JP7017862B2 - Light sensor, photodetector, paper sheet processing device and light detection method - Google Patents

Description

The present invention detects an optical sensor that detects synchrotron radiation emitted from a detection target excited by excitation light, a light detection device including the light sensor, a paper leaf processing device including the light detection device, and the synchrotron radiation. Regarding the light 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 special material that does not emit synchrotron radiation under visible light but emits synchrotron radiation only when it is irradiated with excitation light of a predetermined wavelength such as ultraviolet rays is printed on paper sheets or product packages. The authenticity of paper sheets, products, etc. is determined from the radiation state of the synchrotron radiation. As the synchrotron radiation, fluorescence emitted at the time of irradiation with excitation light and phosphorescence emitted after irradiation with excitation light are used.

Patent Document 1 discloses a device that irradiates an item marked with a luminescence material moving on a production line with excitation light from a light source and detects the luminescence light with five photosensors.

Further, in Patent Document 2, an optical system using a lens is used to irradiate a phosphor in a banknote with ultraviolet rays from a light emitting diode diagonally arranged with respect to the banknote, and to emit fluorescence from the banknote. A device for detecting with a fluorescence detector is disclosed through the device.

Further, in Patent Document 3, an optical system using a lens is used to irradiate a banknote with excitation light from a light source obliquely arranged with respect to the banknote, and to emit luminescence light excited in or on the banknote. A device for detecting by a detector unit is disclosed via the above.

Further, Patent Document 4 discloses a device that irradiates a banknote with excitation light, detects the emitted fluorescence and phosphorescence, and verifies the authenticity of the banknote. In the apparatus disclosed in Patent Document 4, fluorescence and phosphorescence are detected by an array type detector via an optical system including a cylindrical lens.

Japanese Patent Publication No. 2014-51130 U.S. Pat. No. 6,918,482 U.S. Pat. No. 6,777,704 Japanese Patent No. 3790931

Since the device disclosed in Patent Document 1 has a plurality of detectors, it has an advantage that the light receiving range of synchrotron radiation can be increased, but on the other hand, it has a disadvantage that the device becomes complicated and large. Have.

Further, the apparatus disclosed in Patent Document 2, Patent Document 3 or Patent Document 4 uses an optical system using a lens. Therefore, it is necessary to secure a distance corresponding to the focal length of the lens between the lens and the fluorescence detector, the detector unit or the array type detector. That is, the devices disclosed in these documents have a problem that it is difficult to miniaturize them. Further, in an optical system using a lens, the light receiving range is restricted by the lens diameter, so that the devices disclosed in these documents have a problem that it is difficult to increase the light receiving range.

As described above, the conventional device cannot achieve both the miniaturization of the sensor unit for detecting the synchrotron radiation and the enlargement of the synchrotron radiation receiving surface. In view of such a situation, it is an object of the present invention to increase the size of the synchrotron radiation receiving surface of the sensor while reducing the size of the sensor.

The optical sensor according to the present invention has a light source that irradiates excitation light, a light detector that detects radiated light emitted from a detection target excited by the excitation light, and a block shape that transmits the excitation light and the radiated light. A light guide body formed in the above, which guides the excitation light to the detection target and guides the emitted light to the light detector, and means that the excitation light reaches the light detector before reaching the detection target. A light-shielding region for preventing the light source and the light detector are arranged on one side of the light guide , and the light-shielding region is formed on one side of the light guide. The step is formed by a step formed between a portion on one side of the portion on the light source side and a portion on the light detector side .

Further, the light detection method according to the present invention is a light detection method using an optical sensor, and the optical sensor is arranged on one side of a light guide body formed in a block shape and the light guide body. A light source, a light detector, and a step formed on the one side portion of the light guide body, which is a portion on the one side portion on the light source side and a portion on the light detector side. The light detection method includes a step of irradiating the excitation light with the light source, guiding the excitation light to the detection target by the guide body , and the above-mentioned light detection method. A step of preventing the excitation light from reaching the light detector before reaching the detection target by a light -shielding region, with radiation emitted from the detection target excited by the excitation light transmitted through the light guide . The present invention includes a step of detecting the emitted light transmitted through the light guide by the light detector.

