JP3228372B2 - Fluorescence detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the authenticity of a paper sheet containing a fluorescent substance, for example, foreign paper money.
The present invention relates to a fluorescence detection device used to detect fluorescence generated from a fluorescent substance.

[0002]

2. Description of the Related Art Conventionally, some banknotes and the like issued and distributed in foreign countries contain a fluorescent substance.
Specifically, a pattern is printed with ink containing a fluorescent substance on a sheet, or a pattern is printed with normal ink on a sheet containing a thread-like fluorescent substance (fluorescent thread) inside. There are things.

Conventionally, there are many known methods for determining the authenticity by irradiating an object containing a fluorescent substance with ultraviolet light as excitation light and detecting the fluorescence emitted from the fluorescent substance by the irradiation. Have been.

[0004] Commercially available white paper (copy paper) for copying machines contains a fluorescent whitening agent, and paper used for banknotes generally contains no fluorescent substance. As a paper detection method, a method of detecting fluorescence in the same manner as described above is also known.

Conventionally, there has been a method as shown in FIGS. 5 and 6 as a basic method for detecting a fluorescent substance. These are provided with an optical filter b that transmits the range of the excitation light wavelength but is unnecessary, in particular, blocks the visible light region, in front of the excitation light source a such as a black light or a UV lamp. Excitation light is applied to the paper (object to be detected) c through the window f, and the excitation light causes the fluorescent substance of the ink printed on the surface of the object to be detected c or the fluorescent thread woven into the object to be detected c And emit visible light. Then, the visible light and the excitation light (surface reflected light) reflected on the surface of the detection target c.
Is an optical filter d that blocks a short wavelength region from ultraviolet rays.
And the desired reflected light is detected by the light receiver e. The detected signal is subjected to pattern matching (comparing the detected pattern with a reference pattern) and discriminating whether the pattern matches or not from the pattern.

However, the fluorescence generated from the fluorescent substance is very small as compared with excitation light, sunlight, stray light of illumination and the like. Therefore, conventionally, in order to block only excitation light, sunlight, stray light, and the like, and also block reflection of excitation light on the surface of an object to be detected or a glass detection window, etc., and transmit only light having a desired wavelength. Multiple optical filters were used.

[0007]

However, the above-described conventional method for detecting a fluorescent substance has the following problems. . Since a plurality of optical filters are required, a holder for accurately holding the arrangement position of each component is required, and the configuration is complicated. . Due to the thickness of the glass itself constituting the filter, there is a limit in reducing the size of the detection device, and there has been a tendency to increase the size of the detection device. . Since the detected object c moves up and down during transport, the detection window f
The optical path length between the object and the object c changes, and the optical axis (incident angle, reflection angle) also changes. For this reason, precision is required for the positioning of the optical system, and the positioning is troublesome.

It is an object of the present invention to provide a fluorescence detecting apparatus which is small in size, can easily align the optical system, and can minimize the influence of the movement of the object to be detected.

[0009]

According to a first aspect of the present invention, as shown in FIG. 1, a fluorescent substance of an object 1 such as a paper sheet is irradiated with excitation light from an excitation light source 2 as shown in FIG. In a fluorescence detection device for detecting the fluorescence of a fluorescent substance excited by the excitation light by the photodetector 3 through an optical system and detecting the fluorescent substance of an object to be detected, the prismatic unit which does not emit fluorescence by ultraviolet light as the optical system. One glass block 4 is used, and an incident surface 5 on which excitation light is incident on one surface of the glass block 4.
The reflection / emission surface 6 that reflects the excitation light on the other surface and transmits the fluorescent light generated from the fluorescent substance of the object 1, and the reflection / emission surface 6 that faces the object 1 on the other surface and reflects An excitation light reflected by the emission surface 6 is transmitted to irradiate the object 1, and the irradiation surface 5 is provided with a detection surface 7 through which fluorescence generated from a fluorescent substance of the object 1 can be transmitted. A fluorescence detection device comprising: an excitation light source 2 provided outside the light source; and a photodetector 3 provided outside the reflection / emission surface 6.

