Paper sheet identification device, paper sheet processing device, paper sheet identification method, and paper sheet identification program

Abstract

The present invention provides a paper sheet identification device, a paper sheet processing device, a paper sheet identification method, and a paper sheet identification program that can perform highly accurate identification based on light emanating from paper sheets. [Solution] A paper sheet identification device comprising: a light source capable of irradiating paper sheets being transported with light of a specific wavelength; a light receiving unit that receives light arriving from the paper sheets based on the light from the light source and outputs a light detection signal; a light detection control unit that controls the light source and the light receiving unit; and an identification unit that identifies the paper sheets using the light detection signals output from the light receiving unit. The light detection control unit controls the light source and the light receiving unit so that at least one of the irradiation conditions of the light source with light of the specific wavelength and the light receiving conditions of the light receiving unit are different during multiple periods within one detection cycle, thereby causing the light receiving unit to output multiple light detection signals with different signal amounts. The identification unit selects one or more light detection signals from the multiple light detection signals and identifies the paper sheets using the selected one or more light detection signals.

Description

Technical Field

[0001] The present disclosure relates to a paper sheet discrimination device, a paper sheet processing device, a paper sheet discrimination method, and a paper sheet discrimination program.

Background Art

[0002] Conventionally, in an optical line sensor that detects security elements attached to paper sheets such as banknotes, a technique of performing appropriate detection by controlling a light source or a light receiving unit according to a detection target and a required resolution is known. For example, what is shown in the following documents is known.

[0003] In the paper sheet discrimination device described in Patent Document 1, in an optical line sensor, by controlling the emission frequency of each light source of a plurality of wavelengths to a frequency suitable for the discrimination target (the number of emission times is different) during one lighting cycle, a desired image according to the purpose can be obtained, and it is described that efficient and highly accurate banknote discrimination is possible. Further, for example, when it is desired to recognize a reference number with high accuracy, it is described that a green reflection image is acquired at high resolution, and other images are acquired normally or at low resolution.

[0004] In the excitation light detection device described in Patent Document 2, in an optical line sensor, it is described that different types of fluorescence and phosphorescence are detected by changing the current amount or supply time of an excitation light source. For example, it is described that fluorescence is detected at a medium current, bleach light is detected at a small current, and phosphorescence is detected by turning off the light after a large current.

[0005] The optical sensor described in Patent Document generates data for one pixel by adding up the output values of the light components received in a plurality of periods during one cycle.

[0006] Furthermore, Patent Document 4 describes an optical sensor for detecting light from paper sheets printed with at least one of n types of monochromatic inks, comprising: a light source; a light receiving unit equipped with first to (n-1) light receiving elements; a storage unit that stores correction values ​​based on reference data obtained by receiving light emitted by the first to n monochromatic inks individually with the light receiving unit; and a correction processing unit that corrects detection data obtained by receiving light emitted from paper sheets irradiated with light from the light source with the light receiving unit, using correction values ​​based on the inverse matrix of a normalized matrix A of a predetermined n x n matrix A acquired in advance. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5005760 [Patent Document 2] Patent No. 6316148 [Patent Document 3] Patent No. 7418542 [Patent Document 4] Patent No. 7473677 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, with conventional optical sensors, when distinguishing between media with different fluorescence emission levels, insufficient light intensity or saturation can occur, sometimes preventing optimal fluorescence detection.

[0009] More specifically, when detecting fluorescence in banknotes (one or more denominations) containing a mixture of high-luminosity and low-luminosity fluorescent inks during only one period within a cycle, the illumination intensity of the light source is generally set to excitation conditions that prevent the fluorescence detection signal from saturating. However, in banknotes printed with multiple types of fluorescent inks ranging from high-luminosity to low-luminosity, if the difference in emission intensity is large, detection of low-luminosity inks approaches the lower limit and becomes difficult. Furthermore, if the amount of fluorescence emission decreases due to deterioration in the circulation of the banknotes or variations in printing density, detection becomes even more difficult. In other words, the signal has a poor signal-to-noise ratio, making stable detection difficult during only one period within a cycle.

[0010] Similar problems can arise not only when detecting fluorescence from banknotes, but also when detecting phosphorescence from banknotes, and even when detecting reflected or transmitted light from banknotes.

[0011] This disclosure is made in view of the above-mentioned circumstances and aims to provide a paper sheet identification device, a paper sheet processing device, a paper sheet identification method, and a paper sheet identification program that can perform identification based on light arriving from paper sheets with high accuracy. [Means for solving the problem]

[0012] To solve the above-mentioned problems and achieve the objective, (1) a paper sheet identification device according to a first aspect of the present disclosure comprises: a light source capable of irradiating paper sheets being transported with light of a specific wavelength; a light receiving unit that receives light arriving from the paper sheets based on the light from the light source and outputs a light detection signal; a light detection control unit that controls the light source and the light receiving unit; and an identification unit that identifies the paper sheets using the light detection signals output from the light receiving unit. The light detection control unit controls the light source and the light receiving unit such that at least one of the irradiation conditions of the light source with light of the specific wavelength and the light receiving conditions of the light receiving unit are different during multiple periods within a detection time of one cycle, thereby causing the light receiving unit to output multiple light detection signals with different signal amounts. The identification unit selects one or more light detection signals from the multiple light detection signals and identifies the paper sheets using the selected one or more light detection signals.

[0013] (2) In the paper sheet identification device described in (1) above, the identification unit may select one or more light detection signals from among the plurality of light detection signals, the signal amount of which is within a predetermined range, as the one or more light detection signals.

[0014] (3) In the paper sheet identification device described in (1) or (2) above, the light detection control unit may change the light reception time of the light receiving unit during the plurality of periods.

[0015] (4) In the paper sheet identification device described in any of (1) to (3) above, the light detection control unit may change the emission time of the light of the specific wavelength from the light source during the plurality of periods.

[0016] (5) In the paper sheet identification device described in any of (1) to (4) above, the light detection control unit may change the magnitude of the current supplied to the light source during the plurality of periods.

[0017] (6) In the paper sheet identification device described in any of (1) to (5) above, the light source may irradiate the paper sheets with light of any of ultraviolet light, visible light, or infrared light as the light of the specific wavelength.

[0018] (7) In the paper sheet identification device described in any of (1) to (6) above, the light receiving unit may receive fluorescence emitted from the paper sheets and output a plurality of fluorescence detection signals as the plurality of light detection signals, and the identification unit may select one or more fluorescence detection signals from the plurality of fluorescence detection signals as the one or more light detection signals and use the selected one or more fluorescence detection signals to identify the paper sheets.

[0019] (8) In the paper sheet identification device described in (7) above, the identification unit may use the selected one or more fluorescence detection signals to calculate the ratio of fluorescence emission amounts of multiple wavelengths and use that ratio to identify the paper sheets.

[0020] (9) In the paper sheet discrimination device according to (8) above, the ratio of the fluorescence emission amounts of the plurality of wavelengths may be the ratio of the fluorescence emission amount of visible light to the fluorescence emission amount of infrared light.

[0021] (10) In the paper sheet discrimination device according to any one of (1) to (9) above, the light receiving unit may receive phosphorescence emitted from the paper sheet and output a plurality of phosphorescence detection signals as the plurality of light detection signals, and the discrimination unit may select one or more phosphorescence detection signals from the plurality of phosphorescence detection signals as the one or more light detection signals, and perform discrimination of the paper sheet using the selected one or more phosphorescence detection signals.

[0022] (11) In the paper sheet discrimination device according to any one of (1) to (10) above, the discrimination unit may select only one light detection signal from the plurality of light detection signals as the one or more light detection signals, and perform discrimination of the paper sheet using the selected light detection signal.

[0023] (12) In the paper sheet discrimination device according to (11) above, the discrimination unit may select only the light detection signal having the largest signal amount from the plurality of light detection signals as the one or more light detection signals, and perform discrimination of the paper sheet using the selected light detection signal.

[0024] (13) In the paper sheet discrimination device according to any one of (1) to (10) above, the discrimination unit may select two or more light detection signals from the plurality of light detection signals as the one or more light detection signals, and perform discrimination of the paper sheet using the value obtained by adding up the signal amounts of the selected two or more light detection signals.

[0025] (14) In the paper sheet discrimination device according to any one of (1) to (10) or (13) above, the discrimination unit may select two light detection signals from the plurality of light detection signals as the one or more light detection signals, calculate the ratio of the signal amounts of the selected two light detection signals, and perform discrimination of the paper sheet using the ratio.

[0026] (15) In the paper sheet identification device described in any of (1) to (14) above, the light source may irradiate multiple types of light with different wavelengths, including the light of the specific wavelength, within the detection time of one cycle.

[0027] (16) Furthermore, a paper sheet processing device according to a second aspect of the present disclosure is equipped with a paper sheet identification device as described in any of (1) to (15) above.

