a complicated manner is viewed on the pattern on one scanning line, the sensor output changes in a complex manner according to the shade of the pattern as shown in FIG. 5, and there are many peaks. Therefore, for example, the image data is divided into a certain amount of small sections so as to match the number of peak values. Authenticity can be determined by quantifying the pattern information for each section and evaluating the ratio of this information to the quantified information of the same section of another wavelength. Next, two specific processing methods will be described.
[0022]
FIG. 6 is a flowchart showing the flow of the first authenticity determination process. First, transmitted light of red light having a wavelength λ1 is read for one scan as image data (step S1). Next, a plurality of divided sections are set for the image data for one scan (step S2). The maximum value and the minimum value are obtained within each set section, and the difference, that is, the maximum amplitude is obtained (step S3). Similarly, in the case of the wavelength λ2, the transmitted light by the red light having the wavelength λ2 is read as image data for one scan (step S4), and the image data is divided into a plurality of sections (step S5). The maximum amplitude is obtained (step S6). Next, the ratio of the maximum amplitudes obtained for the divided sections at the same position is taken (step S7). Then, the value of this ratio is compared with the reference data that is the result in the case of banknotes obtained in advance (step S8), and authenticity determination is performed to identify the color copy counterfeit bill (step S9). ).
[0023]
FIG. 7 is a flowchart showing the flow of the second authenticity determination process. First, transmitted light of red light having a wavelength λ1 is read for one scan as image data (step S11). Next, a plurality of divided sections are set for the read image data for one scan (step S12). The difference between the pixels is obtained, that is, differentiated within each set section, and the sum of the absolute value or the squared value is obtained (step S13). Hereinafter, the sum of the squared values is referred to as a differential square sum. Similarly, in the case of the wavelength λ2, the transmitted light by infrared light having the wavelength λ2 is read as image data for one scanning (step S14), and the image data is divided into a plurality of sections (step S15). A differential sum of squares within the section is obtained (step S16). Next, the ratios of the respective differential square sums obtained for the divided sections at the same position are taken (step S17). Then, the value of this ratio is compared with the reference data that is the result in the case of banknotes obtained in advance (step S18), and authenticity determination is performed to identify the color copy counterfeit note (step S19). ).
[0024]
That is, the detected waveforms of the four image shades in FIGS. 3A and 3B and FIGS. 4A and 4B are obtained when the same part is scanned, but the maximum value and the minimum A large difference in value means that the difference in shade is large, and conversely that a small difference between the maximum value and the minimum value means that the difference in shade is small. By obtaining a differential square sum for the image data of various wavelengths λ1 and λ2 and using the ratio, it is possible to identify authenticity by comparing with the reference data obtained in advance as in the first method.
[0025]
As a third method, there is a method of evaluating the exposure time of the linear image sensor in the light receiving unit 12, and this method will be described below. The light receiving unit 12 adjusts the exposure time according to the amount of received light, that is, the brightness of the surface of the banknote illuminated by the light source. As a result, the light receiving unit 12 can always read the pattern at an appropriate level, and the illumination light is not too bright and the image data is saturated, or conversely, a sufficient image cannot be obtained due to insufficient light quantity.
[0026]
In other words, such a light receiving unit 12 shortens the exposure time when detecting an object to be detected having a high transmittance and a large amount of transmitted light, and conversely when detecting an object to be detected having a low transmittance and a small amount of transmitted light. In this case, the exposure time is controlled to be long.
[0027]
Therefore, the control unit (not shown) of the light receiving unit 12 measures the time from when the reset signal is transmitted to the light receiving unit 12 to start the exposure until the light receiving unit 12 returns a signal notifying that the exposure has ended. To measure the exposure time.
[0028]
The transmittance and the exposure time are in an inversely proportional relationship, and the equation (1) can be modified as follows. That is,
[0029]
[Expression 2]
Ratio of transmittance = T2 / T1 (2)
It is represented by Here, T1 is the exposure time when illuminated with infrared light, and T2 is the exposure time when illuminated with red light.
[0030]
Therefore, it is possible to evaluate the ratio of transmittance to two different wavelengths by the above equation (2), and by comparing with the evaluation result of banknotes obtained in advance as in the first and second methods. Authenticity is identified.
[0031]
In the above three processing methods, authenticity is identified by scanning data for each adjacent one of two wavelengths, but the pattern of the banknote is complicated, and the state of the pattern is merely shifted by several millimeters. May change significantly, and there is a possibility that the true / false identification may be mistaken with only one scan data for each wavelength. Therefore, the accuracy of authenticity can be improved by combining the method described below with any of the above three methods.
[0032]
FIG. 8 is a diagram for explaining a banknote identification area. As shown in the figure, for the banknote 11, the image data for two adjacent scans of the linear image sensor in the light receiving unit 12 is divided into a plurality, in the example shown in the figure, and further divided into three in the conveying direction of the banknote 11. In the example shown in the figure, a plurality of areas (hereinafter referred to as identification areas 11a) are obtained by dividing the image data for four pairs of scans (each of four scans using red light and infrared light = 8 scans). ) Is set, and the authenticity of the banknote 11 is identified in units of the set identification area. That is, for example, in the first and second methods, the eight image data in the identification area 11a are divided into a plurality of sections, and the magnitude of the amplitude is evaluated in each section.
[0033]
In this way, by performing true / false identification in units of identification areas, evaluation is performed not only on the information on the line but also on the information on the surface with a certain amount of information and a large amount of information. Since the change is also averaged by the number of scanning lines included in the identification region, the possibility of erroneous identification can be greatly reduced.
[0034]
【The invention's effect】
As described above, in the present invention, two types of light emitting elements having different emission wavelengths are used as the light source for illuminating the banknote, and this is alternately emitted to read image data using transmitted light of two types of wavelengths. . This makes it possible not only to accurately identify color copy counterfeits and fake bills in which color copies are cut into genuine banknotes, but also when using a combination of magnetic sensors or sensors with multiple magnetic sensors. Compared with this, the cost can be greatly reduced.
[0035]
In addition, the conventional sensor unit including a monochromatic light source is a sensor capable of identifying a black-and-white copy forged ticket or its fake ticket, but the sensor unit of the present invention device includes a light source composed of two types of light-emitting elements. Therefore, the function is maintained, and it becomes possible to accurately identify all of the counterfeit tickets made up of black-and-white copies and color copies and the counterfeit bills obtained by cutting them.
[Brief description of the drawings]
FIG. 1 is a diagram showing a basic configuration of a bill validating device.
FIG. 2 is a schematic diagram of the results of transmitted light spectroscopic analysis of a bill and a color copy counterfeit.
FIGS. 3A and 3B are diagrams showing output examples of image data of banknotes with two different wavelengths, where FIG. 3A shows a case where scanning is performed with red light, and FIG. 3B shows a case where scanning is performed with infrared light.
FIGS. 4A and 4B are diagrams showing output examples of image data of a color copy counterfeit ticket with two different wavelengths, where FIG. 4A shows a case where scanning is performed with red light, and FIG. 4B shows a case where scanning is performed with infrared light. ing.
FIG. 5 is a diagram for explaining banknote identification processing in a banknote authenticity determination processing unit;
FIG. 6 is a flowchart showing a flow of first authenticity determination processing.
FIG. 7 is a flowchart showing a flow of second authenticity determination processing.
FIG. 8 is a diagram for explaining a banknote identification area;
9A and 9B are diagrams illustrating a configuration example of a sensor unit of a conventional banknote discriminating apparatus, in which FIG. 9A is a plan view of a banknote and FIG. 9B is a side view.
FIGS. 10A and 10B are diagrams showing another configuration example of a sensor unit of a conventional banknote discriminating apparatus, in which FIG. 10A is a diagram viewed from a direction orthogonal to the banknote transport direction, and FIG. FIG.
[Explanation of symbols]
11 Banknote 12 Light-receiving part 13a Red LED array 13b Infrared LED array 14a Red light 14b Infrared light 15 Banknote authenticity determination processing part