According to the present invention, the excitation light can be guided from the light source to the detection target by a single light guide unit, and the synchrotron radiation can be guided from the detection target to the light detector, so that the sensor can be miniaturized. The synchrotron radiation receiving surface of the sensor can be enlarged.

It is a schematic diagram which shows the structure of one Example of the optical sensor which concerns on this invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 6 is a sectional view taken along line IV-IV in FIG. FIG. 3 is a sectional view taken along line VV in FIG. It is a schematic diagram explaining how light is guided in the optical sensor which concerns on this invention. It is explanatory drawing of the method of detecting the synchrotron radiation from the moving detection target. It is a graph which shows the relationship between the moving distance of the detection target after the light source is turned off, and the detected intensity. It is a schematic diagram which shows the structure of one Example of the photodetector which concerns on this invention. It is a flowchart which shows the operation flow of the photodetector which concerns on this invention. It is a schematic diagram which shows the structure of another Example of the optical sensor which concerns on this invention. It is sectional drawing which shows the structure of still another Example of the optical sensor which concerns on this invention. It is sectional drawing which shows the structure of still another Example of the optical sensor which concerns on this invention.

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

(1) Structure of Optical Sensor FIG. 1 is a schematic side sectional view showing the structure of an optical sensor 10 according to an embodiment to which the present invention is applied. 2, FIG. 3, FIG. 4, and FIG. 5 are a cross-sectional view taken along the line II-II, a cross-sectional view taken along the line III-III, a cross-sectional view taken along the line IV-IV, and a cross-sectional view taken along the line V-V in FIG. 1, respectively. Although FIG. 1 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 portion. In this through hole, a light guide body 50, an optical filter 70, a light source 30, and a photodetector 40 are arranged in 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 that can excite 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 (light amount) of the received light, and is attached to the lower surface of the substrate 60. As shown in FIG. 5, 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 having a specific wavelength or detecting the intensity of the synchrotron radiation regardless of the wavelength, the number of photodetectors 40 may be one. Further, by setting the number of the 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 50 guides the excitation light emitted from the light source 30 to the detection target, and guides the radiated light 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 radiated light 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 exciting light incident surface 51 and the radiated light emitting surface 52, and a step is formed by the excited 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 on 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 applied 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 that transmits ultraviolet rays and cuts visible light, which is a kind of optical filter 70. 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 a red wavelength region, a green wavelength region, or a blue wavelength region, respectively. These optical filters 70 may be replaced with filters having other characteristics depending on the purpose, or may not be arranged if unnecessary.

(2) Guidance by the light guide The ultraviolet rays contained in the excitation light emitted from the light source 30 pass through the visible light cut filter 71 and are incident on the light guide 50 from the excitation light incident surface 51. The partition 21 prevents the excitation light before being incident on the light guide 50 from being directly reflected by the excitation light incident surface 51 or the radiated light emitting surface 52 and reaching the photodetector 40. That is, the partition 21 functions as a light-shielding region.

As shown in FIG. 6, the excitation light incident on the light guide body 50 is guided in the light guide body 50 while being reflected by the upright surface 54 and the side surface 55, and reaches the light inlet / output surface 53. As described above, there is a gap between the partition 21 and the surface of the light guide body 50, but there is a step formed by the excitation light incident surface 51, the upright surface 54, and the radiated light emitting surface 52, and the excitation light is incident. The excitation light incident from the surface 51 is reflected by the upright surface 54. That is, the step functions as a light-shielding area. The upright surface 54 also has a function of condensing the excitation light directly below the light source 30.

The excitation light that has reached the light entrance / exit surface 53 is emitted from the light entrance / exit surface 53. The light entrance / exit surface 53 is arranged so as to face the detection target T. The detection target T is a security mark printed on a banknote or the like using ink containing a material that emits synchrotron radiation such as fluorescence or phosphorescence when excited. Therefore, the detection target T is excited by the excitation light emitted from the light inlet / output surface 53 and emits synchrotron radiation such as fluorescence or phosphorescence.

