JP2018163567A - Phosphorescence detector, paper leaves processor, and method for detecting phosphorescence - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine whether detected phosphorescence includes different types of phosphorescences of which wavelengths are in the same range and attenuation time constants are different from each other.SOLUTION: A phosphorescence detector includes: a light source 30 for emitting excitation light to a detection target T containing a phosphorescent body; a light detector 40 for detecting the intensity of the phosphorescence emitted from the detection target T; a detector 92 for controlling the light source 30 and the light detector 40 and conducting detection of the intensity at least three times one by one after the radiation of the excitation light is stopped; and a determination unit 94 for determining whether the phosphorescence includes different types of phosphorescences of which attenuation time constants are different from each other, on the basis of the three intensities detected by the detector 92 and the time of each detection.SELECTED DRAWING: Figure 2

Description

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

  2. Description of the Related Art Conventionally, security marks having predetermined optical characteristics have been used to identify authenticity of paper sheets such as banknotes and documents, merchandise, and the like. For example, a security mark including a phosphor that does not emit phosphorescence under visible light but emits phosphorescence only when irradiated with light of a predetermined wavelength such as ultraviolet rays is printed on paper sheets or product packages by printing or the like. In addition, the authenticity of paper sheets and products is determined from the phosphorescent emission state. As the phosphor, a substance having a single decay time constant or a mixture of a plurality of kinds of substances having different decay time constants is used.

  Patent Document 1 discloses an apparatus that distinguishes two luminescent materials that emit light within the same wavelength range and contain two types of dyes having different decay time constants at different ratios. This device is equipped with a number of photodetectors along the path to detect the luminescence intensity profile, compare the intensity value of the normalized intensity profile and the time required for attenuation to the reference value, or normalized intensity The curve shape of the profile is compared with the curve shape of the reference luminescence intensity profile. This allows the luminescent material to be authenticated even if the normalized luminescence intensity profiles of the two luminescent materials are very similar despite the different ratios of the two dyes.

  Patent Document 2 discloses an apparatus for verifying the authenticity of a bill by irradiating the bill with excitation light and detecting the emitted phosphorescence. This device uses two sensors to detect phosphorescence and verifies the ratio of the intensity of phosphorescence detected by each sensor.

  Patent Document 3 discloses an apparatus that verifies the authenticity of a bill by irradiating the bill with excitation light and detecting the emitted phosphorescence. This apparatus detects the peak of the phosphorescence spectrum obtained by irradiating the excitation light, and detects the attenuation feature for each wavelength of the detected peak.

Special table 2014-519130 gazette US Patent Application Publication No. 2015/348351 US Pat. No. 7,262,420

  However, the device disclosed in Patent Document 1 uses a luminescent material for each luminescent material to distinguish the luminescent material regardless of whether the luminescent material is a single dye or a luminescent material composed of a plurality of types of dyes having different decay time constants. It is necessary to prepare a reference value and a reference curve shape in advance. In other words, for a luminescent material with a standard, what type of luminescent material can be certified, but for a luminescent material without a standard, a luminescent material with a single dye or a luminescent material with multiple types of dyes can be certified. I can't.

  The device disclosed in Patent Document 2 is characterized by the ratio of the intensity of phosphorescence detected by the two sensors, and verifies the authenticity of the banknote. A single luminescent material emitting each phosphorescence is used. It cannot be determined whether the luminescent material is a luminescent material composed of a pigment or a luminescent material composed of a plurality of types of pigments having different decay time constants.

  The apparatus disclosed in Patent Document 3 detects attenuation characteristics for each wavelength of the detected peak, and the luminescent material emitting phosphorescence is a luminescent material with a single dye or a plurality of types with different phosphorescent colors. It may be possible to determine whether the material is a luminescent material composed of the above dyes by the number of peaks. However, it cannot be determined whether the luminescent material that has emitted phosphorescence is a luminescent material with a single dye or a luminescent material that emits light within the same wavelength range and is composed of multiple types of dyes with different decay time constants.

  As described above, all of the apparatuses disclosed in Patent Documents 1 to 3 are phosphors that emit phosphorescence, which are phosphors by a single dye, or a plurality of devices that emit light within the same wavelength range and have different decay time constants. It cannot be determined whether it is a phosphor composed of different types of dyes.

  The present invention has been made in view of such a situation, and determines whether or not the detected phosphorescence is due to a plurality of types of phosphorescence within the same wavelength range and having different attenuation time constants. The task is to do.

  If the detected phosphorescence is emitted from a single phosphor or a plurality of phosphors with the same decay time constant, the intensity is detected twice at different detection times, and the simultaneous equations of the relation between phosphorescence intensity and time are If solved, the decay time constant of the phosphor can be determined. However, if the detected phosphorescence is emitted from multiple types of phosphors with different decay time constants, it is necessary to solve complex exponential simultaneous equations, and it is difficult to determine the decay time constants of multiple types of phosphors. .

