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 identify paper sheets with high accuracy based on the amount of fluorescence emission of fluorescent ink printed on the paper sheets. [Solution] A paper sheet identification device comprising: a light source capable of irradiating paper sheets having printed and unprinted portions to be identified with at least a first light and excitation light; a light receiving unit that receives reflected light reflected by the paper sheets from the first light and outputs a reflected light detection signal, and also receives fluorescence emitted from the paper sheets irradiated with the excitation light and outputs a fluorescence detection signal; a calculation unit that calculates a value P by multiplying the density ratio α of the reflected light detection signal of the printed portion and the reflected light detection signal of the unprinted portion by the output value of the fluorescence detection signal of the unprinted portion, and calculates a value F by subtracting the value P from the output value of the fluorescence detection signal of the printed portion; and an identification unit that identifies the paper sheets based on the value F calculated by the calculation unit.

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, photoluminescence compounds are known as security elements attached to paper sheets such as banknotes. Photoluminescence compounds are excited by ultraviolet light or the like and emit fluorescence or phosphorescence. As a method for detecting those characteristics, for example, those shown in the following documents are known.

[0003] Patent Document 1 describes a paper sheet fluorescence detection sensor for simultaneously performing reflected light detection and transmitted light detection and comparing them to determine whether fluorescent ink is printed on the front surface, back surface, or the paper sheet itself contains a fluorescent component of a banknote.

[0004] Patent Document 2 describes an optical sensor that detects light from a paper sheet on which at least one of n types of single-color inks is printed, the optical sensor including a light source, a light receiving unit including first to (n - 1) light receiving elements, a storage unit that stores correction values based on reference data obtained by separately receiving light emitted from the first to n single-color inks by the light receiving unit for each type of single-color ink, and a correction processing unit that performs correction processing on detection data obtained by receiving light emitted from the paper sheet irradiated with light from the light source by the light receiving unit using correction values based on the inverse matrix of a matrix obtained by normalizing a predetermined n-row n-column matrix A acquired in advance.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] However, conventional sensors detect both the fluorescence emitted by the paper itself (the base material) and the fluorescence emitted by the fluorescent ink printed on the paper. Furthermore, the amount of fluorescence emitted by the fluorescent ink and the paper can fluctuate depending on the condition of the paper, such as the presence or absence of the base color (ink other than fluorescent ink) and the degree of dirtiness on the paper. As a result, conventional sensors could not accurately detect the amount of fluorescence emitted by the fluorescent ink. In particular, if the amount of fluorescence emitted by the fluorescent ink is low, the sensor may not be able to accurately detect the fluorescent ink, which could lead to a deterioration in the accuracy of identification processing based on the detection result, such as authenticity determination.

[0007] 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 identify paper sheets with high accuracy based on the amount of fluorescence emission of fluorescent ink printed on the paper sheets. [Means for solving the problem]

[0008] 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 a paper sheet having a printed portion and a non-printed portion to be identified with at least a first light and excitation light; a light receiving unit that receives reflected light reflected by the paper sheet from the first light and outputs a reflected light detection signal, and receives fluorescence emitted from the paper sheet irradiated with the excitation light and outputs a fluorescence detection signal; a calculation unit that calculates a value P by multiplying the output value of the fluorescence detection signal of the non-printed portion by the density ratio α of the reflected light detection signal of the printed portion and the reflected light detection signal of the non-printed portion, and calculates a value F by subtracting the value P from the output value of the fluorescence detection signal of the printed portion; and an identification unit that identifies the paper sheet based on the value F calculated by the calculation unit.

[0009] (2) In the paper sheet identification device described in (1) above, the light receiving unit may output a color detection signal as the reflected light detection signal, and the density ratio α may be a color density ratio.

[0010] (3) In the paper sheet identification device described in (2) above, the light receiving unit may output reflected light detection signals in each of the R, G, and B wavelength bands as the reflected light detection signal, and the color density ratio may be calculated based on the reflected light detection signals in each of the R, G, and B wavelength bands.

[0011] (4) In the paper sheet identification device described in (1) or (3) above, the light receiving unit may output an infrared reflected light detection signal as the reflected light detection signal, and the density ratio α may be calculated based on the infrared reflected light detection signal.

[0012] (5) In the paper sheet identification device described in any of (1) to (4) above, the calculation unit may calculate the density ratio α from the reflected light detection signal of the printed portion and the reflected light detection signal of the non-printed portion while the paper sheet to be identified is being processed.

[0013] (6) In the paper sheet identification device described in any of (1) to (4) above, the concentration ratio α may be calculated in advance at a stage before processing the paper sheets to be identified.

[0014] (7) The paper sheet identification device described in any of (1) to (6) above may further include an image generation unit that generates a reflected light image based on the reflected light detection signal and generates a fluorescent image based on the fluorescent detection signal, and the calculation unit may acquire the reflected light detection signals of the printed portion and the non-printed portion based on the reflected light image and acquire the fluorescent detection signals of the printed portion and the non-printed portion based on the fluorescent image.

[0015] (8) In the paper sheet identification device described in any of (1) to (7) above, the light source may emit at least one of visible light and infrared light as the first light.

[0016] (9) 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 (8) above.

[0017] (10) A third aspect of the present disclosure provides a method for identifying sheets of paper, comprising the steps of: irradiating a sheet of paper having a printed portion and a non-printed portion to be identified with a first light from a light source; receiving the reflected light from the sheet of paper with a light receiving unit and outputting a reflected light detection signal; irradiating the sheet of paper with excitation light from the light source; receiving the fluorescence emitted from the sheet of paper irradiated with the excitation light with the light receiving unit and outputting a fluorescence detection signal; calculating a value P obtained by multiplying the output value of the fluorescence detection signal of the non-printed portion by the density ratio α of the reflected light detection signal of the printed portion and the reflected light detection signal of the non-printed portion; calculating a value F obtained by subtracting the value P from the output value of the fluorescence detection signal of the printed portion; and identifying the sheet of paper based on the value F.