The synchrotron radiation emitted from the detection target T is incident on the light guide body 50 from the light inlet / output surface 53. The synchrotron radiation incident on the light guide body 50 is guided inside the light guide body 50 while being reflected by the side surface 55, and reaches the synchrotron radiation emission surface 52. The radiated light that has reached the radiated light emitting surface 52 is emitted from the radiated light emitting surface 52. Of the synchrotron radiation emitted from the synchrotron radiation emitting surface 52, the synchrotron radiation of a predetermined color (wavelength) intended for detection passes through the ultraviolet cut filter 72 and the color filter 73, and is detected by the light detector 40. Detected.

The excitation light is reflected on the surface of the detection target T, and the ultraviolet rays contained in the reflected excitation light may reach the radiated light emitting surface 52 and be emitted from the radiated light emitting surface 52, but the ultraviolet rays are ultraviolet rays. Since it cannot pass through the cut filter 72, it does not reach the light detector 40.

As described above, the optical sensor 10 uses the light guide body 50 for the optical system. Therefore, unlike the case where a lens is used, it is not necessary to secure an interval corresponding to the focal length of the lens in front of the photodetector 40. Further, the single light guide body 50 guides the excitation light from the light source 30 to the detection target T and the synchrotron radiation from the detection target T to the photodetector 40. Therefore, the optical sensor 10 has a compact structure as a whole. Moreover, since the synchrotron radiation is not collected on the photodetector 40 as in the case of using a lens, the photodetector 40 having a large light receiving surface can be used. Therefore, the optical sensor 10 is suitable for being installed in the device to detect the synchrotron radiation from the moving detection target T.

Further, the radiated light receiving surface of the light guide 50, that is, the light input / output surface 53 is larger than the light receiving surface of the light detector 40, and the radiated light incident from the light input / output surface 53 is detected by the light detector 40. The light guide body 50 is configured to guide light toward. Therefore, although the optical sensor 10 has a compact structure as a whole, it has a large light receiving range and can detect synchrotron radiation with high sensitivity. Therefore, even when the synchrotron radiation is detected while moving the detection target T as described later, it is possible to reduce the fluctuation of the synchrotron radiation intensity (light amount) due to the variation in the position of the detection target T. It is also possible to reduce the influence of fluctuations in radiant intensity due to uneven printing.

Further, when there is a hollow portion between the photodetector 40 and the light guide body 50 inside the holder 20 as in an optical system using a lens, the light incident on the hollow portion collides with the inner wall of the holder 20. It is absorbed and attenuated when it is used. On the other hand, in the optical sensor 10, since most of the inside of the holder 20 is occupied by the light guide body 50, such light absorption and attenuation hardly occur. Further, since most of the inside of the holder 20 is occupied by the light guide body 50, it is possible to prevent dust from accumulating inside and light being absorbed by the dust and attenuated.

Further, since the light source 30 and the photodetector 40 are mounted on the same substrate 60 and the substrate 60 serves as a lid of the holder 20, it is possible to reduce the member cost and the manufacturing man-hours, and thus the optical sensor. 10 can be manufactured at low cost.

Further, since the photodetector 40 can be separated from the detection target T by at least the height of the light guide body 50, the photodetector 40 is affected by the static electricity carried by the detection target T and the device that conveys the light detector 40. Can be prevented. Moreover, since most of the space between the light detector 40 and the detection target T is occupied by the light guide body 50, the synchrotron radiation emitted from the detection target T reaches the light detector 40. The attenuation of synchrotron radiation is also prevented.

As described above, the optical sensor 10 has a large light receiving range and is compact. Therefore, the optical sensor 10 can be mounted on a device that could not be mounted on the optical sensor due to spatial restrictions in the past, and the photodetector can be configured. Examples of such a photodetector include a paper leaf processing device.