  On the other hand, in authenticity determination of security marks, etc., one of the characteristics is whether or not phosphorescence is emitted by a plurality of types of phosphorescence that emit light within the same wavelength range and have different decay time constants. is there. Specifically, if the intensity of phosphorescence is detected at least three times by changing the detection time, it can be determined whether the detected phosphorescence is due to phosphorescence having a single decay time constant. In other words, it can be determined whether the detected phosphorescence is due to a plurality of types of phosphorescence having different decay time constants.

  That is, the phosphorescence detection apparatus according to the present invention includes a light source that irradiates a detection target including a phosphor with excitation light, a photodetector that detects the intensity of phosphorescence emitted from the detection target, the light source, and the light detection. A detector for controlling the detector and detecting the intensity at least three times by changing the detection timing after the stop of the excitation light irradiation, at least three of the intensities detected by the detection section and their detection timing Based on the above, the above-described problem is solved by including a determination unit that determines whether or not the phosphorescence is due to a plurality of types of phosphorescence having different decay time constants.

  The phosphorescence detection method according to the present invention includes a step of irradiating a detection target including a phosphor with excitation light, and a detection timing of the intensity of phosphorescence emitted from the detection target after the stop of irradiation of the excitation light. And determining whether the phosphorescence is caused by a plurality of types of phosphorescence having different decay time constants based on at least three detected intensities and their detection times. To solve the above-mentioned problem.

  According to the present invention, it is possible to determine whether or not the detected phosphorescence is due to a plurality of types of phosphorescence that emit light within the same wavelength range and have different decay time constants.

It is a graph which shows the attenuation | damping characteristic of the phosphorescence radiated | emitted from a phosphor. 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. It is II-II sectional drawing in FIG. It is III-III sectional drawing in FIG. It is IV-IV sectional drawing in FIG. It is VV sectional drawing in FIG. It is a flowchart which shows the operation | movement flow of the phosphorescence detection apparatus which concerns on this invention. It is the semilogarithm graph which converted the vertical axis | shaft of the graph shown by FIG. 1 into the logarithmic value.

(1) Attenuation characteristics of phosphorescence First, the attenuation characteristics of phosphorescence emitted from a phosphor will be briefly described.

  A phosphor is a substance that emits phosphorescence when excited by receiving excitation light such as visible light or ultraviolet light. The intensity (light quantity) of phosphorescence emitted from the phosphor becomes a maximum value when the excitation light irradiation is stopped, and then gradually attenuates. The color and decay time constant of the phosphor emitted from the phosphor are determined by the phosphor. Even if the phosphors are different, either the phosphor color or the decay time constant may be the same, or both may be the same. Moreover, the phosphorescence emitted from a single phosphor is not limited to one type and may be a plurality of types. Hereinafter, in order to simplify the description, the phosphorescence emitted from a single phosphor will be described as one type. Further, even if the apparent phosphorescence color is different, it is treated as phosphorescence within the same wavelength range as long as it is within the wavelength range detectable 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 the phosphor _α , A _α is a constant determined by the concentration and luminous efficiency of the phosphor α, t is the time elapsed from when the excitation light is extinguished until detection, τ _α Is the decay time constant of phosphorescence emitted from the phosphor α. The relationship between phosphorescence intensity _Pα and time t is a curve like _Lα shown in FIG. The curve L _α is normalized with the maximum intensity being 1.

  In addition, when each phosphorescence emitted from the phosphor α and the phosphor β has the same attenuation time constant and a wavelength within a wavelength range detectable by the photodetector, the intensity of the phosphorescence emitted from the mixture thereof. The relationship between time and time is expressed by Equation 2.

In Equation 2, P _{α + β} is the intensity of phosphorescence emitted from the mixture of phosphor α and phosphor β, A _α and A _β are constants determined by the concentration and luminous efficiency of phosphor α and phosphor β, respectively, t Is the time elapsed from when the excitation light is extinguished until detection, and τ _α is the phosphorescence emitted from the phosphor α and the decay time constant of the phosphorescence emitted from the phosphor β. The relationship between the phosphorescence intensity P _{α + β} and the time t becomes a curve like L _α shown in FIG.

  That is, a normalized curve indicating the relationship between the intensity of phosphorescence emitted from a single phosphor α and time, and the intensity of phosphorescence emitted from a mixture of phosphor α and phosphor β having the same decay time constant Normalized curves showing time relationships are equal. The relationship between the phosphorescence intensity and time is such that the phosphorescence emitted from each phosphor has the same decay time constant, and the phosphors constituting the mixture are within the wavelength range detectable by the photodetector. The same holds true for three or more bodies. Therefore, in the present specification, a single phosphor α will be described as an example of a phosphor that represents a single phosphor and a mixture of a plurality of phosphors having the same decay time constant.

  On the other hand, the relationship between the intensity of phosphorescence emitted from a mixture of two types of phosphors γ and phosphors δ having different decay time constants and time is expressed by Equation 3.