[0018] (11) Furthermore, a paper sheet identification program according to a fourth aspect of the present disclosure causes a paper sheet identification device to perform the following processes: irradiating a paper sheet having a printed portion and a non-printed portion to be identified with a first light from a light source; receiving the reflected light reflected by the paper sheet from the first light with a light receiving unit and outputting a reflected light detection signal; irradiating the paper sheet with excitation light from the light source; receiving the fluorescence emitted from the paper sheet irradiated with the excitation light with the light receiving unit and outputting a fluorescence detection signal; calculating a value P obtained by multiplying the output value of the fluorescence detection signal of the non-printed portion by the density ratio α of the reflected light detection signal of the printed portion and the reflected light detection signal of the non-printed portion; calculating a value F obtained by subtracting the value P from the output value of the fluorescence detection signal of the printed portion; and identifying the paper sheet based on the value F. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to provide a paper sheet discrimination device, a paper sheet processing device, a paper sheet discrimination method, and a paper sheet discrimination program that can accurately discriminate paper sheets based on the fluorescence emission amount of fluorescent ink printed on the paper sheets.

Brief Description of the Drawings

[0020] [Figure 1] It is a plan view schematically showing an example of a genuine banknote, showing the state when irradiated with visible light. [Figure 2] It is a plan view schematically showing an example of a genuine banknote, showing the state when irradiated with excitation light. [Figure 3] It is a schematic diagram for explaining an example of the configuration of the paper sheet discrimination device according to Embodiment 1, and is a view seen from an oblique direction. [Figure 4] It is a cross-sectional view schematically showing the state when the printing portion and the non-printing portion of the banknote are irradiated with the first light and the excitation light, respectively. [Figure 5] It is a flowchart for explaining an example of the operation of the paper sheet discrimination device according to Embodiment 1. [Figure 6] It is a schematic diagram for explaining an example of the configuration of the paper sheet discrimination device according to Embodiment 2, and is a view seen from an oblique direction. [Figure 7] It is a flowchart for explaining an example of the operation of the paper sheet discrimination device according to Embodiment 2. [Figure 8] It is a perspective schematic view showing an example of the appearance of the paper sheet processing device according to Embodiment 3. [Figure 9] It is a cross-sectional schematic diagram for explaining an example of the configuration of the imaging unit included in the paper sheet discrimination device according to Embodiment 3. [Figure 10] It is a perspective schematic view for explaining an example of the configuration of the light receiving unit included in the paper sheet discrimination device according to Embodiment 3. [Figure 11] It is a schematic diagram showing the wavelength characteristics of the color filter of the light receiving unit shown in FIG. 10. [Figure 12] It is a perspective schematic view for explaining another example of the configuration of the light receiving unit included in the paper sheet discrimination device according to Embodiment 3. [Figure 13]Figure 12 is a schematic diagram showing the wavelength characteristics of the color filter in the light-receiving section. [Figure 14] This is a block diagram illustrating an example of the configuration of a paper sheet identification device according to Embodiment 3. [Figure 15] This diagram schematically shows an example of a reflected light image of a banknote to be identified for authenticity determination using fluorescence measurement. [Figure 16] This diagram schematically shows an example of a fluorescence image of a banknote that is to be identified for authenticity determination using fluorescence measurement. [Figure 17] This figure shows the reflected light image of the test medium and its color data (B, G, R) in a specific region, and the fluorescent image of the test medium and its color data (B, G, R) in a specific region. [Figure 18] Figure 17 shows the results of calculating the color density ratio α using the data shown, and the results of calculating the amount of fluorescence emission P of the background (white paper) of the printed area using the calculated color density ratio α. [Figure 19] The results shown in Figure 18 (color density ratio α) were used to calculate the fluorescence emission amount of the fluorescent ink alone, and these results are shown here. [Figure 20] The results of calculating the fluorescence emission amount of fluorescent ink alone, without using the color density ratio α, are shown. [Figure 21] The following shows the results of calculating the fluorescence emission amount of only the fluorescent ink from the fluorescence spectrum for region Fl_1, where fluorescent ink is printed on a blank area of ​​paper. [Figure 22] The following shows the results of calculating the fluorescence emission amount of only the fluorescent ink from the fluorescence spectrum for region Fl_2, where a light cyan color is printed on a blank area and fluorescent ink is also printed. [Figure 23] This figure summarizes the results (each fluorescence emission amount) shown in Figures 19 to 22. [Modes for carrying out the invention]

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] (Embodiment 1) First, let's describe the banknotes to be identified. As shown in Figure 1, the banknotes to be identified (BN) have color printing in designated areas, depicting portraits and designs. Also, as shown in Figure 2, the banknotes to be identified (BN) have fluorescent ink, which is the subject of authenticity determination, printed in designated areas, for example, areas R1 and R2. That is, the printed area FL to be identified corresponds to areas R1 and / or R2 where the fluorescent ink is printed. The printed area FL to be identified does not have to have ink other than fluorescent ink printed on it, as in area R1, or it may have ink other than fluorescent ink, such as color printing ink, printed on it, as in area R2. Furthermore, the banknotes to be identified (BN) have an area R3 where no ink is printed, and in area R3, the base material of the banknote (BN), for example, the paper itself, is exposed. That is, area R3 corresponds to the unprinted area PP of the banknote (BN).

[0026] Furthermore, if there are multiple printed area FLs to be identified (for example, areas R1 and R2), the following processing can be performed for each printed area FL.

[0027] The above-described fluorescent ink contains one or more photoluminescent compounds and emits fluorescence (photoluminescence detectable during excitation light irradiation) in a predetermined wavelength band while being 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 region, or it may emit fluorescence in multiple wavelength bands. Similarly, the fluorescence of the fluorescent ink may have at least one peak wavelength in the visible and / or infrared region.

[0028] Furthermore, if there are multiple printed areas FL to be identified (for example, areas R1 and R2), each printed area FL may be printed with the same type of fluorescent ink, or it may be printed with different types of fluorescent inks, for example, multiple types of fluorescent inks having different emission characteristics. Specifically, for example, fluorescent inks that emit fluorescence in different wavelength bands may be printed.

[0029] 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 component may be visible to the human eye (see Figure 2).

[0030] Next, the configuration of the paper sheet identification device according to this embodiment will be described using Figure 3.

[0031] As shown in Figure 3, the paper sheet identification device 1 according to this embodiment detects fluorescence emitted from a banknote BN having a printed portion FL and a non-printed portion PP to be identified. The device includes a light source 11 capable of irradiating the banknote BN with at least a first light and excitation light, a light receiving unit 13 that receives reflected light from the banknote BN when the first light is reflected and outputs a reflected light detection signal, and also receives fluorescence emitted from the banknote BN irradiated with excitation light and outputs a fluorescence detection signal, a calculation unit 22 that calculates (estimates) the amount of fluorescence emitted by the fluorescent ink of the printed portion FL to be identified using the reflected light detection signal and the fluorescence detection signal, and an identification unit 23 that identifies the banknote BN to be identified based on the calculation result of the calculation unit 22.