[0028] (17) A paper sheet identification method according to a third aspect of the present disclosure comprises: a first step of irradiating the transported paper sheets with light of a specific wavelength from a light source; a second step of receiving light from the paper sheets based on the light from the light source and outputting a photodetection signal; and a third step of identifying the paper sheets using the photodetection signal output from the photodetector, wherein in the first and second steps, at least one of the irradiation conditions of the light source with light of the specific wavelength and the light receiving conditions of the photodetector are made different for multiple periods within one detection time cycle, thereby causing the photodetector to output multiple photodetection signals with different signal amounts; and in the third step, one or more photodetection signals are selected from the multiple photodetection signals, and the paper sheets are identified using the selected one or more photodetection signals.

[0029] (18) Furthermore, a paper sheet identification program according to a fourth aspect of the present disclosure causes a paper sheet identification device to perform a first process of irradiating the transported paper sheets with light of a specific wavelength from a light source; a second process of receiving light arriving from the paper sheets based on the light from the light source and outputting a light detection signal; and a third process of identifying the paper sheets using the light detection signal output from the light detection device. The first and second processes cause the light detection device to output multiple light detection signals with different signal amounts by varying at least one of the irradiation conditions of the light source with light of the specific wavelength and the light receiving conditions of the light detection device during multiple periods within a detection time of one cycle. The third process selects one or more light detection signals from the multiple light detection signals and identifies the paper sheets using the selected one or more light detection signals. [Effects of the Invention]

[0030] This disclosure provides a paper sheet identification device, a paper sheet processing device, a paper sheet identification method, and a paper sheet identification program that can perform identification based on light arriving from paper sheets with high accuracy. [Brief explanation of the drawing]

[0031] [Figure 1] This is a schematic plan view of an example of a genuine banknote, showing its appearance under visible light illumination. [Figure 2] This is a schematic plan view of an example of a genuine banknote, showing it when irradiated with excitation light. [Figure 3] This is a schematic diagram illustrating an example of the configuration of a paper sheet identification device according to Embodiment 1, and is a view from an oblique direction. [Figure 4] This is a schematic diagram illustrating an example of a light detection signal output from a light receiving unit of the paper sheet identification device according to Embodiment 1. [Figure 5] This is a schematic diagram illustrating an example of how the light reception time of the light receiving unit is changed within one detection cycle in the paper sheet identification device according to Embodiment 1. [Figure 6] This is a schematic diagram illustrating an example of how the emission time of light of a specific wavelength from a light source is changed within one detection cycle in the paper sheet identification device according to Embodiment 1. [Figure 7] This is a schematic diagram illustrating an example of how the magnitude of the current supplied to the light source is changed within one detection cycle in the paper sheet identification device according to Embodiment 1. [Figure 8] This graph schematically shows the relationship between the integrated amount of excitation light irradiated onto the fluorescent ink and the amount of fluorescence emitted by the fluorescent ink. [Figure 9] This is a schematic diagram illustrating an example of a method in which the paper sheet identification device according to Embodiment 1 changes the emission time of light of a specific wavelength from the light source and the magnitude of the current supplied to the light source within one detection cycle. [Figure 10]This is a schematic diagram illustrating another example of a photodetection signal output from the light-receiving unit of the paper sheet identification device according to Embodiment 1, showing the case where fluorescence detection signals in multiple wavelength bands are detected. [Figure 11] This is a schematic diagram illustrating an example of how phosphorescence is received in the paper sheet identification device according to Embodiment 1 by changing the light reception time of the light receiving unit within one detection cycle. [Figure 12] This is a schematic diagram illustrating an example of a configuration in which multiple types of light with different wavelengths, including light of a specific wavelength, are irradiated within one detection cycle in the paper sheet identification device according to Embodiment 1. [Figure 13] This is a flowchart illustrating an example of the operation of the paper sheet identification device according to Embodiment 1. [Figure 14] This is a schematic perspective view showing the external appearance of an example of a paper sheet processing device according to Embodiment 2. [Figure 15] This is a schematic cross-sectional diagram illustrating an example of the configuration of the imaging unit of the paper sheet identification device according to Embodiment 2. [Figure 16] This is a schematic perspective view illustrating an example of the configuration of the light-receiving unit of the paper sheet identification device according to Embodiment 2. [Figure 17] Figure 16 is a schematic diagram showing the wavelength characteristics of the color filter in the light-receiving section. [Figure 18] This is a schematic perspective diagram illustrating another example of the configuration of the light-receiving unit of the paper sheet identification device according to Embodiment 2. [Figure 19] Figure 18 is a schematic diagram showing the wavelength characteristics of the color filter in the light-receiving section. [Figure 20] This is a block diagram illustrating an example of the configuration of a paper sheet identification device according to Embodiment 2. [Figure 21] This is a schematic diagram illustrating an example of a photodetection signal output from the light-receiving unit of the paper sheet identification device according to Embodiment 2, showing the case where a fluorescence detection signal in the green wavelength band and a fluorescence detection signal in the infrared region are detected. [Figure 22] This is a schematic diagram illustrating an example of spectral overlap correction and evaluation value calculation using the light detection signal output from the light receiving unit of the paper sheet identification device according to Embodiment 2. [Modes for carrying out the invention]

[0032] Hereinafter, embodiments of the paper sheet identification device, paper sheet processing device, paper sheet identification method, and paper sheet identification program related to this disclosure will be described in detail with reference to the drawings. Various types of paper sheets are applicable to this disclosure, such as banknotes, checks, gift certificates, bills of exchange, business forms, securities, and card-type media, but in the following, this disclosure will be described using a device targeting banknotes as an example.

[0033] The paper sheet identification program may be pre-installed in the paper sheet identification device or paper sheet processing device, or it may be recorded on a computer-readable recording medium or provided to the operator via a network.

[0034] Thus, the paper sheet identification device and paper sheet identification processing device according to this disclosure may include a storage unit composed of a semiconductor memory (RAM or ROM), a hard disk, or other storage device.

[0035] Furthermore, in the following explanation, the same reference numerals are used in common across different drawings for identical parts or parts with similar functions, and repeated explanations are omitted as appropriate. In addition, mutually orthogonal XYZ coordinate systems are shown as appropriate in the drawings illustrating the structure.

[0036] (Embodiment 1) First, let's explain the banknotes to be identified. As shown in Figure 1, the banknotes to be identified (BN) have color printing in a designated area, depicting portraits and designs. In addition, as shown in Figure 2, the banknotes to be identified (BN) have fluorescent ink printed in a designated area R, which can be used for authenticity determination.

[0037] This fluorescent ink contains one or more photoluminescent compounds and emits fluorescence (photoluminescence detectable during excitation light irradiation) in a predetermined wavelength band while irradiated with excitation light (e.g., ultraviolet light). The wavelength of fluorescence emitted from the fluorescent ink is not particularly limited, and the fluorescent ink may emit fluorescence in the visible and / or infrared regions, or in multiple wavelength bands. Similarly, the fluorescence of the fluorescent ink may have at least one peak wavelength in the visible and / or infrared regions.

[0038] Furthermore, in addition to fluorescence, the fluorescent ink may emit phosphorescence (photoluminescence that can be detected after the excitation light is turned off) in a predetermined wavelength band during the period after irradiation with excitation light (e.g., ultraviolet light) has been turned off.

[0039] Furthermore, this fluorescent ink does not emit light when irradiated with visible light, and may transmit visible light, so that it does not need to be visible to the human eye under conditions where visible light is irradiated, such as under natural light or general artificial lighting (see Figure 1). On the other hand, when the fluorescent ink is irradiated with excitation light, it emits light at least in the visible range, and as a result, the fluorescent or phosphorescent component may be visible to the human eye (see Figure 2).

[0040] Next, the configuration of the paper sheet identification device according to this embodiment will be described using Figure 3.

[0041] As shown in Figure 3, the paper sheet identification device 1 according to this embodiment detects light coming from the banknote BN to be identified, and comprises a light source 11 capable of irradiating the transported banknote BN with light of a specific wavelength, a light receiving unit 13 that receives light coming from the banknote BN based on the light from the light source 11 and outputs a light detection signal, a light detection control unit 27 that controls the light source 11 and the light receiving unit 13, and an identification unit 23 that identifies the banknote BN to be identified using the light detection signal output from the light receiving unit 13.

[0042] Here, the banknote BN to be identified may be transported in the X direction within the XY plane. The Y direction may correspond to the main scanning direction of the light receiving unit 13, and the X direction may correspond to the sub-scanning direction of the light receiving unit 13.

[0043] The light detection control unit 27 controls the light source 11 and the light receiving unit 13 so that at least one of the irradiation conditions of the light source 11 with a specific wavelength of light and the light receiving conditions of the light receiving unit 13 are different during multiple periods within one detection cycle, and as a result, multiple light detection signals with different signal amounts are output from the light receiving unit 13. In other words, during these multiple periods, even though light of a specific wavelength, i.e., the same type of light, is irradiated onto substantially the same location on the transported banknote BN (for example, the same location of fluorescent ink), the change in irradiation conditions and / or light receiving conditions causes differences in the magnitude of the output signal from the light receiving unit.

[0044] "Signal amount" refers to the output value (signal value) of the light detection signal output from the light receiving unit, and is a value that fluctuates according to the amount of light incident on the light receiving unit (amount of light received).