In Equation 3, P _{γ + δ} is the intensity of phosphorescence emitted from the mixture of phosphor γ and phosphor δ, A _γ and A _δ are constants determined by the concentration and luminous efficiency of phosphor γ and phosphor δ, and t is the excitation. Τ _γ and τ _δ , the time elapsed from the time when the light is extinguished until the detection, are decay time constants of phosphorescence emitted from the phosphor γ and the phosphor δ, respectively. The relationship between the phosphorescence intensity P _{γ + δ} and the time t is a curve like L _{γ + δ} shown in FIG. Note that L _{γ + δ} is normalized with the maximum intensity being 1.

In the following, with respect to time t in equation 3 from the equation 1, illustrating the detection timing of the phosphorescence as the time t _n. The time t _n is represented by the time elapsed from when the excitation light is extinguished until the detection, and when the excitation light is extinguished, t ₀ = 0. The detection time may be the time elapsed from the time point different from the time when the excitation light is turned off or the standard time, but in this case, the mathematical formula is appropriately corrected.

The intensity of phosphorescence emitted from phosphor α and the intensity of phosphorescence emitted from a mixture of phosphor γ and phosphor δ depend on the decay time constant of those phosphors, as shown in FIG. it may become equal at t _x. Even if the phosphor intensity is detected at such a time t _x , the phosphor included in the detection target is a single phosphor α or a mixture of phosphor γ and phosphor δ having different decay time constants. Cannot determine if there is. For example, consider a case where the true security mark includes a single phosphor α and the authenticity of the security mark is determined by evaluating the phosphorescence intensity detected at time t _x . In this case, if the fake security mark includes a mixture of the phosphor γ and the phosphor δ, the security mark cannot be correctly determined. The same is true if the true security mark contains a mixture of phosphor γ and phosphor δ, and the false security mark contains a single phosphor α.

  However, according to the phosphorescence detection apparatus according to the present invention, such a problem does not occur. Hereinafter, a phosphorescence detection apparatus according to the present invention will be described with reference to the drawings. As described above, when a plurality of types of phosphorescence having different decay time constants are emitted from a single phosphor, it can be considered in the same manner as phosphorescence emitted from a mixture of phosphor γ and phosphor δ. . In the following, a plurality of phosphors having different decay time constants as a single phosphor that emits a plurality of types of phosphors having different decay time constants and a phosphor that represents a mixture of a plurality of phosphors having different decay time constants. The mixture will be described as an example.

  Note that in the present invention, whether the detected phosphorescence is phosphorescence emitted from a single phosphor or phosphorescence emitted from a mixture of a plurality of phosphors is only one aspect of the invention. Absent. According to the present invention, the detected phosphorescence is emitted by the phosphorescence that emits within the same wavelength range and has a single decay time constant, or the phosphorescence that emits within the same wavelength range and has different decay time constants. It is a thing which discriminates.

(2) Configuration of Phosphorescence Detection Device FIG. 2 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 to determine the authenticity of the detection target T attached to the conveyed object X. The phosphorescence detection device 100 includes a transport device 80, a light sensor 10 installed above the transport device 80, and a control device 90 that controls the transport device 80 and the light sensor 10. The transported object X can be a paper sheet such as a banknote, and the phosphorescence detection device 100 can be a paper sheet processing apparatus.

  The structure of the optical sensor 10 will be described with reference to FIGS. FIG. 3 is a schematic side sectional view showing the structure of the optical sensor 10. 4, FIG. 6, FIG. 6 and FIG. 7 are a sectional view taken along line II-II, sectional view taken along line III-III, sectional view taken along line IV-IV and sectional view taken along line VV in FIG. Although FIG. 3 shows a case where the optical sensor 10 is attached downward, the optical sensor 10 can be attached in an arbitrary direction.

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

  The holder 20 is made of a material that does not transmit light, such as black resin, has a through-hole that opens upward and downward, and has a cylindrical shape. In this through hole, a light guide 50, an optical filter 70, a light source 30, and a photodetector 40 are arranged in this order from the lower side. In addition, the upper opening of the through hole is closed by the substrate 60. Moreover, the holder 20 has the partition 21 arrange | positioned between the light source 30 and the photodetector 40 as the part. When the partition 21 comes into contact with the light guide body 50, the surface of the light guide body 50 is damaged, and this damage may cause light leakage, attenuation, or diffusion, thereby reducing the light guide performance of the light guide body 50. For this reason, a slight gap is provided between the lower end of the partition 21 and the surface of the light guide 50. However, if there is no such fear, the partition 21 may be brought into contact with the light guide 50. Of course, the partition 21 may be a separate member from the holder 20.

