JP6944259B2 - Phosphorescence detection device, paper leaf processing device and phosphorescence detection method - Google Patents

Description

The present invention relates to a phosphorescence detection device that detects phosphorescence emitted from a detection target excited by excitation light, a paper sheet processing device including the phosphorescence detection device, and a phosphorescence detection method.

Conventionally, a security mark having predetermined optical characteristics has been used to identify the authenticity of paper sheets such as banknotes and documents, and products. For example, a security mark containing a phosphorescent body that does not emit phosphorescence under visible light and emits phosphorescence only when it is irradiated with light of a predetermined wavelength such as ultraviolet rays is attached by printing on paper sheets or product packages. In addition, the authenticity of paper leaves, products, etc. is determined from the emission state of phosphorescence. As the phosphor, a substance having a single decay time constant or a mixture of a plurality of substances having different decay time constants is used.

Patent Document 1 discloses an apparatus that distinguishes two luminescence materials that emit light within the same wavelength range and contain two types of dyes having different decay times in different ratios. The device detects the decay time characteristics of the luminescent material on items transported at high speed, creates a measured luminescent intensity profile and compares it to the reference intensity profile. The transport speed V is 6 m / s (6000 mm / s). The excitation time interval Δtex of the light source is 100 μs (0.1 ms). The time delay Δtd after the light source is turned off is 40 μs (0.04 ms). The measurement time interval Δtm of the excited luminescence material is 4000 μs (4 ms). The drawings also show that it has five optical sensors. Therefore, assuming that the detection is performed five times during the measurement time interval Δtm and the detections are performed at equal intervals, each detection is performed every 1000 μs (1 ms). The device disclosed in Patent Document 1 creates a measured luminescence intensity profile by these five detections.

Patent Document 2 discloses a device that irradiates a banknote with excitation light, detects the emitted phosphorescence, and verifies the authenticity of the banknote. This device detects the peak of the phosphorescence spectrum obtained by irradiating the excitation light, detects the attenuation feature for each wavelength of the detected peak, and compares it with the registered feature. This device makes the first measurement within 500 μs (0.5 ms) immediately after the light source is turned off (that is, without time delay). Further, after turning on the light source again, the light source is turned off again, and the next measurement is performed within 500 μs (0.5 ms) after 100 μs (0.1 ms) has passed since the second turn off (that is, with a time delay of 100 μs). .. The device repeats the measurement until the emission decay time is exceeded, increasing the time delay.

Patent Document 3 discloses a method of determining the authenticity of a document by obtaining the ratio of the intensity value detected in the first spectral region and the intensity value detected in the second spectral region. 50 μs (0.05 ms) after the excitation of the luminescent material is completed, the detection of the emission intensity starts and lasts for 50 μs (0.05 ms). Further, the detection of the emission intensity starts after a time interval of 100 μs (0.1 ms) and lasts for 50 μs (0.05 ms). The decay time of the intensity value detected in the first spectral region is τ1 = 200 μs (0.2 ms), and the decay time of the intensity value detected in the second spectral region is τ2 = 400 μs (0.4 ms). be.

Japanese Patent Application Laid-Open No. 2014-511130 U.S. Pat. No. 7,262,420 U.S. Patent Application Publication No. 2015/348351

As in the device disclosed in Patent Document 1 or Patent Document 2, the phosphorescence can be detected accurately by repeating the detection a plurality of times to obtain the phosphorescence attenuation feature and comparing it with the registered phosphorescence feature. Although it can be done, it takes time to detect. Therefore, it is difficult to speed up the processing.

The invention disclosed in Patent Document 3 detects phosphorescence only twice, but only obtains the ratio of two phosphorescences, and does not detect phosphorescence characteristics such as an attenuation time constant.

A phosphor is a substance that is excited to emit phosphorescence when it receives excitation light such as visible light or ultraviolet rays. The intensity (amount of light) of phosphorescence emitted from the phosphor is the maximum value when the irradiation of the excitation light is stopped, and then gradually attenuates. The color and decay time constant of phosphorescence emitted from the phosphor are determined by the phosphor. Even if the phosphors are different, either the phosphorescence color or the decay time constant may be the same, or both may be the same. Further, the phosphorescence emitted from a single phosphorescent body is not limited to one type, and may be a plurality of types. In the following, for the sake of simplicity, the phosphorescence emitted from a single phosphorescent body will be described as one type. Further, even if the apparent phosphorescence color is different, it can be treated as phosphorescence within the same wavelength range as long as it is within the wavelength range that can be detected by the photodetector. The relationship between the intensity of phosphorescence emitted from a single phosphor α and time is expressed by Equation 1.

In Equation 1, P _α is the intensity of phosphorescence emitted from phosphorescent body α, A _α is a constant determined by the concentration and emission efficiency of phosphorescent body α, t is the time elapsed from when the excitation light is extinguished to detection, τ _α. Is the decay time constant of the phosphorescence emitted from the phosphorescent body α. Even if the phosphor α is a mixture of a plurality of phosphors having the same decay time constants, the relationship between the intensity of phosphorescence emitted from the phosphor α and the time is similarly expressed by Equation 1.

If the detected phosphorescence is phosphorescence having a single decay time constant or phosphorescence emitted from a plurality of phosphorescent bodies having the same decay time constant, the intensity is detected twice by changing the detection timing (detection timing), and the intensity is detected twice. By solving the simultaneous equations, the decay time constant of the phosphorescent body can be obtained.

In the following, with respect to the time t in the above equation 1, the phosphorescence detection timing will be described as the _{time t n.} The time t _n is represented by the time elapsed from when the excitation light is extinguished to detection, and when the excitation light is extinguished, t ₀ = 0.

Specifically, after the excitation light stops _{emitting, the phosphorescence intensity P 1} and the phosphorescence emitted from the detection target T _{at time t 1} (first timing) and second time t _{2 (second timing)} The intensity P ₂ is detected. This intensity P ₁ and the intensity P _2, they use the time t ₁ and time t ₂ is detected, based on the following equation 2 to calculate the _alpha tau decay time constant phosphorescence emitted from the detection target T ..

In this way, the attenuation time constant of the phosphorescence emitted from the detection target T is calculated from the difference in detection timing t _{2 −} t ₁ and the intensity ratio P ₂ / P _{1, and the phosphorescence is identified to determine the detection target T.} It is possible to determine the authenticity of the provided paper leaves and the like.

If the phosphorescence emitted from the detection target T is due to a plurality of types of phosphorescence having different decay time constants, the phosphorescence intensity cannot be expressed by Equation 1, but a single decay time constant can be used. The decay time constant when approximated by the phosphorescence possessed can be obtained by the above calculation method. It is also possible to identify this as a feature of phosphorescence.