[0045] Hereinafter, multiple periods set within the detection time of one cycle may be referred to as "frames." The multiple frames included in one cycle include frames in which the irradiation conditions of the light source 11 and / or the light receiving conditions of the light receiving unit 13 are different from each other. Furthermore, among the multiple frames, the "multiple periods" used to output multiple light detection signals with different signal amounts may be referred to as "specific frames."

[0046] Note that multiple frames may be set at regular time intervals within a single cycle. Also, adjacent frames represent periods that do not overlap in time.

[0047] In this embodiment, the identification unit 23 selects one or more light detection signals from among a plurality of light detection signals output from the light receiving unit 13, and uses the selected one or more light detection signals to identify the banknote BN to be identified. As a result, for the same identification target (e.g., fluorescent ink) that can be detected within one detection cycle, the appropriate light detection signal can be used from among a plurality of light detection signals with different signal amounts. Therefore, even if there are differences in the intensity of the light coming from the banknote BN, for example, the amount of fluorescence emission, the light can be accurately detected. In other words, it becomes possible to perform identification based on the light coming from the banknote BN with high accuracy.

[0048] In the case of fluorescence detection, the following effects can be achieved more specifically. That is, even if the fluorescence decreases due to degradation during distribution, etc., the fluorescence can still be detected. This is because, while conventional fluorescence detection performs fluorescence detection on one frame per cycle, as described above, by having multiple frames with different conditions, it is possible to accurately detect the emission signals of fluorescent ink from strong to weak emission.

[0049] Furthermore, in banknotes containing a mixture of highly luminescent and weakly luminescent fluorescent inks, the weakly luminescent ink can be reliably detected. This is because, while the signal amount for weakly luminescent ink is small in a single-frame fluorescence detection signal, using fluorescence detection signals acquired from multiple frames allows for the summing of these signal amounts. As a result, the signal-to-noise ratio improves, and fluorescence detection becomes more stable.

[0050] The identification unit 23 may also be used to determine the authenticity of the banknote BN (e.g., fluorescent ink) to be identified.

[0051] Hereinafter, the optical detection signal selected by the identification unit 23 and used to identify the banknote BN to be identified may be referred to as the "identification signal."

[0052] The light source 11 irradiates the banknote BN with light of a specific wavelength. The light source 11 may be located on the same side as the light receiving unit 13 relative to the banknote BN.

[0053] The light source 11 may be longer than the length of the banknote BN in the Y direction, and may illuminate the entire banknote BN in the Y direction in a straight line extending in the Y direction. In this case, the light source 11 may comprise a transparent, linear rod-shaped light guide and light-emitting elements (usually multiple, for example, LEDs (Light Emitting Diodes)) facing at least one of the end faces of the light guide, and may illuminate the banknote BN with light via the light guide.

[0054] The light-receiving unit 13 is configured to receive light arriving from the banknote BN based on light from the light source 11. For example, the light-receiving unit 13 may be configured to receive fluorescence emitted from the banknote BN while it is irradiated with light of a specific wavelength. That is, the light-receiving unit 13 may be configured to detect fluorescence from the banknote BN. Alternatively, the light-receiving unit 13 may be configured to receive reflected or transmitted light reflected or transmitted by the banknote BN while it is irradiated with light of a specific wavelength, or it may be configured to receive phosphorescence emitted from the banknote BN after it has been irradiated with light of a specific wavelength. In this case, the light-receiving unit 13 can function as a sensor sensitive to at least one wavelength band among the wavelength band of fluorescence emitted from the fluorescent ink, the wavelength band of reflected or transmitted light of the specific wavelength, and the wavelength band of phosphorescence emitted from the fluorescent ink. The light-receiving unit 13 then outputs an electrical signal (which may be a digital signal) corresponding to the amount of incident light (amount of light received). In other words, the light detection signal is an electrical signal corresponding to the amount of incident light coming from the banknote (BN).

[0055] The light-receiving unit 13 may include one or more light-receiving elements, which may receive light, convert it into an electrical signal corresponding to the amount of incident light, and output it.

[0056] The light-receiving unit 13 may be longer than the length of the banknote BN in the Y direction, and may receive light that has been transmitted, reflected, or emitted along the entire Y direction of the banknote BN.

[0057] The light-receiving unit 13 may output an electrical signal corresponding to the amount of incident light as image data. In this case, the light-receiving unit 13 may have multiple pixels arranged in a row in the Y direction (main scanning direction). That is, the light-receiving unit 13 may output an electrical signal corresponding to the amount of incident light in multiple channels corresponding to multiple pixels (positions in the Y direction (main scanning direction)). Note that a channel (row) is a number assigned sequentially to the light-receiving element (image sensor) in the Y direction. In this case, the light-receiving unit 13 may output line data as image data, which is data relating to the light received simultaneously in each channel. By repeatedly irradiating the banknote BN with light from the light source 11 and receiving the light with the light-receiving unit 13 while transporting the banknote BN in the X direction (sub-scanning direction), image data of the entire banknote BN may be output.

[0058] Thus, the light source 11 and the light receiving unit 13 may acquire an image of the entire banknote BN by continuously repeating the imaging process, with a predetermined cycle of imaging being considered as one period.

[0059] In this specification, one cycle refers to a control pattern in which the timing of turning on and off the light-emitting elements in each wavelength band, and the timing of signal reading are set. One cycle of this control pattern is considered one period, and by continuously repeating this, a light detection signal may be obtained from the entire sheet of paper. One cycle may also represent a periodic control pattern related to turning on, off, and receiving light set to acquire reflected and / or transmitted light images of the sheet of paper.

[0060] A reflected light image is an image based on light reflected by paper sheets that are illuminated from a light source positioned on the same side as the light-receiving unit. A transmitted light image is an image based on light transmitted through paper sheets that are illuminated from a light source positioned on the opposite side of the light-receiving unit. Therefore, reflected light images and transmitted light images are distinct from fluorescent or phosphorescent images, which are based on fluorescence or phosphorescence emitted from the paper sheets.

[0061] The image data acquired by the light-receiving unit 13 consists of multiple pixels arranged in a matrix in the Y direction (main scanning direction) and the X direction (sub-scanning direction). The address of each pixel is identified by the channel (column) of the light-receiving unit 13 corresponding to its position in the Y direction and the line (row) corresponding to its position in the X direction. The line (row) is a number sequentially assigned to the line data output sequentially by the light-receiving unit 13.

[0062] Furthermore, the light-receiving unit 13 may receive light of multiple wavelength bands arriving from the banknote BN and output electrical signals (photodetection signals) for each of the multiple wavelength bands. In this case, each pixel may be equipped with multiple light-receiving elements that selectively receive light of different wavelength bands.

[0063] Multiple wavelength bands that the light-receiving unit 13 can selectively receive include red (R), green (G), blue (B), infrared (IR), and others.

[0064] In this specification, "blue" generally refers to light (color) with a wavelength of approximately 400 nm to 500 nm, and may also refer to light (color) having a peak wavelength in this wavelength range. "Green" generally refers to light (color) with a wavelength of approximately 500 nm to 600 nm, and may also refer to light (color) having a peak wavelength in this wavelength range. "Red" generally refers to light (color) with a wavelength of approximately 600 nm to 750 nm, and may also refer to light (color) having a peak wavelength in this wavelength range. Furthermore, "infrared light" generally refers to light with a wavelength of 750 nm or more, and may also refer to light having a peak wavelength in this wavelength range. "Near-infrared light" generally refers to light with a wavelength of approximately 750 nm to 1500 nm, and may also refer to light having a peak wavelength in this wavelength range.

[0065] The light-receiving unit 13 may receive both visible and infrared light emitted from the banknote BN without separating them, and output a light detection signal that includes a signal value corresponding to the total light intensity of both components. In this case, the signal value corresponding to the total light intensity of both components may be separated into a signal amount corresponding to the visible light and a signal amount corresponding to the infrared light by spectral overlap correction, and these separated signal amounts may be used as the output values ​​for the visible light and infrared light of the banknote BN.

[0066] On the other hand, the light receiving unit 13 may separate the visible light and infrared light emitted from the banknote BN, receive them independently, and output signal values ​​corresponding to the light intensity of each component. In this case, these signal values ​​can be used as the output values ​​for the visible light and infrared light of the banknote BN, respectively, without spectral overlap correction.

[0067] The specific method for performing spectral overlap correction is not particularly limited, and for example, the method described in Patent Document 4 or the method described in Embodiment 2 below may be used.

[0068] As shown in Figure 4, the identification unit 23 may select one or more optical detection signals from among multiple optical detection signals, where the signal amount is within a predetermined range, as one or more identification signals. In the case shown in Figure 4, the signal amount of optical detection signal A is below the detection limit, and the signal amount of optical detection signal D is saturated. On the other hand, the signal amounts of optical detection signals B and C are within a predetermined range, that is, within a range that exceeds the detection limit but does not saturate. Therefore, the identification unit 23 selects and uses optical detection signal B of frame 2 and / or optical detection signal C of frame 3.