FIG. 1 shows a fluorescence detecting apparatus according to a second embodiment of the present invention.
Is provided with a filter function of blocking the visible light component of the excitation light and transmitting the ultraviolet light region on the incident surface 5 of the glass block 4 shown in FIG.

FIG. 2 is a block diagram showing a fluorescence detecting apparatus according to a third embodiment of the present invention;
As shown in (1), a filter 10 that blocks the visible light component of the excitation light and transmits the ultraviolet region is disposed in front of the incident surface 5 of the glass block 4 of the first aspect.

FIG. 3 shows a fluorescence detecting apparatus according to a fourth aspect of the present invention.
As shown in (1), the excitation light is emitted from the excitation light source 2 to the fluorescent substance of the detection target 1 such as a paper sheet, and the fluorescence of the fluorescent substance excited by the excitation light is detected by the photodetector 3 through the optical system. In a fluorescence detecting device for detecting a fluorescent substance of a paper sheet, a single prism-shaped glass block 4 which does not emit fluorescent light by ultraviolet rays is used in the optical system, and visible light of excitation light incident on one surface of this glass block 4 is used. An incident / reflective surface 8 having a filter function of blocking a light component and transmitting only an ultraviolet region and reflecting fluorescence generated from a fluorescent substance of the object 1 is provided on the other surface facing the object 1 and Incident / reflective surface 8
The detection surface 7 through which the excitation light that has passed through and irradiates the object 1 to be detected and through which the fluorescence generated from the fluorescent substance of the object 1 can be transmitted, and the detection surface 7 on the other surface An emission surface 9 through which the fluorescent light transmitted and reflected by the incident / reflective surface 8 is transmitted is provided, and the excitation light source 2 is provided outside the incident / reflective surface 8.
The light detector 3 is provided outside the emission surface 9.

[0013]

The operation of the fluorescence detecting device according to the first aspect of the present invention is as follows. . Excitation light emitted from the excitation light source 2 in FIG. 1 (excitation light only in the ultraviolet region) enters the glass block 4 from the incident surface 5 of the glass block 4. . The excitation light that has entered the glass block 4 is reflected by the reflection / emission surface 6 and reaches the detection surface 7, passes through the detection surface 7, and irradiates the detection target 1. At this time, a part of the excitation light is reflected by the detection surface 7 and the surface of the detection target 1 and returns to the reflection / emission surface 6, but is reflected by the reflection / emission surface 6. 6 does not exit to the outside. . Fluorescence emitted from the fluorescent substance of the detection target 1 by the irradiation of the excitation light passes through the detection surface 7 and enters the glass block 4. . The fluorescent light that has entered the glass block 4 reaches the reflection / emission surface 6 and passes therethrough to be emitted outside. At this time, the light reflected on the detection surface 7 and the surface of the detection target 1 and returned to the reflection / emission surface 6 does not exit to the outside from the reflection / emission surface 6 as described above. Emits only the above-mentioned fluorescence. . The emitted fluorescence is detected by the photodetector 3. . When no fluorescent substance is contained in the detection section 1, the photodetector 3 does not detect the fluorescence because the detection section 1 does not generate fluorescence even when the excitation light is irradiated.

The operation of the fluorescence detector according to the second aspect of the present invention is as follows. . Excitation light (including a visible light component and a component in the ultraviolet region) generated from the excitation light source 2 in FIG. Incident on. . The excitation light (ultraviolet region) incident on the glass block 4 is reflected on the reflection / emission surface 6 and reaches the detection surface 7, passes through the detection surface 7 and irradiates the detection target 1. At this time, a part of the excitation light (ultraviolet region) is reflected by the detection surface 7 and the surface of the detection target 1 and returns to the reflection / emission surface 6. The light does not exit from the reflection / exit surface 6 to the outside. . Fluorescence emitted from the fluorescent substance of the detection object 1 by irradiation with the excitation light (ultraviolet region) passes through the detection surface 7 and enters the glass block 4. . The fluorescent light that has entered the glass block 4 reaches the reflection / emission surface 6 and passes therethrough to be emitted outside. At this time, the light reflected on the detection surface 7 and the surface of the detection target 1 and returned to the reflection / emission surface 6 does not exit to the outside from the reflection / emission surface 6 as described above. Emits only the above-mentioned fluorescence. . The emitted fluorescence is detected by the photodetector 3. . When no fluorescent substance is contained in the detection section 1, the photodetector 3 does not detect the fluorescence because the detection section 1 does not generate fluorescence even when the excitation light is irradiated.