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

  The photodetector 40 detects the emitted light emitted from the detection target. Specifically, the photodetector 40 is a photodiode that outputs a signal that changes in accordance with the intensity (light quantity) of received light, and is attached to the lower surface of the substrate 60. As shown in FIG. 7, the optical sensor 10 includes two photodetectors 40. These photodetectors 40 have different detectable wavelength ranges. Therefore, two types of radiation can be detected simultaneously. In addition, when detecting only the radiated light of a specific wavelength, or detecting the intensity | strength of radiated light irrespective of a wavelength, the number of the photodetectors 40 may be one. In addition, by setting the number of the photodetectors 40 to three or more, it is possible to detect three or more types of emitted light at the same time.

  The light guide 50 guides the excitation light emitted from the light source 30 to the detection target and guides the radiation emitted from the detection target to the photodetector 40. That is, the light guide 50 functions as a light guide. The light guide 50 is a block made of a transparent resin such as acrylic or polycarbonate, and has an excitation light incident surface 51 and a radiated light exit surface 52 in the upper part, and a light incident / exit surface 53 in the lower part. Have. The light incident / exit surface 53 is larger than the light receiving surface of the photodetector 40. In addition, the light guide 50 has a rising surface 54 between the excitation light incident surface 51 and the emitted light exit surface 52, and a step is formed by the excitation light incident surface 51, the standing surface 54, and the emitted light exit surface 52. Has been. The light guide 50 also has a side surface 55 that extends between the excitation light incident surface 51 and the emitted light exit surface 52 and the light incident / exit 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 this embodiment, the shape of the portion surrounded by the side surface 55 of the light guide 50 is substantially the same as that of the light source 30 and the light detector 30 when viewed from the light source 30 and the photodetector 40 side. Hexagonal shape with two corners chamfered. With this shape, the detection target can be efficiently irradiated with the excitation light from the light source 30. The material of the light guide 50 is not limited to transparent resin, and may be transparent glass. In addition, the material of the light guide 50 should just be a material which permeate | transmits excitation light and radiation | emission light, and is not restricted to a transparent material.

  The light source 30 and the excitation light incident surface 51 are a kind of optical filter 70 and are disposed so as to face each other via a visible light cut filter 71 that transmits ultraviolet rays and cuts visible light. Further, the photodetector 40 and the emitted light exit surface 52 are arranged so as to face each other with an ultraviolet cut filter 72 and a color filter 73 which are a kind of the 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 red, green, and blue radiation, three color filters 73 are arranged between the three photodetectors 40 and the radiation output surface 52, one each. Each color filter 73 transmits light in the red wavelength range, the green wavelength range, or the blue wavelength range. These optical filters 70 may be replaced with filters having other characteristics according to the purpose, or may not be arranged if unnecessary.

  Returning to FIG. 2, 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 which the detection target T is attached at a predetermined position in the direction indicated by the arrow, and according to the characteristics such as the shape of the object X, the belt It can be set as a conveyor, a roller conveyor, a levitation conveyance apparatus, etc. In this embodiment, the conveying device 80 is a belt conveyor. The belt conveyor includes a belt and a pulley that drives 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 passage detection sensor (not shown) that detects the passage of the transported object X on the upstream side of the optical sensor 10.

  In the phosphorescence detection device 100, the optical sensor 10 is arranged such that the light source 30 is located upstream in the conveyance direction of the object X in the conveyance device 80, and the photodetector 40 is located downstream. In addition, the optical sensor 10 is arranged so that the light incident / exit surface 53 of the light guide 50 faces the detection target T attached to the object X to be conveyed that is conveyed on the conveying device 80.

  The control device 90 includes a power supply, a CPU, a memory, and the like, and includes a transport device control unit 91, a detection unit 92, a correction unit 93, a determination unit 94, and a storage unit 95 as functional units.

  The transport device control unit 91 controls the operation of the transport device 80. Further, the transport device control unit 91 determines the belt travel distance, that is, the travel distance of the detection target T (detection target) based on the number of pulses of the rotary encoder after the passage of the transport object X is detected by the passage detection sensor. Information on the position of T) is calculated.

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

  The correction unit 93 obtains information on the position where the detection target T is present from the transport device control unit 91 and obtains information on the intensity of phosphorescence detected by the photodetector 40 from the detection unit 92. The correction unit 93 further obtains information regarding the correction coefficient from the storage unit 95 described later. The correcting unit 93 corrects the detected phosphorescence intensity based on these pieces of 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. In addition, the determination unit 94 can calculate the phosphorescence decay time constant τ, determine the substance contained in the detection target T based on the decay time constant τ, and determine whether the detection target T is true or false.

  The storage unit 95 stores information related to the correction coefficient used for correcting the phosphorescence intensity. This information is, for example, a function or table indicating the relationship between the relative position between 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 phosphorescence decay time constant. These pieces of information are the basis for determining the authenticity of the detection target T.

(3) Method for detecting phosphorescence The phosphorescence is detected as follows. Note that phosphorescence is emitted light 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 as time passes after the irradiation of excitation light is stopped.