[0032] 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.

[0033] The calculation unit 22 then calculates a value P by multiplying the output value of the fluorescence detection signal of the non-printed portion PP by the density ratio α between the reflected light detection signal of the printed portion FL and the reflected light detection signal of the non-printed portion PP. The calculation unit 22 then calculates a value F by subtracting value P from the output value of the fluorescence detection signal of the printed portion FL. The identification unit 23 then identifies the banknote BN to be identified based on the value F calculated by the calculation unit 22. This makes it possible to identify the banknote BN with high accuracy based on the amount of fluorescence emission of the fluorescent ink printed on the printed portion FL to be identified. Thus, the identification unit 23 may also perform a determination of the authenticity of the banknote BN (the fluorescent ink to be identified).

[0034] Here, we will explain in more detail the effects of the calculation unit 22 and the identification unit 23 using Figure 4.

[0035] To calculate the amount of fluorescence emitted by the fluorescent ink itself, it is necessary to subtract the amount of fluorescence emitted by the unnecessary background from the output value of the fluorescence detection signal. Therefore, it is usually considered that the amount of fluorescence emitted by the white paper, which is the background of the non-printed PP portion that does not contain fluorescent ink, is directly subtracted from the output value of the fluorescence detection signal of the printed portion FL. That is, as shown in Figure 4, when excitation light is shone from the light source 11 onto the printed portion FL on which the fluorescent ink is printed, and the output value of the fluorescence detection signal obtained by receiving the fluorescence emitted from the printed portion FL is defined as UVn, and when excitation light is shone from the light source 11 onto the non-printed portion PP on which no ink such as fluorescent ink is printed, and the output value of the fluorescence detection signal obtained by receiving the fluorescence emitted from the non-printed portion PP is defined as UV0, the value calculated from the following formula (A) is defined as the amount of fluorescence emitted by the fluorescent ink. UVn-UV0 (A)

[0036] However, in this case, if, for example, the non-printed PP base material is colored, the amount of fluorescence emitted by the fluorescent ink will decrease, and (fluorescence emission of fluorescent ink) < (fluorescence emission of the non-printed paper) may occur, potentially leading to incorrect detection of the fluorescent ink's fluorescence emission. Furthermore, in the printed FL area, excitation light is absorbed by the fluorescent ink, and fluorescence emitted from the base material may also be absorbed by the fluorescent ink printed on top of it. Therefore, the amount of fluorescence emitted by the base material in the printed FL area should be less than the amount of fluorescence emitted by the non-printed PP area, but this point is not taken into account in the above formula (A).

[0037] Therefore, in this embodiment, the density ratio α between the reflected light detection signal of the printed portion FL and the reflected light detection signal of the non-printed portion PP is multiplied by the output value of the fluorescence detection signal of the non-printed portion PP, and the resulting value P is subtracted from the output value of the fluorescence detection signal of the printed portion FL. By multiplying the output value of the fluorescence detection signal of the non-printed portion PP by the density ratio α, the effects of excitation light by the fluorescent ink and absorption of fluorescence from the substrate can be reduced.

[0038] More specifically, a first light source different from the excitation light is irradiated from the light source 11 onto the printed portion FL and the non-printed portion PP, and a reflected light detection signal obtained by receiving the reflected light reflected from the printed portion FL and the non-printed portion PP is used. As shown in Figure 4, when the first light source 11 is irradiated onto the printed portion FL and the output value of the reflected light detection signal obtained by receiving the reflected light reflected from the printed portion FL is taken as Wn, and when the first light source 11 is irradiated onto the non-printed portion PP and the output value of the reflected light detection signal obtained by receiving the reflected light reflected from the non-printed portion PP is taken as the fluorescence emission amount of the fluorescent ink. UVn-UV0×(Wn / W0) (B)

[0039] Here, the Wn / W0 term corresponds to the density ratio α between the reflected light detection signal of the printed portion FL and the reflected light detection signal of the non-printed portion PP, the UV0 × (Wn / W0) term corresponds to the value P obtained by multiplying the density ratio α by the output value of the fluorescence detection signal of the non-printed portion PP, UVn corresponds to the output value of the fluorescence detection signal of the printed portion FL, and the value calculated by the above formula (B) corresponds to the value F obtained by subtracting the value P from the output value of the fluorescence detection signal of the printed portion FL.

[0040] This reduces the influence of excitation light from the fluorescent ink and absorption of the underlying fluorescence, while also removing the unwanted amount of underlying fluorescence emission from the output value of the fluorescence detection signal in the printed area (FL). In other words, it becomes possible to more accurately separate the fluorescence from the paper from the fluorescence from the original fluorescent ink (phosphor), enabling highly accurate detection and quantitative evaluation of the presence or absence of fluorescent ink (phosphor), leading to improved counterfeit detection accuracy.

[0041] Here, the density ratio α is the ratio obtained by dividing the output value of the reflected light detection signal of the printed portion FL by the output value of the reflected light detection signal of the non-printed portion PP, as expressed in Wn / W0 above.

[0042] Note that "fluorescence emission amount" is a value that indicates the intensity (brightness) of the fluorescence in question.

[0043] Furthermore, the locations where the output values ​​UVn and Wn are detected (the locations where the fluorescence detection signal and reflected light detection signal are obtained from the printed portion FL) are not particularly limited as long as they are printed portions with the same fluorescent ink. They may be substantially the same, adjacent, or distant locations. When detection is performed at distant locations, the locations may be those where the condition of the base coat and inks other than the fluorescent ink is substantially the same, and in that case, the locations may be those from which the same output values ​​can be obtained as at the same location.

[0044] Similarly, the points where output values ​​UV0 and W0 are detected (points where fluorescence detection signals and reflected light detection signals are obtained from the non-printed PP area) are not particularly limited as long as they are non-printed areas where no ink has been printed at all. They may be substantially the same, adjacent, or distant points.

[0045] Furthermore, the targets for detecting these output values ​​may be a single location, multiple locations, or an area with a broad geographical scope. When detecting at multiple locations, a value F may be calculated for each location. When detecting at an area, the average value of the output values ​​obtained at each location within that area may be used as the output value. Expanding the target from a single location to multiple locations or an area improves the accuracy of calculating the fluorescence emission amount of the fluorescent ink, but it takes more time due to the computational processing. Conversely, narrowing the target from an area to multiple locations or a single location shortens the computational processing time, but the accuracy of calculating the fluorescence emission amount of the fluorescent ink may decrease.