The operation of the fluorescence detecting device according to claim 3 of the present invention is as follows. . Excitation light (including a visible light component and a component in the ultraviolet region) generated from the excitation light source 2 in FIG. 2 is blocked in the filter 10 by the filter 10, only the ultraviolet region is transmitted, and the excitation light is transmitted from the entrance surface 5 of the glass block 4. The light enters the glass block 4. . The excitation light (ultraviolet region) incident on the glass block 4 is reflected on the reflection / emission surface 6 and reaches the detection surface 7, passes through the detection surface 7 and irradiates the detection target 1. At this time, a part of the excitation light (ultraviolet region) is reflected by the detection surface 7 and the surface of the detection target 1 and returns to the reflection / emission surface 6. The light does not exit from the reflection / exit surface 6 to the outside. . Fluorescence generated from the fluorescent substance of the detection target 1 by irradiation with the excitation light (ultraviolet region) passes through the detection surface 7 and enters the glass block 4. . The fluorescent light that has entered the glass block 4 reaches the reflection / emission surface 6 and passes therethrough to be emitted to the outside. At this time, the light reflected on the detection surface 7 and the surface of the detection target 1 and returned to the reflection / emission surface 6 does not exit to the outside from the reflection / emission surface 6 as described above. Emits only the above-mentioned fluorescence. . The emitted fluorescence is detected by the photodetector 3. . When no fluorescent substance is contained in the detection section 1, the photodetector 3 does not detect the fluorescence because the detection section 1 does not generate fluorescence even when the excitation light is irradiated.

The operation of the fluorescence detecting device according to claim 4 of the present invention is as follows. . Excitation light generated from the excitation light source 2 shown in FIG. 3 has its visible light component blocked at the incident / reflection surface 8 of the glass block 4, and transmits only in the ultraviolet region and enters the glass block 4. . The excitation light (ultraviolet region) incident on the glass block 4 travels straight through the block, reaches the detection surface 7, passes through the detection surface 7, and irradiates the detection target 1. At this time, a part of the excitation light (ultraviolet region) is supplied to the detection surface 7 and the detection target 1.
The light is reflected by the surface and returns to the entrance / reflection surface 8, which passes through the entrance / reflection surface 8 having a filter function of transmitting the excitation light in the ultraviolet region and exits to the outside. do not do. . Fluorescence emitted from the fluorescent substance of the detection object 1 by irradiation with the excitation light (ultraviolet region) passes through the detection surface 7 and enters the glass block 4. . The fluorescent light that has entered the glass block 4 reaches the incident / reflective surface 8, is reflected there, and exits from the exit surface 9 to the outside. At this time, as described above, the light reflected on the detection surface 7 and the surface of the detection target 1 and returned to the reflection surface 8 does not exit from the emission surface 9 to the outside. Emit. . The emitted fluorescence is detected by the photodetector 3. . When no fluorescent substance is contained in the detection section 1, no fluorescence is generated from the detection section 1 even when the excitation light is irradiated, so that the photodetector 3 does not detect the fluorescence.

[0017]

Embodiment 1 The first and second aspects of the invention will be described in detail with reference to the embodiment shown in FIG. In the embodiment shown in FIG. 1, the excitation light source 2 having the largest outer shape of the fluorescence detection device is installed in the lateral direction of the glass block 4 in order to suppress the height direction with respect to the transport direction of the detection object.

In FIG. 1, reference numeral 1 denotes an object to be detected, such as a paper sheet containing a fluorescent substance.

In FIG. 1, reference numeral 4 denotes a single prism-shaped glass block as an optical system, which comprises an excitation light source 2 and an object 1 to be detected.
And a photodetector 3 for optically coupling them. For example, synthetic quartz glass that does not emit fluorescent light due to ultraviolet light is suitable for the material. Its shape is a prismatic shape with a slope on one side.