(3) Method for detecting synchrotron radiation Next, a method for detecting synchrotron radiation using the optical sensor 10 will be described. When detecting synchrotron radiation using the optical sensor 10, the optical sensor 10 is connected to a control device (not shown in FIG. 1) via the substrate 60. The control device turns on the light source 30 (that is, starts irradiation of the excitation light) and turns off the light source 30 (that is, stops the irradiation of the excitation light). Further, the control device receives the signal transmitted by the photodetector 40 that has detected the synchrotron radiation, and calculates the intensity (light amount) of the synchrotron radiation.

(3-1) Fluorescence detection method Fluorescence detection is performed as follows. The fluorescence is synchrotron radiation emitted from the detection target while the detection target is irradiated with the excitation light. When the irradiation of the excitation light is stopped, the emission of fluorescence from the detection target is also 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. The excited detection target emits fluorescence. The fluorescence emitted from the detection target passes through the light guide body 50. The photodetector 40 detects the fluorescence transmitted through the light guide 50.

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

Fluorescence can be detected at any timing and time as long as it is irradiated with the excitation light. The intensity of the fluorescence 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.

(3-2) Phosphorescent detection method Phosphorescent detection is performed 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 50.

The photodetector 40 that has detected phosphorescence transmits a signal 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 the decay time constant is calculated as described later, the shorter the detection time, the more accurately the decay time constant can be calculated. The intensity of the 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.

Each phosphorescent radiation substance has a unique phosphorescence intensity attenuation time constant (time required for the phosphorescence intensity to become 1 / e). That is, the phosphorescence intensity attenuation curve drawn in the coordinate system with the horizontal axis representing the elapsed time after the light source 30 is turned off and the vertical axis representing the phosphorescence intensity differs depending on each phosphorescence radiation substance. Therefore, after the light source 30 is turned off, the phosphorescence intensity is calculated many times, and each calculated phosphorescence intensity is compared with the reference phosphorescence intensity to determine the phosphorescence radioactive substance contained in the detection target. be.

It is also possible to determine the phosphorescent radioactive substance contained in the detection target by calculating the decay time constant of the phosphorescence intensity and comparing the calculated decay time constant with the reference decay time constant. The decay time constant of the phosphorescence intensity can be calculated based on the following formula 1 by detecting the phosphorescence intensity twice after turning off the light source 30.

In Equation 1, τ is the decay time constant of the phosphorescence intensity. t ₁ and t ₂ are the elapsed times from the extinguishing of the light source 30 to the first and second phosphorescence detection, respectively. P ₁ and P ₂ are the intensities of phosphorescence detected at the first and second times, respectively.

Further, by calculating the phosphorescence intensity at least three times after the light source 30 is turned off, it is possible to determine whether or not the detection target contains a plurality of types of phosphorescent radioactive substances having different attenuation time constants. Is.

(3-3) Method for detecting synchrotron radiation emitted from a moving detection target Further, by using the optical sensor 10, it is possible to detect synchrotron radiation emitted from a moving detection target. The method will be described with reference to FIG. 7, which schematically shows the positional relationship between the optical sensor 10 and the detection target T.

When detecting the synchrotron radiation emitted from the moving detection target, the optical sensor 10 is arranged so that the light input / output surface 53 faces the transport path of the detection target. As shown in FIG. 7A, when the detection target T is transported to a position facing the light inlet / output surface 53, for example, in front of the light source 30, the light source 30 irradiates the excitation light. do. The irradiated excitation light passes through the light guide body 50. The excitation light transmitted through the light guide 50 reaches the detection target T and excites the detection target T.

When the fluorescence is emitted from the detection target T, the fluorescence is transmitted through the light guide body 50. The photodetector 40 detects the fluorescence transmitted through the light guide 50.

Subsequently, the light source 30 is turned off. When phosphorescence is emitted from the detection target T, the phosphorescence passes through the light guide body 50. The photodetector 40 detects phosphorescence transmitted through the light guide 50. At this time, as shown in FIG. 7B, the detection target T has moved a distance L to the downstream side in the moving direction.