However, as _{the difference between the time t 1} and the time t ₂ becomes smaller, the amount of change in the phosphorescence intensity becomes smaller, so that the phosphorescence α on the detection target T is more susceptible to uneven printing and detector errors. It may be difficult to correctly calculate the decay time constant τ. Therefore, it is important to set an appropriate phosphorescence detection timing according to the attenuation characteristics of the phosphorescent body to be detected.

The present invention has been made in view of such a situation, and an object of the present invention is to provide an apparatus capable of identifying phosphorescence to be identified in a short time.

The phosphorescence detection device according to the present invention is a light source that irradiates a detection target that emits at least one of a plurality of types of phosphorescence to be identified with excitation light, and light that detects the intensity of phosphorescence emitted from the detection target. The detector is provided with a control unit that controls the light source and the light detector, and the control unit performs the first detection of the intensity at the first timing after the irradiation of the excitation light is stopped, and the above-mentioned. after Tsu row subsequent detection of the intensity at a second timing later than the first detection, have further row of additional detection of the intensity at the third timing, the second timing, the classification target The first ratio of the intensity detected in the first detection to the intensity detected in the subsequent detection in all of the plurality of types of phosphorescence is equal to or greater than the threshold value, and the plurality of types of phosphorescence are timing der absolute value of the first difference in specific at least two while is equal to or greater than a predetermined value out is, in the third timing, at least one phosphorescence of the plurality kinds of phosphorescent The second ratio of the intensity detected in the first detection to the intensity detected in the additional detection is less than the threshold, and the difference between the first ratios at the second timing. This is the timing at which the absolute value of the difference between the second ratios between phosphorescences whose absolute value is less than the predetermined value becomes equal to or more than the predetermined value .

Further, the phosphorescence detection method according to the present invention includes a step of irradiating a detection target that emits at least one of a plurality of types of phosphorescence to be identified with excitation light, a step of stopping irradiation of the excitation light, and the above-mentioned. A step of first detecting the intensity of phosphorescence emitted from the phosphorescent body contained in the detection target at the first timing after the stop of irradiation of the excitation light, and a second step after the first detection. It has a step of performing subsequent detection of the intensity at a timing and a step of performing additional detection of the intensity at a third timing after the subsequent detection, and the second timing is the identification. The first ratio of the intensity detected in the first detection to the intensity detected in the subsequent detection in all of the plurality of types of phosphorescence of interest is equal to or greater than the threshold value, and the plurality of types of phosphorescence are present. timing der absolute value of said first difference ratio is equal to or greater than a predetermined value in at least two among of is, the third timing, at least one phosphorescence of the plurality kinds of phosphorescent The second ratio of the intensity detected in the first detection to the intensity detected in the additional detection is less than the threshold value, and the first ratio at the second timing is This is the timing at which the absolute value of the difference of the second ratio between phosphorescences whose absolute value of the difference is less than the predetermined value becomes equal to or more than the predetermined value .

There are various types of phosphors, and the emission color and decay time constant of phosphorescence are various, but here it is suitable as a security feature of paper sheets represented by value documents such as banknotes and securities. A phosphorescent body having a decay time constant of 0.2 msec to 10 msec, which is considered to be, is to be detected. Specifically, for example, when a banknote processing device that conveys banknotes at 4000 mm / sec detects phosphorescence with an attenuation time constant of 0.2 to 10 msec, the phosphorescence is reduced to about 37% (1/e e) of the initial value. The distance to which the detection target is conveyed and moved before reaching the detection target is 0.8 to 40 mm. Therefore, if the phosphorescence detection range of the sensor is about 10 mm to 20 mm in the transport direction of the detection target, the phosphorescent body having the above attenuation time constant can be distinguished.

According to the present invention, it is possible to provide an apparatus capable of identifying phosphorescence to be identified in a short time.

It is a block diagram which shows the structure of one Example of the phosphorescence detection apparatus which concerns on this invention. It is a schematic diagram which shows the structure of an optical sensor. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. FIG. 2 is a sectional view taken along line IV-IV in FIG. It is a VV cross-sectional view in FIG. It is a flowchart which shows the operation flow of the phosphorescence detection apparatus which concerns on this invention. It is a graph which shows the attenuation curve of the intensity ratio of three kinds of phosphorescences with different decay time constants. It is a graph which shows the attenuation curve of the intensity ratio of four kinds of phosphorescences with different decay time constants. It is a graph which shows the attenuation curve of the intensity ratio of 5 kinds of phosphorescences with different decay time constants.

Hereinafter, the present invention will be described in detail with reference to the drawings.

(1) Configuration of Phosphorescence Detection Device FIG. 1 is a block diagram schematically showing the configuration of the phosphorescence detection device 100 according to the present invention. The phosphorescence detection device 100 is a device used for determining the authenticity of the detection target T attached to the transported object X. The phosphorescence detection device 100 includes a transfer device 80, an optical sensor 10 installed above the transfer device 80, and a control device 90 that controls the transfer device 80 and the optical sensor 10. The transported object X can be used as a paper sheet such as a banknote, and the phosphorescence detection device 100 can be used as a paper sheet processing device.

The structure of the optical sensor 10 will be described with reference to FIGS. 2 to 6. FIG. 2 is a schematic side sectional view showing the structure of the optical sensor 10. 3, FIG. 4, FIG. 5, and FIG. 6 are a cross-sectional view of II-II, a cross-sectional view of III-III, a cross-sectional view of IV-IV, and a cross-sectional view of V-V in FIG. 2, respectively. Although FIG. 2 shows a case where the optical sensor 10 is mounted downward, the optical sensor 10 can be mounted in any direction.

The optical sensor 10 includes a holder 20, a light source 30, a photodetector 40, a light guide body 50, a substrate 60, and an optical filter 70.

The holder 20 is made of a substance that does not transmit light, such as black resin, has through holes that are open at the top and bottom, and has a cylindrical shape. In this through hole, a light guide body 50, an optical filter 70, a light source 30, and a photodetector 40 are arranged in this order from the lower side. Further, the upper opening of the through hole is closed by the substrate 60. Further, the holder 20 has a partition 21 arranged between the light source 30 and the photodetector 40 as a part thereof. When the partition 21 comes into contact with the light guide body 50, the surface of the light guide body 50 is scratched, and the scratches may cause light leakage, attenuation, or diffusion, and may deteriorate the light guide performance of the light guide body 50. Therefore, a slight gap is provided between the lower end of the partition 21 and the surface of the light guide body 50. However, if there is no such fear, the partition 21 may be brought into contact with the light guide body 50. Further, it goes without saying that the partition 21 may be a member separate from the holder 20.