[0069] The identification unit 23 may select only one optical detection signal from among multiple optical detection signals as one or more identification signals, and use this selected optical detection signal to identify the banknote BN. This simplifies the calculations for the identification process using the identification signal.

[0070] In particular, the identification unit 23 may select only the optical detection signal with the highest signal intensity from among multiple optical detection signals as one or more identification signals, and use this selected single optical detection signal to identify the banknote BN. This allows identification to be performed using an identification signal with a higher S / N ratio, thus enabling more accurate identification of banknote BNs. The selected single optical detection signal may have a signal intensity within a predetermined range, as described above.

[0071] The identification unit 23 may select two or more optical detection signals from among multiple optical detection signals as one or more identification signals, and use the sum of the signal amounts of those two or more selected optical detection signals (sum value) to identify the banknote BN. This also allows identification to be performed using an identification signal with a higher S / N ratio, thus enabling more accurate identification of banknote BNs.

[0072] The number of light detection signals to be combined is not particularly limited as long as it is two or more. For example, the signal amounts of all light detection signals whose signal amounts are within a predetermined range, as described above, may be added together. Thus, the signal amounts of the two or more light detection signals to be combined may all be within a predetermined range, as described above.

[0073] The identification unit 23 may use the above summation value to determine whether or not fluorescent ink is present on the banknote BN to be identified.

[0074] The identification unit 23 may select two optical detection signals from among multiple optical detection signals as one or more identification signals, calculate the ratio of the signal amounts of the two selected optical detection signals, and use that ratio to identify banknote BN. For example, in the case shown in Figure 4, the ratio of the signal amounts of optical detection signals B and C (for example, the value obtained by dividing the signal amount of optical detection signal C by the signal amount of optical detection signal B) may be used to identify banknote BN. That is, the signal amounts of the two optical detection signals from which the ratio is calculated may both be within a predetermined range, as described above.

[0075] As described above, the identification unit 23 may identify banknotes BN using the signal amount of the selected light detection signal itself, or it may identify banknotes BN using an evaluation value (for example, a sum or ratio) based on that signal amount.

[0076] In either case, the identification unit 23 may determine the identification of the banknote BN, for example, whether or not it contains fluorescent ink, based on whether the signal amount or evaluation value of the selected light detection signal is within an acceptable range relative to the reference data.

[0077] The "reference data" referenced by the identification unit 23 is information that defines a standard (e.g., a threshold) for the signal amount of a (genuine) light-detection signal that is acceptable as being from a genuine banknote. This may include, for example, the upper and lower limits of the signal amount or evaluation value of a light-detection signal detected from a genuine banknote. Furthermore, determining whether a signal amount or evaluation value is within an acceptable range with respect to the reference data may mean determining whether that signal amount or evaluation value is between the upper and lower limits of the signal amount or evaluation value of the light-detection signal defined by the reference data.

[0078] The reference data may include a reference corresponding to each of several specific frames. That is, the reference data may include a reference set for each of several conditions with different irradiation conditions of the light source 11 and / or light receiving conditions of the light receiving unit 13. Also, when using a summation value, the reference data may include a reference corresponding to the summation value (a reference for the summation value for each combination of signal quantities that can be summed), or it may include a reference corresponding to each of several specific frames (a reference for the signal quantity). In the latter case, the references for the signal quantities corresponding to the signal quantities used to calculate the summation value may be added together and used. Also, when using a ratio, the reference data may include a reference for the ratio, or it may include a reference corresponding to each of several specific frames (a reference for the signal quantity). In the latter case, the ratio may be calculated from the reference for the signal quantities corresponding to the signal quantities used to calculate the ratio and used.

[0079] The conditions for making the signal amounts differ from one another in multiple specific frames, namely the irradiation conditions of the light source 11 with light of a specific wavelength and the light receiving conditions of the light receiving unit 13, are not particularly limited and include, for example, the light receiving time (exposure time) of the light receiving unit 13, the light emission time (lighting time) of the light source 11, and the magnitude of the current supplied to the light source 11. The longer the light receiving time of the light receiving unit 13, the greater the signal amount. The longer the light emission time of the light source 11, the greater the signal amount. The larger the current supplied to the light source 11, the greater the irradiation intensity of the light source 11, and therefore the greater the signal amount.

[0080] In other words, as shown in Figure 5, the light detection control unit 27 may change the light reception time of the light receiving unit 13 in a plurality of specific frames. In this case, the light emission time of the light source 11 and the magnitude of the current supplied to the light source 11 may be constant in the plurality of specific frames.

[0081] Furthermore, as shown in Figure 6, the light detection control unit 27 may change the emission time of light of a specific wavelength from the light source 11 in a plurality of specific frames. In this case, the light reception time of the light receiving unit 13 and the magnitude of the current supplied to the light source 11 may be constant in the plurality of specific frames.

[0082] Furthermore, as shown in Figure 7, the light detection control unit 27 may change the magnitude of the current supplied to the light source 11 in a plurality of specific frames. In this case, the light reception time of the light receiving unit 13 and the light emission time of the light source 11 may be constant in a plurality of specific frames.

[0083] Furthermore, at least two of the following—the light-receiving time of the light-receiving unit 13, the light-emitting time of the light source 11, and the magnitude of the current supplied to the light source 11—do not necessarily have to be constant for multiple specific frames. In other words, the signal amount can be changed by changing two or three of these three conditions.

[0084] For example, as shown in Figure 8, the amount of fluorescence emission is proportional to the integrated amount of excitation light on the fluorescent ink; that is, as the integrated amount of light increases, the amount of fluorescence emission also increases. Furthermore, the integrated amount of light is proportional to the product of the emission time of the light source 11 and the current supplied to the light source 11. Therefore, as shown in Figure 9, the emission time of the light source 11 and the current supplied to the light source 11 can be made different for multiple specific frames. In the case shown in Figure 9, since the integrated amount of light (relative value) increases to 3, 6, and 8, the amount of fluorescence emission also increases, and it is thought that the signal amount acquired for multiple specific frames also increases.

[0085] The wavelength of light that the light source 11 irradiates onto the banknote BN to be identified is not particularly limited, but examples include ultraviolet light, visible light, infrared light, etc. That is, the light source 11 may irradiate the banknote BN with light of a specific wavelength, which may be ultraviolet light, visible light, or infrared light.

[0086] Furthermore, the light source 11 may irradiate the banknote BN with excitation light of a specific wavelength, and the light receiving unit 13 may receive fluorescence or phosphorescence emitted from the banknote BN.

[0087] Thus, the light-receiving unit 13 receives fluorescence emitted from the banknote BN and outputs multiple fluorescence detection signals as multiple photodetection signals, and the identification unit 23 may select one or more fluorescence detection signals from the multiple fluorescence detection signals as one or more identification signals, and use the selected one or more fluorescence detection signals to identify the banknote BN. This makes it possible to determine the authenticity of the ink based on the fluorescence characteristics emitted by the fluorescent ink printed on the banknote BN with high accuracy.

[0088] In this case, the identification unit 23 may calculate the ratio of fluorescence emission amounts at multiple wavelengths using the selected one or more fluorescence detection signals and use that ratio to identify the banknote BN. This allows for more accurate determination of the authenticity of the fluorescent ink in the banknote BN when the fluorescent ink emits fluorescence in multiple wavelength bands.

[0089] For example, suppose the fluorescent ink in banknote BN emits fluorescence in a first wavelength band and a second wavelength band, and as shown in Figure 10, the fluorescence detection signals in the first wavelength band and the fluorescence detection signals in the second wavelength band are detected in multiple specific frames. Furthermore, suppose that the fluorescence detection signals E and F in the first wavelength band and the fluorescence detection signals J and K in the second wavelength band have fluorescence emission amounts (signal amounts) that fall within a predetermined range, that is, a range that exceeds the detection limit but does not saturate. In this case, the ratio of fluorescence emission amounts can be the ratio of at least one fluorescence emission amount of the fluorescence detection signals E and F in the first wavelength band to the fluorescence emission amount of at least one fluorescence emission amount of the fluorescence detection signals J and K in the second wavelength band.

[0090] Furthermore, if two or more fluorescence detection signals are used for a given wavelength band, their combined values ​​may be used. For example, the ratio of the combined fluorescence emission values ​​of fluorescence detection signals E and F to the combined fluorescence emission values ​​of fluorescence detection signals J and K may be used. Alternatively, the ratio may be expressed as a percentage.

[0091] When using a combined value, the number of photodetection signals being combined may be the same across multiple wavelength bands, or it may differ depending on the wavelength band.

[0092] The ratio of fluorescence emission at the multiple wavelengths mentioned above may be the ratio of fluorescence emission at visible light to fluorescence emission at infrared light. This allows for highly accurate determination of the authenticity of fluorescent inks that emit fluorescence in both the visible and infrared regions. For example, in the case shown in Figure 10, the first wavelength band may be the visible region and the second wavelength band may be the infrared region. Examples of the first and second wavelength bands include combinations of red (R), green (G), or blue (B) wavelength bands with the infrared or near-infrared region.