The detection target T is moving from the time when the light source 30 irradiates the excitation light until the fluorescence or phosphorescence is detected, but since the light input / output surface 53 is wide, the light guide 50 emits these synchrotron radiation. It can be incident on the light guide body 50. Further, if the synchrotron radiation is incident on the light guide body 50, the light guide body 50 can guide the synchrotron radiation to the photodetector 40. Therefore, the optical sensor 10 can detect the synchrotron radiation even if the detection target T is moving. Although it depends on the moving speed of the detection target and the size of the light inlet / output surface 53, the phosphorescence emitted after the irradiation of the excitation light is stopped is detected when 0 to 3.0 msec has elapsed after the light source 30 is turned off. It is preferable to do it in.

However, the intensity of the radiated light detected by the light detector 40 is the relative position between the detection target T that emits the radiated light and the light detector 40, that is, the distance L that the detection target T has moved after the light source 30 is turned off. Accordingly, it changes as shown in FIG. FIG. 8 shows the moving distance L of the detection target T after the light source 30 is turned off and the phosphorescence detected by the photodetector 40, assuming that the intensity of the phosphorescence emitted from the detection target is always constant. A curve showing the relationship between the intensities of is schematically shown.

As shown in FIG. 8, the intensity of phosphorescence detected by the photodetector 40 becomes a maximum value when the distance L becomes a predetermined value L ₀ , and decreases as the distance L moves away from L ₀ .

If the moving speed of the detection target T is constant, the relative position between the detection target T and the photodetector 40 can always be kept constant by detecting phosphorescence at a predetermined timing after the light source 30 is turned off. However, it may be difficult to keep the relative positions of the detection target T and the photodetector 40 always constant due to speed fluctuations of the device that conveys the detection target T. In that case, the phosphorescence intensity cannot be accurately detected because the relative positions of the detection target T and the photodetector 40 fluctuate.

Therefore, in order to accurately detect the intensity of the synchrotron radiation, it is desirable to correct the intensity of the detected synchrotron radiation according to the relative position between the detection target T and the photodetector 40.

Therefore, the control device stores information about the curve illustrated in FIG. 8 and obtains a correction coefficient from the information and the distance L that the detection target T has moved before detecting phosphorescence after the light source 30 is turned off. By multiplying the detected phosphorescence intensity by this correction coefficient, the phosphorescence intensity can be corrected. As such information, for example, a function or table representing the relationship between the distance L to which the detection target T travels before the phosphorescence is detected after the light source 30 is turned off and the phosphorescence intensity detected by the photodetector 40 is controlled. The device can be stored.

By comparing the corrected phosphorescence intensity with the reference value, it is possible to more accurately determine the phosphorescence radioactive substance contained in the detection target T. Thereby, it is possible to determine the authenticity of the detection target T or the paper sheets, products, etc. to which the detection target T is attached.

In addition, by calculating the decay time constant of the phosphorescence intensity based on the corrected phosphorescence intensity and comparing the calculated decay time constant with the reference decay time constant, the phosphorescent radioactive material contained in the detection target can be detected. It is also possible to distinguish. The attenuation time constant based on the corrected phosphorescence intensity can be calculated based on the following equation 2 by detecting the phosphorescence intensity twice after turning off the light source 30.

In Equation 2, τ is the decay time constant of the phosphorescence intensity. t ₁ and t ₂ are the elapsed times from the extinguishing of the light source 30 to the first and second phosphorescence detection, respectively. P ₁ and P ₂ are the intensities of phosphorescence detected at the first and second times, respectively. Y is a function representing the relationship between the moving distance of the detection target T after the light source 30 is turned off and the intensity of phosphorescence detected by the photodetector 40. L ₁ and L ₂ are the moving distances of the detection target T after the light source 30 is turned off until the first and second phosphorescence detections, respectively.

