JP2024007792A - Paper sheet identification device and paper sheet processing device - Google Patents

Abstract

To provide a paper sheet identification device and a paper sheet processing device which are capable of identifying a paper sheet with high accuracy based on phosphorescence.SOLUTION: A paper sheet identification device for detecting fluorescence and phosphorescence emitted from paper sheets being conveyed includes: a light source that emits excitation light onto the paper sheets; a light source control unit that controls the light source so that the excitation light is emitted during a light-on period and turned off during a light-off period after the light-on period; a light receiving unit that outputs a fluorescent phosphorescence detection signal based on light emitted from the paper sheets during the light-on period and a phosphorescence detection signal based on light emitted from the paper sheets during the light-off period; a calculation unit that calculates an estimated phosphorescence signal value, which is estimated to be a signal value based on the phosphorescence received by the light receiving unit from the paper sheets in the fluorescent phosphorescence detection signal; and an identification unit that identifies the paper sheets based on the estimated phosphorescence signal value.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a paper sheet identification device and a paper sheet processing device.

In recent years, devices have been developed that detect phosphorescence from phosphorescent ink printed on banknotes as a security element to prevent counterfeiting. Specifically, a device is known that irradiates excitation light onto a paper sheet being conveyed, then turns off the excitation light, and detects phosphorescence emitted from the paper sheet. Here, phosphorescence generally has a long lifetime (emission time) but low intensity, so there is a problem that it is difficult to detect.

An example of a device for detecting such phosphorescence is the excitation light detection device described in Patent Document 1. In the excitation light detection device of Patent Document 1, a light source is supplied with a current to irradiate the paper sheet with light, and the detection unit detects the fluorescence emitted from the paper sheet, and the amount of current supplied to the light source is Or, if the intensity of the phosphorescence is low, by increasing the supply time to irradiate the paper sheet with light, and after stopping the irradiation of light by the light source, the detection unit detects the phosphorescence emitted from the paper sheet. This makes it possible to detect phosphorescence even when

Patent No. 6316148

In order to accurately classify the various phosphors used in banknotes (for example, phosphorescent ink), it is effective to distinguish between the time constants of the phosphors. There is a need to. However, when detecting phosphorescence in gaps where multiple images such as visible images and infrared images are collected using a contact image sensor, it is necessary to detect many optical features in a short time, making it difficult to detect phosphorescence. The available time is limited, and it is difficult to discern differences in the time constants of phosphors within that time. In particular, when the time constant of the phosphor is long (for example, 1 ms (millisecond) or more), the error in phosphorescence detection becomes large.

On the other hand, Patent Document 1 does not disclose a phosphor discrimination method based on a time constant.

The present disclosure has been made in view of the above-mentioned current situation, and aims to provide a paper sheet identification device and a paper sheet processing device that can identify paper sheets with high accuracy based on phosphorescence. It is something.

In order to solve the above-mentioned problems and achieve the objectives, (1) a paper sheet identification device according to a first aspect of the present disclosure provides a paper sheet identification device that detects fluorescence and phosphorescence emitted from paper sheets being conveyed; The leaf identification device includes a light source that irradiates excitation light onto paper sheets, and a light source that irradiates the excitation light during a lighting period and turns off during a non-lighting period after the lighting period. a light source control unit that outputs a fluorescent phosphorescence detection signal based on the light emitted from the paper sheet during the lighting period, and outputs a phosphorescence detection signal based on the light emitted from the paper sheet during the lighting period; a light receiving unit; a calculating unit that calculates an estimated phosphorescence signal value that is estimated to be a signal value based on phosphorescence received by the light receiving unit from the paper sheet in the fluorescent phosphorescence detection signal; and an identification section that identifies the paper sheet.

(2) In the paper sheet identification device according to (1) above, the light source control unit may control the light source to emit the excitation light in a plurality of lighting periods, and the light receiving unit may , a plurality of fluorescent phosphorescence detection signals based on the light emitted from the paper sheet during the plurality of lighting periods may be sequentially output, and the calculation unit may output the second and subsequent fluorescent phosphorescence detection signals among the plurality of fluorescent phosphorescence detection signals. By subtracting the signal value of the first output fluorescence phosphorescence detection signal from the signal value of the output fluorescence phosphorescence detection signal, the estimated phosphorescence signal value is determined in the second and subsequent output fluorescence phosphorescence detection signals. may be calculated.

(3) In the paper sheet identification device according to (2) above, the light source control unit, before the plurality of lighting periods, sets a lighting period shorter than a first lighting period among the plurality of lighting periods, and The light source may be controlled so as to irradiate the excitation light for a short period of time during which phosphorescence is not substantially emitted from the paper sheet, and the light receiving section may be configured to emit light emitted from the paper sheet during the short period of time. The calculation unit may output a fluorescence detection signal based on the first lighting period, where T is the time of the first lighting period, and t is the short period of time. Calculating the estimated phosphorescence signal value in the first output fluorescent phosphorescence detection signal by subtracting a value obtained by multiplying the signal value of the fluorescence detection signal by (T/t) from the signal value of the detection signal. You may.

(4) In the paper sheet identification device according to (1) above, the light source control unit is configured to emit the excitation light in a plurality of lighting periods, and to turn off the excitation light in a plurality of off periods after the plurality of lighting periods. The light source may be controlled, and the light receiving unit sequentially outputs a plurality of fluorescent phosphorescence detection signals based on the light emitted from the paper sheet during the plurality of lighting periods, and the light receiving unit sequentially outputs a plurality of fluorescent phosphorescence detection signals based on the light emitted from the paper sheet during the plurality of lighting periods. A plurality of phosphorescence detection signals based on light emitted from the paper sheets may be sequentially output, and the calculation unit calculates the plurality of fluorescence detection signals based on the plurality of fluorescence phosphorescence detection signals and the plurality of phosphorescence detection signals. In the phosphorescence detection signal, an estimated fluorescence signal value that is estimated to be a signal value based on fluorescence received by the light receiving unit from the paper sheet may be calculated.

(5) In the paper sheet identification device according to (4) above, the calculation unit subtracts at least the estimated fluorescence signal value from at least one signal value of the plurality of fluorescent phosphorescence detection signals. The estimated phosphorescence signal value may be calculated from the fluorescence phosphorescence detection signal.

(6) In the paper sheet identification device according to (4) or (5) above, the light source is located upstream of the measurement position of the light receiving unit and the measurement position in the transport direction of the paper sheet. The excitation light may be applied to a region including at least a region, and the light source control unit controls the light source to repeat a predetermined cycle including the plurality of lighting periods and the plurality of lighting periods. The calculation unit may calculate, as the estimated phosphorescence signal value, a signal value estimated to be based on an afterglow component of phosphorescence caused by the excitation light irradiated on the paper sheet before reaching the measurement position. may be calculated.

(7) In the paper sheet identification device according to any one of (1) to (6) above, the identification unit selects at least one signal value of the estimated phosphorescence signal value and the signal value of the phosphorescence detection signal. The presence or absence of phosphorescence emitted from the paper sheet may be determined based on the above.

(8) In the paper sheet identification device according to any one of (1) to (7) above, the calculation unit may calculate the estimated phosphorescence signal value for each of a plurality of wavelength bands, and the identification unit The color of phosphorescence emitted from the paper sheet may be determined based on at least one of the estimated phosphorescence signal value of the plurality of wavelength bands and the signal value of the phosphorescence detection signal of the plurality of wavelength bands. good.

(9) In the paper sheet identification device according to any one of (1) to (8) above, the identification unit normalizes the estimated phosphorescence signal value and the signal value of the phosphorescence detection signal; The phosphor provided on the paper sheet is identified based on the signal value.

(10) In the paper sheet identification device according to any one of (1) to (9) above, the identification unit may detect phosphorescence based on at least one of the estimated phosphorescence signal value and the signal value of the phosphorescence detection signal. A determination value that varies depending on a time constant may be calculated, and the phosphor provided on the paper sheet may be identified based on the determination value.

(11) Further, a paper sheet processing device according to a second aspect of the present disclosure includes the paper sheet identification device according to any one of (1) to (10) above.

According to the present disclosure, it is possible to provide a paper sheet identification device and a paper sheet processing device that can identify paper sheets with high accuracy based on phosphorescence.

FIG. 2 is a schematic diagram showing an example of temporal changes in the amounts of fluorescence and phosphorescence. 1 is a schematic diagram for explaining an overview of a paper sheet identification device according to a first embodiment; FIG. 1 is a schematic diagram illustrating an example of the configuration of a paper sheet identification device according to Embodiment 1, as viewed from an oblique direction. FIG. 2 is a timing chart illustrating the timing of lighting up a light source and the timing of light reception by a light receiving unit included in the paper sheet identification device according to the first embodiment. 2 is a flowchart illustrating an example of the operation of the paper sheet identification device according to the first embodiment. FIG. 7 is a schematic diagram for explaining a method of calculating an estimated phosphorescence signal value by the paper sheet identification device according to the second embodiment. FIG. 7 is a schematic diagram for explaining a method of calculating an estimated phosphorescence signal value according to a modified example of the paper sheet identification device according to the second embodiment. FIG. 7 is a schematic diagram for explaining a method of calculating an estimated phosphorescence signal value by the paper sheet identification device according to Embodiment 3; FIG. 7 is a schematic diagram of a banknote, seen from the side, which is irradiated with excitation light while being conveyed in the paper sheet identification device according to Embodiment 3; FIG. 7 is a schematic diagram for explaining an overview of a paper sheet identification device according to a fourth embodiment. FIG. 7 is a schematic perspective view showing the appearance of an example of a paper sheet processing device according to a fourth embodiment. FIG. 7 is a schematic cross-sectional view illustrating an example of the configuration of an imaging unit included in the paper sheet identification device according to Embodiment 4. FIG. 7 is a schematic perspective view illustrating an example of the configuration of a light receiving section included in the imaging section of Embodiment 4. FIG. FIG. 7 is a schematic diagram showing wavelength characteristics of a color resist of a light receiving section included in an imaging section of Embodiment 4. FIG. 7 is a block diagram illustrating an example of the configuration of a paper sheet identification device according to a fourth embodiment. 12 is a timing chart illustrating the timing of lighting up a light source and the timing of light reception by a light receiving unit included in the paper sheet identification device according to Embodiment 4. FIG. 11 is a timing chart illustrating a modification of the lighting timing of a light source and the timing of light reception by a light receiving unit included in the paper sheet identification device according to Embodiment 4. FIG. 12 is a graph showing estimated phosphorescent signal values and phosphorescent signal values in each phase obtained from four types of phosphorescent inks A to D by the paper sheet identification device according to Embodiment 4. 19 is a graph showing the results of normalizing each signal value shown in FIG. 18 by the signal value of phase D for each phosphorescent ink. 13 is a flowchart illustrating an example of the operation of the paper sheet identification device according to the fourth embodiment. FIG. 7 is a schematic diagram for explaining a method of calculating an estimated phosphorescence signal value according to a modification of the paper sheet identification device according to the fourth embodiment. FIG. 7 is a schematic side view illustrating an example of the configuration of a paper sheet identification device according to a fifth embodiment. FIG. 23 is a schematic diagram in which the broken line portion shown in FIG. 22 is enlarged. FIG. 2 is a schematic diagram showing the classification of components included in the amount of light emitted after excitation over multiple cycles when there is a fluorescence feature and a phosphorescence feature. It is a graph simulating the rise characteristics of five types of phosphorescent inks having different time constants. It is a graph simulating the fall characteristics of five types of phosphorescent inks having different time constants. FIG. 3 is a diagram showing the results of simulating the emission and decay characteristics of a phosphorescent ink having only phosphorescent characteristics. FIG. 7 is a schematic diagram showing the relationship between the integrated amount of received light in adjacent integration sections at the time of rising. FIG. 7 is a schematic diagram showing the relationship between adjacent integration sections during excitation and the amount of increase β in the amount of light emission due to phosphorescence characteristics at the time of rise. FIG. 7 is another diagram illustrating the results of simulating the emission and decay characteristics of a phosphorescent ink having only phosphorescent characteristics. FIG. 7 is a schematic diagram showing the relationship between adjacent integration sections at the time of attenuation and the attenuation amount α of the amount of light emission due to the phosphorescence characteristic at the time of falling. It is a schematic diagram showing the relationship between the first integration section PH_1 and attenuation amount α at the time of falling, and a virtual integration section PH_0. It is another schematic diagram showing the relationship between the first integration section PH_1 and the attenuation amount α at the time of falling, and the virtual integration section PH_0. It is a schematic diagram showing the relationship between a virtual integration section PH_0 and an increased phosphorescence light amount SIM_FL_3 during excitation. It is another schematic diagram showing the relationship between the virtual integration period PH_0 and the phosphorescence increase light amount SIM_FL_3 during excitation. FIG. 3 is a diagram showing the results of simulating light emission and attenuation characteristics when fluorescent ink and phosphorescent ink are mixed. FIG. 3 is a diagram illustrating the results of simulating the emission and decay characteristics after excitation over multiple cycles in the presence of fluorescence and phosphorescence characteristics. FIG. 2 is a schematic diagram showing emission and decay characteristics upon excitation over multiple cycles in the presence of fluorescence and phosphorescence characteristics. FIG. 3 is a schematic diagram for explaining a method of calculating a fluorescence component F. FIG. FIG. 3 is a schematic diagram showing an example of a temporal change in the amount of phosphorescence. FIG. 2 is a schematic diagram showing an example of temporal changes in the amounts of fluorescence and phosphorescence.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a paper sheet identification device and a paper sheet processing device according to the present disclosure will be described in detail with reference to the drawings. Various paper sheets can be applied to paper sheets that are subject to this disclosure, such as banknotes, checks, gift certificates, bills, forms, securities, and card-like media, but in the following, banknotes are applicable. The present disclosure will be described using an example of a device.