  First, the light source 30 emits excitation light. The irradiated excitation light passes through the light guide 50. The excitation light that has passed 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. The phosphorescence emitted from the detection target passes through the light guide 50. The photodetector 40 detects phosphorescence that has passed through the light guide 50.

  The photodetector 40 that has detected the phosphorescence transmits a signal notifying the detection of phosphorescence or a signal that changes in accordance with the intensity of the detected phosphorescence to the control device. The control device that has received a signal from the photodetector 40 calculates the intensity of phosphorescence. In this way, phosphorescence is detected.

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

(4) 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.

  When the operation of the phosphorescence detection device 100 is started, the transport device 80 transports the transported object X, and the passage detection sensor detects the passage of the transported object X (S1).

  After the passage of the transported object X is detected by the passage detection sensor, the light source 30 is turned on when the number of pulses of the rotary encoder reaches a predetermined number (S2). At this time, the detection target T attached to the transported object X has moved below the optical sensor 10. The excitation light emitted from the light source 30 is guided to the detection target T by the light guide 50 and excites the detection target T. While the excitation light is irradiated, fluorescence is emitted from the detection target T.

  Next, the photodetector 40 detects 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 stops. Further, emission of phosphorescence from the detection target T starts.

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

  Fluorescence intensity and phosphorescence decay characteristics are detected for each light detector 40 (for each color of emitted light), and based on them, the substance contained in the detection target T is determined, and the transported object X Authenticity is determined (S6).

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

(5) Method for discriminating phosphor In step S6, the phosphor detection device 100 emits phosphors of substances contained in the detection target T within the same wavelength range, and a plurality of types of dyes having different decay time constants. It is determined whether or not the phosphor is made of.

That is, for all of the at least three phosphorescence intensities detected in step S5 and their detection times, if there is no A _α and τ _α satisfying the relationship between the phosphorescence intensity P _α and the time t expressed by Equation 1, It is determined that the phosphorescence emitted is emitted from a plurality of types of phosphors having different decay time constants. On the other hand, if there is A _α and τ _α satisfying the relationship between the phosphorescence intensity P _α and the time t expressed by Equation 1 for at least three phosphorescence intensities and their detection times, the detected phosphorescence is It is determined that the light is emitted from a single phosphor.

  A specific example of the determination method will be described below.

  In step S5, the phosphorescence intensity is detected at least three times. However, when the relative position of the detection target T with respect to the photodetector 40 is constant, it is not necessary to correct the detected phosphorescence intensity, and the detected phosphorescence is detected. The discrimination method described below is performed using the intensity. On the other hand, when the relative position of the detection target T with respect to the light detector 40 fluctuates or is likely to be detected each time phosphorescence is detected, the detected phosphorescence intensity is corrected and will be described below using the corrected phosphorescence intensity. A determination method is performed. Thus, in the following description, the term intensity is used to encompass both corrected and uncorrected intensity.

(5-1) Specific example 1 of discrimination method
The discrimination method of this example utilizes the fact that the intensity of phosphorescence emitted from a single phosphor α satisfies the relationship shown by the curve L _{α in} FIG. 1 regardless of the detection time.

Specifically, the detection unit 92 has the intensity P ₁ and the intensity P _{2 of the} phosphorescence emitted from the detection target T when the time t ₁ , the time t _2, and the time t ₃ have elapsed since the stop of the excitation light emission. and detecting the intensity _{P 3.} The discriminating unit 94 uses two of these three intensities, for example, the intensity P ₁ and the intensity P _2, and the time t ₁ and the time t _{2 at} which they are detected, to detect based on the following Equation 4. The decay time constant τ ₁ of phosphorescence emitted from the object T is calculated.

The relationship between the phosphorescence intensity P represented by the decay time constant τ ₁ and the time t elapsed from when the excitation light is extinguished until it is detected is expressed by the following Equation 5.

  In Equation 5, A is a constant determined by the concentration of phosphor in the detection target T and the light emission efficiency.

The constant A can be calculated by substituting the phosphorescence intensity used for obtaining the decay time constant τ ₁ and its detection time (for example, P ₁ and t ₁ ) into Equation 5.

The determination unit 94 determines whether or not the intensity P ₃ that is not used in the calculation of the decay time constant τ ₁ and its detection time t ₃ are applicable to the relationship expressed by Equation 5, that is, at time t in Equation 5. It is determined whether or not the strength P becomes the strength P ₃ when the time t ₃ is substituted. When this is the case, the determination unit 94 determines that the detected phosphor is emitted from a single phosphor or a plurality of types of phosphors having the same decay time constant.

On the other hand, when the intensity P ₃ that is not used in the calculation of the decay time constant τ ₁ and the detection time t ₃ do not correspond to the relationship expressed by Equation 5, the detected phosphorescence has different decay time constants. The determining unit 94 determines that the light is emitted from a plurality of types of phosphors.