As described above, according to the optical sensor 10, the synchrotron radiation can be detected while the detection target T is moved, and the phosphorescence intensity can be corrected according to the position of the detection target T. Therefore, the detection of the synchrotron radiation from the detection target T and the discrimination of the phosphorescent radioactive substance contained in the detection target T can be performed quickly and accurately.

(4) Configuration of PhotoDetector Next, a photodetector equipped with the photosensor 10 will be described. FIG. 9 is a block diagram schematically showing the configuration of the photodetector 100. The photodetector 100 is a device used to determine the authenticity of the detection target T attached to the object X to be transported. The photodetector 100 has a transfer device 80, an optical sensor 10 installed above the transfer device 80, and a control device 90 for controlling 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 photodetector 100 can be used as a paper sheet processing device.

The transport device 80 is a device that continuously transports the transported object X having 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 transported object X. 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 rotation speed (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) for detecting the passage of the transported object X on the upstream side of the optical sensor 10.

In the photodetector 100, the photosensor 10 is arranged so that the light source 30 is located on the upstream side of the transported object X in the transport device 80 in the transport direction, and the photodetector 40 is located on the downstream side of the transport device X. 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 X to be conveyed on the transfer 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 of the object X is detected by the passage detection sensor. 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 synchrotron radiation.

The correction unit 93 obtains information on the existence position of the detection target T from the transport device control unit 91, and also obtains information on the intensity of the synchrotron radiation 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 synchrotron radiation detected based on this information.

The discriminating unit 94 compares the intensity of the synchrotron radiation obtained by the detection unit 92 or the intensity of the corrected synchrotron radiation obtained by the correction unit 93 with the reference value stored in the storage unit 95. Determines the substance contained in the detection target T and determines the authenticity of the detection target T. Further, the discrimination unit 94 can calculate the phosphorescence decay time constant τ, 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 regarding the correction coefficient used for correcting the synchrotron radiation 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 the synchrotron radiation emitted from the true detection target T and the decay time constant of the phosphorescence. This information is the basis for determining the authenticity of the detection target T.

(5) Operation of PhotoDetector An example of the operation flow of the photodetector 100 configured as described above will be described with reference to FIG.

When the operation of the optical 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).

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 is turned on (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, each of the plurality of photodetectors 40 detects phosphorescence emitted from the detection target T a plurality of times at a predetermined timing (S5).

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 photodetector 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 transported object X passes through. Further, it is also possible to determine the authenticity of the transported object X 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.

(6) Other Examples of Optical Sensors The optical sensor 10 to which the present invention is applied is not limited to that shown in FIG. For example, the heights of the excitation light incident surface 51 and the emitted light emitting surface 52 are changed according to the presence or absence of the optical filter 70 arranged between the light guide body 50, the light source 30, and the photodetector 40 and the thickness thereof. However, a more compact optical sensor 10 can be obtained without creating a wasteful space between the light guide body 50, the light source 30, and the photodetector 40. Specifically, the optical sensor 10 may include a light guide body 50 having a low step on the excitation light incident surface 51 side and a high step on the synchrotron radiation emission surface 52 side. Further, as shown in FIG. 11, the optical sensor 10 may include a light guide body 50 in which the excitation light incident surface 51 and the synchrotron radiation emitting surface 52 have the same height. In this case, a lower intermediate surface 56 is formed between the excitation light incident surface 51 and the synchrotron radiation emitting surface 52, and a step portion that functions as a light-shielding region is formed.

Further, in the optical sensor 10 to which the present invention is applied, the light guide body 50 can guide the excitation light from the light source 30 to the detection target T, and can guide the emitted light from the detection target T to the photodetector 40. It is not necessary to be arranged at a position sandwiched between the light source 30, the photodetector 40, and the detection target T facing the optical sensor 10. For example, as shown in FIG. 12, the light guide body 50 may have an excitation light incident surface 51 and a synchrotron radiation emitting surface 52 in the front and rear, and may have a light entering / exiting surface 53 in the lower direction.