In addition, in the following description, the same reference numerals are appropriately used for the same parts or parts having similar functions in different drawings, and repeated explanations are omitted as appropriate. Further, in the drawings explaining the structure, mutually orthogonal XYZ coordinate systems are appropriately shown.

(Embodiment 1)
First, an overview of this embodiment will be explained.

The paper sheet identification device according to this embodiment irradiates excitation light onto a banknote being conveyed and detects fluorescence and phosphorescence emitted from the banknote. As shown in Figure 1, when irradiated with excitation light, fluorescent substances such as fluorescent ink emit fluorescence, and phosphorescent substances such as phosphorescent ink emit phosphorescence, but the amount of phosphorescence depends on its time constant. gradually increases and eventually saturates. Thereafter, when the excitation light is turned off, the luminescence of the phosphor disappears in a very short time. On the other hand, the amount of light emitted by the phosphor gradually decreases depending on its time constant. That is, the phosphorescence increases (increases) or attenuates (diminishes) depending on the individual time constants both during irradiation with the excitation light and after the excitation light is turned off. In addition, when the excitation light is irradiated multiple times, the phosphorescence emitted during the excitation light irradiation includes, in addition to the phosphorescence component that increases due to the excitation light irradiation, the phosphorescence that has decreased after increasing due to the previous excitation light irradiation. component (afterglow component) may also be included.

Therefore, in this embodiment, as shown in FIG. 2, excitation light is irradiated onto the banknote during at least one lighting period during one cycle, and fluorescence and phosphorescence emitted from the banknote are received during each lighting period. It outputs a fluorescent phosphorescence detection signal Sfp, and also receives phosphorescence emitted from a banknote during at least one light-off period and outputs a phosphorescence detection signal Sp. The main feature is that in the fluorescent phosphorescence detection signal Sfp, an estimated phosphorescence signal value that is estimated to be a signal value based on the phosphorescence emitted from the banknote is calculated, and the banknote is identified using the estimated phosphorescence signal value. There is.

This estimated phosphorescence signal value is a value that changes depending on the time constant of the phosphor, as shown in FIG. In addition, since the estimated phosphorescence signal value is based on the signal obtained during the excitation light ON period rather than the phosphorescence-off period when only phosphorescence is detected, the phosphorescence detection is The detection time can be used longer (more effectively). Therefore, the accuracy of discrimination based on the difference in the time constant of the phosphor can be improved. Moreover, the presence or absence of phosphorescence emitted from banknotes can be determined with higher accuracy. Therefore, banknotes can be identified with high precision based on phosphorescence.

Note that in this specification, one cycle refers to a control pattern in which the timing of turning on and off the light emitting elements of each wavelength band, the timing of signal reading, and the like are set. A control pattern of one cycle is defined as one period, and by continuously and repeatedly executing this control pattern, a fluorescent phosphorescence detection signal and a phosphorescence detection signal are obtained from the entire paper sheet. One cycle may indicate a periodic control pattern related to lighting, turning off, and light reception that is set in order to obtain a reflected image and/or a transmitted image of a paper sheet.

The reflected image is an image based on light that is emitted from a light source placed on the same side of the paper sheet as the light receiving unit and reflected by the paper sheet. A transmitted image is an image based on light that is emitted from a light source placed on the opposite side of the light receiving unit to the paper sheet and transmitted through the paper sheet. Therefore, reflected images and transmitted images are distinguished from fluorescence images based on fluorescence (including a phosphorescent component) emitted from paper sheets and phosphorescence images based on phosphorescence emitted from paper sheets.

Next, the configuration of the paper sheet identification device according to this embodiment will be explained using FIG. 3.

As shown in FIG. 3, the paper sheet identification device 1 according to the present embodiment detects fluorescence and phosphorescence emitted from the transported banknote BN, and includes a light source 11, a light source control section 21, and a light receiving section 13. , a calculating section 22 and an identifying section 23.

Here, the banknote BN is conveyed in the X direction within the XY plane. The Y direction corresponds to the main scanning direction of the light receiving section 13, and the X direction corresponds to the sub scanning direction of the light receiving section 13. Fluorescent ink containing a fluorescent substance and phosphorescent ink containing a phosphorescent substance are printed on at least a portion of the banknote BN. When irradiated with excitation light, the phosphor emits fluorescence, for example in the visible light region, during irradiation with the excitation light. When irradiated with excitation light, the phosphor emits phosphorescence, for example in the visible light range, after the excitation light is turned off.

The light source 11 irradiates the banknote BN with excitation light. The light source 11 may be provided on the same side of the bill BN as the light receiving section 13. The light source 11 may irradiate the bill BN with excitation light in a straight line extending in the Y direction (main scanning direction).

The type (wavelength band) of excitation light is not particularly limited, but visible light and/or ultraviolet light (UV) may be used.

Further, the light source 11 may emit excitation light in different wavelength bands for excitation of the phosphor and excitation of the phosphor, or may emit excitation light in a common wavelength band.

The light source control unit 21 controls lighting and extinguishing of the light source 11. Specifically, under the control of the light source control unit 21, the light source 11 emits excitation light during a lighting period, and turns off during a lighting period following the lighting period.

The light source control unit 21 may control the light source 11 to emit excitation light in a plurality of lighting periods, as shown in FIG. 2 . In that case, the types (wavelength bands) of excitation light irradiated during the plurality of lighting periods may be different from each other, but are usually the same type (wavelength band). Further, the lengths of the plurality of lighting periods (light emission times) may be different from each other, but here they are set to substantially the same length.

Furthermore, as shown in FIG. 2, the light source control unit 21 may control the light source 11 so that the light source 11 is turned off in a plurality of turn-off periods after the turn-on period. In that case, the lengths of the plurality of light-out periods (light-out time) may be different from each other, but here they are set to substantially the same length.

Note that the length of each lighting period (light emission time) may be different from the length of each lighting period (lights out time), but here, the length of each lighting period (lights out time) is substantially the same as the length of each lighting period (lights out time). It is set to

The light receiving unit 13 receives the light emitted from the banknote BN during the lighting period, and outputs the fluorescent phosphorescence detection signal Sfp based on the light, and also receives the light emitted from the banknote BN during the non-lighting period, and outputs the phosphorescence detection signal Sfp based on the light. A detection signal Sp is output (see FIG. 2). More specifically, as shown in FIG. 1, the light emitted from the banknote BN during the lighting period includes a fluorescent component emitted by the phosphor and a phosphorescent component emitted by the phosphor. On the other hand, the light emitted from the banknote BN during the lights-out period does not contain the fluorescent component emitted by the phosphor, but contains the phosphorescent component emitted by the phosphor. Then, the light receiving section 13 outputs an electric signal (a digital signal may be used) according to the amount of incident light (amount of received light). That is, the fluorescent phosphorescence detection signal Sfp is an electric signal corresponding to the amount of incident fluorescence and phosphorescence emitted from the banknote BN during the lighting period, and the phosphorescence detection signal Sp is an electric signal corresponding to the amount of incident phosphorescence emitted from the banknote BN during the lighting period. This is an electrical signal that corresponds to the amount of light.

The light receiving section 13 may include a plurality of pixels arranged in a line in the Y direction (main scanning direction). That is, the light receiving unit 13 sends electrical signals (fluorescent phosphorescence detection signal Sfp and phosphorescence detection signal Sp) according to the amount of incident light to a plurality of channels corresponding to a plurality of pixels (positions in the Y direction (main scanning direction)). You can also output it.

Further, the light receiving unit 13 may receive light in a plurality of wavelength bands coming from the banknote BN, and output electric signals (fluorescence phosphorescence detection signal Sfp and phosphorescence detection signal Sp) for each of the plurality of wavelength bands. In this case, each pixel may include a plurality of light receiving elements (imaging elements) that selectively receive light in different wavelength bands.

When the light source 11 emits excitation light in a plurality of lighting periods, as shown in FIG. The fluorescent phosphorescence detection signals Sfp may be sequentially output. In that case, the time periods during which light is received during the plurality of lighting periods (light reception time periods) may be different from each other, but here they are set to substantially the same length.

Further, when the light source 11 is turned off in a plurality of light-off periods after the lighting period, the light receiving unit 13 sequentially receives the light emitted from the banknote BN in the plurality of light-off periods, and uses the light to A plurality of phosphorescence detection signals Sp based on the above may be sequentially output. In that case, the time periods during which light is received during the plurality of light-off periods (light reception time periods) may be different from each other, but here they are set to substantially the same length.