  The phosphorescence intensity is detected four times or more, and two of them are selected as appropriate to calculate the decay time constant, and the decay time constant is calculated according to the relationship between the phosphorescence intensity and the time represented by the decay time constant. It goes without saying that it may be determined whether or not one or more phosphorescence intensities not used in the above and the detection time thereof are applicable.

(5-2) Specific example 2 of discrimination method
In the discrimination method of this example, the attenuation time constant calculated based on the phosphorescence intensity at any two points on the curve L _α in FIG. 1 and the detection time thereof is selected no matter how these two points are selected. The fact that the value is unique to the phosphor α is used.

In this example, the detection unit 92 includes the intensity P _{4 of} the phosphorescence emitted from the detection target T when the time t ₄ , the time t ₅ , the time t _6, and the time t ₇ have elapsed since the emission of the excitation light is stopped. The intensity P ₅ , the intensity P ₆ and the intensity P ₇ are detected. If the first combination which is a combination of two of these four intensities is, for example, a combination of intensity P ₄ and intensity P ₅ , the determination unit 94 determines from the detection target T based on the following Equation 6. The decay time constant τ ₂ of the emitted phosphorescence is calculated.

Further, if a second combination that is a combination of two of the four intensities and is different from the first combination is, for example, a combination of the intensity P ₆ and the intensity P ₇ , the determination unit 94. Calculates the decay time constant τ ₃ of the phosphorescence emitted from the detection target T based on the following Expression 7.

The determination unit 94 compares the decay time constant τ ₂ with the decay time constant τ ₃ . When the difference is not more than the threshold value, the determination unit 94 determines that the detected phosphor is emitted from a single phosphor or a plurality of types of phosphors having the same decay time constant. . (The threshold may be 0.)

On the other hand, when the difference between the decay time constant τ ₂ and the decay time constant τ ₃ exceeds the threshold value, the discriminating unit 94 emits the detected phosphorescence from a plurality of types of phosphors having different decay time constants. It is determined that

In this example, the phosphorescence is detected by detecting the phosphorescence intensity four times, but the phosphorescence intensity may be detected three times. For example, the first combination is a combination of strengths P ₄ and P ₅ and the second combination is a combination of strengths P ₅ and P ₆ or a combination of strengths P ₄ and P ₆ . Phosphorescence can be determined according to the method of this example. In addition, it is optional to select and use three or four of the detected phosphorescence intensities by setting the number of detections of phosphorescence intensity to five or more.

Here, the interval of time t ₄ and time t ₅ is a timing to detect the two phosphorescence intensity which constitutes the first combination, the time t is a timing to detect the two phosphorescence intensity which constitutes the second combination Consider the case where the interval between ₆ and time t ₇ is equal. In this case, as easily understood from Equation 6 and Equation 7, instead of comparing the decay time constant τ ₂ and the decay time constant τ ₃ , ln (P ₅ / P ₄ ) and ln (P ₇ / P ₆ ), or (P ₅ / P ₄ ) and (P ₇ / P ₆ ) can be compared to determine the detected phosphorescence. In that case, since the number of divisions performed by the CPU of the control device 90 in order to determine phosphorescence can be reduced, phosphorescence can be determined in a short time.

(5-3) Specific example 3 of discrimination method
Discriminating method of the present example, the graph of FIG. 1, when the vertical axis as shown in FIG. 9 is converted into semi-log plot of common logarithm, whereas the curve L _alpha is represented by a straight line downward to the right, curve L _{The fact that γ + δ} is expressed by a downward-sloping curve that intersects L _α at time t _x is used.

Specifically, the detection unit 92 detects the intensity P ₈ , the intensity P _9, and the intensity P ₁₀ of phosphorescence emitted from the detection target T when the time t ₈ , the time t _9, and the time t ₁₀ have elapsed. A first combination that is a combination of two of these three intensities is, for example, a combination of intensity P ₈ and intensity P ₉ . In this case, the determination unit 94 calculates the first change rate (first change amount per unit time) R ₁ of the logarithmic value of the phosphorescence intensity based on the following Equation 8.

Further, the second combination is a combination of two out of the three intensities, for example, a combination of intensity P ₉ and intensity P _10. In this case, the determination unit 94 calculates a _second change rate (second change amount per unit time) R ₂ of the logarithmic value of the phosphorescence intensity based on the following Equation 9. Note that the second combination is a combination different from the first combination.

Determination unit 94 compares the first change rate _{R 1} and a second change rate _{R 2.} When the difference is less than or equal to the threshold value, the determination unit 94 determines that the detected phosphor is emitted from a single phosphor or a plurality of types of phosphors having the same decay time constant. (The threshold may be 0.)

On the other hand, when the difference between the first change rate R ₁ and the second change rate R ₂ exceeds the threshold value, the determination unit 94 emits the detected phosphor from a plurality of types of phosphors having different decay time constants. It is determined that it has been done.