The light source 30 irradiates the detection target with excitation light. Specifically, the light source 30 is an ultraviolet LED, which is attached to the lower surface of the substrate 60. The excitation light emitted by the light source 30 includes a wavelength capable of exciting the detection target, and preferably does not include the wavelength range of the synchrotron radiation to be detected.

The photodetector 40 detects the synchrotron radiation emitted from the detection target. Specifically, the photodetector 40 is a photodiode that outputs a signal that changes according to the intensity (amount of light) of the received light, and is attached to the lower surface of the substrate 60. As shown in FIG. 6, the optical sensor 10 includes two photodetectors 40. These photodetectors 40 have different wavelength ranges that can be detected. Therefore, two types of synchrotron radiation can be detected at the same time. When detecting only the synchrotron radiation of a specific wavelength or the intensity of the synchrotron radiation regardless of the wavelength, the number of photodetectors 40 may be one. Further, by setting the number of photodetectors 40 to three or more, it is possible to detect three or more types of synchrotron radiation at the same time.

The light guide body 50 guides the excitation light emitted from the light source 30 to the detection target, and guides the synchrotron radiation emitted from the detection target to the photodetector 40. That is, the light guide body 50 functions as a light guide unit. The light guide body 50 is a block made of a transparent resin such as acrylic or polycarbonate, and has an excitation light incident surface 51 and a synchrotron radiation emitting surface 52 at the upper portion thereof, and a light entering / exiting surface 53 at the lower portion thereof. Have. The light entrance / exit surface 53 is larger than the light receiving surface of the photodetector 40. Further, the light guide body 50 has an upright surface 54 between the excitation light incident surface 51 and the radiated light emitting surface 52, and a step is formed by the exciting light incident surface 51, the upright surface 54, and the radiated light emitting surface 52. Has been done. Further, the light guide body 50 has a side surface 55 extending between the excitation light incident surface 51 and the synchrotron radiation emitting surface 52 and the light entering / exiting surface 53. A slight gap is provided between the side surface 55 and the inner surface of the holder 20. Although not particularly limited, in the present embodiment, the shape of the portion surrounded by the side surface 55 of the light guide body 50 is the side of the light source 30 which is substantially square when viewed from the side of the light source 30 and the photodetector 40. It is a hexagonal shape with two corners chamfered. With this shape, the excitation light from the light source 30 can be efficiently irradiated to the detection target. Further, the material of the light guide body 50 is not limited to the transparent resin, and may be transparent glass. The material of the light guide body 50 may be any material that transmits excitation light and synchrotron radiation, and is not limited to a transparent material.

The light source 30 and the excitation light incident surface 51 are arranged so as to face each other via a visible light cut filter 71 which is a kind of optical filter 70 and transmits ultraviolet rays to cut visible light. Further, the photodetector 40 and the synchrotron radiation emitting surface 52 are arranged so as to face each other via an ultraviolet cut filter 72 and a color filter 73, which are a kind of optical filter 70. When a plurality of photodetectors 40 are provided as in the optical sensor 10 according to the present embodiment, the type of the color filter 73 facing each photodetector 40 is changed, and each photodetector 40 has a different wavelength. It is possible to detect (color) light. For example, when detecting synchrotron radiation of red, green, and blue, a total of three color filters 73 are arranged between the three photodetectors 40 and the synchrotron radiation emitting surface 52. Each color filter 73 transmits light in the red wavelength range, the green wavelength range, or the blue wavelength range, respectively. These optical filters 70 may be replaced with filters having other characteristics depending on the purpose, or may not be arranged if unnecessary.

Returning to FIG. 1, the description of the phosphorescence detection device 100 will be continued. The transport device 80 is a device that continuously transports the object X to be conveyed with the detection target T at a predetermined position in the direction indicated by the arrow, and is a belt according to the characteristics such as the shape of the object X to be conveyed. It can be a conveyor, a roller conveyor, a floating transfer device, or the like. In this embodiment, the transport device 80 is a belt conveyor. The belt conveyor has a belt and a pulley for driving the belt. A rotary encoder that detects the number of rotations (rotation angle) of the pulley is connected to the rotation shaft of the pulley. Further, the transport device 80 has a pass detection sensor (not shown) that detects the passage of the object X to be transported on the upstream side of the optical sensor 10.

In the phosphorescence detection device 100, the optical sensor 10 is arranged so that the light source 30 is located on the upstream side in the transport direction of the object X to be transported in the transport device 80, and the photodetector 40 is located on the downstream side. Further, the optical sensor 10 is arranged so that the light entrance / exit surface 53 of the light guide body 50 faces the detection target T attached to the object to be transported X transported on the transport device 80.

The control device 90 is composed of a power supply, a CPU, a memory, and the like, and has a transfer device control unit 91, a detection unit 92, a correction unit 93, a discrimination unit 94, and a storage unit 95 as functional units.

The transfer device control unit 91 controls the operation of the transfer device 80. Further, the transport device control unit 91 determines the movement distance of the belt, that is, the movement distance of the detection target T (detection target) based on the number of pulses of the rotary encoder after the passage detection sensor detects the passage of the object X to be transported. Information about the existence position of T) is calculated.

After the passage of the object X to be transported is detected by the passage detection sensor, the detection unit 92 commands the light source 30 to irradiate the excitation light and stop the excitation light at a predetermined timing. Further, the detection unit 92 receives the signal transmitted from the photodetector 40 and calculates the intensity of the detected fluorescence and phosphorescence.

The correction unit 93 obtains information on the existence position of the detection target T from the transfer device control unit 91, and also obtains information on the phosphorescence intensity detected by the photodetector 40 from the detection unit 92. The correction unit 93 further obtains information on the correction coefficient from the storage unit 95, which will be described later. The correction unit 93 corrects the intensity of the phosphorescence detected based on this information.

The determination unit 94 compares the phosphorescence intensity obtained by the detection unit 92 or the corrected phosphorescence intensity obtained by the correction unit 93 with the reference value stored in the storage unit 95. The substance contained in the detection target T is determined, and the authenticity of the detection target T is determined. Further, the discrimination unit 94 can calculate the decay time constant τ of phosphorescence, discriminate the substance contained in the detection target T based on the decay time constant τ, and determine the authenticity of the detection target T.

The storage unit 95 stores information on the correction coefficient used for correcting the phosphorescence intensity. This information is, for example, a function or a table showing the relationship between the relative position of the photodetector 40 and the detection target T and the correction coefficient.

Further, the storage unit 95 stores information such as the intensity of phosphorescence emitted from the true detection target T and the decay time constant of phosphorescence. This information is the basis for determining the authenticity of the detection target T.