Note that the time for receiving light in each lighting period (light receiving time) may be different from the time for receiving light in each turning off period (light receiving time), but here, the time for receiving light in each turning off period (light receiving time) The length is set to be substantially the same as the light reception time).

More specifically, for example, the light source control section 21 may control the lighting and extinguishing of the light source 11 according to the control pattern shown in FIG. 4, and the light receiving section 13 may control the detection signal according to the control pattern shown in FIG. It may be output sequentially. In FIG. 4, UV1 to UV5 are lighting periods in which the light source 11 emits excitation light, and phases in which the light receiving unit 13 receives light emitted from the banknote BN during the lighting period and outputs a fluorescent phosphorescence detection signal Sfp. It shows. Further, PH1 to PH4 indicate a light-off period in which the light source 11 does not emit excitation light, and a phase in which the light receiving unit 13 receives light emitted from the banknote BN during the light-off period and outputs a phosphorescence detection signal Sp. Furthermore, the blank space may be a blank phase in which neither the light source 11 is turned on nor the light receiving unit 13 receives light, or may be a phase for acquiring a reflected image or a transmitted image.

In this way, between two adjacent lighting periods, between two adjacent lighting periods, or between two adjacent lighting periods and a lighting-off period, there is a blank phase, a reflection image, or a transmission image. Phases etc. may be provided as appropriate.

The calculation unit 22 calculates an estimated phosphorescence signal value in the fluorescence phosphorescence detection signal Sfp. Here, the estimated phosphorescence signal value is a signal value estimated based on the phosphorescence received by the light receiving unit 13 from the banknote BN. That is, the fluorescent phosphorescence detection signal Sfp is an electrical signal that corresponds to the incident light amount of fluorescence and phosphorescence emitted from the banknote BN during the lighting period, and the signal value of the fluorescent phosphorescence detection signal Sfp is a signal that corresponds to the incident light amount of fluorescence. The estimated phosphorescence signal value corresponds to the signal value corresponding to the amount of incident phosphorescence.

However, the estimated phosphorescence signal value only needs to capture the tendency of the signal value according to the amount of incident phosphorescence light, and does not necessarily need to exactly match the signal value according to the amount of incident phosphorescence light. This is because the purpose of this embodiment is not to calculate the time constant of the phosphor per se, but to identify the banknote BN based on characteristics such as an evaluation value according to the time constant of the phosphor.

Note that the "signal value" indicates the light intensity (brightness) of the signal, and when the light receiving section 13 includes a plurality of pixels, it is represented by a pixel value.

Then, the identification unit 23 identifies the banknote BN based on the estimated phosphorescent signal value. Therefore, as described above, the identification unit 23 can identify the banknote BN with high accuracy based on the phosphorescence.

More specifically, the identification unit 23 may determine the presence or absence of phosphorescence emitted from the banknote BN based on at least one signal value of the estimated phosphorescence signal value and the signal value of the phosphorescence detection signal Sp. Thereby, the presence or absence of phosphorescence can be determined by short-time detection. Hereinafter, the signal value of the phosphorescence detection signal Sp may be referred to as a phosphorescence signal value.

The identification unit 23 may determine the presence or absence of phosphorescence emitted from the banknote BN based on the total value of the estimated phosphorescence signal value and the phosphorescence signal value. Further, as described above, when the light receiving section 13 sequentially outputs a plurality of fluorescent phosphorescence detection signals Sfp and a plurality of phosphorescence detection signals Sp, the identification section 23 outputs a plurality of estimated phosphorescence signal values and a plurality of phosphorescence detection signals Sfp and phosphorescence detection signals Sp. The presence or absence of phosphorescence emitted from the banknote BN may be determined based on the total value of all the signal values.

On the other hand, the identification unit 23 determines the presence or absence of phosphorescence emitted from the banknote BN based only on the phosphorescence signal value, for example, based only on the phosphorescence signal value obtained during the first non-lighting period after the lighting period. Good too. Hereinafter, the light-off period that first arrives after the lighting period may be referred to as the first light-off period.

Further, the identification unit 23 adds up the signal values (estimated phosphorescence signal value and/or phosphorescence signal value) of the two wavelength bands, and determines the presence or absence of phosphorescence emitted from the banknote BN based on the obtained total value. You can. Thereby, the presence or absence of broad or intermediate color phosphorescence can be determined. For example, in the case of yellow light emission, the determination can be made based on the sum of the signal value in the red wavelength band and the signal value in the green wavelength band.

The calculation unit 22 may calculate the estimated phosphorescence signal value for each of the plurality of wavelength bands, and the identification unit 23 may calculate the estimated phosphorescence signal value for each of the plurality of wavelength bands and the signal of the phosphorescence detection signal for each of the plurality of wavelength bands. The color of phosphorescence emitted from the banknote BN may be determined based on at least one of the value (phosphorescence signal value). This makes it possible to determine the color of phosphorescence in a short period of time.

More specifically, the identification unit 23 adds up the estimated phosphorescence signal value for each of the plurality of wavelength bands and the phosphorescence signal value for each of the plurality of wavelength bands, and adds up the obtained total value for each wavelength band. Based on this, the color of phosphorescence emitted from the banknote BN may be determined.

Note that "multiple wavelength bands" include, for example, a red wavelength band (approximately 600 nm to 750 nm), a green wavelength band (approximately 500 nm to 600 nm), a blue wavelength band (approximately 400 nm to 500 nm), and infrared light. The wavelength band may be at least two of the wavelength bands (approximately 750 nm to 1500 nm). That is, the colors determined by the identification unit 23 are not limited to colors in the visible range, and may include light in wavelength ranges other than visible (for example, infrared light).

Further, here, the type of wavelength band of the signal value used for the color determination process by the identification unit 23 may completely correspond to (match) the type of wavelength band of the signal output from the light receiving unit 13. However, at least some of them may not correspond (match). In the former case, for example, the light receiving section 13 may output R, G, and B signals, and the identification section 23 may perform color determination processing for each of the R, G, and B signals. In the latter case, for example, even if the light receiving unit 13 outputs R, G, and B signals (all of which include IR components), and the identification unit 23 performs color determination processing for each of the R, G, and IR signals. good.

In the case of broad light emission, for example, the total value of B signal and G signal, the total value of G signal and R signal, the total value of R signal and IR signal, or the total value of G signal, R signal, and IR signal. Color determination processing may be performed based on this. In the case of broad and weak light emission centered on the green wavelength band, it is difficult to judge because the signal amount in each wavelength band is small, but it may be possible to judge the color based on the sum of the G signal, R signal, and IR signal. Alternatively, white may be determined from the sum of the B signal, G signal, and R signal. Furthermore, if the SO correction described later is not performed, if the signal values of the B signal, G signal, and R signal are substantially the same, it may be determined that the light is white or infrared light.

Up to this point, we have described the presence/absence determination of phosphorescence and color determination based on the estimated phosphorescence signal value and/or the phosphorescence detection signal. The presence or absence of fluorescence or the color may be determined based on the value.

The identification unit 23 may standardize the estimated phosphorescence signal value and the signal value (phosphorescence signal value) of the phosphorescence detection signal, and identify the phosphor provided on the banknote BN based on the standardized signal value. This makes it possible to reduce the influence of the printing density of individual banknotes, allowing for more stable identification based on time constants.

More specifically, the identification unit 23 may normalize the phosphorescent signal value obtained during the first light-off period. That is, the identification unit 23 may normalize the estimated phosphorescent signal value and the phosphorescent signal value by dividing them by the phosphorescent signal value obtained during the first light-off period.

The identification unit 23 calculates a determination value that varies according to the time constant of phosphorescence based on at least one of the estimated phosphorescence signal value and the signal value of the phosphorescence detection signal (phosphorescence signal value), and identifies the banknote BN based on the determination value. The identification of a phosphor (e.g., phosphorescent ink) provided in the image may also be performed. Thereby, since banknotes BN can be identified based on the difference in the time constant of the phosphor, it is possible to further improve the identification accuracy of banknotes BN. Hereinafter, a determination value that varies depending on the time constant of phosphorescence may be referred to as a time constant determination value.

Although the specific time constant judgment value is not particularly limited, the time constant judgment value may be, for example, an estimated phosphorescence signal value obtained in the last lighting period of a plurality of lighting periods and a value obtained in the first lighting period. It may be calculated from the phosphorescence signal value obtained. Further, the time constant determination value may be calculated from the estimated phosphorescence signal value obtained in the first lighting period of the plurality of lighting periods and the phosphorescence signal value obtained in the first non-lighting period. In either case, a difference or a ratio between two signal values (which may be normalized signal values as described above) may be used as the time constant determination value. Further, the estimated phosphorescence signal value obtained in the last lighting period among the plurality of lighting periods may be used as it is, or may be normalized as described above and used as the time constant determination value.

Note that the light source control section 21, the calculation section 22, and the identification section 23 may function by executing corresponding programs by a control section described later.

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

As shown in FIG. 5, first, the light source 11 irradiates the banknote BN with excitation light during a lighting period, and turns off the light during a non-lighting period after the lighting period (step S11).

Next, the light receiving unit 13 outputs a fluorescent phosphorescence detection signal Sfp based on the light emitted from the banknote BN during the lighting period, and outputs a phosphorescence detection signal Sp based on the light emitted from the banknote BN during the non-lighting period (step S12 ).

Next, the calculation unit 22 calculates an estimated phosphorescence signal value in the fluorescence phosphorescence detection signal Sfp (step S13).

Thereafter, the identification unit 23 identifies the banknote BN based on the estimated phosphorescence signal value (step S14), and the operation of the paper sheet identification device 1 ends.

(Embodiment 2)
In this embodiment, a more specific method of calculating an estimated phosphorescence signal value by the calculation unit of Embodiment 1 will be described.

As shown in FIG. 6, in this embodiment, the light source control unit (not shown) controls the light source (not shown) to emit excitation light in a plurality of lighting periods, and the light receiving unit (not shown) controls the light source (not shown) to emit excitation light in multiple lighting periods. ) sequentially outputs a plurality of fluorescent phosphorescence detection signals based on the light emitted from the banknote BN during a plurality of lighting periods.

Then, a calculation unit (not shown) calculates the first output fluorescence phosphorescence detection signal Sfp from the signal value of the second and subsequent output fluorescence phosphorescence detection signals Sfp among the plurality of fluorescence phosphorescence detection signals Sfp. By subtracting the signal values, estimated phosphorescence signal values are calculated for the second and subsequent output fluorescent phosphorescence detection signals Sfp. As a result, a signal value that is estimated to be based on a phosphorescent component (afterglow component) that has increased and then attenuated due to excitation light irradiation in a lighting period prior to the lighting period is calculated as an estimated phosphorescence signal value. Can be done.

For example, in the example shown in FIG. 6, the signal value of the phosphorescence component ph1, which increased and then attenuated due to excitation light irradiation in the first lighting period, is calculated from the second output fluorescent phosphorescence detection signal Sfp. Can be done. Also, from the third outputted fluorescence phosphorescence detection signal Sfp, the signal value of this phosphorescence component ph1 and the signal value of the phosphorescence component ph2 which increased and then attenuated due to excitation light irradiation in the second lighting period are summed. The value can be calculated.