[0093] The ratio of visible light fluorescence emission to infrared light fluorescence emission may be calculated by dividing the visible light fluorescence emission by the infrared light fluorescence emission, or vice versa, or by the percentages thereof.

[0094] "Fluorescence emission amount" refers to a value indicating the intensity (brightness) of the fluorescence. The fluorescence emission amount may be the signal amount of the fluorescence detection signal itself, a corrected version of the fluorescence detection signal (for example, the signal amount of the fluorescence detection signal corrected by overlap correction), or the signal amount of the fluorescence detection signal divided by the signal amount due to the fluorescence of the fluorescent ink's base material (e.g., paper).

[0095] The light receiving unit 13 receives phosphorescence emitted from the banknote BN and outputs multiple phosphorescence detection signals as multiple light detection signals. The identification unit 23 may select one or more phosphorescence detection signals from the multiple phosphorescence detection signals as one or more identification signals and use the selected one or more phosphorescence detection signals to identify the banknote BN. This makes it possible to determine the authenticity of the ink based on the phosphorescence characteristics emitted by the fluorescent ink printed on the banknote BN with high accuracy.

[0096] In this case, as shown in Figure 11, the light receiving unit 13 receives phosphorescence after the light source 11 is turned off (during the period when the light source 11 is off). The periods when the light source 11 is on and the periods when the light receiving unit 13 receives light may be arranged alternately.

[0097] In Figure 11, only the light reception time of the light receiving unit 13 is changed in multiple specific frames. However, as explained in Figures 5-7 and 9, the emission time of light of a specific wavelength from the light source 11 and / or the magnitude of the current supplied to the light source 11 may also be changed.

[0098] Furthermore, as explained above, multiple specific pieces may be placed consecutively within one cycle, or they may be placed discretely between other pieces, as shown in Figure 12.

[0099] Thus, the light source 11 may emit multiple types of light with different wavelengths, including light of a specific wavelength for a specific frame, within the detection time of one cycle. This makes it possible to perform identification using types of light other than light of a specific wavelength.

[0100] As shown in Figure 12, the light source 11 may irradiate with excitation light as light of a specific wavelength, and as other types of light, it may irradiate with infrared light (IR1 to IR3) in different wavelength bands and white light (W) including red light, green light, and blue light.

[0101] Next, the operation of the paper sheet identification device 1 according to this embodiment will be explained using Figure 13.

[0102] As shown in Figure 13, first, the light source 11 irradiates the banknote BN to be identified with light of at least a specific wavelength (first step S11).

[0103] Next, the light receiving unit 13 receives light arriving from the banknote BN to be identified, which is irradiated with light of a specific wavelength, and outputs a light detection signal (second step S12).

[0104] In the first step S11 and the second step S12, the light detection control unit 27 causes the light receiving unit 13 to output multiple light detection signals with different signal amounts by varying at least one of the irradiation conditions of light of a specific wavelength from the light source 11 and the light receiving conditions of the light receiving unit 13 in multiple frames within the detection time of one cycle.

[0105] Subsequently, the identification unit 23 identifies the banknote BN to be identified using the light detection signal output from the light receiving unit 13 (third step S13), and the operation of the paper sheet identification device 1 ends.

[0106] In the third step S13, one or more optical detection signals are selected from among multiple optical detection signals, and the selected one or more optical detection signals are used to identify the banknote BN.

[0107] The light detection control unit 27 and the identification unit 23 may function by executing corresponding programs by the control units described later.

[0108] (Embodiment 2) The paper sheet processing device according to this embodiment may have, for example, the configuration shown in Figure 14. The paper sheet processing device 300 shown in Figure 14 is a small paper sheet processing device that is installed and used on a table, and comprises a paper sheet identification device (not shown in Figure 14) that performs banknote identification processing, a hopper 301 on which a plurality of banknotes to be processed are placed in a stacked state, two reject units 302 that discharge rejected banknotes such as counterfeit bills and bills of uncertain authenticity that are fed from the hopper 301 into the housing 304, an operation unit 303 for inputting instructions from the operator, four stacking units 306a to 306d for classifying and stacking banknotes whose denomination, authenticity, and condition have been identified within the housing 304, and a display unit 305 for displaying information such as the banknote identification counting results and the stacking status of each stacking unit 306a to 306d. Based on the results of the paper sheet identification device's determination of whether a banknote is genuine or damaged, genuine banknotes are stored in storage units 306a to 306c, and damaged banknotes are stored in storage unit 306d. The method for distributing banknotes to storage units 306a to 306d can be set arbitrarily.

[0109] Next, the configuration of the imaging unit, which is the main part of the paper sheet identification device according to this embodiment, will be described using Figure 15. As shown in Figure 15, the imaging unit 211 comprises an upper unit 110 and a lower unit 120 that are arranged facing each other. A gap is formed between the upper unit 110 and the lower unit 120, which are spaced apart in the Z direction, through which banknotes BN are transported in the X direction within the XY plane. This gap constitutes part of the transport path of the paper sheet processing device according to this embodiment. The upper unit 110 and the lower unit 120 are located on the upper side (+Z direction) and lower side (-Z direction) of the transport path, respectively. The Y direction corresponds to the main scanning direction of the imaging unit 211, and the X direction corresponds to the sub-scanning direction of the imaging unit 211.

[0110] As shown in Figure 15, the upper unit 110 is equipped with two reflective light sources 111, a condensing lens 112, and a light receiving unit 113. The reflective light sources 111 sequentially irradiate the main surface (hereinafter referred to as surface A) of the banknote BN on the light receiving unit 113 side with illumination light having different wavelength bands, specifically infrared light, white light including red, green, and blue light, and ultraviolet light as excitation light for fluorescence. The condensing lens 112 collects the light emitted from the reflective light sources 111 and reflected from surface A of the banknote BN, the light emitted from the transmitting light source 124 provided in the lower unit 120 and transmitted through the banknote BN, and the fluorescence emitted from surface A of the banknote BN. The light receiving unit 113 receives the light collected by the condensing lens 112 and converts it into an electrical signal. After amplifying the electrical signal, it performs A / D conversion to digital data and outputs it. Here, the light received by the light-receiving unit is also called incident light, and the light emitted by the light source is also called emitted light.

[0111] The lower unit 120 includes two reflective light sources 121 and one transmissive light source 124, a condensing lens 122, and a light receiving unit 123. The reflective light sources 121 irradiate the main surface (hereinafter referred to as the B-side) of the banknote BN on the light receiving unit 123 side with illumination light having different wavelength bands, specifically infrared light, white light including red, green, and blue light, and ultraviolet light as excitation light for fluorescence. The condensing lens 122 focuses the light emitted from the reflective light sources 121 and reflected from the B-side of the banknote BN, as well as the fluorescence emitted from the B-side of the banknote BN. The light receiving unit 123 receives the light focused by the condensing lens 122 and converts it into an electrical signal. After amplifying the electrical signal, it performs A / D conversion to digital data and outputs it.

[0112] The light source 124 for transmission is positioned on the optical axis of the focusing lens 112 of the upper unit 110. A portion of the light emitted from the light source 124 passes through the banknote BN and is focused by the focusing lens 112 of the upper unit 110 and detected by the light receiving unit 113. The light source 124 may sequentially irradiate the B side of the banknote BN with light having different wavelength bands, or it may irradiate them simultaneously.

[0113] In this specification, light with different wavelength bands (irradiated light, incident light, etc.) refers, for example, to light with different colors in the case of visible light, and to light with wavelength bands that overlap only partially or that do not overlap in the case of infrared and ultraviolet light.

[0114] Each light source 111, 121, and 124 includes a line-shaped light guide (not shown) extending in a direction perpendicular to the plane of the paper in Figure 15 (main scanning direction D1), and a plurality of LED elements (not shown) provided at both ends (or one end) of the light guide.

[0115] Each light source 111, 121 may include an LED element that emits infrared light with a peak wavelength of 750 nm or more, an LED element that emits red light (R) with a peak wavelength of 600 nm or more and less than 750 nm, an LED element that emits green light (G) with a peak wavelength of 500 nm or more and less than 600 nm, an LED element that emits blue light (B) with a peak wavelength of 400 nm or more and less than 500 nm, and an LED element that emits ultraviolet light (UV) with a peak wavelength of less than 400 nm. One light source 111 is placed on the upstream and downstream sides in the transport direction, flanking the condensing lens 112, and one light source 121 is placed on the upstream and downstream sides in the transport direction, flanking the condensing lens 122.

[0116] The light source 124 may include multiple LED elements that emit light having different peak wavelengths. The peak wavelength refers to the wavelength at which the light emission intensity is maximum.

[0117] As shown in Figure 16, in this embodiment, each light-receiving unit 113, 123 includes a first light-receiving element 31B having a color filter 32B, a second light-receiving element 31G having a color filter 32G, and a third light-receiving element 31R having a color filter 32R.

[0118] More specifically, each light-receiving unit 113, 123 is equipped with a plurality of pixels 30 arranged in a row in the main scanning direction D1 (the direction perpendicular to the transport direction of the banknote BN, the Y direction). Each pixel 30 is equipped with one first light-receiving element (image sensor) 31B, one second light-receiving element (image sensor) 31G, and one third light-receiving element (image sensor) 31R. The first light-receiving element 31B, the second light-receiving element 31G, and the third light-receiving element 31R are arranged in this order in a row in the main scanning direction D1.