(2) Phosphorescence detection method Phosphorescence is detected as follows. Phosphorescence is synchrotron radiation emitted from the detection target after the irradiation of the excitation light to the detection target is stopped. The intensity of phosphorescence emitted from the detection target gradually attenuates with the passage of time after the irradiation of the excitation light is stopped.

First, the light source 30 irradiates the excitation light. The irradiated excitation light passes through the light guide body 50. The excitation light transmitted through the light guide 50 reaches the detection target and excites the detection target. Subsequently, the light source 30 is turned off. Then, the excited detection target emits phosphorescence. Phosphorescence emitted from the detection target passes through the light guide body 50. The photodetector 40 detects phosphorescence transmitted through the light guide body 50.

The photodetector 40 that has detected phosphorescence transmits a signal for notifying the detection of phosphorescence or a signal that changes according to the intensity of the detected phosphorescence to the control device. The control device that receives the signal from the photodetector 40 calculates the intensity of phosphorescence and the like. Phosphorescence is detected in this way.

The detection of phosphorescence is preferably started immediately after the irradiation of the excitation light is stopped. The phosphorescence detection time can be arbitrarily determined, but when calculating the attenuation time constant as described later, the shorter the detection time, the more accurately the attenuation time constant can be calculated. The intensity of phosphorescence to be detected may be calculated from the signal of one measurement performed during detection, or may be calculated by integrating or averaging the signals of a plurality of measurements performed during detection.

(3) Operation of Phosphorescence Detection Device An example of the operation flow of the phosphorescence detection device 100 configured as described above will be described with reference to FIG. 7.

When the operation of the phosphorescence detection device 100 is started, the transfer device 80 conveys the object to be conveyed X, and the passage detection sensor detects the passage of the object X to be conveyed (S1).

When the number of pulses of the rotary encoder reaches a predetermined number after the passage detection sensor detects the passage of the object to be transported X, the light source 30 lights up (S2). At this time, the detection target T attached to the transported object X is moving under the optical sensor 10. Further, the excitation light emitted from the light source 30 is guided to the detection target T by the light guide body 50 and excites the detection target T. Fluorescence is emitted from the detection target T while the excitation light is irradiated.

Next, the photodetector 40 detects the fluorescence (S3).

After a predetermined time has elapsed from the start of lighting of the light source 30, the light source 30 is turned off (S4). Then, the emission of fluorescence from the detection target T is stopped. Further, the emission of phosphorescence from the detection target T starts.

Subsequently, after the light source 30 is turned off, the phosphorescence emitted from the detection target T is detected a plurality of times by each of the plurality of photodetectors 40 at a predetermined timing (S5).

The fluorescence intensity and phosphorescence attenuation characteristics are detected for each photodetector 40 (for each color of synchrotron radiation), and based on these, the substance contained in the detection target T is discriminated, and the transported object X is identified. Authenticity is determined (S6).

The operation of the phosphorescence detection device 100 is not limited to that of detecting fluorescence or phosphorescence once as described above. That is, fluorescence or phosphorescence may be detected a plurality of times while the object X to be transported passes through. Further, the authenticity of the transported object X can be determined by irradiating the excitation light at a position where the detection target T of the transported object X should not be attached and confirming that the synchrotron radiation is not emitted. It is possible. Further, by irradiating one object X with excitation light at both the position where the detection target T should be attached and the position where the detection target T should not be attached, the object to be conveyed is irradiated with excitation light. It is also possible to determine the authenticity of X. In this case, if it is confirmed that the synchrotron radiation is emitted from the position where the detection target T should be attached and the synchrotron radiation is not emitted from the position where the detection target T should not be attached, the transported object is to be transported. X is determined to be true, otherwise it is determined to be false.

(4) Phosphorescence Discrimination Method In step S6, the phosphorescence detection device 100 calculates the phosphorescence decay time constant for each photodetector 40 (for each color of synchrotron radiation), and from the phosphorescent body included in the detection target T. Determine the phosphorescence to be irradiated.

Specifically, when phosphorescence is detected in step S5, the discriminating unit 94 determines _{the intensity P 1} and the intensity P of the phosphorescence emitted from the detection target T at the detected _{time t 1} and time t _{2. 2} using, for each photodetector 40, based on equation 2 to calculate the _alpha tau decay time constant phosphorescence emitted from the detection target. Then, compared with the _α decay time constant and the calculated decay time constant of the phosphor to be identified tau, phosphorescence identification object is determined not to have been detected.

When three types of phosphorescence are identified and the decay time constants are 0.2 msec, 1 msec, and 10 msec, respectively, the discriminating unit 94 calculates three types of predetermined ranges including 0.2 msec, 1 msec, and 10 msec, respectively. Compare with the constant τ _α. As a result, for example, if within a predetermined range decay time constant tau _alpha comprises 1msec, discrimination unit 94, phosphorescence decay time constant 1msec is determined to have been detected.

(5) Authenticity determination method of the detection target The authenticity determination of the detection target T (security feature) attached to the transported object X is performed as follows, for example.

First, the presence or absence of phosphorescence is confirmed for each photodetector 40. If phosphorescence is emitted, calculate its decay time constant. Compare these results with the reference attributes. As a result of the comparison, if the two match, it is determined that the detection target T is true. If they do not match, the detection target T is determined to be false.

Table 1 shows an example of the reference attribute.

In Table 1, the horizontal axis represents the wavelength range of phosphorescence detected. That is, the horizontal axis means that phosphorescence is divided into wavelength ranges of red wavelength range, green wavelength range, and blue wavelength range. The vertical axis represents the attenuation characteristics of the detected phosphorescence. That is, the vertical axis means that the decay time constant of phosphorescence is divided into 0.2 msec, 1 msec, and 10 msec. “Yes” means that the relevant phosphorescence is emitted from a single phosphor or a plurality of types of phosphors having the same decay time constant. Also, "none" means that phosphorescence is not detected.

When the reference attribute is the attribute shown in Table 1, the true detection target T has a single or multiple types that emit phosphorescence having an attenuation time constant of 0.2 msec and a blue color. Phosphorescent body is included. Further, a single or a plurality of types of phosphors that emit phosphorescence having an attenuation time constant of 1 msec and a red color are included. Further, a single or a plurality of types of phosphors that emit phosphorescence having an attenuation time constant of 1 msec and a green color are included.

In this case, the authenticity determination of the detection target T is performed as follows. First, the detection unit 92 individually detects red, green, and blue phosphorescence via the three photodetectors 40. Subsequently, the discriminating unit 94 calculates the decay time constant of the phosphorescence of each color. The discriminating unit 94 refers to the information according to Table 1 stored in the storage unit 95, and compares it with the phosphorescence attenuation time constant obtained for each color. As a result, if the attribute of the phosphorescence emitted from a certain detection target T matches the attribute shown in Table 1, it is determined that the detection target T is true. On the contrary, if it does not match the phosphorescence attribute shown in Table 1, the detection target T is determined to be false.