As shown in FIG. 7, in the present embodiment, the light source control unit, before the plurality of lighting periods, causes the lighting period to be shorter than the first lighting period among the plurality of lighting periods, and substantially emit phosphorescence from the banknote BN. The light source may be controlled so as to irradiate excitation light for a short period of time when no excitation light is emitted, and the light receiving section may output a fluorescence detection signal Sf based on the light emitted from the banknote BN during this short period of time.

Here, when the time of the first lighting period is T and the time of this short period is t, the calculation unit calculates the fluorescence detection signal Sf from the signal value of the first output fluorescent phosphorescence detection signal Sfp. The estimated phosphorescence signal value may be calculated in the first output fluorescent phosphorescence detection signal Sfp by subtracting a value obtained by multiplying the signal value by (T/t). Thereby, a signal value estimated to be based on the phosphorescence component increased by the excitation light irradiation during the first lighting period can be calculated as the estimated phosphorescence signal value.

(Embodiment 3)
In this embodiment, another more specific calculation method of the estimated phosphorescence signal value by the calculation unit of Embodiment 1 will be described.

As shown in FIG. 8, in the present embodiment, the light source control unit (not shown) controls the light source so that the excitation light is emitted in a plurality of lighting periods and is turned off in a plurality of off periods after the plurality of lighting periods. (not shown), and the light receiving unit (not shown) sequentially outputs a plurality of fluorescent phosphorescence detection signals Sfp based on the light emitted from the banknote BN during a plurality of lighting periods, and outputs a plurality of fluorescent phosphorescence detection signals Sfp based on the light emitted from the banknote BN during a plurality of lighting periods, and a A plurality of phosphorescence detection signals Sp based on light emitted from the BN are sequentially output.

Then, based on the plurality of fluorescent phosphorescence detection signals Sfp and the plurality of phosphorescence detection signals Sp, the calculation section (not shown) calculates a signal based on the fluorescence received by the light receiving section from the banknote BN in the plurality of fluorescent phosphorescence detection signals Sfp. Calculate the estimated fluorescence signal value. Thereby, the estimated phosphorescence signal value can be calculated from each fluorescence phosphorescence detection signal Sfp using the estimated fluorescence signal value.

Specifically, the calculation unit calculates the estimated phosphorescence signal value in the fluorescent phosphorescence detection signal Sfp by subtracting at least the estimated fluorescence signal value from at least one signal value of the plurality of fluorescent phosphorescence detection signals Sfp. You can. Thereby, a signal value estimated to be based on a phosphorescence component (an afterglow component) excluding a fluorescence component can be calculated as an estimated phosphorescence signal value.

In this embodiment, as shown in FIG. 9, the light source includes at least the measurement position of the light receiving unit and a region located upstream of the measurement position in the transport direction of the banknote BN (arrow direction in FIG. 9). The region may be irradiated with excitation light. For example, the light source may irradiate excitation light to a region including the measurement position and regions located upstream and downstream of the measurement position in the transport direction of the banknote BN.

Further, the light source control unit may control the light source to repeat a predetermined cycle including a plurality of lighting periods and a plurality of lighting periods. As a result, the detection region (fluorescent material and phosphor material) of the banknote BN that is excited and signal-detected in the cycle corresponding to the measurement position of the light receiving section is also on the upstream side of the measurement position in at least one previous cycle. Excitation light is irradiated to excite it.

Then, the calculation unit calculates, as the estimated phosphorescence signal value, a signal value that is estimated to be based on the afterglow component PHn of phosphorescence (see FIG. 8) caused by the excitation light irradiated on the banknote BN before reaching the measurement position. You may. Hereinafter, this signal value may be referred to as an estimated afterglow signal value.

By calculating the estimated afterglow signal value, it is possible to estimate the phosphorescence amount value whose decay time is farthest from the lights-out period. Therefore, for example, a phosphor such as a phosphorescent ink can be identified by calculating a time constant determination value from the estimated afterglow signal value and the phosphorescence signal value obtained during the first light-off period. As a result, the detection error of phosphorescent ink whose time constant is longer than the phosphorescent detection period within one cycle can be reduced. For example, in FIG. 8, the second outputted fluorescent phosphorescence detection signal Sfp, the third outputted fluorescent phosphorescence detection signal Sfp, ..., the third outputted phosphorescence detection signal Sp, the first outputted Considering the fluorescent phosphorescence detection signal Sfp as one cycle, the estimated afterglow signal value is calculated from the phosphorescence signal values obtained during the first to third turn-off periods and the first output fluorescent phosphorescence detection signal Sfp. may be used to determine the time constant of the phosphor.

Note that in Embodiment 2 as well, excitation may be repeated before reaching the measurement position as shown in FIG. 9, and even in that case, the estimated phosphorescence signal value may be calculated by the calculation method of Embodiment 2. Can be done.

(Embodiment 4)
In this embodiment, a more specific example of the paper sheet identification device of Embodiment 2 will be described. First, an overview of this embodiment will be explained using FIG. 10.

As shown in FIG. 10, in this embodiment, for example, ultraviolet light as excitation light is irradiated onto a banknote from a light source (not shown) in three lighting periods, and the light emitted from the banknote in each lighting period is transmitted to the light receiving unit. (not shown). Furthermore, with the light source turned off during three turn-off periods after three turn-on periods, the light-receiving section receives light emitted from the bill during each turn-off period. At this time, the light received in each lighting period includes a fluorescent component and a phosphorescent component p1, p2, or p3 that increases depending on the irradiation of the excitation light. In addition, the second and subsequent lighting periods include a phosphorescent component (afterglow component) ph1 or ph2 that has been increased by excitation light irradiation in the previous lighting period and then attenuated. Further, the light received in each light-off period includes phosphorescence components (afterglow components) ph1, ph2, and ph3 that are increased by excitation light irradiation in any of the light-on periods and then attenuated. The amount of phosphorescence of each of the phosphorescent components ph1, ph2, and ph3 decreases over time.

Here, the amounts of phosphorescence of the phosphorescent components p1, p2, and p3, which increase in accordance with the irradiation of the excitation light, are strictly different from each other, but since the amount of variation is small, the phosphorescence component p1, which increases in response to the irradiation of the excitation light, is different from each other. , p2 and p3 are assumed to have the same amount of phosphorescence. Then, the total amount of the fluorescent component and the phosphorescent component p1 in the first lighting period becomes equal to the total amount of the fluorescent component and the phosphorescent component p2 in the second lighting period. Therefore, it is possible to estimate the phosphorescence signal that occupies the fluorescence phosphorescence detection signal Sfp in each lighting period.

More specifically, by subtracting the signal value of the first fluorescent phosphorescence detection signal Sfp from the signal value of the second fluorescent phosphorescence detection signal Sfp, the estimated phosphorescence signal value is determined by the phosphorescence component (afterglow component) ph1. Signal values can be calculated (estimated). In addition, by subtracting the signal value of the first fluorescent phosphorescence detection signal Sfp from the signal value of the third fluorescent phosphorescence detection signal Sfp, the signal value due to the phosphorescence components (afterglow components) ph1 and ph2 is obtained as an estimated phosphorescence signal value. can be calculated (estimated).

Then, a time constant evaluation value is calculated using the estimated phosphorescence signal values (ph1 and ph2) in the last lighting period and the phosphorescence signal values (ph1, ph2, and ph3) in the first lighting period, and the evaluation value is The phosphorescent ink is determined based on this.

Next, the configuration of the paper sheet processing apparatus according to this embodiment will be described using FIG. 11.

The paper sheet processing apparatus according to this embodiment may have the configuration shown in FIG. 11, for example. The paper sheet processing device 300 shown in FIG. 11 is a small paper sheet processing device that is installed on a table and used, and includes a paper sheet identification device (not shown in FIG. 11) that performs banknote identification processing. , a hopper 301 on which a plurality of banknotes to be processed are placed in a stacked state, and a case where the banknote fed out from the hopper 301 into a housing 304 is a rejected banknote such as a counterfeit banknote or a banknote whose authenticity is uncertain. There are two reject units 302 for discharging rejected banknotes, an operation unit 303 for inputting instructions from the operator, and a housing 304 for classifying and accumulating banknotes whose denomination, authenticity, and fitness are identified. It includes four stacking units 306a to 306d for displaying banknotes, and a display unit 305 for displaying information such as banknote identification and counting results and the stacking status of each stacking unit 306a to 306d. Based on the result of the fitness determination by the sheet identification device, of the four stacking units 306a to 306d, the stacking units 306a to 306c store normal bills, and the stacking unit 306d stores soiled bills. Note that the method of distributing banknotes to the stacking units 306a to 306d can be set arbitrarily.

Next, with reference to FIG. 12, the configuration of the imaging unit, which is the main part of the paper sheet identification device according to this embodiment, will be described. As shown in FIG. 12, the imaging section 211 includes an upper unit 110 and a lower unit 120 that are arranged to face each other. A gap is formed between the upper unit 110 and the lower unit 120 that are separated in the Z direction, through which banknotes BN are conveyed in the X direction within the XY plane, and this gap is It forms part of the conveyance path. The upper unit 110 and the lower unit 120 are located above (+Z direction) and below (−Z direction) the conveyance path, respectively. The Y direction corresponds to the main scanning direction of the imaging section 211, and the X direction corresponds to the sub-scanning direction of the imaging section 211.

As shown in FIG. 12, the upper unit 110 includes two reflective light sources 111, a condenser lens 112, and a light receiving section 113. The light source 111 for reflection irradiates the main surface (hereinafter referred to as A surface) of the banknote BN on the side of the light receiving section 113 with irradiation light having different wavelength bands, specifically, infrared light, red light, green light, and blue light. White light containing light and ultraviolet light as excitation light for fluorescence and phosphorescence are sequentially irradiated. The condenser lens 112 collects the light emitted from the reflection light source 111 and reflected on the A side of the banknote BN, and the light emitted from the transmission light source 124 provided in the lower unit 120 and transmitted through the banknote BN. , and collects the fluorescence and phosphorescence emitted from the A side of the banknote BN. The light receiving unit 113 receives the light focused by the condensing lens 112 and converts it into an electrical signal. Then, after amplifying the electrical signal, it is A/D converted into digital data and output. Here, the light received by the light receiving section is also referred to as incident light, and the light emitted by the light source is also referred to as irradiated light.

The lower unit 120 includes two reflection light sources 121 , one transmission light source 124 , a condensing lens 122 , and a light receiving section 123 . The light source 121 for reflection irradiates the main surface (hereinafter referred to as B surface) of the banknote BN on the side of the light receiving section 123 with irradiation light having different wavelength bands, specifically, infrared light, red light, green light, and blue light. White light containing light and ultraviolet light as excitation light for fluorescence and phosphorescence are irradiated. The condenser lens 122 condenses the light emitted from the reflection light source 121 and reflected by the B side of the banknote BN, and the fluorescence and phosphorescence 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. Then, after amplifying the electrical signal, it is A/D converted into digital data and output.