Claims (5)

Intermittently at predetermined intervals with a sensor means comprising a light receiving unit having a linear image sensor arranged in the conveying direction and perpendicular direction of the light source and the banknote for illuminating the banknote, the transmitted light from the bill in the conveying said sensor means of the banknote In a banknote discriminating apparatus comprising authenticity identification processing means for identifying the authenticity of a banknote based on the grayscale data of the image detected in
The sensor means comprises the light source by two types of light emitting elements having different emission wavelengths, and the light receiving unit alternately reads the grayscale data of the image by the transmitted light of the two types of wavelengths ,
The true / false identification processing means divides the image grayscale data for each adjacent scan of each wavelength obtained by the sensor means into a plurality of sections, and sets the maximum value of the image grayscale data for each wavelength section. A bill discriminating apparatus characterized in that the difference between the minimum value is obtained and a ratio is obtained, and the authenticity of the bill is identified by comparing the ratio with reference data . Sensor means comprising a light source for illuminating a bill and a linear image sensor arranged in a direction perpendicular to the bill conveyance direction, and transmitted light from the bill intermittently at predetermined intervals as the bill is conveyed. In a banknote discriminating apparatus comprising authenticity identification processing means for identifying the authenticity of a banknote based on the grayscale data of the detected image,
  The sensor means comprises the light source by two types of light emitting elements having different emission wavelengths, and the light receiving unit alternately reads the grayscale data of the image by the transmitted light of the two types of wavelengths,
  The true / false discrimination processing means divides the image density data for each adjacent scan of each wavelength obtained by the sensor means into a plurality of sections, and the density data between adjacent pixels for each wavelength section. The difference between the absolute values of the differences and the sum of the squared values are taken to quantitatively evaluate the density difference of the scanned image in that interval, and the ratio of the evaluation results for the two wavelengths is compared with the reference data A bill discriminating apparatus characterized by identifying authenticity of a bill. The banknote identification device according to claim 1 or 2, wherein the two types of light emitting elements are elements that emit light in a red light region and an infrared light region. The sensor means has a function of receiving an appropriate amount of light by automatically controlling an exposure time in accordance with the amount of received light, and the authenticity identification processing means receives each exposure and performs one adjacent scan by two wavelengths. The bill discrimination device according to claim 1 or 2, wherein authenticity of a bill is identified by comparing a transmittance ratio obtained from a ratio of exposure times taken to perform with reference data. The whole image of the banknote obtained by the sensor means is divided into a plurality of vertical and horizontal areas, and authenticity is identified for image data included in each area. Banknote discrimination device.

Images