In this way, it is possible to determine the authenticity of the detection target T (security feature) and, by extension, the authenticity of the transported object X such as paper sheets, characterized by the presence or absence of phosphorescence and the decay time constant.

Although an example in which only the feature of phosphorescence is used as the feature of the detection target T is shown here, the feature of the detected fluorescence can be further added as the feature of the detection target T. Specifically, in Table 1, the presence or absence of fluorescence detection can be added as a feature for each of the red wavelength range, the green wavelength range, and the blue wavelength range.

(6) Attenuation time constant of phosphorescence to be identified In order to identify a large amount of detection target T in a short time, the phosphorescence to be identified must be phosphorescence that is attenuated in a certain short time. On the other hand, if the phosphorescence is attenuated too quickly, the phosphorescence is attenuated in an extremely short time, and it becomes difficult to accurately detect the phosphorescence intensity. Therefore, as the phosphorescence to be identified, phosphorescence having an attenuation time constant of 0.2 msec or more and 10 msec or less is desirable.

Further, in order to identify which of the phosphorescences to be identified corresponds to the detected phosphorescence, it is necessary that the decay time constants (that is, the phosphorescence curves) of the phosphorescences to be identified are discrete to some extent. be.

For example, consider the case of identifying which of the three types of phosphorescence the phosphorescence emitted by the detection target T corresponds to. FIG. 8 shows the attenuation curves of the phosphorescence intensity ratios in which the attenuation time constants are 0.2 msec, 1 msec, and 10 msec, respectively. In FIG. 8, the vertical axis represents the phosphorescence intensity ratio to the maximum intensity (that is, the phosphorescence intensity detected in the first detection), and the horizontal axis represents the elapsed time from the first detection of the phosphorescence intensity. As can be seen from FIG. 8, these three attenuation curves are almost evenly discrete. Therefore, when it is necessary to identify which of the three types of phosphorescence the phosphorescence emitted by the detection target T corresponds to, for example, the phosphorescence used for the detection target T has an attenuation time constant of 0.2 msec and 1 msec, respectively. And three types of phosphors that emit phosphorescence of 10 msec may be used.

Next, consider a case of identifying which of the four types of phosphorescence the phosphorescence emitted by the detection target T corresponds to. FIG. 9 shows the attenuation curves of the phosphorescence intensity ratios in which the attenuation time constants are 0.2 msec, 0.4 msec, 1 msec, and 10 msec, respectively. In FIG. 9, the vertical axis is the phosphorescence intensity ratio to the maximum intensity (that is, the phosphorescence intensity detected in the first detection), and the horizontal axis is the elapsed time from the first detection of the phosphorescence intensity. As can be seen from FIG. 9, these four attenuation curves are almost evenly discrete. Therefore, when it is necessary to identify which of the four types of phosphorescence the phosphorescence emitted by the detection target T corresponds to, for example, the phosphorescence used for the detection target T has a phosphorescence decay time constant of 0.2 msec. , 0.4 msec, 1 msec, and 4 types of phosphorescent bodies that emit phosphorescence of 10 msec may be used.

Next, consider a case of identifying which of the five types of phosphorescence the phosphorescence emitted by the detection target T corresponds to. FIG. 10 shows the attenuation curves of the phosphorescence intensity ratios in which the decay time constants are 0.2 msec, 0.4 msec, 0.9 msec, 2 msec, and 10 msec, respectively. In FIG. 10, the vertical axis represents the phosphorescence intensity ratio to the maximum intensity (that is, the phosphorescence intensity detected in the first detection), and the horizontal axis represents the elapsed time from the first detection of the phosphorescence intensity. As can be seen from FIG. 10, these five attenuation curves are almost evenly discrete. Therefore, when it is necessary to identify which of the five types of phosphorescence the phosphorescent body emitted by the detection target T corresponds to, the phosphorescence used for the identification target T has a phosphorescence decay time constant of 0.2 msec, respectively. Five types of phosphors that emit phosphorescence of 0.4 msec, 0.9 msec, 2 msec, and 10 msec may be used.

(7) Timing of initial detection The photodetector 40 has a large change in the intensity of light reception at the moment when the irradiation of the excitation light is stopped, so that the photodetector 40 has an abnormality depending on the circuit system including the photodiode and the amplifier that it has. It may output a signal. Specifically, when the response speed of the photodetector 40 is slow, the photodetector 40 outputs a light detection signal derived from the excitation light for a while even after the irradiation of the excitation light from the light source 30 is stopped. It ends up. In that case, the intensity of phosphorescence emitted from the detection target cannot be detected correctly for a while. On the other hand, if the phosphorescence intensity is detected after a sufficiently long time has elapsed after the irradiation of the excitation light from the light source 30 is stopped, the influence of the abnormal signal at the moment when the irradiation of the excitation light is stopped disappears, but the phosphorescence can be identified. The time required is long, and in the first place, phosphorescence may be attenuated and undetectable. Therefore, the present inventors examined at what timing should the initial detection of the phosphorescence intensity be performed after stopping the irradiation of the excitation light from the light source 30 (what should be the first timing). bottom.

In the circuit constituting the photodetector 40, there is a portion equivalent to the CR circuit. Therefore, the response speed of the photodetector 40 depends on _{the time constant τ CR of the CR circuit.} That is, after stopping the irradiation of the excitation light, from the light detector 40, a decaying voltage constant as tau _CR time is output as a light detection signal from the excitation light. If the voltage output from the excitation light is less than 1% of the voltage when the excitation light irradiation is stopped at the time when the phosphorescence intensity is first detected, it is considered that there is no influence of the excitation light. Can be done.

For example, assuming that the capacitance of the capacitor C in the circuit of the photodetector 40 is 1 to 80 pF which is usually selected and the resistance value of the resistor R in the circuit of the photodetector is 100 to 500 kΩ which is usually selected, the time constant is described above. The τ _CR is 0.0001 to 0.04 msec. For example, if the capacitance of the capacitor C is 80 pF and the resistance value of the resistor R is 500 kΩ, the voltage output from the photodetector 40 will be the voltage 0.04 msec after the excitation light irradiation is stopped. It means that it is reduced to 1 / e, that is, about 36%. In order for the voltage output from the photodetector 40 to be less than 1% of the output voltage when the excitation light is irradiated, it takes 4.6 times the time _{constant τ CR.} That is, a time of 0.0046 to 0.184 msec is required.