[0119] Here, a light-receiving element (image sensor) means an element that detects (converts into an electrical signal) the intensity of light in a predetermined wavelength band, and may be configured to include a photodetector such as a photodiode, and a color filter (color resist) provided on the light-receiving surface of the photodetector that suppresses the transmission of light in wavelength bands other than the predetermined wavelength band to be detected (for example, the blue and infrared wavelength bands) (for example, the green and red wavelength bands).

[0120] As shown in Figure 16, the first light-receiving element 31B may include a photodetector 33 and a color filter 32B, the second light-receiving element 31G may include a photodetector 33 and a color filter 32G, and the third light-receiving element 31R may include a photodetector 33 and a color filter 32R.

[0121] Furthermore, as shown in Figure 17, color filter 32B transmits blue light and infrared light, color filter 32G transmits green light and infrared light, and color filter 32R transmits red light and infrared light. Therefore, the first light-receiving element 31B, the second light-receiving element 31G, and the third light-receiving element 31R each receive infrared light along with their corresponding visible light. Color filter 32B absorbs green light and red light, color filter 32G absorbs blue light and red light, and color filter 32R absorbs blue light and green light.

[0122] Therefore, each light-receiving unit 113, 123 receives the reflected light, transmitted light, or fluorescence in the visible range and the reflected light, transmitted light, or fluorescence in the infrared range emitted from the banknote BN together without separating them, and outputs a photodetection signal that includes a signal value corresponding to the total light intensity of both components. As a result, spectral overlap correction may be necessary depending on the object to be identified.

[0123] On the other hand, as shown in Figure 18, in this embodiment, each light-receiving unit 113, 123 may include a first light-receiving element 41B having a color filter 42B, a second light-receiving element 41G having a color filter 42G, a third light-receiving element 41R having a color filter 42R, and a fourth light-receiving element 41IR having a color filter 42IR.

[0124] More specifically, each light-receiving unit 113, 123 may include a plurality of pixels 40 arranged in a row in the main scanning direction D1 (the direction perpendicular to the transport direction of the banknote BN, the Y direction), and each pixel 40 may include one first light-receiving element (image sensor) 41B, one second light-receiving element (image sensor) 41G, one third light-receiving element (image sensor) 41R, and one fourth light-receiving element (image sensor) 41IR, and the first light-receiving element 41B, the second light-receiving element 41G, the third light-receiving element 41R, and the fourth light-receiving element 41IR may be arranged in this order in a row in the main scanning direction D1.

[0125] As shown in Figure 18, the first light-receiving element 41B may include a photodetector 43 and a color filter 42B, the second light-receiving element 41G may include a photodetector 43 and a color filter 42G, the third light-receiving element 41R may include a photodetector 43 and a color filter 42R, and the fourth light-receiving element 41IR may include a photodetector 43 and a color filter 42IR.

[0126] As shown in Figure 19, color filter 42B transmits blue light, color filter 42G transmits green light, and color filter 42R transmits red light, but color filters 42B, 42G, and 42R do not transmit infrared light. Therefore, the first photodetector 41B, the second photodetector 41G, and the third photodetector 41R each receive only their corresponding visible light and do not receive infrared light. Color filter 42B absorbs green light, red light, and infrared light, color filter 42G absorbs blue light, red light, and infrared light, and color filter 42R absorbs blue light, green light, and infrared light. Color filter 42IR transmits infrared light but absorbs visible light without transmitting it.

[0127] Therefore, in this case, each light-receiving unit 113, 123 separates the reflected light, transmitted light, or fluorescence in the visible range from the reflected light, transmitted light, or fluorescence in the infrared range emitted from the banknote BN, and receives the light independently, outputting signal values ​​corresponding to the light intensity of each component. Thus, spectral overlap correction is unnecessary.

[0128] The upper unit 110 and the lower unit 120 each repeatedly capture images of the banknote BN being transported in the transport direction and output signals corresponding to the amount of light received, thereby enabling the imaging unit 211 to acquire an image of the entire banknote BN. Specifically, the imaging unit 211 acquires a transmitted light image and a reflected light image of side A of the banknote BN based on the output signal of the upper unit 110, and acquires a reflected light image of side B of the banknote BN based on the output signal of the lower unit 120.

[0129] Furthermore, the imaging unit 211 acquires a fluorescence detection signal across the entire banknote BN on both side A and side B of the banknote BN. In other words, the imaging unit 211 can acquire fluorescence images of both side A and side B of the banknote BN. The imaging unit 211 can also acquire a phosphorescence detection signal across the entire banknote BN on both side A and side B of the banknote BN, and acquire phosphorescence images of both side A and side B of the banknote BN.

[0130] Next, the configuration of the paper sheet identification device according to this embodiment will be described using Figure 20. As shown in Figure 20, the paper sheet identification device 200 according to this embodiment includes a detection unit 210, a control unit 220, and a storage unit 230.

[0131] The control unit 220 is a controller that controls each part of the paper sheet identification device 200, and is composed of a program for realizing various processes stored in the memory unit 230, a CPU (Central Processing Unit) that executes the program, and various hardware (e.g., FPGA (Field Programmable Gate Array)) controlled by the CPU. The control unit 220 controls each part of the paper sheet identification device 200 based on signals output from each part of the paper sheet identification device 200 and control signals from the control unit 220, according to the program stored in the memory unit 230. In addition, the control unit 220 has the functions of a light detection control unit 227, an image generation unit 225, and an identification unit 223, according to the program stored in the memory unit 230. The light detection control unit 227 includes a light source control unit 221 and a sensor control unit 224.

[0132] The detection unit 210 includes a magnetic detection unit 212 and a thickness detection unit 213, in addition to the imaging unit 211 described above, along the banknote transport path. The imaging unit 211 captures images of the banknotes as described above and outputs an image signal (image data). The magnetic detection unit 212 is equipped with a magnetic sensor (not shown) for measuring magnetism, and detects magnetism such as magnetic ink and security threads printed on the banknotes using the magnetic sensor. The magnetic sensor is a magnetic line sensor in which multiple magnetic detection elements are arranged in a line. The thickness detection unit 213 is equipped with a thickness detection sensor (not shown) for measuring the thickness of the banknotes, and detects tape, double feeding, etc. using the thickness detection sensor. The thickness detection sensor detects the amount of displacement when banknotes pass through rollers facing each other across the transport path using sensors provided on each roller.

[0133] The memory unit 230 is composed of a non-volatile storage device such as a semiconductor memory or a hard disk, and stores various programs and data for controlling the paper sheet identification device 200. The memory unit 230 also stores imaging parameters such as the wavelength band of the illumination light emitted from each light source 111, 121, and 124 during one imaging cycle by the imaging unit 211, the timing for turning each light source 111, 121, and 124 on and off, the value of the forward current flowing through the LED elements of each light source 111, 121, and 124, and the timing for reading signals from the upper unit 110 and the lower unit 120, respectively.

[0134] One cycle of imaging refers to an imaging pattern in which the wavelength range of the light emitted from each light source 111, 121, and 124, as well as the timing of turning each light source 111, 121, and 124 on and off, and reading the signal, are set. One cycle of imaging constitutes one period, and by continuously repeating this process, an image of the entire banknote is acquired.

[0135] The light source control unit 221 dynamically controls the illumination of each light source 111, 121, and 124 in order to capture individual banknote images using each light source 111, 121, and 124. Specifically, the light source control unit 221 controls the illumination and extinguishing of each light source 111, 121, and 124 based on the timing set in the imaging parameters. This control is performed using a mechanical clock that changes according to the banknote transport speed and a system clock that is always output at a constant frequency regardless of the banknote transport speed. As a result, the light source control unit 221 can change the illumination time (lighting time) of each light source 111, 121, and 124 in multiple specific frames. In addition, the light source control unit 221 controls the magnitude of the forward current supplied to the LED elements of each light source 111, 121, and 124 based on the forward current value set in the imaging parameters. As a result, the light source control unit 221 can change the magnitude of the current supplied to each light source 111, 121, and 124 in multiple specific frames.

[0136] The sensor control unit 224 controls the timing of reading signals from the upper unit 110 and the lower unit 120 based on the timing set in the imaging parameters, and reads signals from the upper unit 110 and the lower unit 120 in synchronization with the timing of the on and off of each light source 111, 121, and 124. This control is performed using the mechanical clock and the system clock. The sensor control unit 224 also controls the timing of light reception (exposure) of each light receiving unit 113 and 123 based on the light reception timing of each light receiving unit 113 and 123 set in the imaging parameters. This makes it possible for the sensor control unit 224 to change the light reception time of each light receiving unit 113 and 123 in multiple specific frames. The sensor control unit 224 then sequentially stores the read signals, i.e., line data, in the ring buffer (line memory) of the storage unit 230.