Further, as long as the optical sensor 10 to which the present invention is applied has a light guide unit capable of guiding the excitation light from the light source 30 to the detection target T and guiding the radiated light from the detection target T to the photodetector 40. The light guide body 50 is not limited to the one having the light guide body 50. For example, the optical sensor 10 as shown in FIG. 13 may be used.

The optical sensor 10 shown in FIG. 13 differs from the optical sensor 10 shown in FIG. 1 in that it does not have the light guide body 50. Further, the cover 150 made of a material that transmits excitation light and synchrotron radiation is different in that the lower opening of the through hole of the cylindrical holder 20 is closed. Further, it is different in that the inner surface of the cylindrical holder 20 is a reflective surface.

The reflective surface on the inner surface of the cylindrical holder 20 is, for example, a mirror surface. The mirror surface is formed by coating the inner surface of the holder 20 with a metal such as aluminum or silver or an alloy thereof, and finishing the surface of the metal by a known method. Of course, the reflective surface on the inner surface of the cylindrical holder 20 is not limited to the mirror surface formed by the above method as long as most of the excitation light and the synchrotron radiation are reflected. Further, in the tubular holder 20, for example, even if a part of the tubular portion has a slit or a hole through which a part of the excitation light or the reflected light leaks, most of the tubular holder 20 is surrounded and the excitation light or the reflected light leaks. A small amount may work well. The inner surface of the holder 20 also includes the side surface and the lower surface of the partition 21.

In the optical sensor 10 shown in FIG. 13, the excitation light emitted from the light source 30 is directed toward the cover 150 while being substantially totally reflected by the inner surface of the holder 20 (including the side surface of the partition 21). The excitation light that reaches the cover 150 passes through the cover 150 and excites the detection target. The excited detection target emits synchrotron radiation. The synchrotron radiation radiated from the detection target passes through the cover 150 and is almost totally reflected by the inner surface of the holder 20 (including the side surface of the partition 21) toward the photodetector 40.

That is, in the optical sensor 10 shown in FIG. 13, the holder 20 guides the excitation light from the light source 30 to the detection target, and the synchrotron radiation is guided from the detection target to the photodetector 40. That is, the holder 20 functions as a light guide unit. Further, although not particularly limited, the shape of the inner surface of the holder 20 may be a hexagonal shape in which two corners on the light source 30 side, which are substantially square, are chamfered when viewed from the side of the light source 30 and the photodetector 40. can. With this shape, the excitation light from the light source 30 can be efficiently applied to the detection target.

The partition 21 has a stepped portion formed by a lower surface thereof, a pair of facing side surfaces thereof, and a member covering the upper opening of the through hole of the holder 20 (in the case of FIG. 13, the substrate 60). Therefore, in the optical sensor 10 shown in FIG. 13, the partition 21 is directly exposed to the excitation light emitted from the light source 30 between the portion on the light source 30 side and the portion on the photodetector 40 side inside the holder 20. It functions as a light-shielding area that prevents the light detector 40 from reaching the light detector 40.

The shape of the cover 150 is such that the lower opening of the through hole of the holder 20 can be closed, the excitation light can be transmitted toward the detection target, and the synchrotron radiation can be transmitted toward the inside of the through hole of the holder 20. Anything can be used as long as it is available. For example, it may be a flat plate having no protrusion into the holder 20. On the contrary, the protruding portion into the holder 20 may be thickened to have the function of the light guide portion. That is, even if the light guide portion is formed by the inner surface of the holder 20 and the protruding portion of the cover 150, the excitation light and the synchrotron radiation are guided by the reflection of the inner surface of the holder 20 and the reflection of the side surface of the protruding portion of the cover 150. good.

The optical sensor and the optical detection device of the present invention detect a luminescent substance attached as a security feature on the surface of a valuable document such as a bank note or a securities, and are a detection target. The luminescent material is irradiated with excitation light, and synchrotron radiation such as fluorescence or phosphorescence emitted from the luminescent material is detected. Since the synchrotron radiation characteristics such as the fluorescence and phosphorescence spectra and the phosphorescence attenuation characteristics are determined by the composition of the luminescent substance, the authenticity of the security characteristics can be determined by detecting the synchrotron radiation and comparing the characteristics.