In FIG. 1, one surface (ABEF surface in FIG. 4) of the glass block 4 is used as an incident surface 5. The incident surface 5 is provided with a film having a filter function of blocking the visible light component of the excitation light from the excitation light source 2 incident thereon and transmitting only the ultraviolet region by vapor deposition or the like. Excitation light source 2
In the case where the excitation light emitted from does not include the visible light component but includes only the ultraviolet region, the incident surface 5 may not have a filter function.

Reference numeral 6 in FIG. 1 denotes a reflection / emission surface formed on another surface (the ABCD surface in FIG. 4) of the glass block 4. The reflection / emission surface 6 reflects the excitation light but the object to be detected. A film having a filter function of transmitting the fluorescence generated from the one fluorescent substance is provided by vapor deposition or the like.

Reference numeral 7 in FIG. 1 denotes a detection surface 7 formed on another surface (the EFGH surface in FIG. 4) of the glass block 4. The detection surface 7 faces the object 1 in parallel and reflects and emits light. The excitation light reflected by the surface 6 transmits and irradiates the detection target 1,
Fluorescent light emitted from the fluorescent substance of the object 1 can be transmitted by the irradiation.

Reference numeral 2 in FIG. 1 denotes an excitation light source for emitting excitation light, which is disposed outside the entrance surface 5. As the excitation light source 2, for example, a black light, a UV lamp or the like is used.

In FIG. 1, reference numeral 3 denotes a photodetector, which is arranged outside the reflection / emission surface 6. This photodetector 3
For example, light / electricity (O /
E) A converter is used.

[0025]

Embodiment 2 The invention of claim 3 will be described in detail based on the embodiment shown in FIG. The embodiment shown in FIG. 2 is basically the same as that shown in FIG. 1 except that the filter function of blocking the visible light component of the excitation light and transmitting the ultraviolet region is provided. 5, a filter 10 is provided separately from the incident surface 5, and the filter 10 is disposed in front of the incident surface 5.

[0026]

Embodiment 3 The invention of claim 4 will be described in detail based on the embodiment shown in FIG. In the embodiment shown in FIG. 3, the excitation light source 2 having the largest outer shape of the fluorescence detection device is installed above the glass block 4 in order to suppress the outer shape of the detection object in the transport direction.

In FIG. 3, reference numeral 1 denotes an object to be detected, 2 an excitation light source for generating excitation light, and 3 an optical detector, all of which are the same as those in FIG.

Reference numeral 4 in FIG. 3 denotes a glass block constituting the optical system, and synthetic silica glass which does not emit fluorescent light due to ultraviolet rays is used as the material of the glass block. Its shape is a prismatic shape with a slope on one side.

In FIG. 3, one surface (the ABCD surface in FIG. 4) of the glass block 4 is used as the incident / reflective surface 8. The incident / reflective surface 8 blocks the visible light component of the excitation light incident on the incident / reflective surface 8 and transmits only the ultraviolet region, and the object 1 to be detected.
A film having a filter function of reflecting the fluorescence generated from the fluorescent substance is provided by vapor deposition or the like.

Reference numeral 7 in FIG. 3 denotes a detection surface formed on the other surface (the EFGH surface in FIG. 4) of the glass block 4. The detection surface 7 is opposed to the vicinity of the object 1 in parallel, The excitation light incident on the reflecting surface 8 transmits and irradiates the object 1 to be detected, and the irradiation allows the fluorescence emitted from the fluorescent substance of the object 1 to be transmitted.

Numeral 9 in FIG. 3 denotes an emission surface formed on the other surface (ABEF surface in FIG. 4) of the glass block 4, which is fluorescent light transmitted through the detection surface 7 and reflected by the incident / reflection surface 8. Are permeable.

In each of the cases of FIGS. 1 to 3, the shape of the block 4 is prismatic and the detection surface 7 is
The excitation light emitted from the detection surface 7 is irradiated perpendicularly to the detection surface of the detection target 1 by disposing the excitation light closer to the detection surface.