[0046] The targets from which to acquire fluorescent detection signals and reflected light detection signals from the printed portion FL to be identified, and the targets from which to acquire fluorescent detection signals and reflected light detection signals from the non-printed portion PP, may each be prepared in advance as template information according to the type and direction of the banknote BN to be identified. In this case, the identification unit 23 first identifies the type and direction of the banknote BN to be identified, and then the calculation unit 22 may refer to the template information based on this identification result and acquire fluorescent detection signals and reflected light detection signals at the target point or target area corresponding to the type and direction of the banknote BN to be identified.

[0047] Template information refers to the reference information used in the identification process, defining at least one (usually two or more) attributes (characteristics) of each type of banknote being identified.

[0048] Furthermore, in this specification, the term "type of banknote" encompasses not only the denomination (a concept indicating the issuing country (including region), currency, and amount of the banknote), but also concepts indicating the issuing country (including region) and currency of the banknote, such as US dollars, euros, Japanese yen, Hong Kong dollars, etc., regardless of the amount.

[0049] Furthermore, the orientation of the banknote may refer to one of four directions: the front of the banknote, the back of the banknote, the back of the banknote, and the back of the banknote.

[0050] The targets from which to acquire fluorescent detection signals and reflected light detection signals from the printed portion FL to be identified, and the targets from which to acquire fluorescent detection signals and reflected light detection signals from the non-printed portion PP, may be determined during the processing of the banknote BN to be identified, rather than being prepared in advance as template information. In this case, for example, the point where the output value of the reflected light detection signal is the maximum value may be set as the target point for acquiring fluorescent detection signals and reflected light detection signals from the non-printed portion PP, and the point where the output value of the fluorescent detection signal is the maximum value may be set as the target point for acquiring fluorescent detection signals and reflected light detection signals from the printed portion FL.

[0051] The light source 11 irradiates the banknote BN with at least a first light and excitation light. The light source 11 may also irradiate the banknote BN with the first light and excitation light at different timings. That is, the irradiation period of the first light does not have to overlap temporally with the irradiation period of the excitation light. The light source 11 may also be provided on the same side of the banknote BN as the light receiving unit 13. The first light and excitation light are light in different wavelength bands. Examples of the first light include visible light and infrared light, and examples of the excitation light include ultraviolet light, visible light, and infrared light.

[0052] Thus, the light source 11 may emit at least one of visible light and infrared light as the first light. That is, the reflected light detection signal may be a signal detecting reflected light in the visible range, a signal detecting reflected light in the infrared range, or a signal that includes both a signal detecting reflected light in the visible range and a signal detecting reflected light in the infrared range.

[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 reflected light reflected from the banknote BN while the first light is irradiated, and fluorescence emitted from the banknote BN while the excitation light is irradiated. In other words, the light-receiving unit 13 is configured to detect reflected light and fluorescence from the banknote BN, respectively. At this time, the light-receiving unit 13 can function as a sensor that is sensitive to at least the wavelength band of the reflected light of the first light and the wavelength band of the fluorescence emitted from the fluorescent ink. The light-receiving unit 13 then outputs an electrical signal (which may also be a digital signal) corresponding to the amount of incident light (amount of light received). That is, the reflected light detection signal and the fluorescence detection signal are electrical signals corresponding to the amount of incident light of reflected light and fluorescence emitted from the banknote BN during the illumination period of the first light and excitation light, respectively.

[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 counting 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 fluorescence 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 fluorescence images, which are based on fluorescence emitted from 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 (reflected light detection signals and fluorescence detection 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 from each other.

[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 the visible-range reflected light or fluorescence and the infrared-range reflected light or fluorescence emitted from the banknote BN together without separating them, and output a reflected light detection signal or fluorescence 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-range reflected light or fluorescence and a signal amount corresponding to the infrared-range reflected light or fluorescence by spectral overlap correction, and these separated signal amounts may be used as the visible light output value and infrared light output value of the banknote BN.

[0066] On the other hand, the light-receiving unit 13 may separate the reflected light or fluorescence in the visible range and the reflected light or fluorescence in the infrared range 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 visible light output value and infrared light output value 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 2 may be used.

[0068] The light-receiving unit 13 may output a color detection signal as a reflected light detection signal, and the density ratio α may be a color density ratio. This makes it possible to calculate the above value F according to the respective colors of the printed portion FL and the unprinted portion PP of the banknote BN to be identified, and to accurately calculate the amount of fluorescence emission that takes into account the color of the fluorescent ink.

[0069] More specifically, the light-receiving unit 13 may output reflected light detection signals in each wavelength band of red (R), green (G), and blue (B) as reflected light detection signals, and the color density ratio may be calculated based on these reflected light detection signals in each wavelength band of R, G, and B. This makes it possible to calculate the amount of fluorescence emission of fluorescent ink using a general optical sensor that uses the three primary colors of light, RGB, such as an optical line sensor.

[0070] In this case, the color density ratio may also be calculated for each reflected light detection signal in the R, G, and B wavelength bands. That is, the color density ratio may include the ratio α_R obtained by dividing the output value of the red reflected light detection signal of the printed area FL by the output value of the red reflected light detection signal of the non-printed area PP, the ratio α_G obtained by dividing the output value of the green reflected light detection signal of the printed area FL by the output value of the green reflected light detection signal of the non-printed area PP, and the ratio α_B obtained by dividing the output value of the blue reflected light detection signal of the printed area FL by the output value of the blue reflected light detection signal of the non-printed area PP.

[0071] The calculation unit 22 may then calculate the above value F for each wavelength band of R, G, and B using the ratios α_R, α_G, and α_B. That is, the values ​​calculated from the following formulas (C1) to (C3) may be used as the fluorescence emission amount of the fluorescent ink. UVn_R-UV0_R×α_R (C1) UVn_G-UV0_G×α_G (C2) UVn_B - UV0_B × α_B (C3)

[0072] Here, UVn_R, UVn_G, and UVn_B represent the output values ​​of the red, green, and blue fluorescence detection signals of the printed portion FL, respectively, while UV0_R, UV0_G, and UV0_B represent the output values ​​of the red, green, and blue fluorescence detection signals of the non-printed portion PP, respectively.

[0073] The light receiving unit 13 may output a reflected light detection signal in the infrared region as a reflected light detection signal, and the density ratio α may be calculated based on the reflected light detection signal in the infrared region. This makes it possible to calculate the above value F according to the infrared characteristics of the printed portion FL and the unprinted portion PP of the banknote BN to be identified, and to accurately calculate the amount of fluorescence emission that takes into account the infrared characteristics of the fluorescent ink.