The light source 124 for transmission is arranged on the optical axis of the condensing lens 112 of the upper unit 110, and a part of the light emitted from the light source 124 for transmission is transmitted through the banknote BN and is reflected in the upper unit 110. The light is focused by a condensing lens 112 and detected by a light receiving section 113. The light source 124 for transmission may irradiate the B side of the banknote BN with irradiation light having different wavelength bands sequentially or simultaneously.

Note that in this specification, light with different wavelength bands (irradiated light, incident light, etc.) refers to, for example, visible light with different colors, and infrared light and ultraviolet light with different wavelength bands. This is light whose wavelength bands only partially overlap with each other, or whose wavelength bands do not overlap with each other.

Each of the light sources 111, 121, and 124 includes a linear light guide (not shown) extending in a direction perpendicular to the paper surface of FIG. (not shown).

Each of the light sources 111 and 121 includes 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, and an LED element that emits red light (R) with a peak wavelength of 600 nm or more and less than 750 nm. As described above, it may include an LED element that emits green light (G) with a peak wavelength of less than 600 nm, and an LED element that emits blue light (B) with a peak wavelength of 400 nm or more and less than 500 nm. One light source 111 is arranged on the upstream side and one downstream in the transport direction with the condenser lens 112 in between, and one light source 121 is arranged on the upstream side and one downstream in the transport direction with the condenser lens 122 in between. be done.

The light source 124 may include a plurality of LED elements that emit light having different peak wavelengths. Note that the peak wavelength refers to the wavelength at which the light emission intensity is maximum.

As shown in FIG. 13, each light receiving section 113, 123 includes a plurality of pixels 131GP arranged in a line in the main scanning direction D1 (direction orthogonal to the conveyance direction of banknotes BN, Y direction), and each pixel 131GP includes one first light receiving element (image sensor) 131B, one second light receiving element (image sensor) 131G, and one third light receiving element (image sensor) 131R. The first light receiving element 131B, the second light receiving element 131G, and the third light receiving element 131R are arranged in this order in a line in the main scanning direction D1.

The first light receiving element 131B is a blue light receiving element that includes a photodetector 1310 and a blue color resist (color filter) 1311B that transmits infrared light and blue light and absorbs red light and green light. It is. The second light receiving element 131G is a green light receiving element that includes a photodetector 1310 and a green color resist (color filter) 1311G that transmits infrared light and green light and absorbs red light and blue light. It is. The third light receiving element 131R is a red light receiving element that includes a photodetector 1310 and a red color resist (color filter) 1311R that transmits infrared light and red light and absorbs green light and blue light. It is.

Here, the light-receiving element (imaging element) means an element that detects the intensity of light in a predetermined wavelength band (converts it into an electrical signal), and includes a photodetector such as a photodiode and a light-receiving surface of the photodetector. It may also be configured to include a color resist that is provided to suppress transmission of light in wavelength bands (for example, green and red) other than predetermined wavelength bands to be detected (for example, blue and infrared wavelength bands).

As shown in FIG. 14, the blue color resist (color filter) 1311B mainly transmits blue light and infrared light (see broken line), and the green color resist (color filter) 1311G mainly transmits green light and infrared light. The red color resist (color filter) 1311R mainly transmits red light and infrared light (see the two-dot chain line). Therefore, the first light-receiving element 131B, the second light-receiving element 131G, and the third light-receiving element 131R receive blue light (approximately 400 nm to 500 nm in wavelength), green light (approximately 500 nm to 600 nm in wavelength), and red light (approximately 500 nm to 600 nm in wavelength), respectively. The first light receiving element 131B, the second light receiving element 131G, and the third light receiving element 131R are all capable of receiving infrared light (approximately wavelengths of 750 nm to 1500 nm). It is.

However, since the color resist of each color can usually transmit a certain amount of light of colors other than the corresponding color, the first light receiving element 131B, the second light receiving element 131G, and the third light receiving element 131R are A certain amount of light of colors other than colors may also be received.

The upper unit 110 and the lower unit 120 each repeatedly image the banknote BN being transported in the transport direction, and output a signal according to the amount of received light, so that the imaging unit 211 captures an image of the entire banknote BN. get. Specifically, the imaging unit 211 acquires a transmitted image of the banknote BN and a reflection image of the A side based on the output signal of the upper unit 110, and acquires a reflection image of the B side of the banknote BN based on the output signal of the lower unit 120. Get the image.

The imaging unit 211 also acquires a fluorescent phosphorescence detection signal and a phosphorescence detection signal for the entire banknote BN on each of the A side and the B side of the banknote BN. That is, the imaging unit 211 can acquire a fluorescent image (including a phosphorescent component) and a phosphorescent image of the A side and the B side of the banknote BN.

Next, the configuration of the paper sheet identification device according to this embodiment will be explained using FIG. 15. As shown in FIG. 15, the paper sheet identification device 200 according to this embodiment includes a detection section 210, a control section 220, and a storage section 230.

The control unit 220 is a controller that controls each unit of the paper sheet identification device 200, and includes programs for realizing various processes stored in the storage unit 230, and a CPU (Central Processing Unit) that executes the programs. , and various hardware (for example, FPGA (Field Programmable Gate Array)) controlled by the CPU. The control section 220 controls each section of the paper sheet identification device 200 based on the signals output from each section of the paper sheet identification device 200 and the control signal from the control section 220 according to the program stored in the storage section 230. control. Further, 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, a correction unit 226, and an identification unit 223 according to a program stored in a storage unit 230. .

The detection unit 210 includes a magnetic detection unit 212 and a thickness detection unit 213 in addition to the above-described imaging unit 211 along the banknote conveyance path. The imaging unit 211 images the bill as described above and outputs an image signal (image data). The magnetic detection unit 212 includes a magnetic sensor (not shown) that measures magnetism, and uses the magnetic sensor to detect the magnetism of magnetic ink, security threads, etc. printed on banknotes. The magnetic sensor is a magnetic line sensor in which a plurality of magnetic detection elements are arranged in a line. The thickness detection unit 213 includes a thickness detection sensor (not shown) that measures the thickness of banknotes, and detects tapes, double feeding, etc. by the thickness detection sensor. The thickness detection sensor detects the amount of displacement of the rollers facing each other across the conveyance path when the banknote passes, using a sensor provided on each roller.

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

Note that one cycle of imaging is an imaging pattern in which the wavelength band of the irradiation light emitted from each light source 111, 121, and 124, the timing of turning on and off each light source 111, 121, and 124, and the timing of signal reading are set. I'm talking about By continuously and repeatedly performing one cycle of imaging as one cycle, an image of the entire banknote is acquired.

The light source control unit 221 performs dynamic lighting control of each light source 111 , 121 , 124 in order to capture an image of an individual banknote using each light source 111 , 121 , 124 . Specifically, the light source control unit 221 controls lighting and extinguishing of each light source 111, 121, and 124 based on the timing set in the imaging parameter. This control is performed using a mechanical clock that changes depending on the banknote transport speed and a system clock that is always output at a constant frequency regardless of the banknote transport speed.

Here, the control (lighting timing) of each light source 111, 121, and 124 by the light source control section 221 and the timing of light reception by the light receiving sections 113 and 123 will be described in more detail using FIG. 16. Note that FIG. 16 shows the details and timing of light source lighting and light reception. Further, PH in FIG. 16 indicates the off period (OFF) of the light source. In addition, L1, L2, and L3 in FIG. 16 indicate light in predetermined wavelength bands other than white light emitted from the light sources 111, 121, and 124, respectively, and L1 of a plurality of phases indicate mutually different wavelength bands. It may be light of the same wavelength band, or it may contain light of the same wavelength band. The same applies to L2 and L3 of multiple phases.

As shown in FIG. 16, the upper unit 110 and the lower unit 120 acquire data corresponding to the entire surface of the banknote by repeating the 18 phases of phases 1 to 18 as one cycle.

More specifically, the upper unit 110 reads side A of the banknote BN, and the light receiving unit 113 receives transmitted light from the light L3 emitted from the light source 124 in phases 1, 2, and 4, and in phases 5, 7. and 8, the reflected light from the light L1 emitted from the light source 111 is received.

The light receiving unit 113 also receives reflected light (RGB) of white light including red light, green light, and blue light emitted from the light source 111 in phases 3, 6, 9, 12, 15, and 18.

Furthermore, the light receiving unit 113 receives fluorescence (including a phosphorescent component) due to ultraviolet light as excitation light irradiated from the light source 111 in phases 10, 11, and 13, and generates fluorescence based on the received fluorescence (including a phosphorescent component). Sequentially outputs phosphorescence detection signals.

The light receiving unit 113 receives phosphorescence in phases 14, 16, and 17 when all the light sources 111, 121, and 124 are turned off (PH and OFF in the figure), and generates a phosphorescence detection signal based on the received phosphorescence. Output sequentially.

Further, the lower unit 120 reads the B side of the banknote BN, and the light receiving section 123 receives reflected light from the light L2 emitted from the light source 121 in phases 1, 2, 5, 7, and 8.

The light receiving unit 123 also receives reflected light (RGB) of white light including red light, green light, and blue light emitted from the light source 121 in phases 3, 6, 9, 12, 15, and 18.

Furthermore, the light receiving unit 123 receives fluorescence (including a phosphorescent component) due to ultraviolet light as excitation light irradiated from the light source 121 in phases 10, 11, and 13, and detects fluorescence based on the received fluorescence (including a phosphorescent component). Fluorescent phosphorescence detection signals are sequentially output.

The light receiving unit 123 receives phosphorescence in phases 14, 16, and 17 when all the light sources 111, 121, and 124 are turned off (PH and OFF in the figure), and generates a phosphorescence detection signal based on the received phosphorescence. Output sequentially.

The light emission time and light reception time of each phase can be set as appropriate, but here, the light reception time of fluorescence (including phosphorescence) and the light reception time of phosphorescence are all set to the same time.

The phase for fluorescence (including phosphorescence) detection and the phase for phosphorescence detection can be set as appropriate, and may be a control pattern shown in FIG. 17, for example. PH in FIG. 17 indicates the turn-off period of the light source, and the control pattern C in FIG. 17 corresponds to the control pattern shown in FIG. 16. Note that although FIG. 17 illustrates the lighting and extinguishing patterns of the reflective light source 111 of the upper unit 110, the lower unit 120 can also detect fluorescence and phosphorescence using a similar control pattern.

The sensor control unit 224 controls the timing of reading signals from each of the upper unit 110 and the lower unit 120 based on the timing set in the imaging parameter, and adjusts the timing of turning on and turning off each light source 111, 121, and 124. Signals are read out from each of the upper unit 110 and lower unit 120 in synchronization. This control is performed using a mechanical clock and a system clock. Then, the sensor control unit 224 sequentially stores the read signals, that is, line data, in a ring buffer (line memory) of the storage unit 230.

Note that the line data herein refers to data based on signals obtained by one imaging by each of the upper unit 110 and the lower unit 120, and refers to data in the lateral direction of the acquired image (perpendicular to the banknote conveyance direction). This corresponds to one row of data in the Y direction).