Therefore, if the timing of the first detection of the phosphorescence intensity (first timing) is the time when 0.005 msec or more and 0.18 msec or less elapses after the irradiation of the excitation light from the light source 30 is stopped, the excitation light It is possible to detect the phosphorescence intensity with almost no influence from.

Examples of desirable values for the capacitance of the capacitor C and the resistance value of the resistor R in the circuit of the photodetector 40 are 15 pF and 500 kΩ, respectively. The time constant τ _{CR in} this case is 0.0075 msec, and the time 4.6 times that is 0.0345 msec. Therefore, the preferable initial detection timing in this case is 0.035 msec or more after the stop of the irradiation of the excitation light. However, considering the variation in the capacitance of the capacitor C and the resistance value of the resistor R, the variation in the response characteristics of the light source 30, the variation in the position of the detection target T, and the like, it is necessary to expect a certain safety factor. Therefore, it is preferable to perform the first detection when 0.05 msec or more has elapsed after the irradiation of the excitation light is stopped, assuming a safety factor of about 50%. However, after an excessively long time has passed, the time required to identify the phosphorescence becomes long, and the phosphorescence may be attenuated and undetectable. Therefore, it is 0.1 msec or less, which is twice 0.05 msec. It is preferable that the first detection is performed when the time of 0.15 msec or less, which is three times 0.05 msec, has elapsed.

Further, the capacitance of the capacitor C and the resistance value of the resistor R in the circuit of the photodetector 40 are not limited to the above range, and the resistance value of the resistor R may be set to 1 MΩ, for example. Since the time constant τ _CR also increases as the resistance value increases, it is desirable to adjust the capacitance of the capacitor C to keep the time constant τ _CR within the above range.

(8) Timing of Subsequent Detection The positions of the object to be transported X transported on the transport device 80 and the detection target T attached to the transport device 80 are located in the vertical direction when the phosphorescence intensity is detected by the photodetector 40. It varies to some extent. If the position of the detection target T varies in the vertical direction, the distance between the detection target T and the photodetector 40 also varies, so that the intensity of the detected phosphorescence inevitably varies. Although it is not impossible for the correction unit 93 to detect the vertical position of the detection target T and correct it, in that case, the identification processing speed of the detection target T may be significantly reduced. Therefore, it is necessary to anticipate that such variation will occur in advance and determine the timing (second timing) for subsequent detection of the phosphorescence intensity.

After trial and error, the present inventors have found that the difference between the intensity ratio of phosphorescence emitted from a certain phosphorescent body to be identified and the intensity ratio of phosphorescence emitted from another phosphorescent body to be identified is 0. It has been found that if the phosphorescence intensity is detected at a timing of 15 or more, it is possible to reliably identify which of the phosphorescent bodies to be identified emits the detected phosphorescence. .. Here, the intensity ratio is the ratio P _{2 of the phosphorescence intensity P 2} detected in the subsequent detection performed at the second timing _{to the phosphorescence intensity P 1} detected in the first detection performed at the first timing. / is a _{P 1.}

Further, the present inventors have found that the difference between the intensity ratio of phosphorescence emitted from a certain phosphorescent body to be identified and the intensity ratio of phosphorescence emitted from another phosphorescent body to be identified is 0.2 or more. It has been found that if the phosphorescence intensity is detected at the timing when the phosphorescence is detected, it is possible to more reliably identify which of the phosphorescent bodies to be identified emits the detected phosphorescence.

(8-1) When identifying three types of phosphors Table 2 shows the values on the three attenuation curves shown in FIG.

As shown in Table 2, after 0.05 msec or more has passed after the initial detection of the phosphorescence intensity, the phosphorescence intensity ratio having a decay time constant of 0.2 msec and the phosphorescence intensity ratio having a decay time constant of 1 msec. The difference is 0.15 or more. Therefore, by performing the subsequent detection of the phosphorescence intensity at a time of 0.05 msec or more after the initial detection of the phosphorescence intensity, it is possible to confirm whether the decay time constant of the detected phosphorescence is 0.2 msec or 1 msec. Can be identified.

When 0.50 msec or more elapses after the initial detection of phosphorescence intensity, the phosphorescence intensity ratio having an attenuation time constant of 0.2 msec becomes smaller than 0.1. In that case, since the phosphorescence is weak, it may be difficult for the photodetector 40 to detect the phosphorescence. Therefore, in order to identify whether the detected phosphorescence decay time constant is 0.2 msec or 1 msec, subsequent detection is performed before a time of 0.50 msec elapses from the initial detection of phosphorescence intensity. Is preferable.

Further, as shown in Table 2, after 0.20 msec or more has passed after the initial detection of the phosphorescence intensity, the phosphorescence intensity ratio having a decay time constant of 1 msec and the phosphorescence intensity ratio having a decay time constant of 10 msec. The difference from is 0.15 or more. Therefore, by performing the subsequent detection of the phosphorescence intensity at a time of 0.20 msec or more after the initial detection of the phosphorescence intensity, it is possible to reliably identify whether the time constant of the detected phosphorescence is 1 msec or 10 msec. be able to. However, if the subsequent detection of the phosphorescence intensity is performed after a long time has passed after the initial detection of the phosphorescence intensity, it becomes impossible to identify a large number of detection targets T in a short time. Therefore, subsequent detection is preferably performed within 1 msec after the initial detection.

Further, as shown in Table 2, when a time of 0.20 msec or more and 0.45 msec or less elapses after the initial detection of the phosphorescence intensity, the phosphorescence intensity ratio having a decay time constant of 0.2 msec and the decay time The difference in the intensity ratio of phosphorescence with a constant of 1 msec is greater than 0.15. At the same time, the difference between the intensity ratio of phosphorescence having an attenuation time constant of 1 msec and the intensity ratio of phosphorescence having an attenuation time constant of 10 msec is also larger than 0.15. Therefore, by performing the subsequent detection of the phosphorescence intensity at a time of 0.20 msec or more and 0.45 msec or less after the first detection of the phosphorescence intensity, the decay time constants of the detected phosphorescence are 0.2 msec and 1 msec. It is possible to reliably identify which of 10 msec and 10 msec.

Further, as shown in Table 2, after 0.10 msec or more has passed after the initial detection of the phosphorescence intensity, the phosphorescence intensity ratio having a decay time constant of 0.2 msec and the phosphorescence having a decay time constant of 1 msec. The difference from the intensity ratio is 0.2 or more. Therefore, by performing the subsequent detection of the phosphorescence intensity at a time of 0.10 msec or more after the initial detection of the phosphorescence intensity, it is possible to determine whether the detected phosphorescence decay time constant is 0.2 msec or 1 msec. Can be reliably identified.