[0074] More specifically, the density ratio α may be the ratio α_IR obtained by dividing the output value of the infrared reflected light detection signal of the printed portion FL by the output value of the infrared reflected light detection signal of the non-printed portion PP, and the calculation unit 22 may calculate the above value F using the ratio α_IR. That is, the value calculated from the following formula (D) may be used as the fluorescence emission amount of the fluorescent ink. UVn_IR-UV0_IR×α_IR (D)

[0075] Here, UVn_IR represents the output value of the infrared fluorescence detection signal for the printed portion FL, and UV0_IR represents the output value of the infrared fluorescence detection signal for the non-printed portion PP.

[0076] Furthermore, the light-receiving unit 13 may output a color detection signal and an infrared region reflected light detection signal as reflected light detection signals, and the density ratio α may include the color density ratio and a ratio calculated based on the infrared region reflected light detection signal. Also, the light-receiving unit 13 may output reflected light detection signals for each wavelength band of red (R), green (G), and blue (B), and an infrared region reflected light detection signal as reflected light detection signals, and the density ratio α may include a ratio calculated based on the reflected light detection signals for each wavelength band of R, G, and B, and a ratio calculated based on the infrared region reflected light detection signal. In these cases, the values ​​calculated from the above formulas (C1) to (C3) and (D) may be used as the fluorescence emission amount of the fluorescent ink, respectively.

[0077] The paper sheet identification device 1 may calculate the density ratio α while processing the banknote BN to be identified. That is, while processing the banknote BN to be identified, the calculation unit 22 may calculate the density ratio α from the reflected light detection signal of the printed portion FL and the reflected light detection signal of the non-printed portion PP, and use this density ratio α to perform the identification process of the banknote BN.

[0078] On the other hand, the concentration ratio α may be predetermined. That is, the concentration ratio α may be calculated in advance at a stage before processing the banknote BN to be identified. In this case, the concentration ratio α may be calculated from genuine banknotes of the same denomination as the banknote BN to be identified.

[0079] The identification unit 23 may determine the authenticity of the printed portion to be identified, i.e., the fluorescent ink to be identified, by whether the value F related to the banknote BN to be identified, calculated by the calculation unit 22, i.e., the amount of fluorescence emission of the fluorescent ink calculated by the calculation unit 22, is within an acceptable range with respect to the reference data.

[0080] The identification unit 23 may compare the value F itself with reference data, or it may compare an evaluation value based on the value F with reference data. As the evaluation value, for example, the ratio of two fluorescence emission amounts in different wavelength bands may be used. In this case, the identification unit 23 may calculate the ratio of two fluorescence emission amounts in different wavelength bands obtained from the banknote to be identified, and identify the printed portion to be identified based on whether or not that ratio is within an acceptable range with respect to the ratio included in the reference data. This makes it possible to determine the authenticity of the fluorescent ink with higher accuracy. Here, examples of different wavelength bands include a combination of the wavelength band of red (R), green (G), or blue (B) and the wavelength band of the infrared or near-infrared region.

[0081] The "reference data" referenced by the identification unit 23 is information that defines a standard (e.g., a threshold) for the amount of fluorescence emission of (authentic) fluorescent ink that is acceptable as being from an authentic banknote. This may include, for example, the upper and lower limits of the amount of fluorescence emission of the fluorescent ink or its evaluation value measured and calculated in the same manner as the value F described above at the corresponding location on an authentic banknote. Furthermore, determining whether a certain value F or its evaluation value is within the acceptable range for the reference data may mean determining whether that value F or its evaluation value is between the upper and lower limits of the amount of fluorescence emission of the fluorescent ink or its evaluation value as defined by the reference data.

[0082] Next, the operation of the paper sheet identification device 1 according to this embodiment will be explained using Figure 5.

[0083] As shown in Figure 5, first, the light source 11 irradiates the banknote BN to be identified with a first light (step S11).

[0084] Furthermore, the light receiving unit 13 receives the reflected light from the banknote BN that the first light has reflected and outputs a reflected light detection signal (step S12). Here, the period during which the light receiving unit 13 receives the reflected light overlaps temporally with the period during which the light source 11 emits the first light.

[0085] Subsequently, the light source 11 irradiates the banknote BN to be identified with excitation light (step S13).

[0086] Furthermore, the light-receiving unit 13 receives fluorescence emitted from the banknote BN irradiated with excitation light and outputs a fluorescence detection signal (step S14). Here, the period during which the light-receiving unit 13 receives fluorescence overlaps temporally with the period during which the light source 11 irradiates with excitation light.

[0087] The order of steps S11 and S12, in which the first light is irradiated and the reflected light is received, and steps S13 and S14, in which the excitation light is irradiated and the resulting fluorescence is received, is not particularly limited. Furthermore, these steps may be repeated over the entire surface of the banknote BN.

[0088] Next, the calculation unit 22 calculates a value P by multiplying the output value of the fluorescence detection signal of the non-printed portion PP by the density ratio α of the reflected light detection signal of the printed portion FL to be identified and the reflected light detection signal of the non-printed portion PP, and then calculates a value F by subtracting value P from the output value of the fluorescence detection signal of the printed portion FL (step S15).

[0089] Subsequently, the identification unit 23 identifies the banknote BN to be identified based on the value F calculated by the calculation unit 22 (step S16), and the operation of the paper sheet identification device 1 ends.

[0090] The calculation unit 22 and the identification unit 23 may each function by executing corresponding programs by the control unit described later.

[0091] (Embodiment 2) In this embodiment, the case in which the above-described identification process is performed based on the reflected light image and the fluorescence image will be explained in more detail.

[0092] As shown in Figure 6, the paper sheet identification device 2 according to this embodiment further includes an image generation unit 24 in addition to the light source 11, light receiving unit 13, calculation unit 22, and identification unit 23 described in Embodiment 1.

[0093] The image generation unit 24 generates a reflected light image based on the reflected light detection signal output from the light receiving unit 13, and also generates a fluorescence image based on the fluorescence detection signal output from the light receiving unit 13.

[0094] The calculation unit 22 then acquires reflected light detection signals for the printed portion FL and the non-printed portion PP based on the reflected light image, and acquires fluorescence detection signals for the printed portion FL and the non-printed portion PP based on the fluorescence image. In this case, the pixel values ​​of the corresponding pixels in the image data may be used as the output values ​​for the reflected light detection signal and the fluorescence detection signal.