[0137] Here, line data refers to data based on signals obtained from a single image capture by each of the upper unit 110 and the lower unit 120, and corresponds to data for one row in the horizontal direction (the direction perpendicular to the banknote transport direction, the Y direction) of the acquired image.

[0138] The image generation unit 225 has the function of generating images based on various signals related to banknotes acquired from the detection unit 210. Specifically, the image generation unit 225 first decomposes the data (image signals) stored in the ring buffer into data for each light irradiation and reception condition. Then, according to the characteristics of each decomposed data, the image generation unit 225 performs correction processing such as dark output cut, gain adjustment, and bright output level correction to generate various image data of banknotes and store them in the storage unit 230.

[0139] Furthermore, the image generation unit 225 performs spectral overlap correction on the light detection signal acquired by the imaging unit 211 as needed.

[0140] Specifically, for example, before shipment or during maintenance of the paper sheet identification device 200, the fluorescence emitted from a visible fluorescent ink that fluoresces in a specific visible color and the fluorescence emitted from an infrared fluorescent ink that fluoresces in infrared light are individually received by the light receiving unit, and the reference emission amount (output value) of each fluorescent ink is measured, resulting in output values ​​such as those shown in Table 1 below. Here, it is assumed that the visible fluorescent inks that fluoresce in a specific visible color are, for example, a green visible fluorescent ink that fluoresces in green and a red visible fluorescent ink that fluoresces in red.

[0141] Furthermore, the peak wavelength in the visible range of fluorescence emission from visible fluorescent inks that fluoresce in specific visible colors lies in the same wavelength band as the peak wavelength in the visible range of fluorescence emission from fluorescent inks printed on genuine banknotes. For example, these peak wavelengths lie in the blue, green, or red wavelength band. Similarly, the peak wavelength in the infrared range of fluorescence emission from infrared fluorescent inks that fluoresce in infrared light lies in the same wavelength band as the peak wavelength in the infrared range of fluorescence emission from fluorescent inks printed on genuine banknotes. For example, these peak wavelengths lie in the near-infrared wavelength band.

[0142] [Table 1]

[0143] CH_B represents the output value of the first photodetector 31B, CH_G represents the output value of the second photodetector 31G, and CH_R represents the output value of the third photodetector 31R. As a result, the following equation (1) holds true.

[0144]

number

[0145] Green_INK represents the amount of light emitted (fluorescence signal) of the corrected green visible fluorescent ink, Red_INK represents the amount of light emitted (fluorescence signal) of the corrected red visible fluorescent ink, and IR_INK represents the amount of light emitted (fluorescence signal) of the corrected infrared fluorescent ink.

[0146] By transforming equation (1) above into equation (2) below, the relationship shown in equation (3) below holds.

[0147]

number

[0148]

number

[0149] In other words, by performing a calculation that multiplies the fluorescence detection signal obtained by receiving light in the light receiving unit 13 by the inverse matrix shown below, as shown in equation (4) below, it is possible to calculate (separate) Green_INK, i.e., the amount of light emitted by the corrected green visible fluorescent ink, Red_INK, i.e., the amount of light emitted by the corrected red visible fluorescent ink, and IR_INK, i.e., the amount of light emitted by the corrected infrared fluorescent ink.

[0150]

number

[0151] This inverse matrix may be stored in the memory unit as a correction value.

[0152] Similarly, when using blue visible fluorescent ink, the luminescence of the corrected blue visible fluorescent ink (Blue_INK), the luminescence of the corrected green or red visible fluorescent ink (Green_INK or Red_INK), and the luminescence of the corrected infrared fluorescent ink (IR_INK) can be separated.

[0153] Furthermore, although spectral overlap correction using a 3x3 matrix has been described here, spectral overlap correction using a 4x4 matrix or a 2x2 matrix may also be performed. For example, when using a 4x4 matrix, the fluorescence emitted from three visible fluorescent inks that fluoresce in blue, green, and red, respectively, and the fluorescence emitted from an infrared fluorescent ink that fluoresces in infrared light are individually received by the light receiving unit, and the reference emission amount (output value) of each fluorescent ink is measured. Similar to Table 1 above, a correction formula similar to (4) above can be obtained based on the relationship between the output values ​​of each CH for each fluorescent ink.

[0154] The following provides a more detailed explanation of spectral overlap correction using a 2x2 matrix.

[0155] First, similar to spectral overlap correction using a 3x3 matrix, before shipment or during maintenance of the paper sheet identification device 1, the fluorescence emitted from a visible fluorescent ink that fluoresces in a specific visible color and the fluorescence emitted from an infrared fluorescent ink that fluoresces in infrared light are individually received by the light receiving unit, and the reference emission amount (output value) of each fluorescent ink is measured, resulting in output values ​​such as those shown in Table 2 below. Here, it is assumed that, for example, a green visible fluorescent ink that fluoresces in green is used as the visible fluorescent ink that fluoresces in a specific visible color.

[0156] [Table 2]

[0157] CH_B represents the output value of the first photodetector 31B, CH_G represents the output value of the second photodetector 31G, and CH_R represents the output value of the third photodetector 31R. Furthermore, assuming that the measurement result for the green visible fluorescent ink is at its maximum value b, and the measurement result for the infrared fluorescent ink is at its maximum value f, then the following equation (5) holds.

[0158]

number

[0159] Green_INK represents the amount of light emitted (fluorescence signal) of the corrected green visible fluorescent ink, and IR_INK represents the amount of light emitted (fluorescence signal) of the corrected infrared fluorescent ink.

[0160] When matrix A in equation (5) above is normalized, the following relationship (6) holds.

[0161]

number

[0162] Transforming equation (6) above yields the relationship shown in equation (7) below.

[0163]

number

[0164] Then, as shown in equation (7) above, the inverse matrix B is applied to the fluorescence detection signal obtained by receiving light at the light receiving unit. -1 By performing a multiplication operation, it is possible to calculate (separate) Green_INK, i.e., the amount of light emitted by the corrected green visible fluorescent ink, and IR_INK, i.e., the amount of light emitted by the corrected infrared fluorescent ink.

[0165] This inverse matrix B -1 This value may be stored in the memory unit as a correction value.

[0166] Similarly, when using blue or red visible fluorescent ink as a specific color, it is possible to separate the luminescence of the corrected blue or red visible fluorescent ink (Blue_INK or Red_INK) from the luminescence of the corrected infrared fluorescent ink (IR_INK).

[0167] Furthermore, while this explanation described the case where the output value of the photodetector (second photodetector 31G) that yields the maximum measurement result for a specific color of visible fluorescent ink and the output value of the photodetector (third photodetector 31R) that yields the maximum measurement result for infrared fluorescent ink are used, from the perspective of separation accuracy for spectral overlap correction, spectral overlap correction using a 2x2 matrix is ​​possible regardless of the combination of photodetectors.

[0168] The identification unit 223 then selects one or more light detection signals from among the multiple light detection signals output from the light receiving units 113 and / or 123 in multiple specific frames, and uses the selected one or more light detection signals to identify the banknote BN to be identified.

[0169] Here, we will explain in more detail the spectral overlap correction and the calculation processing by the identification unit 223 using Figures 21 and 22.

[0170] As shown in Figure 21, assume that fluorescence detection signals in the green wavelength band and in the infrared region are detected in three specific frames. Furthermore, assume that the fluorescence detection signals a and b in the green wavelength band and the fluorescence detection signals e and f in the infrared region have fluorescence emission amounts (signal amounts) that fall within a predetermined range, i.e., a range that exceeds the detection limit but does not saturate. On the other hand, assume that the fluorescence detection signal c in the green wavelength band has saturated fluorescence emission amounts (signal amounts), and the fluorescence detection signal d in the infrared region has fluorescence emission amounts (signal amounts) that fall below the detection limit.

[0171] Furthermore, the state of the detection signal of each photodetector in each specific frame is assumed to be as shown in the top row of Figure 22. Here, the symbol "○" indicates that the amount of fluorescence emission (signal amount) is within a predetermined range, that is, within a range that exceeds the detection limit but does not saturate.

[0172] The lower section of Figure 22 shows the status of the fluorescence detection signals in the green wavelength band and the infrared region, as shown in Figure 21. Here, the symbol "○" indicates that the fluorescence emission amount (signal amount) is within a predetermined range, i.e., it exceeds the detection limit but does not saturate, while the symbol "×" indicates that the fluorescence emission amount (signal amount) is not within the predetermined range.

[0173] Further down in Figure 22, we see the combination of photodetectors used for spectral overlap correction, specifically spectral overlap correction using a 2x2 matrix.

[0174] In other words, in a specific frame 2, spectral overlap correction is performed using a 2x2 matrix based on the output value of the second photodetector 31G and the output value of the third photodetector 31R to calculate the corrected emission amount G2 of the green visible fluorescent ink and the corrected emission amount IR2 of the infrared fluorescent ink (see bottom row of Figure 22). Equation (7) above can be used as the matrix for this calculation.