Further, as shown in Table 2, when a time of 0.25 msec or more and 0.45 msec or less elapses after the initial detection of the phosphorescence intensity, the phosphorescence intensity ratio having a decay time constant of 0.2 msec and the decay time The difference in the intensity ratio of phosphorescence with a constant of 1 msec is greater than 0.2. At the same time, the difference between the intensity ratio of phosphorescence having an attenuation time constant of 1 msec and the intensity ratio of phosphorescence having an attenuation time constant of 10 msec is also larger than 0.2. Therefore, by performing the subsequent detection of the phosphorescence intensity when a time of 0.25 msec or more and 0.45 msec or less has elapsed after the initial detection of the phosphorescence intensity, the time constants of the detected phosphorescence are 0.2 msec and 1 msec. It is possible to more reliably identify which is 10 msec.

(8-2) When identifying four types of phosphors Table 3 shows the values on the four attenuation curves shown in FIG.

As shown in Table 3, when a time of 0.20 msec or more and 0.45 msec or less elapses after the initial detection of phosphorescence intensity, the phosphorescence intensity ratio having a decay time constant of 0.2 msec and the decay time constant are The difference from the phosphorescence intensity ratio of 0.4 msec is larger than 0.15. At the same time, the difference between the intensity ratio of phosphorescence having a decay time constant of 0.4 msec and the intensity ratio of phosphorescence having a decay time constant of 1 msec is also larger than 0.15. Further, at this time, the difference between the intensity ratio of phosphorescence having an attenuation time constant of 1 msec and the intensity ratio of phosphorescence having an attenuation time constant of 10 msec is also larger than 0.15. Therefore, the time constant of the detected phosphorescence is 0.2 msec and 0. It is possible to reliably identify whether it is 4 msec, 1 msec, or 10 msec.

Further, as shown in Table 3, when a time of 0.30 msec or more and 0.45 msec or less elapses after the initial detection of the phosphorescence intensity, the phosphorescence intensity ratio having a decay time constant of 0.2 msec and the phosphorescence intensity ratio at the time of attenuation The difference from the phosphorescence intensity ratio, which has a constant of 0.4 msec, is greater than 0.2. At the same time, the difference between the intensity ratio of phosphorescence having a decay time constant of 0.4 msec and the intensity ratio of phosphorescence having a decay time constant of 1 msec is also larger than 0.2. Further, at this time, the difference between the intensity ratio of phosphorescence having an attenuation time constant of 1 msec and the intensity ratio of phosphorescence having an attenuation time constant of 10 msec is also larger than 0.2. Therefore, the time constant of the detected phosphorescence is 0.2 msec and 0. It is possible to more reliably identify whether it is 4 msec, 1 msec, or 10 msec.

(8-3) When identifying five types of phosphors Table 4 shows the values on the five attenuation curves shown in FIG.

As shown in Table 4, when 0.45 msec has elapsed after the initial detection of the phosphorescence intensity, the phosphorescence intensity ratio having a decay time constant of 0.2 msec is 0.11 and the decay time constant is 0.4 msec. The intensity ratio of phosphorescence is 0.32, the intensity ratio of phosphorescence having a decay time constant of 0.9 msec is 0.61 msec, and the intensity ratio of phosphorescence having an decay time constant of 2 msec is 0.80 msec. The intensity ratio of phosphorescence having a decay time constant of 10 msec is 0.96 msec. The difference between these intensity ratios is greater than 0.15. Therefore, by performing subsequent detection of phosphorescence intensity 0.45 msec after the initial detection of phosphorescence intensity, the time constants of the detected phosphorescence are 0.2 msec, 0.4 msec, 0.9 msec, and 2 msec. It is possible to reliably identify which of 10 msec it is.

Further, as can be understood from Table 4, there is no timing in which the phosphorescence intensity ratio differences of the attenuation time constants of 0.2 msec, 0.4 msec, 0.9 msec, 2 msec and 10 msec are 0.2 or more, respectively. .. However, as shown in Table 4, if the subsequent detection is performed when a time of 0.25 msec or more and 0.45 msec or less has elapsed after the initial detection of the phosphorescence intensity, the decay time constant of the phosphorescence is 0.2 msec. The difference between the intensity ratio, the intensity ratio of phosphorescence having a decay time constant of 0.4 msec, and the intensity ratio of phosphorescence having an decay time constant of 0.9 msec is larger than 0.2. Further, the value of these intensity ratios is 0.1 or more. That is, by performing subsequent detection when a time of 0.25 msec or more and 0.45 msec or less has elapsed after the initial detection of phosphorescence intensity, the decay time constants of the detected phosphorescence are 0.2 msec, 0.4 msec, and 0. It is possible to identify which is 0.9 msec.

Further, as shown in Table 4, if the additional detection of the phosphorescence intensity is performed when a time of 0.60 msec or more and 0.90 msec or less has elapsed after the initial detection of the phosphorescence intensity, the decay time constant is 0.4 msec. The difference between the phosphorescence intensity ratio, the phosphorescence intensity ratio having a decay time constant of 0.9 msec, the phosphorescence intensity ratio having a decay time constant of 2 msec, and the phosphorescence intensity ratio having an decay time constant of 10 msec. Are both greater than 0.2. Further, the value of these intensity ratios is 0.1 or more. That is, by performing additional detection when a time of 0.60 msec or more and 0.90 msec or less has elapsed after the initial detection of phosphorescence intensity, the decay time constant of the detected phosphorescence is 0.9 msec, 2 msec, or 10 msec. It is possible to identify whether it is.

Therefore, the subsequent detection is performed when a time of 0.25 msec or more and 0.45 msec or less elapses after the first detection of the phosphorescence intensity (second timing), and 0.60 msec or more and 0.60 msec or more after the first detection of the phosphorescence intensity. By performing additional detection of phosphorescence intensity when a time of 90 msec or less has elapsed (third timing), the decay time constants of the detected phosphorescence are 0.2 msec, 0.4 msec, 0.9 msec, 2 msec, and 10 msec. It is possible to identify which of the above.

The additional detection of the phosphorescence intensity is not limited to the case where the subsequent detection is performed at the timing when the difference between the intensity ratios becomes 0.2 or more, and is also limited to the case where there are five types of phosphorescent bodies to be identified. I can't. For example, when there are four types of phosphorescent bodies to be identified and subsequent detection is performed at a timing when the difference between the intensity ratios is 0.15 or more, additional phosphorescence intensity detection may be performed. Also, additional detections are not limited to those that occur after subsequent detections. In other words, additional detections may be made after the first detection and before subsequent detections. That is, either the second timing or the third timing may come first.

(9) Authenticity determination method 2 for detection target
When the detection timing is determined as described above, the authenticity determination of the detection target T (security feature) attached to the transported object X may be performed as follows, for example.