[0033]

The fluorescence detecting apparatus of the present invention has the following effects because the optical system is constituted by a single prism-shaped glass block 4 which does not emit fluorescence by ultraviolet rays. . The accuracy of the glass block can be improved simply by increasing the accuracy of the machining, including the polishing step of the glass block 4, and the design of the optical system is facilitated. . Since the configuration of the optical system is simplified, the positioning and fixing of the glass block 4 becomes easy, and the space for disposing the optical system is smaller than that of the conventional optical system including a plurality of components. It is possible to reduce the size. . Since the optical system is only the glass block 4, the number of times that the excitation light and the fluorescent light pass through the media having different refractive indexes is reduced, and the loss generated each time the light passes between the media having different refractive indexes is also reduced. . Since the excitation light can be irradiated at right angles to the detection surface of the detection target 1, the influence of the optical path length fluctuation and the fluctuation of the optical axis due to the fluctuation of the distance from the detection window to the detection target 1 due to the movement blur of the detection target 1 or the like. Can be minimized.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of a fluorescence detection device of the present invention.

FIG. 2 is an explanatory view showing a second embodiment of the fluorescence detection device of the present invention.

FIG. 3 is an explanatory view showing a third embodiment of the fluorescence detection device of the present invention.

FIG. 4 is a detailed explanatory view of a glass block in the fluorescence detection device of the present invention.

FIG. 5 is an explanatory diagram showing an example of a conventional fluorescence detection device.

FIG. 6 is an explanatory view showing another example of a conventional fluorescence detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detected object 2 Excitation light source 3 Photodetector 4 Glass block 5 Incident surface 6 Reflection / emission surface 7 Detection surface 8 Incident / reflection surface 9 Emission surface

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-47-3851 (JP, A) JP-A-57-88063 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G07D 7/00-7/20 G06K 7/12 G06T 1/00

Claims (4)

(57) [Claims] An excitation light source irradiates a fluorescent substance of an object to be detected 1 such as a paper sheet with an excitation light, and a fluorescent light excited by the excitation light and emitted from the fluorescent substance is detected by an optical detector 3 through an optical system. Then, in a fluorescence detection device for detecting a fluorescent substance of an object to be detected, a single prismatic glass block 4 which does not emit fluorescence by ultraviolet rays is used as the optical system, and excitation light is incident on one surface of the glass block 4. Incident surface 5
A reflection / emission surface 6 that reflects the excitation light on another surface and transmits the fluorescence generated from the fluorescent substance of the object 1 and a reflection / emission surface that faces the object 1 in close proximity to the other surface. A detection surface 7 through which the excitation light reflected by 6 transmits and irradiates the object 1 to be detected, and through which the fluorescence generated from the fluorescent substance of the object 1 can pass, is provided outside the entrance surface 5. And a photodetector 3 outside the reflection / emission surface 6. 2. The fluorescence detecting apparatus according to claim 1, wherein the incident surface of the glass block has a filter function of blocking a visible light component of the excitation light and transmitting an ultraviolet region. 3. The fluorescence detection device according to claim 1, wherein a filter that blocks a visible light component of the excitation light and transmits an ultraviolet region is disposed in front of the entrance surface of the glass block. 4. A fluorescent substance of an object 1 to be detected, such as a paper sheet, is irradiated with excitation light from an excitation light source 2, and fluorescence excited by the excitation light and emitted from the fluorescent substance is detected by an optical detector 3 through an optical system. Then, in a fluorescence detecting device for detecting a fluorescent substance of a paper sheet, a single prism-shaped glass block 4 which does not emit fluorescence by ultraviolet light is used for the optical system, and excitation light incident on one surface of the glass block 4 is used. An incident / reflective surface 8 having a filter function of blocking a visible light component of light, transmitting an ultraviolet region, and reflecting fluorescence generated from a fluorescent substance of the object 1, and facing the object 1 on other surfaces. The detection surface 7 through which the excitation light transmitted through the incident / reflection surface 8 transmits and irradiates the object 1 and through which the fluorescence generated from the fluorescent substance of the object 1 can be transmitted, Enters through the detection surface 7 An emission surface 9 through which the fluorescence reflected by the emission / reflection surface 8 passes is provided, the excitation light source 2 is provided outside the incidence / reflection surface 8, and the photodetector 3 is provided outside the emission surface 9. Characteristic fluorescence detection device.