Further, the optical sensor of the present invention is not limited to one having a set of a light source 30 and a photodetector 40, and has a so-called line sensor configuration in which a plurality of sets of light sources 30 and a photodetector 40 are arranged in a row. You may be doing it.

Further, the photodetector of the present invention may have a plurality of optical sensors 10 arranged in addition to the one in which one optical sensor 10 is arranged. In this case, the plurality of optical sensors 10 can scan a plurality of positions of one object X to be transported and detect synchrotron radiation at each position.

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.

INDUSTRIAL APPLICABILITY The present invention is suitable for use in a photosensor, a photodetector, a paper leaf processing device, or a photodetection method for detecting synchrotron radiation emitted from a detection target that emits synchrotron radiation when excited.

10 Optical sensor 20 Holder 21 Partition 30 Light source 40 Photodetector 50 Light guide 51 Excited light incident surface 52 Emitted light emission surface 53 Light input / output surface 54 Erecting surface 55 Side surface 56 Intermediate surface 60 Substrate 70 Optical filter 71 Visible light cut filter 72 Ultraviolet cut filter 73 Color filter 80 Conveyor device 90 Control device 91 Conveyor device Control unit 92 Detection unit 93 Correction unit 94 Discrimination unit 95 Storage unit 100 Optical detection device 150 Cover

Claims (8)

A light source that irradiates excitation light,
A photodetector that detects synchrotron radiation emitted from a detection target excited by the excitation light, and
A light guide body formed in a block shape that transmits the excitation light and the synchrotron radiation, and guides the excitation light to the detection target and guides the synchrotron radiation to the light detector.
It comprises a light-shielding region that prevents the excitation light from reaching the photodetector before it reaches the detection target.
The light source and the photodetector are arranged on one side of the light guide body , and the light source and the photodetector are arranged on one side of the light guide body.
The light -shielding region is a step formed on the one-sided portion of the light guide, and is between a portion of the one-sided portion on the light source side and a portion on the photodetector side. An optical sensor composed of steps formed in . The step is
An excitation light incident surface facing the light source and
A synchrotron radiation emitting surface facing the photodetector and located closer to the other side of the light guide or farther from the other side than the excitation light incident surface.
The optical sensor according to claim 1, which is composed of a planar upright surface connecting the excitation light incident surface and the synchrotron radiation emitting surface. The optical sensor according to claim 1 or 2 , wherein an optical filter is provided between the light source and the light guide and / or between the photodetector and the light guide . The optical sensor according to any one of claims 1 to 3 , wherein the light source and the photodetector are arranged on the same substrate. The optical sensor according to any one of claims 1 to 4 ,
A correction unit that corrects the intensity of the synchrotron radiation detected by the photodetector based on the relative position of the detection target with respect to the photodetector when the synchrotron radiation is detected.
A photodetector equipped with. The light detection device according to claim 5 , wherein the light source irradiates the excitation light while the detection target is moving, and is arranged on the upstream side of the detection target in the moving direction with respect to the photodetector. A paper leaf processing apparatus comprising the photodetector according to claim 5 or 6 . It is a photodetection method that uses an optical sensor.
The optical sensor is formed on a light guide body formed in a block shape, a light source and a light detector arranged on one side of the light guide body, and a portion on the one side of the light guide body. It is provided with a light-shielding region which is a step and is formed by a step formed between a portion on the light source side and a portion on the light detector side in the portion on one side .
The light detection method is
The step of irradiating the excitation light with the light source,
A step of guiding the excitation light to a detection target by the light guide and preventing the excitation light from reaching the photodetector before reaching the detection target by the light-shielding region.
A step in which a light detector detects synchrotron radiation emitted from a detection target excited by the excitation light transmitted through the light guide and transmitted through the light guide .
Light detection method having.

Images