First, for each phosphorescence of each attenuation time constant, the range of the intensity ratio at the second timing (and the third timing if necessary) is predetermined and stored in the storage unit 95. Then, the intensity of phosphorescence is first detected for each photodetector 40, that is, for each color of phosphorescence. Next, the subsequent detection of the phosphorescence intensity is performed at the second timing for each photodetector 40, that is, for each phosphorescence color, and the intensity ratio for each phosphorescence color at the second timing is calculated. Subsequently, for each color of phosphorescence, it is determined whether or not the intensity ratio at the second timing is within a predetermined range. If the values are within a predetermined range for all colors, the detection target T is determined to be true. If this is not the case, the detection target T is determined to be false. If the decay time constant of the phosphorescence to be detected is different for each color, the second timing may be different for each photodetector 40. Further, when performing additional detection, the third timing may be different for each photodetector 40.

As described above, the intensity ratio of phosphorescence at the second timing (and the third timing if necessary) is characteristic, and the authenticity of the detection target T (security feature), and eventually the transported object X such as paper sheets, etc. The truth can be determined.

The phosphorescence detection device and the phosphorescence detection method of the present invention detect phosphorescent bodies attached as security features on the surface of paper sheets, such as value documents such as banknotes and securities. The phosphorescent body to be detected is irradiated with excitation light, and the phosphorescence emitted from the phosphorescent body is detected. Since features such as phosphorescence spectrum and attenuation features are determined by the composition of the phosphorescent body, the authenticity of security features can be determined by detecting phosphorescence and comparing the features.

Although the examples of the present invention have been described above, the present invention is not limited to the above examples, and various modifications can be made without departing from the spirit of the present invention.

The present invention can be applied to a device for identifying a type of paper sheet or a product such as a banknote with a security mark containing a phosphor, for example, a banknote processing device, and thus its industrial applicability. Is huge.

10 Optical sensor 20 Holder 30 Light source 40 Optical detector 50 Light guide 51 Excited light incident surface 52 Emitted light emitting surface 53 Light input / exit surface 54 Standing surface 55 Side surface 60 Substrate 70 Optical filter 71 Visible light cut filter 72 Ultraviolet light cut filter 73 Color filter 80 Conveyor 90 Control device 91 Conveyor control unit 92 Detection unit 93 Correction unit 94 Discrimination unit 95 Storage unit 100 Phosphorus detection device

Claims (13)

A light source that irradiates an excitation light to a detection target that emits at least one of a plurality of types of phosphorescence to be identified.
A photodetector that detects the intensity of phosphorescence emitted from the detection target, and
A control unit that controls the light source and the photodetector is provided.
The control unit performs the first detection of the intensity at the first timing after the irradiation of the excitation light is stopped, and subsequently detects the intensity at the second timing after the first detection. after Tsu, it had further row of additional detection of the intensity at the third timing,
In the second timing, the first ratio of the intensity detected in the first detection to the intensity detected in the subsequent detection in all the phosphorescences of the plurality of types to be identified is equal to or higher than the threshold value. There, and Ri timing der absolute value of the plurality of types of the first difference in specific at least two among of phosphorescence is equal to or greater than a prescribed value,
In the third timing, the second ratio of the intensity detected in the initial detection to the intensity detected in the additional detection in at least one phosphorescence of the plurality of types of phosphorescence is the threshold value. The absolute value of the difference of the second ratio between phosphorescences having less than the predetermined value and the absolute value of the difference of the first ratio at the second timing is less than the predetermined value is equal to or more than the predetermined value. Phosphorescence detector, which is the timing. The phosphorescence detection device according to claim 1, wherein the second timing is a timing at which a time of 0.05 msec or more and 1.00 msec or less has elapsed after the first detection. The phosphorescence detection device according to claim 2, wherein the second timing is a timing at which a time of 0.10 msec or more and 1.00 msec or less has elapsed after the first detection. The phosphorescence detection device according to claim 3, wherein the second timing is a timing at which a time of 0.20 msec or more and 0.45 msec or less has elapsed after the first detection. The phosphorescence detection device according to claim 4, wherein the second timing is a timing at which a time of 0.25 msec or more and 0.45 msec or less has elapsed after the first detection. The second timing is the absolute difference in the ratio of the intensity detected in the first detection to the intensity detected in the subsequent detection among all of the plurality of types of phosphorescence to be identified. The phosphorescence detection device according to any one of claims 1 to 5, wherein the value becomes equal to or higher than a predetermined value. The second timing is a timing at which a time of 0.25 msec or more and 0.45 msec or less has elapsed after the first detection.
The phosphorescence detection device according to any one of claims 1 to 6, wherein the third timing is a timing at which a time of 0.60 msec or more and 0.90 msec or less has elapsed after the first detection. The phosphorescence detection device according to any one of claims 1 to 7 , wherein the first timing is a timing at which a time of 0.005 msec or more and 0.18 msec or less has elapsed after the irradiation of the excitation light is stopped. The phosphorescence detection device according to any one of claims 1 to 8 , wherein the phosphorescence attenuation time constant is 0.2 msec or more and 10 msec or less. The phosphorescence detection device according to any one of claims 1 to 9 , further comprising a plurality of the photodetectors, each of the plurality of photodetectors detecting the intensity of phosphorescence having a different wavelength. The phosphorescence detection device according to any one of claims 1 to 10 , wherein the control unit performs identification processing of a phosphorescent substance contained in the detection target based on the intensity. A paper leaf processing device including the phosphorescence detection device according to any one of claims 1 to 11. A step of irradiating a detection target that emits at least one of a plurality of types of phosphorescence to be identified with excitation light, and a step of irradiating the detection target with excitation light.
The step of stopping the irradiation of the excitation light and
A step of first detecting the intensity of phosphorescence emitted from a phosphor contained in the detection target at the first timing after the irradiation of the excitation light is stopped.
A step of performing subsequent detection of the intensity at a second timing after the first detection , and
It comprises a step of performing additional detection of the intensity at a third timing after the subsequent detection .
In the second timing, the first ratio of the intensity detected in the first detection to the intensity detected in the subsequent detection in all the phosphorescences of the plurality of types to be identified is equal to or higher than the threshold value. There, and Ri timing der absolute value of the plurality of types of the first difference in specific at least two among of phosphorescence is equal to or greater than a prescribed value,
In the third timing, the second ratio of the intensity detected in the initial detection to the intensity detected in the additional detection in at least one phosphorescence of the plurality of types of phosphorescence is the threshold value. The absolute value of the difference of the second ratio between phosphorescences having less than the predetermined value and the absolute value of the difference of the first ratio at the second timing is less than the predetermined value is equal to or more than the predetermined value. Phosphorescence detection method, which is the timing.

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