The image generation unit 225 has a function of generating an image based on various signals related to banknotes acquired from the detection unit 210. Specifically, the image generation unit 225 first decomposes the data (image signal) stored in the ring buffer into data for each light irradiation and light reception condition. Then, the image generation unit 225 performs correction processing such as dark output cut, gain adjustment, and bright output level correction according to the characteristics of each decomposed data, generates various image data of the banknote, and stores it in the storage unit. Save to 230.

Here, a method of SO (spectral overlap) correction will be explained. Here, a case will be described in which the colors of four types of phosphorescent ink having different wavelength bands of emitted phosphorescence are discriminated. The four types of phosphorescent inks are a first monochrome ink (B) that emits blue light with a peak wavelength of 400 nm or more and less than 500 nm, and a second monochrome ink that emits green light that has a peak wavelength of 500 nm or more and less than 600 nm. (G), a third monochrome ink (R) that emits red light having a peak wavelength of 600 nm or more and less than 750 nm, and a fourth monochrome ink (IR) that emits light that has a peak wavelength of 750 nm or more and less than 2500 nm. show.

First, before shipping the paper sheet identification device 200, the phosphorescence emitted from four types of phosphorescent inks is individually received by the light receiving unit 113 for each type of phosphorescent ink, and the amount of light emitted as a reference for each phosphorescent ink ( When the output value) is measured, for example, the output values shown in Table 1 below are obtained.

Here, although the light receiving element 113 is not equipped with a light receiving element that selectively receives infrared light, each of the first light receiving element 131B, the second light receiving element 131G, and the third light receiving element 131R is capable of receiving infrared light. Receive light. Therefore, as an output value related to infrared light, an added value (total value) of the output values (signal values) of the first light receiving element 131B, the second light receiving element 131G, and the third light receiving element 131R is calculated. Note that when measuring the reference light emission amount for each type of phosphorescent ink, excitation light is irradiated from the light source 111 under the same conditions as when acquiring the fluorescent phosphorescence detection signal and the phosphorescence detection signal from the banknote to be identified. to detect phosphorescence.

From the results in Table 1 above, the following relationship (Equation 1) holds true between each light receiving element and monochromatic ink.

（上記（式１）中、ＣＨ＿Ｂは識別対象の紙幣に励起光を照射したときの第１の受光素子１３１Ｂの出力値を表し、ＣＨ＿Ｇは識別対象の紙幣に励起光を照射したときの第２の受光素子１３１Ｇの出力値を表し、ＣＨ＿Ｒは識別対象の紙幣に励起光を照射したときの第３の受光素子１３１Ｒの出力値を表し、ＣＨ＿ＩＲは、識別対象の紙幣に励起光を照射したときの第１の受光素子１３１Ｂ、第２の受光素子１３１Ｇ及び第３の受光素子１３１Ｒの出力値の加算値を表し、Ｂ＿ＩＮＫは補正後の第１の単色インク（Ｂ）の燐光信号を表し、Ｇ＿ＩＮＫは補正後の第２の単色インク（Ｇ）の燐光信号を表し、Ｒ＿ＩＮＫは補正後の第３の単色インク（Ｒ）の燐光信号を表し、ＩＲ＿ＩＮＫは補正後の第４の単色インク（ＩＲ）の燐光信号を表す。）

(In the above (Formula 1), CH_B represents the output value of the first light receiving element 131B when the banknote to be identified is irradiated with excitation light, and CH_G is the output value of the first light receiving element 131B when the banknote to be recognized is irradiated with excitation light. CH_R represents the output value of the third light receiving element 131R when excitation light is irradiated to the banknote to be identified, and CH_IR represents the output value of the third light receiving element 131R when the banknote to be identified is irradiated with excitation light. represents the sum of the output values of the first light receiving element 131B, the second light receiving element 131G, and the third light receiving element 131R, B_INK represents the phosphorescent signal of the first monochrome ink (B) after correction, represents the phosphorescence signal of the second monochrome ink (G) after correction, R_INK represents the phosphorescence signal of the third monochrome ink (R) after correction, and IR_INK represents the phosphorescence signal of the fourth monochrome ink (IR) after correction. represents the phosphorescence signal of

When matrix A(4) in the above (Formula 1) is normalized, the following relationship (Formula 2) holds true. In addition, in the following (Formula 2), the fourth decimal place and below are rounded down.

When the above (Formula 2) is transformed, the following relationship (Formula 3) holds true.

Here, CH_B, CH_G, CH_R, CH_IR, B_INK, G_INK, R_INK, and IR_INK in (Formula 2) and (Formula 3) are the same as in (Formula 1).

The correction unit 226 performs arithmetic processing of multiplying the detection data (estimated phosphorescence signal value and phosphorescence detection signal value of each phase) by an inverse matrix B(4) ^-1 as shown in the above (Equation 3). SO correction processing is performed.

Note that in cases where the emitted light color of the phosphorescent ink to be identified is red, green, or blue, this SO correction process can be omitted.

As described using FIG. 10, the calculation unit 222 calculates the first output fluorescence phosphorescence from the signal value of the second and subsequent output fluorescence phosphorescence detection signals Sfp among the plurality of fluorescence phosphorescence detection signals Sfp. By subtracting the signal value of the detection signal Sfp, estimated phosphorescence signal values are calculated in the second and subsequent output fluorescent phosphorescence detection signals Sfp.

Specifically, the first fluorescent phosphorescence signal value UV1 is subtracted from the second fluorescent phosphorescence signal value UV2 to obtain the signal value of the phosphorescence component (afterglow component) ph1 in the second fluorescent phosphorescence detection signal Sfp (hereinafter referred to as The estimated phosphorescence signal value (UV2-UV1) is calculated. In addition, the signal values of the phosphorescence components (afterglow components) ph1 and ph2 in the third fluorescence phosphorescence detection signal Sfp (hereinafter, estimated The phosphorescent signal value (UV3-UV1) is calculated.

The correction unit 226 performs SO correction of the estimated phosphorescence signal value and the phosphorescence detection signal value for each phase using an SO (spectral overlap) correction coefficient obtained from reference medium data collected and processed under the same sensor control conditions. Specifically, R, G, and IR signals are obtained by performing SO correction on the R, G, and B output signals from the imaging unit 211. Thereby, the color of the phosphorescent ink that emits light in the red, green, and infrared wavelength bands can be determined using the imaging unit 211 having the above-described RGB pixel configuration.

The identification unit 223 calculates a phosphorescence presence/absence determination value. Specifically, the estimated phosphorescence signal value (UV2-UV1), the estimated phosphorescence signal value (UV3-UV1), and the signal value of the first output phosphorescence detection signal Sp (hereinafter referred to as phosphorescence signal value PHA1). , the signal value of the second output phosphorescence detection signal Sp (hereinafter referred to as phosphorescence signal value PHA2), and the signal value of the third output phosphorescence detection signal Sp (hereinafter referred to as phosphorescence signal value PHA3). Add up and. This phosphorescence presence/absence determination value is calculated for each R, G, and IR signal.

Then, the identification unit 223 determines the presence or absence of phosphorescence from the banknote BN by comparing the phosphorescence presence/absence determination value of each R, G, and IR signal with a predetermined threshold value (which may be common to the R, G, and IR signals). judge. That is, when the phosphorescence presence/absence determination value of any one of the R, G, and IR signals exceeds the threshold value, the identification unit 223 determines that phosphorescence is present, and the phosphorescence presence/absence determination value of any of the R, G, and IR signals exceeds the threshold value. If the threshold value is not exceeded, it is determined that there is no phosphorescence.

Further, the identification unit 223 determines the color of phosphorescence emitted from the banknote BN based on the phosphorescence presence/absence determination value of each R, G, and IR signal. Specifically, if there is a phosphorescence presence/absence determination value that exceeds a threshold value, it is determined that phosphorescence of a color corresponding to the wavelength band of the signal is emitted from the banknote BN.

Note that when the emitted color of the phosphorescent ink is red, green, or blue (there is no infrared light), the SO correction process may not be performed, and the presence or absence of phosphorescence may be determined based on each color of the R, G, and B signals.

Further, the identification unit 223 performs a process of standardizing (normalizing) each estimated phosphorescence signal value and each phosphorescence signal value in order to correct variations in the time constant determination value due to the printing density of each banknote BN. Specifically, the estimated phosphorescent signal value (UV2-UV1), the estimated phosphorescent signal value (UV3-UV1), the phosphorescent signal value PHA1, the phosphorescent signal value PHA2, and the phosphorescent signal value PHA3 are each divided by the phosphorescent signal value PHA1.

Note that the signal value used for standardization is not particularly limited to the phosphorescence signal value PHA1, and may be any other signal value.

The identification unit 223 also calculates a time constant determination value τ. Specifically, the time constant determination value τ is calculated from the estimated phosphorescence signal value (UV2-UV1) and the phosphorescence signal value PHA1, and is calculated from the following (Equation 4).
τ=1-(UV2-UV1)/PHA1 (Formula 4)

Note that the time constant determination value τ is not limited to that calculated using the above (Formula 4), but may be calculated using the following (Formula 5), for example.
τ=(UV2-UV1)/PHA1 (Formula 5)

In either case, the time constant determination value τ is a value that reflects the time constant of the phosphorescent ink provided on the banknote BN. That is, as the time constant of the phosphorescent ink becomes larger, the time constant determination value τ becomes larger or smaller. More specifically, when the time constant of the phosphorescent ink becomes large, τ in the above (Formula 4) becomes large, and τ in the above (Formula 5) becomes small.

The identification unit 223 then identifies the phosphorescent ink provided on the banknote BN based on the calculated time constant determination value τ. Specifically, a determination table is prepared in advance by calculating time constant determination values τ of various phosphorescent inks having different time constants. Here, the numerical range of the time constant determination value τ is defined for each phosphorescent ink in the determination table. Then, the identification unit 223 identifies the phosphorescent ink to which the time constant determination value τ corresponds by comparing the calculated time constant determination value τ with the determination table.

FIG. 18 shows estimated phosphorescent signal values and phosphorescent signal values (both after OS correction and offset removal) in each phase actually obtained from four types of phosphorescent inks A to D. Here, the time constants of the four types of phosphorescent inks A to D are:
Phosphorescent ink A<phosphorescent ink B<phosphorescent ink C<phosphorescent ink D
are increasing in the order of

Further, FIG. 19 shows the result of normalizing each signal value shown in FIG. 18 by the phosphorescence signal value PHA1 of phase D (the signal value of the first output phosphorescence detection signal Sp) for each phosphorescent ink. The size of the arrow shown in FIG. 19 corresponds to the time constant determination value τ calculated from the above (Formula 4). Therefore, as shown in FIG. 19, the time constant determination value τ obtained for each phosphorescent ink has the same magnitude relationship as the time constants of the four types of phosphorescent inks A to D. That is, it can be seen that the phosphorescent ink can be determined based on the time constant using the time constant determination value τ.

Furthermore, using the estimated phosphorescent signal values and phosphorescent signal values (both after OS correction and offset removal) in each phase actually obtained from the above four types of phosphorescent inks A to D, phosphorescence was calculated for each R, G, and IR signal. When the presence/absence determination value was calculated, the presence/absence of each ink could be determined with a determination margin. That is, for each phosphorescent ink, the phosphorescence presence/absence determination value based on the corresponding color signal exceeded a predetermined numerical range, while the phosphorescence presence/absence determination value based on other color signals fell below the numerical range. For example, for phosphorescent ink A, the phosphorescence presence/absence determination value based on the G signal exceeds a predetermined numerical range, while the phosphorescence presence/absence determination value based on the R and IR signals falls below the numerical range.