[0175] Furthermore, in specific frame 3, spectral overlap correction is performed using a 2x2 matrix based on the output values ​​of the first photodetector 31B and the third photodetector 31R to calculate the corrected emission amount IR3 of the infrared fluorescent ink (see bottom row of Figure 22). As the matrix equation at this time, the formula obtained in the same manner as in (5) to (7) above, using the output values ​​(a, d) of the first photodetector 31B and the output values ​​(c, f) of the third photodetector 31R shown in Table 2 above, can be used. Although the emission amount of the corrected green visible fluorescent ink is also calculated by this correction, as described above, the fluorescence detection signal c in the green wavelength band is saturated in specific frame 3, so it is not used in the subsequent identification process.

[0176] Furthermore, for specific frame 1, the output value of the second light-receiving element 31G is used directly as the light emission amount G1 of the green visible fluorescent ink.

[0177] From the above, the luminescence amount G1 of the green visible fluorescent ink in specific frame 1, the luminescence amount G2 of the green visible fluorescent ink in specific frame 2, the luminescence amount IR2 of the infrared fluorescent ink in specific frame 2, and the luminescence amount IR3 of the infrared fluorescent ink in specific frame 3 can be obtained.

[0178] The identification unit 223 then selects one or more fluorescence emission values ​​from these values ​​and uses the selected values ​​to identify the banknote BN. Specifically, for example, as shown in Figure 22, the ratio of the emission amount of green visible fluorescent ink to the emission amount of infrared fluorescent ink may be used. Alternatively, the sum of the emission amounts of the green visible fluorescent inks (G1 + G2) or the sum of the emission amounts of the infrared fluorescent inks (IR2 + IR3) may be used.

[0179] (Variation 1) In the above embodiment, the case in which the light-receiving unit constitutes an optical line sensor that acquires optical data (optical characteristics) of banknotes over the entire width of the transport path was described. However, the light-receiving unit may also be a point sensor that acquires optical data (optical characteristics) of banknotes at one point in the width of the transport path.

[0180] (Modification 2) In the above embodiment, a case was described in which fluorescence or phosphorescence is detected in multiple specific frames, and one or more fluorescence detection signals or one or more phosphorescence detection signals are selected from the multiple fluorescence detection signals or multiple phosphorescence detection signals and used for identification. However, in multiple specific frames, reflected light reflected by the banknote or transmitted light transmitted through the banknote may also be detected. Furthermore, one or more reflected light detection signals or one or more transmitted light detection signals may be selected from the multiple reflected light detection signals or multiple transmitted light detection signals and used for identification.

[0181] Although embodiments have been described above with reference to the drawings, this disclosure is not limited to the embodiments described above. Furthermore, the configurations of each embodiment may be combined or modified as appropriate without departing from the spirit of this disclosure. [Industrial applicability]

[0182] As described above, this disclosure is a useful technique for identifying paper sheets based on the light emanating from them. [Explanation of symbols]

[0183] 1,200: Paper sheet identification device 11, 111, 121, 124: Light source 13, 113, 123: Light receiving section 23, 223: Identification section 27, 227: Photodetection and Control Unit 30, 40: pixels 31B, 31G, 31R, 41B, 41G, 41R, 41IR: Photodetector 32B, 32G, 32R, 42B, 42G, 42R, 42IR: Color filters 33, 43: Photodetector 110: Upper unit 112, 122: Focusing lens 120: Lower unit 210: Detection unit 211: Imaging Department 212: Magnetic detection unit 213: Thickness detection unit 220: Control Unit 221: Light source control unit 224: Sensor Control Unit 225: Image generation unit 230: Storage section 300: Banknote Processing Device 301: Hoppa 302: Rejection Department 303:Operation unit 304: Enclosure 305: Display section 306a~306d: Accumulation section BN:Banknote

Claims

1. A light source capable of irradiating the paper sheets being transported with light of a specific wavelength, A light receiving unit that receives light arriving from the paper sheets based on the light from the light source and outputs a light detection signal, A light detection control unit that controls the light source and the light receiving unit, An identification unit that identifies the paper sheets using the light detection signal output from the light receiving unit, Equipped with, The light detection control unit controls the light source and the light receiving unit such that at least one of the irradiation conditions of the light source at a specific wavelength and the light receiving conditions of the light receiving unit are different during multiple periods within one detection cycle, thereby causing the light receiving unit to output multiple light detection signals with different signal amounts. The identification unit selects one or more light detection signals from the plurality of light detection signals and uses the selected one or more light detection signals to identify the paper sheets. A paper sheet identification device characterized by the following features.

2. The identification unit selects one or more light detection signals from among the plurality of light detection signals, the signal amount of which is within a predetermined range, as the one or more light detection signals. The paper sheet identification device according to claim 1, characterized in that it is a paper sheet identification device.

3. The light detection control unit changes the light reception time of the light receiving unit during the plurality of periods. The paper sheet identification device according to claim 1 or 2, characterized in that it is a paper sheet identification device.

4. The light detection control unit changes the emission time of the light of the specific wavelength from the light source during the plurality of periods. A paper sheet identification device according to any one of the features 1 to 3.

5. The light detection control unit changes the magnitude of the current supplied to the light source during the plurality of periods. A paper sheet identification device according to any one of features 1 to 4.

6. The light source irradiates the paper sheets with light of the specified wavelength, which is either ultraviolet light, visible light, or infrared light. A paper sheet identification device according to any one of the features 1 to 5.

7. The light-receiving unit receives fluorescence emitted from the paper sheets and outputs a plurality of fluorescence detection signals as the plurality of photodetection signals. The identification unit selects one or more fluorescent detection signals from the plurality of fluorescent detection signals as the one or more light detection signals, and uses the selected one or more fluorescent detection signals to identify the paper sheets. A paper sheet identification device according to any one of the features 1 to 6.

8. The identification unit calculates the ratio of fluorescence emission amounts at multiple wavelengths using the selected one or more fluorescence detection signals, and uses that ratio to identify the paper sheets. The paper sheet identification device according to claim 7, characterized in that it is a paper sheet identification device.

9. The ratio of fluorescence emission amounts at multiple wavelengths is the ratio of fluorescence emission amounts in visible light to fluorescence emission amounts in infrared light. The paper sheet identification device according to claim 8, characterized in that it is a paper sheet identification device.

10. The light-receiving unit receives phosphorescence emitted from the paper sheets and outputs a plurality of phosphorescence detection signals as the plurality of light detection signals. The identification unit selects one or more phosphorescent detection signals from the plurality of phosphorescent detection signals as the one or more light detection signals, and uses the selected one or more phosphorescent detection signals to identify the paper sheets. A paper sheet identification device according to any one of features 1 to 9.

11. The identification unit selects one light detection signal from among the multiple light detection signals as the one or more light detection signals, and uses the selected light detection signal to identify the paper sheets. A paper sheet identification device according to any one of claims 1 to 10.

12. The identification unit selects only the light detection signal with the maximum signal intensity from among the plurality of light detection signals as the one or more light detection signals, and uses the selected light detection signal to identify the paper sheets. The paper sheet identification device according to claim 11, characterized in that it is a paper sheet identification device.

13. The identification unit selects two or more light detection signals from the plurality of light detection signals as one or more light detection signals, and uses the sum of the signal amounts of the two or more selected light detection signals to identify the paper sheets. A paper sheet identification device according to any one of claims 1 to 10.

14. The identification unit selects two light detection signals from the plurality of light detection signals as one or more light detection signals, calculates the ratio of the signal amounts of the two selected light detection signals, and uses that ratio to identify the paper sheets. A paper sheet identification device according to any one of 1 to 10 or 13, characterized by the above.

15. The light source emits multiple types of light with different wavelengths, including the specific wavelength, within one detection cycle. A paper sheet identification device according to any one of features 1 to 14.

16. A paper sheet processing device characterized by comprising a paper sheet identification device according to any one of claims 1 to 15.

17. The first step involves irradiating the paper sheets being transported with light of a specific wavelength from a light source, A second step involves receiving light from the paper sheets based on the light from the light source and outputting a light detection signal. A third step involves identifying the paper sheets using the light detection signal output from the light receiving unit, Equipped with, In the first and second steps, multiple light detection signals with different signal amounts are output from the light receiving unit by varying at least one of the irradiation conditions of the light source with the specific wavelength of light and the light receiving conditions of the light receiving unit during multiple periods within one detection cycle. In the third step described above, one or more light detection signals are selected from the plurality of light detection signals, and the selected one or more light detection signals are used to identify the paper sheets. A method for identifying paper sheets, characterized by the features described herein.

18. A first process involves irradiating the paper sheets being transported with light of a specific wavelength from a light source, A second process involves receiving light from the paper sheets based on the light from the aforementioned light source using a light receiving unit and outputting a light detection signal. A third process for identifying the paper sheets using the light detection signal output from the light receiving unit, This is to be performed by the paper sheet identification device. In the first and second processes, by varying at least one of the irradiation conditions of the light source with the specific wavelength of light and the light receiving conditions of the light receiving unit during multiple periods within one detection cycle, multiple light detection signals with different signal amounts are output from the light receiving unit. In the third process described above, one or more light detection signals are selected from the plurality of light detection signals, and the selected one or more light detection signals are used to identify the paper sheets. A paper sheet identification program characterized by the following features.

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