[0095] Next, the operation of the paper sheet identification device 2 according to this embodiment will be explained using Figure 7.

[0096] As shown in Figure 7, first, the first light and excitation light are irradiated, and the reflected light detection signal and fluorescence detection signal are output, similar to steps S11 to S14 described in Embodiment 1 (steps S21 to S24). These steps are repeated over the entire surface of the banknote BN.

[0097] The order of steps S21 and S22, in which the first light is irradiated and the reflected light is received, and steps S23 and S24, in which the excitation light is irradiated and the resulting fluorescence is received, is not particularly limited.

[0098] Then, the image generation unit 24 generates a reflected light image based on the reflected light detection signal output in step S22, and generates a fluorescence image based on the fluorescence detection signal output in step S24 (step S25).

[0099] Next, the calculation unit 22 calculates the density ratio α based on the reflected light image and calculates the above values ​​P and F (see Embodiment 1) based on the fluorescence image (step S26).

[0100] Subsequently, the identification unit 23 identifies the banknote BN to be identified based on the value F calculated by the calculation unit 22 (step S27), and the operation of the paper sheet identification device 2 ends.

[0101] The image generation unit 24 may function by executing a corresponding program by a control unit, which will be described later, similar to the calculation unit 22 and the identification unit 23.

[0102] (Embodiment 3) The paper sheet processing device according to this embodiment may have, for example, the configuration shown in Figure 8. The paper sheet processing device 300 shown in Figure 8 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 8) 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.

[0103] 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 9. As shown in Figure 9, 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.

[0104] As shown in Figure 9, 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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 9 (main scanning direction D1), and a plurality of LED elements (not shown) provided at both ends (or one end) of the light guide.

[0109] 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.

[0110] 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.

[0111] As shown in Figure 10, 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.

[0112] 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.

[0113] 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).

[0114] As shown in Figure 10, 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.

[0115] Furthermore, as shown in Figure 11, 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.

[0116] Therefore, each light-receiving unit 113, 123 receives the visible-range reflected light or fluorescence and the infrared-range reflected light or fluorescence emitted from the banknote BN together without separating them, and outputs a reflected light detection signal or fluorescence detection signal that includes a signal value corresponding to the total light intensity of both components. As a result, spectral overlap correction is necessary.

[0117] On the other hand, as shown in Figure 12, 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.

[0118] 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.

[0119] As shown in Figure 12, 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.

[0120] As shown in Figure 13, 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 light-receiving element 41B, the second light-receiving element 41G, and the third light-receiving element 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.

[0121] Therefore, in this case, each light-receiving unit 113, 123 separates the visible-range reflected light or fluorescence and the infrared-range reflected light or fluorescence emitted from the banknote BN, receives the light independently, and outputs a signal value corresponding to the light intensity of each component, thus eliminating the need for spectral overlap correction.

[0122] 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.

[0123] 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.

[0124] Next, the configuration of the paper sheet identification device according to this embodiment will be described using Figure 14. As shown in Figure 14, the paper sheet identification device 200 according to this embodiment includes a detection unit 210, a control unit 220, and a storage unit 230.

[0125] 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 source control unit 221, a sensor control unit 224, an image generation unit 225, a calculation unit 222, and an identification unit 223, according to the program stored in the memory unit 230.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] The light source control unit 221 performs dynamic lighting control 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 lighting 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.

[0130] 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 then sequentially stores the read signals, i.e., line data, in the ring buffer (line memory) of the storage unit 230.

[0131] 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.

[0132] 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.

[0133] Furthermore, the image generation unit 225 performs spectral overlap correction on the reflected light detection signal and fluorescence detection signal acquired by the imaging unit 211 as needed.

[0134] The calculation unit 222 calculates a value P by multiplying the output value of the fluorescence detection signal of the non-printed portion PP by the density ratio α between the reflected light detection signal of the printed portion FL, which is the target of identification of the banknote BN, and the reflected light detection signal of the non-printed portion PP. Then, it calculates a value F by subtracting value P from the output value of the fluorescence detection signal of the printed portion FL.

[0135] The identification unit 223 then identifies the banknote BN to be identified based on the value F calculated by the calculation unit 222.

[0136] Here, we will explain in more detail the calculation process performed by the calculation unit 222.

[0137] Here, as shown in Figure 15, the reflected light image of the banknote BN to be identified contains a region that is color-printed in a predetermined area. Also, as shown in Figure 16, the fluorescent image of the banknote BN to be identified contains regions R1 and R2 where fluorescent ink, which is the subject of authenticity determination, is printed. Regions R1 and R2 are assumed to have fluorescent inks with different luminescence characteristics printed on them. Furthermore, regions R1 and R2 contain printed portions FL_1 and FL_2, respectively, which are the subject of identification. Printed portion FL_1 is the portion of the banknote BN where fluorescent ink is printed on the white paper portion, and printed portion FL_2 is the portion of the banknote BN where color printing and fluorescent ink are printed on the white paper portion. In addition, the reflected light image and fluorescent image of the banknote BN to be identified contain a region R3, i.e., an unprinted portion PP, where no ink is printed.

[0138] The calculation unit 222 first obtains color data W_0(B,G,R) and UV_0(B,G,R) of the non-printed PP area from the reflected light image and the fluorescent image. The color data W_0(B,G,R) indicates the output values ​​of the red, green, and blue reflected light detection signals of the non-printed PP area. The color data UV_0(B,G,R) indicates the output values ​​of the red, green, and blue fluorescent detection signals of the non-printed PP area. For example, output values ​​like those shown in Tables 1 and 2 below can be obtained.

[0139] [Table 1]

[0140] [Table 2]

[0141] Furthermore, the calculation unit 222 obtains color data W_n(B,G,R) and UV_n(B,G,R) for the printed portions FL_1 and FL_2 from the reflected light image and the fluorescent image. The color data W_n(B,G,R) indicates the output values ​​of the red, green, and blue reflected light detection signals for the printed portions FL_1 and FL_2. The color data UV_n(B,G,R) indicates the output values ​​of the red, green, and blue fluorescent detection signals for the printed portions FL_1 and FL_2. Also, n represents 1 or 2, W_1(B,G,R) and UV_1(B,G,R) indicate the output values ​​for the printed portion FL_1, and W_2(B,G,R) and UV_2(B,G,R) indicate the output values ​​for the printed portion FL_2. For example, output values ​​like those shown in Tables 1 and 2 above can be obtained.