The identification unit 223 uses the above-described determination results of the presence or absence of phosphorescence, the color of the emitted light, and the phosphorescent ink (phosphor) in order to identify the denomination, authenticity, fitness, etc. For example, the identification unit 223 identifies authenticity based on the above-described determination result regarding phosphorescence.

Next, the operation related to phosphorescence determination of the paper sheet identification device 200 according to this embodiment will be explained using FIG. 20.

As shown in FIG. 20, first, the control unit 220 acquires a fluorescent phosphorescence detection signal and a phosphorescence detection signal for the A side and B side of the banknote BN for each R, G, and B output signal from the imaging unit 211. (Step S21).

Next, the calculation unit 222 calculates estimated phosphorescence signal values in the second and third fluorescent phosphorescence detection signals Sfp for each of the R, G, and B signals (step S22).

Next, the correction unit 226 performs SO correction on the estimated phosphorescence signal value and the phosphorescence detection signal value for each phase, and converts them into R, G, and IR signals (step S23).

Next, the identification unit 223 calculates a phosphorescence presence/absence determination value for each of the R, G, and IR signals (step S24).

Next, the identification unit 223 determines the presence or absence of phosphorescence from the banknote BN for each R, G, and IR signal based on the phosphorescence presence/absence determination value, and also determines the color of the phosphorescence emitted from the banknote BN (R, G, or IR) is determined (step S25).

Next, the identification unit 223 divides each estimated phosphorescence signal value and each phosphorescence signal value by the phosphorescence signal value PHA1 for the signal determined to have phosphorescence among the R, G, and IR signals in step S25. Standardize (step S26).

Next, the identification unit 223 calculates a time constant determination value τ based on, for example, the above (Equation 4) from the signal value standardized in Step S26 (Step S27).

Thereafter, the identification unit 223 identifies the phosphorescent ink provided on the banknote BN based on the time constant determination value τ (step S28), and the operation of the paper sheet identification device 200 ends.

Next, a modification of this embodiment will be described using FIG. 21.

As shown in FIG. 21, even if ultraviolet light as excitation light is irradiated from a light source for a short period of time, which is shorter than the first lighting period and during which phosphorescence is not substantially emitted from the banknote, before the plurality of lighting periods. good. Then, the light emitted from the banknote during this short period of time may be received by the light receiving section, and the fluorescence detection signal Sf may be output from the light receiving section. Fluorescence has an extremely short time constant and a signal can be obtained even after receiving light for a short period of time, so the light received during this short period of time consists almost only of fluorescent components.

Therefore, if the light emission time in the first lighting period is T and the short-term light emission time is t, the value obtained by multiplying the signal value of the fluorescence detection signal Sf by (T/t) is the value of the first fluorescence phosphorescence detection signal Sfp. It is equal to the signal value of the fluorescent component that occupies Therefore, by subtracting the value obtained by multiplying the signal value of the fluorescence detection signal Sf by (T/t) from the signal value of the first fluorescence phosphorescence detection signal Sfp, the estimated phosphorescence signal is obtained in the first fluorescence phosphorescence detection signal Sfp. As a value, it is possible to calculate (estimate) a signal value due to the phosphorescent component p1 that increases in accordance with the irradiation of the excitation light.

Note that the light emitting time t (short period) can be set as appropriate as long as it is shorter than the first lighting period and during which phosphorescence is not substantially emitted from the banknote; ) may be about 1/10 to 1/20 of that.

This estimated phosphorescence signal value can be used in the above-described process of determining the presence or absence of phosphorescence. For example, this estimated phosphorescence signal value may be added to the phosphorescence presence/absence determination value described above.

(Embodiment 5)
In this embodiment, a more specific example of the paper sheet identification device of Embodiment 3 will be described. Further, this embodiment is substantially the same as Embodiment 4, except that the calculation method of the estimated phosphorescence signal value by the calculation unit is different. First, an overview of this embodiment will be explained.

As shown in FIG. 22, when the banknote BN conveyed by the paper sheet identification device 200 passes between the upper unit 110 and the lower unit 120 of the imaging section 211, an excitation light source (not shown) is turned on periodically. In this case, since there is an irradiation width, excitation is repeated before reaching the measurement position as shown in FIG. 23. The result at the measurement position of the light receiving section (not shown) is shown by the dashed line on the right side of FIG. Furthermore, the features included during excitation include three components, as shown in FIG. That is, the fluorescent component F of the fluorescent ink (the fluorescent component from paper may be used), the attenuated phosphorescent component α of the phosphorescent ink, the excited phosphorescent component β of the phosphorescent ink, and the afterglow component PHn of the phosphorescent ink due to excitation from the previous irradiation. be. In this embodiment, an estimated fluorescence signal value estimated based on this fluorescence component F is calculated, and this estimated fluorescence signal value is used to calculate a signal value estimated based on the afterglow component PHn, that is, estimated afterglow. Calculate the signal value. This method will be explained in detail below.

Note that in the fourth embodiment as well, excitation may be repeated before reaching the measurement position as shown in FIG. 23, and even in that case, the estimated phosphorescence signal value may be calculated by the calculation method of the fourth embodiment. Can be done.

First, as a premise, as described above, the characteristics of the ink that emit light include fluorescent characteristics and phosphorescent characteristics. Fluorescence is characterized by emitting light only when it is irradiated with excitation light, and the amount of light emitted does not change as the irradiation time changes. The phosphorescence characteristic is that when irradiated with excitation light, the amount of emitted light increases and changes with the irradiation time. In addition, the phosphorescence characteristic is that it emits light even when the excitation light is stopped, and the amount of light emission also decreases with respect to time changes after the irradiation is stopped.

To make the explanation easier, we will first focus on the phosphorescence characteristics.

It is assumed that the phosphorescence characteristic increases and decreases linearly in both the measurement results during excitation light irradiation (rise) and the measurement results after excitation light irradiation (fall) (see FIGS. 25 and 26). For example, if the time constant τ is 400 μs and the rising lighting time is 60 μs, a linear increasing feature can be assumed as shown in FIG.

In the case of linearity, the integrated amount of received light during excitation light irradiation is set to integration section A: FL_1, integration section B: FL_2, and integration section C: FL_3 (see FIG. 27). If the three integrated times (measurement times) are the same,
FL_2-FL_1=FL_1×2 or 3×FL_1=FL_2
It can be seen that the calculation holds true (see FIG. 28).

Furthermore, if defined as linear, the relationship between the integrated amount A during the first exposure (for example, 0 to 20 μs) and the integrated amount B during the second exposure (for example, 20 to 40 μs) is as follows.
B=3×A
It can be defined as

From the above results, the amount of increase in luminescence amount β due to the phosphorescent feature during excitation is
β=(FL_2-FL_1)/2
(See Figure 29).

Note that β may be calculated from FL_2 and FL_3. In this case, β is
β=(FL_3-FL_2)/2
It can be defined as

Next, as shown in FIG. 30, the amount of decrease in the amount of phosphorescent light emission after the excitation light is turned off is measured in the integration section D: PH_1, the integration section E: PH_2, and the integration section F: PH_3. However, the cumulative time is the same for PH_1, PH_2, and PH_3.

Assuming a case of 3 data (PH_1, 2, 3), it is assumed that both falling edges decrease linearly. Then, as with the rise characteristic, the attenuation amount α of the light emission amount is
α=(PH_1-PH_2)/2
It can be defined as (see Figure 31).

Then, from PH_1 and α, the virtual integration interval PH_0 is
PH_0=PH_1+2α
(See FIGS. 32 and 33).

Note that α may be calculated from PH_2 and PH_3. In this case, α is
α=(PH_3-PH_2)/2
It can be defined as

As shown in FIG. 34, PH_0 is
PH_0=γ+SIM_FL_3
The increasing component of the phosphorescence feature during excitation is obtained from SIM_FL_3.

Here, if we express γ using α and β, we get
γ=α+β
becomes.

Therefore, SIM_FL_3 is
SIM_FL_3=PH_0-γ
It can be calculated from (see Figure 35).

Therefore, FL_3, which is the increasing component of the phosphorescent feature during excitation, is
FL_3≒SIM_FL_3
It is.

Next, as shown in FIG. 36, assume that phosphorescent ink and fluorescent ink are mixed, or that paper printed with phosphorescent ink emits fluorescence. In this case, the fluorescent component F is added only during excitation.

In this case, β is
β={(FL_2+F)-(FL_1+F)}/2
=(FL_2-FL_1)/2
It can be seen that β can be obtained without being influenced by the amount of fluorescence emission.

α and PH_0 are
α=(PH_1-PH_2)/2
PH_0 PH_1+2α
It can be seen that α and PH_0 can be obtained without being influenced by the amount of fluorescent light emission.

Also, from γ=α+β,
SIM_FL_3=PH_0-γ
, SIM_FL_3 is calculated.
Therefore, the fluorescence component F included in the integration interval C is
F=FL_3-SIM_FL_3
It can be calculated from

Finally, an example is given for the case where there are fluorescent and phosphorescent features and after multiple cycles of excitation, as shown in FIGS. 37 and 38. Note that the area surrounded by the thick broken line in FIG. 38 is the measured quantity, that is, the signal value.

First, from the two data (PH1_1, 2) after the excitation light is turned off,
α=(PH1_1-PH1_2)/2
It can be defined as

In addition, from two other data (PH1_2, 3) after the excitation light was turned off,
α=(PH1_2-PH1_3)/2
It may be defined as

From PH1_1 and α,
PH1_0=PH1_1+2α
Calculate.

From the two data (FL1_1, 2) while the excitation light is on,
β=(FL1_2-FL1_1)/2
can be calculated.

In addition, from two other data (FL1_2, 3) when the excitation light is on,
β=(FL1_3-FL1_2)/2
may be calculated.

Furthermore,
SIM_FL1_3=PH1_0-(α+β)
SIM_FL1_3 can be calculated from, and the included fluorescence amount F is
F=FL1_3-SIM_FL1_3
(See Figure 39). This fluorescence amount F becomes the estimated fluorescence signal value.

and,
PHn=FL1_1-F-α-β
PHn is obtained from (see FIG. 38). Note that since F is the amount of fluorescence, it is constant. This PHn becomes the estimated afterglow signal value.

For example, by using PHn and PH1_1 as attenuation features, it is possible to use phosphorescent features to determine authenticity.

Here, in the first to fifth embodiments described above, the range of the time constant of the phosphor to be identified will be explained.

As shown on the left side of FIG. 40, in the first to fifth embodiments described above, it is assumed that the intensity of phosphorescence emitted by a phosphor such as a phosphorescent ink increases linearly when the excitation light is irradiated. Therefore, if the amount of phosphorescence (integrated amount of received light) from time t0 to t1 is m, the amount of phosphorescence (integrated amount of received light) from time t1 to t2 is m×3, and the amount of phosphorescence (integrated amount of received light) from time t2 to t3 is Quantity) l is expressed as m×5, respectively. Note that this relationship is established when t0=0, t1=T, t2=2T, and t3=3T. That is, this is a case where the light reception times of the phosphorescence amounts m, n, and l are the same.