Here, the interval of time t ₈ and time t ₉ is the timing to detect the two phosphorescence intensity which constitutes the first combination, the time t is a timing to detect the two phosphorescence intensity which constitutes the second combination interval of ₉ and the time _{t 10} consider the case are equal. In that case, as easily understood from Equation 8 and Equation 9, instead of comparing the first change rate R ₁ and the second change rate R ₂ , the difference between log P ₉ and log P ₈ , and log P by comparing the difference between ₁₀ and the logP _9, it is possible to discriminate the detected phosphorescence. In that case, since the number of divisions performed by the CPU of the control device 90 in order to determine phosphorescence can be reduced, phosphorescence can be determined in a short time.

In the present example, it the second combination may be a combination of P ₈ and P ₁₀ is a matter of course. Also detects phosphorescence intensity _{P 11} at time _{t 11,} the second combination with a first combination is a combination of _{P 8} and _{P 9} may be a combination of _{P 10} and _{P 11.} Furthermore, the number of phosphorescence detections is 5 times or more, and it is optional to select and use three or four of the detected phosphorescence intensities.

  Further, since the phosphorescence detection apparatus 100 can detect phosphorescence by detecting the phosphorescence intensity three times at different detection times, the amount of data to be processed is small. That is, the phosphorescence detection apparatus 100 can perform data processing, and in other words, phosphorescence discrimination in a short time. Therefore, the phosphorescence detection apparatus 100 can perform true / false identification processing for a large amount of detection targets T in a short time.

  In addition, since the phosphorescence detection apparatus 100 detects the phosphorescence intensity a plurality of times using the single optical sensor 10, the time interval of the plurality of phosphorescence detections can be reduced. Therefore, even when the decay time constant of the phosphor contained in the detection target T is small (the phosphorescence decays in a short time), the phosphorescence intensity before the detection limit or less can be detected a plurality of times. Therefore, even if the decay time constant of the phosphor contained in the detection target T is small, the authenticity identification process of the detection target T can be performed.

  Furthermore, since the phosphorescence detection apparatus 100 detects the phosphorescence intensity a plurality of times by the single optical sensor 10, the phosphorescence detection timing is determined according to the decay time constant of phosphorescence emitted from the phosphor included in the detection target T. Can be set flexibly.

(6) 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 emission is confirmed for each photodetector 40. If phosphorescence is emitted, the decay time constant is calculated. Further, according to the method described above, it is determined whether or not the phosphor is emitted from a plurality of types of phosphors having different decay time constants. These results are compared with the reference attribute. As a result of the comparison, if the two match, it is determined that the detection target T is true. If the two do not match, it is determined that the detection target T is false.

  Table 1 shows examples of reference attributes.

  In Table 1, the horizontal axis represents the wavelength range of detected phosphorescence. That is, the horizontal axis means that phosphorescence is divided into wavelength ranges of a red wavelength range, a green wavelength range, and a blue wavelength range. The vertical axis represents the attenuation characteristics of the detected phosphorescence. That is, the vertical axis means that the phosphorescence decay time constant is divided into 0.2 msec, 1 msec, and 10 msec. “Single” means that the corresponding phosphor is emitted from a single phosphor or a plurality of types of phosphors having the same decay time constant. “Complex” means that the corresponding phosphorescence is emitted from a plurality of types of phosphors having different decay time constants. “None” means that no phosphorescence is detected.

  When the reference attribute is the attribute shown in Table 1, the true detection target T has a single or a plurality of types that emit phosphorescence whose attenuation time constant is 0.2 msec and whose color is blue. Of phosphor. In addition, single or plural kinds of phosphors that emit phosphorescence having an attenuation time constant of 1 msec and a red color are included. Also, a plurality of types of phosphors that emit phosphorescence whose decay time constants are different from each other and whose colors are all green, and are calculated based on the total intensity of green phosphorescence detected at a predetermined timing. A phosphor having an attenuation time constant of 1 msec is included.

  In this case, the authenticity determination of the detection target T is performed as follows. First, the detection unit 92 detects red, green, and blue phosphorescences individually through the three photodetectors 40. Subsequently, the determination unit 94 calculates the decay time constant of phosphorescence of each color. Further, the determination unit 94 determines whether or not the phosphors of the respective colors are emitted from a plurality of types of phosphors having different decay time constants (“complex” or “single”). The determination unit 94 refers to the information according to Table 1 stored in the storage unit 95 and compares it with the phosphorescence decay time constant and the determination result obtained for each color. As a result, if the attribute of 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 coincide with the phosphorescence attribute shown in Table 1, it is determined that the detection target T is false.