[0142] Furthermore, the calculation unit 222 calculates the color density ratio α_n(B,G,R) for each of the R, G, and B wavelength bands using the following formula (E). α_n(B,G,R)=W_n(B,G,R) / W_0(B,G,R) (E)

[0143] Here, n represents 1 or 2, α_1(B,G,R) represents the color density ratio between the printed area FL_1 and the unprinted area PP, and α_2(B,G,R) represents the color density ratio between the printed area FL_2 and the unprinted area PP. For example, in the case shown in Table 1 above, the color density ratio α_n(B,G,R) shown in Table 3 below is obtained.

[0144] [Table 3]

[0145] Then, the calculation unit 222 calculates F_n(B,G,R) for each of the R, G, and B wavelength bands using the following formula (F). F_n(B,G,R)=UV_n(B,G,R)-α_n(B,G,R)×UV_0(B,G,R) (F)

[0146] Here, n represents 1 or 2, F_1(B,G,R) corresponds to the amount of fluorescence emission of the fluorescent ink in the printed area FL_1, and F_2(B,G,R) corresponds to the amount of fluorescence emission of the fluorescent ink in the printed area FL_2. Also, α_n(B,G,R)×UV_0(B,G,R) corresponds to the amount of fluorescence emission P_1 of the background (white paper) of the printed area FL_1, and F_2(B,G,R) corresponds to the amount of fluorescence emission P_2 of the background (white paper) of the printed area FL_2. For example, in the case shown in Tables 1 and 2 above, the amount of fluorescence emission P_n(B,G,R) of the background (white paper) of the printed area as shown in Table 4 below is obtained, as well as the amount of fluorescence emission F_n(B,G,R) of the fluorescent ink in the printed area as shown in Table 5 below.

[0147] [Table 4]

[0148] [Table 5]

[0149] The following describes the results of an evaluation of the effectiveness of the method for calculating the fluorescence emission amount of the fluorescent ink relating to this disclosure, using a test medium on which the fluorescent ink was printed.

[0150] As shown in the reflected light image under a white light source in Figure 17, this test medium consisted of a white base with two shades of cyan printed on the left and right sides. Furthermore, as shown in the fluorescence image under a UV light source in Figure 17, fluorescent ink that emits green light was printed in the center of each of the left and right cyan printed areas, as well as in the white area between the left and right cyan printed areas.

[0151] The upper right of Figure 17 shows the measurement data when a reflected light image from a white light source was captured by a contact image sensor (CIS). Here, the color data (B,G,R) for the white paper area R_0, the white paper area with fluorescent ink printed on it R_1, and the white paper area with a light cyan color printed on it and also with fluorescent ink printed on it R_2 are shown.

[0152] The lower right of Figure 17 shows the measurement data when a fluorescence image was captured using a contact image sensor (CIS) with a UV light source. Here, the color data (B, G, R) for the white area with no printing (Fl_0), the white area with fluorescent ink printed (Fl_1), and the white area with light cyan printing and fluorescent ink printed (Fl_2) are shown. Areas Fl_0, Fl_1, and Fl_2 correspond to areas R_0, R_1, and R_2, respectively.

[0153] Note that in all measurement data, the RGB values ​​are calculated as the average value within the specified range.

[0154] Next, as shown in Figure 18, the color density ratio α was calculated using these measurement data. Here, color density ratio α_1 represents the color density ratio between region R_1 and region R_0, and color density ratio α_2 represents the color density ratio between region R_2 and region R_0. Furthermore, the fluorescence emission amount P of the background (white paper) of the printed area was calculated using the calculated color density ratio α. That is, the color data (B, G, R) of region Fl_0 of the fluorescence image was multiplied by the color density ratios α_1 and α_2, respectively. Here, fluorescence emission amount P_1 corresponds to the fluorescence emission amount of the background (white paper) of region Fl_1 where fluorescent ink is printed on the white paper area, and fluorescence emission amount P_2 corresponds to the fluorescence emission amount of the background (white paper) of region Fl_2 where light cyan and fluorescent ink are printed on the white paper area.

[0155] Then, as shown in Figure 19, these results were used to calculate the fluorescence emission amount of only the fluorescent ink in regions Fl_1 and Fl_2, respectively. Specifically, the fluorescence emission amounts P_1 and P_2 of the background (white paper) in regions Fl_1 and Fl_2 of the fluorescent image were subtracted from the color data (B, G, R) of regions Fl_1 and Fl_2 of the fluorescent image, respectively. Here, fluorescence emission amount F1 corresponds to the fluorescence emission amount of only the fluorescent ink in region Fl_1 where fluorescent ink is printed on the white paper portion, and fluorescence emission amount F2 corresponds to the fluorescence emission amount of only the fluorescent ink in region Fl_2 where light cyan and fluorescent ink are printed on the white paper portion.

[0156] Figure 20 also shows the results of calculating the fluorescence emission amount of fluorescent ink alone without using the color density ratio α. Specifically, the fluorescence emission amount F1 was calculated by subtracting the color data (B,G,R) of region Fl_0 from the color data (B,G,R) of region Fl_1 of the fluorescent image, and the fluorescence emission amount F2 was calculated by subtracting the color data (B,G,R) of region Fl_0 from the color data (B,G,R) of region Fl_2 of the fluorescent image.

[0157] Next, in order to examine the fluorescence emission amount of only the fluorescent ink in regions Fl_1 and Fl_2 in more detail, the fluorescence emission amount of only the fluorescent ink was estimated from the fluorescence spectrum.

[0158] First, the upper part of Figure 21 shows the fluorescence spectrum of region Fl_1. This fluorescence spectrum is thought to be a combination of the spectrum derived solely from the fluorescent ink and the spectrum derived solely from the blank paper area. Here, the spectrum derived solely from the fluorescent ink corresponds to the peak portion of this fluorescence spectrum, and the spectrum derived solely from the blank paper area corresponds to the baseline portion of this fluorescence spectrum. Therefore, when the fluorescence spectrum of region Fl_0 was subtracted from the fluorescence spectrum of region Fl_1, the spectrum shown by the dashed line in the upper part of Figure 21 was obtained. Since this spectrum lacks a baseline portion and consists only of peak portions, it is thought to accurately represent the spectrum derived solely from the fluorescent ink. Therefore, the fluorescence emission amount of the fluorescent ink alone in region Fl_1 was calculated by multiplying this spectrum, which is thought to be derived solely from the fluorescent ink, by the sensitivity characteristics of the CIS (see the middle part of Figure 21) (see the lower part of Figure 21).