However, strictly speaking, as shown on the right side of FIG. 40, the intensity of phosphorescence increases exponentially and eventually becomes saturated. The amount of phosphorescence (integrated amount of received light) N from time t2 to time t3 (integrated amount of received light) L is expressed by the formula shown in the figure. In each formula, A represents a constant, and τ represents a time constant.

At this time, it is considered that the above assumption is established if the following (Formula 6) is satisfied. This error range will be defined below.

Since the general SN ratio of a contact image sensor (hereinafter abbreviated as CIS) is about 40 dB, it can be assumed that when CIS is 8 bits, there is a noise component of 255/100=2.5 digits. If an error is allowed for the output fluctuation equivalent to the above-mentioned noise, the amount of phosphorescence M is expressed by the following formula (Formula 7). However, it is assumed that t0=0, t1=T, t2=2T, and t3=3T.

Furthermore, when the phosphorescence amount L expressed by the following formula (Formula 8) is transformed into the following (Formula 9), the above (Formula 7), this (Formula 9), and the following (Formula 10) representing the phosphorescence amount M are obtained. The amount of phosphorescence L expressed by the following (Equation 11) is calculated from.

Here, the relationship between the amount of fluorescence and the amount of phosphorescence of a medium (banknote) that emits fluorescence and contains phosphorescent ink will be explained. As a result of measurements by the present inventors, the luminescence amount of the fluorescent ink is taken as the luminescence amount immediately after the excitation light source is turned on, and the luminescence ratio of the fluorescent ink and the phosphorescent ink is calculated from the luminescence amount after a predetermined period of time (in this case, after 60 μs has elapsed). The result was that the ratio of the amount of fluorescence to the amount of phosphorescence was approximately in the range of 0.3:0.7 to 0.6:0.4.

Therefore, the light emission by the medium is expressed by the following (Equation 12).
Fluorescence amount: Phosphorescence amount = FO: (1-FO) (Formula 12)
However, FO shall be 1 or less.

Furthermore, since the sensor here is assumed to be an 8-bit CIS, if the output value is 255 or more, phosphorescence and fluorescence can be detected without being affected by errors. Therefore, the amount of light received by the sensor, that is, the amount of phosphorescence L and the amount of fluorescence F can be expressed by the following (Equation 13).
L+F=255 (Formula 13)

Further, the following (Formula 14) is established from the above (Formula 12), and when this is substituted into the above (Formula 13), the following (Formula 15) is obtained.

By transforming this (Formula 15), the following (Formula 16) is obtained.

Table 2 below shows the results of calculating the relationship between the time constant and the fluorescence amount ratio with respect to fluctuations in time T using this (Equation 16) and the above (Equation 11).

As a result of investigation, the fluorescence amount ratio is about 30% to 60% as mentioned above, and Table 2 shows the results from 10% to 90%. If the time constants are larger than these, the CIS can detect phosphorescence and fluorescence without error.

From this result, if it is a general medium (banknote) with a fluorescence amount ratio of about 30% to 60%, the time constant may be 120 μs or more or 150 μm or more. Note that the upper limit of the time constant is not particularly limited, but may be, for example, 10 ms or less, or 7 ms or less.

Further, from Table 2, the ratio of the time constant τ to the time T (τ/T) was calculated and the results are shown in Table 3 below.

From this result, if the time constant is T x 13.5 (μs) or more when the fluorescence amount ratio is 30%, and T x 7.5 (μs) or more when the fluorescence amount ratio is 60%, then Phosphorescence and fluorescence can be detected with CIS without error. That is, if it is a general medium (banknote) with a fluorescence amount ratio of about 30% to 60%, the time constant may be T×7.5 (μs) or more.

(Modification 1)
In Embodiments 1 to 5 above, when the excitation light is irradiated, other types of light are not irradiated, but the reflected light, transmitted light, fluorescence, and phosphorescence caused by the excitation light irradiation have an influence on the detection of other feature quantities. If it does not affect the image, the excitation light may be irradiated at the same time as the light that is irradiated to obtain the reflected image and/or the transmitted image.

(Modification 2)
In the above embodiments 4 and 5, white light is irradiated, and blue light, green light, and red light are simultaneously received by three types of light receiving elements: the light receiving element 133B, the green light receiving element 133G, and the red light receiving element 133R, respectively. However, in the first to fifth embodiments described above, blue light, green light, and red light may be turned on alternately, and the light arriving from the banknote may be received by one type of light receiving element.

(Modification 3)
In the first to fifth embodiments described above, a case has been described in which one or more fluorescent phosphorescence detection signals and one or more phosphorescence detection signals regarding one or more lighting periods and one or more non-lighting periods in the same one cycle are processed. The one or more fluorescent phosphorescence detection signals and the one or more phosphorescence detection signals that are processed may be light-based and received in different cycles. Here, the plurality of cycles may be a plurality of consecutive (for example, two) cycles.

Although the embodiments have been described above with reference to the drawings, the present disclosure is not limited to the above embodiments. Furthermore, the configurations of each embodiment may be combined or modified as appropriate without departing from the gist of the present disclosure.

As described above, the present disclosure is a technology useful for identifying paper sheets with high precision based on phosphorescence.

1, 200: Paper sheet identification device 11, 111, 121, 124: Light source 13, 113, 123: Light receiving section 20, 220: Control section 21, 221: Light source control section 22, 222: Calculation section 23, 223: Identification Section 110: Upper unit 120: Lower unit 112, 122: Condenser lenses 131B, 131G, 131R: Light receiving element 131GP: Pixel 210: Detection section 211: Imaging section 212: Magnetic detection section 213: Thickness detection section 224: Sensor control section 225: image generation section 226: correction section 230: storage section 300: banknote processing device 301: hopper 302: reject section 303: operation section 304: housing 305: display sections 306a to 306d: accumulation section 1310: photodetector 1311B, 1311G, 1311R: Color resist BN: Banknote Sfp: Fluorescent phosphorescence detection signal Sp: Phosphorescence detection signal Sf: Fluorescence detection signal

Claims (11)

A paper sheet identification device that detects fluorescence and phosphorescence emitted from paper sheets being conveyed,
a light source that irradiates excitation light onto paper sheets;
a light source control unit that controls the light source so that the excitation light is irradiated during a lighting period and is turned off during a non-lighting period after the lighting period;
a light receiving unit that outputs a fluorescent phosphorescence detection signal based on the light emitted from the paper sheet during the lighting period, and outputs a phosphorescence detection signal based on the light emitted from the paper sheet during the lights-out period;
a calculation unit that calculates an estimated phosphorescence signal value that is estimated to be a signal value based on phosphorescence received by the light receiving unit from the paper sheet in the fluorescent phosphorescence detection signal;
A paper sheet identification device comprising: an identification section that identifies the paper sheet based on the estimated phosphorescence signal value. The light source control unit controls the light source to emit the excitation light in a plurality of lighting periods,
The light receiving unit sequentially outputs a plurality of fluorescent phosphorescence detection signals based on light emitted from the paper sheet during the plurality of lighting periods,
The calculation unit subtracts the signal value of the first outputted fluorescent phosphorescence detection signal from the signal value of the second and subsequent outputted fluorescent phosphorescence detection signals among the plurality of fluorescent phosphorescence detection signals, The paper sheet identification device according to claim 1, wherein the estimated phosphorescence signal value is calculated in the second and subsequent outputted fluorescent phosphorescence detection signals. Before the plurality of lighting periods, the light source control unit controls the excitation for a short period of time that is shorter than a first lighting period of the plurality of lighting periods and in which phosphorescence is not substantially emitted from the paper sheet. controlling the light source to emit light;
The light receiving unit outputs a fluorescence detection signal based on light emitted from the paper sheet during the short period of time,
When the time of the first lighting period is T and the time of the short period is t,
The calculation unit outputs the first output by subtracting a value obtained by multiplying the signal value of the fluorescence detection signal by (T/t) from the signal value of the first output fluorescence phosphorescence detection signal. 3. The paper sheet identification device according to claim 2, wherein the estimated phosphorescence signal value is calculated from the detected fluorescence phosphorescence detection signal. The light source control unit controls the light source to emit the excitation light in a plurality of lighting periods, and to turn off the light in a plurality of turn-off periods after the plurality of lighting periods,
The light receiving unit sequentially outputs a plurality of fluorescent phosphorescence detection signals based on the light emitted from the paper sheet during the plurality of lighting periods, and outputs a plurality of fluorescent phosphorescence detection signals based on the light emitted from the paper sheet during the plurality of non-lighting periods. sequentially outputs phosphorescence detection signals,
The calculation unit estimates, based on the plurality of fluorescent phosphorescence detection signals and the plurality of phosphorescence detection signals, a signal value based on the fluorescence received by the light receiving unit from the paper sheet in the plurality of fluorescent phosphorescence detection signals. 2. The paper sheet identification device according to claim 1, wherein the paper sheet identification device calculates an estimated fluorescence signal value. The calculation unit calculates the estimated phosphorescence signal value in the fluorescence phosphorescence detection signal by subtracting at least the estimated fluorescence signal value from at least one signal value of the plurality of fluorescence phosphorescence detection signals. The paper sheet identification device according to claim 4. The light source irradiates the excitation light to a region including at least a measurement position of the light receiving unit and a region located upstream of the measurement position in the conveyance direction of the paper sheet,
The light source control unit controls the light source to repeat a predetermined cycle including the plurality of lighting periods and the plurality of lighting periods,
The calculation unit calculates, as the estimated phosphorescence signal value, a signal value estimated to be based on an afterglow component of phosphorescence caused by the excitation light irradiated on the paper sheet before reaching the measurement position. The paper sheet identification device according to claim 4 or 5, characterized in that: 2. The identification unit determines the presence or absence of phosphorescence emitted from the paper sheet based on at least one signal value of the estimated phosphorescence signal value and the signal value of the phosphorescence detection signal. 5. The paper sheet identification device according to any one of items 5 to 5. The calculation unit calculates the estimated phosphorescence signal value for each of a plurality of wavelength bands,
The identification unit determines the color of phosphorescence emitted from the paper sheet based on at least one of the estimated phosphorescence signal value of the plurality of wavelength bands and the signal value of the phosphorescence detection signal of the plurality of wavelength bands. The paper sheet identification device according to any one of claims 1 to 5. The identification unit is characterized in that it normalizes the estimated phosphorescence signal value and the signal value of the phosphorescence detection signal, and identifies the phosphor provided on the paper sheet based on the standardized signal value. The paper sheet identification device according to any one of claims 1 to 5. The identification unit calculates a determination value that varies according to a time constant of phosphorescence based on at least one of the estimated phosphorescence signal value and the signal value of the phosphorescence detection signal, and determines whether the paper sheet is labeled based on the determination value. The paper sheet identification device according to any one of claims 1 to 5, characterized in that the device identifies a phosphor provided therein. A paper sheet processing device comprising the paper sheet identification device according to any one of claims 1 to 5.

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