  When phosphorescence is emitted from a plurality of types of phosphors having different decay time constants, the decay time constant of the total intensity of phosphorescence emitted from the phosphor is any decay time constant included in the reference attribute. It ’s just a clue to know if it ’s compatible. Therefore, it is sufficient that an approximate value is calculated. For example, it can be obtained as follows. That is, the first provisional attenuation time constant is calculated based on any two combinations of the three or more intensities detected within the detectable wavelength range for each detection unit 92 and their detection timing. Next, a second temporary decay time constant is calculated based on a combination of any two of the detected three or more intensities that are different from the previous combination and their detection times. Subsequently, an average value of the first temporary decay time constant and the second temporary decay time constant is obtained, and this is set as the decay time constant of the full intensity. Further, the first temporary decay time constant may be used as it is as the full strength decay time constant.

  As described above, whether or not phosphorescence is emitted from a plurality of types of phosphors having different decay time constants, whether or not the detection target T (security feature) is true or false, and, for example, a paper sheet or the like, is detected. The authenticity of the conveyed product X can be determined.

  In this example, only the feature of phosphorescence is shown as the feature of the detection target T. However, the feature of the detection target T can be added by further adding the feature of the detected fluorescence. Specifically, in Table 1, the presence or absence of fluorescence detection can be added as a feature for each wavelength range of the red wavelength range, the green wavelength range, and the blue wavelength range.

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

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

For example, the phosphorescence detection apparatus 100 has three or more optical sensors arranged at intervals in the conveyance direction on the conveyance path of the object to be conveyed X, and once for each optical sensor, a total of three or more times. The phosphorescence intensity may be detected. Each intensity P is detected over 3 times and with their detection timing t _n, it is possible to perform the above determination. In this case, the phosphor contained in the detection target T has a large decay time constant (it takes a long time for decay of phosphorescence), and even if the transport speed of the transport device 80 is large, the phosphor has a significantly reduced intensity. Can be detected by a downstream optical sensor. Therefore, even when the decay time constant of the phosphor included in the detection target T is large, it is possible to perform true / false identification processing of a large amount of the detection target T while transporting the transported object X.

  INDUSTRIAL APPLICABILITY Since the present invention can be applied to a paper sheet such as a banknote with a security mark including a phosphor and a device for identifying authenticity of a product, for example, a banknote processing apparatus, it can be used in the industry. Sex is enormous.

DESCRIPTION OF SYMBOLS 10 Optical sensor 20 Holder 30 Light source 40 Photodetector 50 Light guide 51 Excitation light incident surface 52 Radiation light output surface 53 Light incident / 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 Transport device 90 Control device 91 Transport device control unit 92 Detection unit 93 Correction unit 94 Discrimination unit 95 Storage unit 100 Phosphorescence detection device

Claims (7)

A light source for irradiating a detection target including a phosphor with excitation light;
A photodetector for detecting the intensity of phosphorescence emitted from the detection target;
A detector that controls the light source and the photodetector and detects the intensity at least three times at different detection times after the irradiation of the excitation light is stopped;
A determination unit for determining whether or not the phosphorescence is due to a plurality of types of phosphorescence having different decay time constants based on at least three of the intensities detected by the detection unit and their detection times;
A phosphorescence detection device comprising:   The determination unit calculates an attenuation time constant of the phosphorescence based on two of the at least three intensities, and the intensity that was not used for the calculation and the detection time thereof are calculated at the calculated attenuation time. The phosphorescence detection device according to claim 1, wherein when the relationship between the phosphorescence intensity represented by a constant and the detection timing does not apply, it is determined that the phosphorescence is due to a plurality of types of phosphorescence having different decay time constants.   The determination unit calculates a first decay time constant of the phosphorescence based on a first combination that is a combination of two of the at least three intensities, and a combination of two of the at least three intensities. The second decay time constant of the phosphorescence is calculated based on a second combination different from the first combination, and the difference between the first decay time constant and the second decay time constant is calculated. The phosphorescence detection device according to claim 1, wherein when the threshold value is exceeded, it is determined that the phosphorescence is caused by a plurality of types of phosphorescence having different decay time constants.   The determination unit calculates a first change rate of a logarithmic value of the intensity based on a first combination that is a combination of two of the at least three intensities, and two of the at least three intensities. A second change rate of the logarithmic value of the intensity is calculated based on a second combination different from the first combination, and the first change rate and the second change rate are calculated. The phosphorescence detection device according to claim 1, wherein when the difference exceeds a threshold value, it is determined that the phosphorescence is due to a plurality of types of phosphorescence having different decay time constants.   5. The determination unit according to claim 1, wherein the determination unit determines whether the detection target is true or false based on whether the phosphorescence is due to a plurality of types of phosphorescence having different decay time constants. 6. Phosphorescence detection device.   A paper sheet processing apparatus comprising the phosphorescence detection device according to claim 1. Irradiating a detection target including a phosphor with excitation light;
Detecting the intensity of phosphorescence emitted from the detection target at least three times after changing the detection time after the stop of the irradiation of the excitation light;
Determining whether or not the phosphorescence is caused by a plurality of types of phosphorescence having different decay time constants based on at least three detected intensities and their detection times.

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