[0159] Similarly, the fluorescence emission amount of only the fluorescent ink in region Fl_2 was calculated from the fluorescence spectrum of region Fl_2 (see Figure 22). Here, the fluorescence spectrum of region Fl_3 (see bottom left of Figure 17) was subtracted from the fluorescence spectrum of region Fl_2. Region Fl_3 is the region in the fluorescence image where a light cyan color is printed on the white paper area, but no fluorescent ink is printed.

[0160] The results are summarized in Figure 23. As a result, as shown in the lower part of Figure 23, in particular in the region Fl_2 where color printing was performed on a white background, the fluorescence emission amount of the fluorescent ink alone calculated using the color density ratio α was more similar to the fluorescence emission amount of the fluorescent ink alone estimated from the fluorescence spectrum than the fluorescence emission amount of the fluorescent ink alone calculated by simple subtraction without using the color density ratio α.

[0161] In this example, cyan was printed on the test medium's background. However, even if other colors or combinations of multiple inks (for example, combinations selected from cyan, magenta, and yellow, or combinations selected from blue, red, and green, or gray and black) are printed on the test medium's background, the fluorescence emission amount of only the fluorescent ink can be calculated using the color density ratio α. This will yield results that are closer to the fluorescence emission amount of only the fluorescent ink estimated from the fluorescence spectrum.

[0162] (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.

[0163] 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]

[0164] As described above, this disclosure is a useful technique for identifying paper sheets based on the amount of fluorescence emitted by fluorescent ink printed on those paper sheets. [Explanation of symbols]

[0165] 1, 2, 200: Paper sheet identification device 11, 111, 121, 124: Light source 13, 113, 123: Light receiving section 22, 222: Calculation section 23, 223: Identification section 24, 225: Image generation 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 230: Storage section 300: Paper sheet processing equipment 301: Hoppa 302: Rejection Department 303:Operation unit 304: Enclosure 305: Display section 306a~306d: Accumulation section BN:Banknote FL, FL_1, FL_2: Printed portion to be identified PP: Non-printing part

Claims

1. A light source capable of irradiating paper sheets having printed and unprinted portions to be identified with at least a first light and excitation light, A light receiving unit that receives the reflected light from the paper sheets that the first light has reflected and outputs a reflected light detection signal, and also receives the fluorescence emitted from the paper sheets that have been irradiated with the excitation light and outputs a fluorescence detection signal, A calculation unit calculates a value P obtained by multiplying the density ratio α between the reflected light detection signal of the printed portion and the reflected light detection signal of the non-printed portion by the output value of the fluorescence detection signal of the non-printed portion, and calculates a value F obtained by subtracting the value P from the output value of the fluorescence detection signal of the printed portion. An identification unit that identifies the paper sheets based on the value F calculated by the calculation unit, A paper sheet identification device characterized by being equipped with the following features.

2. The light receiving unit outputs a color detection signal as the reflected light detection signal. The density ratio α is a color density ratio. The paper sheet identification device according to claim 1, characterized in that it is a paper sheet identification device.

3. The light receiving unit outputs reflected light detection signals in each of the R, G, and B wavelength bands as the reflected light detection signals. The aforementioned color density ratio is calculated based on the reflected light detection signals in each of the R, G, and B wavelength bands. The paper sheet identification device according to claim 2, characterized in that it is a paper sheet identification device.

4. The light receiving unit outputs a reflected light detection signal in the infrared region as the reflected light detection signal. The aforementioned concentration ratio α is calculated based on the reflected light detection signal in the infrared region. The paper sheet identification device according to claim 1 or 3, characterized in that it is a paper sheet identification device.

5. While processing the paper sheets to be identified, the calculation unit calculates the density ratio α from the reflected light detection signal of the printed portion and the reflected light detection signal of the unprinted portion. A paper sheet identification device according to any one of features 1 to 4.

6. The aforementioned concentration ratio α was calculated in advance at a stage before processing the paper sheets to be identified. A paper sheet identification device according to any one of features 1 to 4.

7. The system further includes an image generation unit that generates a reflected light image based on the reflected light detection signal and generates a fluorescent image based on the fluorescent detection signal, The calculation unit acquires reflected light detection signals of the printed portion and the non-printed portion based on the reflected light image, and acquires fluorescence detection signals of the printed portion and the non-printed portion based on the fluorescence image. A paper sheet identification device according to any one of the features 1 to 6.

8. The light source emits at least one of visible light and infrared light as the first light. A paper sheet identification device according to any one of the features 1 to 7.

9. A paper sheet processing device characterized by comprising a paper sheet identification device according to any one of claims 1 to 8.

10. The steps include irradiating a sheet of paper having a printed portion and a non-printed portion to be identified with a first light from a light source, The steps include: receiving the reflected light from the paper sheets that the first light has reflected with a light receiving unit and outputting a reflected light detection signal; The steps include irradiating the aforementioned paper sheets with excitation light from the light source, The steps include: receiving the fluorescence emitted from the paper sheets irradiated with the excitation light with the light receiving unit and outputting a fluorescence detection signal; The steps include calculating a value P obtained by multiplying the output value of the fluorescence detection signal of the non-printed portion by the density ratio α of the density ratio α of the reflected light detection signal of the printed portion and the reflected light detection signal of the non-printed portion, The steps include: calculating a value F obtained by subtracting the value P from the output value of the fluorescence detection signal of the printed portion; A step of identifying the paper sheets based on the value F, A method for identifying paper sheets, characterized by comprising the following features.

11. A process in which a sheet of paper having a printed area and an unprinted area to be identified is irradiated with a first light from a light source, The process involves receiving the reflected light from the paper sheets that the first light reflects off of the paper sheets with a light receiving unit and outputting a reflected light detection signal. The process involves irradiating the aforementioned paper sheets with excitation light from the aforementioned light source, The process involves receiving the fluorescence emitted from the paper sheets irradiated with the excitation light using the light-receiving unit and outputting a fluorescence detection signal. A process to calculate a value P obtained by multiplying the output value of the fluorescence detection signal of the non-printed portion by the density ratio α of the density ratio α of the reflected light detection signal of the printed portion and the reflected light detection signal of the non-printed portion, A process to calculate a value F obtained by subtracting the value P from the output value of the fluorescence detection signal of the printed portion, A process for identifying the paper sheets based on the aforementioned value F, A paper sheet identification program characterized by causing a paper sheet identification device to execute the following.

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