JPS63154943A - Filamentous fluorescent substance detector - Google Patents

Abstract

PURPOSE:To detect a fluorescent filament with a better S/N ratio, by a method wherein a foreign paper note containing a fluorescent filament is irradiated with an excitation light and fluorescence generated from the fluorescent filament is received with a SELFOC lens to detect light outputted to the lens with a photodiode. CONSTITUTION:A paper note path surface 12 and a support member 13 are arranged horizontally at an interval to detect a fluorescent filament 22 contained in a paper note 20 sliding over the path surface 12. In this construction, a total transmission filter 7 for path is provided at the center of the member 13 to transmit an excitation light BL and an inclined guide member 6 is mounted thereon. A black light 3 which generates an excitation light with a specified wavelength and a quantity of light sensor 4 are provided at an end of the member 6 wrapped up by a reflection mirror 2 and an excitation light BL from the light 3 is transmitted through a visible light leakage cut filter 5 and the filter 7 to be directed to the paper note 20. Then, fluorescence KL generated is made incident into a CCD image sensor 9 through excitation light cutoff filters 8A and 8B housing a SELFOC lens 10 provided on the member 6 inclined to detect a fluorescent system 22 as electrical signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thread-like fluorescent substance detection device that efficiently detects thread-like fluorescent substances contained in a portion of foreign banknotes and the like.

(Technical Background of the Invention and its Problems) Some of the banknotes and the like that have been issued and circulated in the past have contained fluorescent substances. Many devices are known that detect the fluorescence of such a contained optical substance to determine the authenticity of banknotes.

For example, Japanese Utility Model Application Publication No. 58-101279 discloses a banknote authenticity discriminating device that determines the authenticity of a banknote by projecting light of a specific wavelength onto the banknote using a light projecting means and detecting the transmitted fluorescence of the banknote. It is shown.

By the way, some banknotes issued overseas (for example, banknotes from Spain and the Netherlands) contain thread-like fluorescent substances (hereinafter referred to as fluorescent threads). Also, in some countries, the fluorescent thread is not included in banknotes, but the paper of the banknote itself contains fluorescent material. However, with conventional discrimination devices, the ability to detect fluorescent substances is low and the S/N ratio is small, so even if fluorescence is detected from banknotes, it is impossible to clearly distinguish between the fluorescence of the paper itself and the fluorescence of the fluorescent threads. there were. Also, the structure of the optical device. ? Ift, there was a problem that it was difficult to miniaturize the device.

(Object of the invention) This invention was made under the above circumstances,
The purpose of this invention is to detect fluorescent threads contained in banknotes etc. within a minute area using a SELFOC lens array, thereby increasing the S/N ratio and detecting the fluorescent threads.
An object of the present invention is to provide a filamentous fluorescent substance detection device that is miniaturized.

(Summary of the Invention) The present invention relates to a filamentous fluorescent substance detection device, and includes an excitation light source that irradiates excitation light to a filamentous fluorescent substance contained in banknotes, etc., and a cell that receives fluorescence from the filamentous fluorescent substance excited by the excitation light. It is equipped with a Fock lens array and a light receiving means for detecting light output from the SELFOC lens array, and the thread-like fluorescent material is S in a minute area of the banknote or the like.
Detection is performed by increasing the /N ratio.

(Embodiment of the invention) This invention irradiates excitation light from an excitation light source to a banknote or the like containing fluorescent threads, and receives the fluorescence emitted from the fluorescent threads with a SELFOC lens array. By detecting the light output from each SELFOC lens with a light receiving means such as a photodiode, fluorescent threads are detected with a good S/N ratio.

First, the principle of detecting fluorescent threads will be explained.

Here, a banknote containing fluorescent thread will be described as an example.

FIG. 1 shows a banknote 21 containing a fluorescent thread 22, and the banknote 21 includes a banknote paper material 2 that does not contain fluorescent material.
3, fluorescent threads 22 are randomly included, and their appearance is shown enlarged. Also, Fig. 2 (A), (B
) shows an enlarged example in which different banknotes are compared in the same area. Corresponding to FIG. 1, FIG. ) indicates a banknote that does not contain any fluorescent material and also contains a fluorescent material in the banknote paper material 23A itself.
) and (B) are irradiated with excitation light from an excitation light source (for example, a black light), the fluorescent thread 22 in the figure (A) emits fluorescence, and the banknote paper material 23A in the figure (8) emits fluorescence, but In A), the fluorescent area of the fluorescent thread 22 is extremely small compared to the area of the surrounding banknote paper material 23, and the fluorescent characteristics of the banknote paper material 23A in FIG. 2B are also small. Therefore, when comparing the amount of fluorescence between Figure 2 (Δ) and Figure 2 (B), the difference in absolute fluorescence amount is small in both cases.
It is difficult to determine which banknotes have the fluorescent thread 22 based on this difference. On the other hand, Fig. 3 (8) and (B) show an example in which the detection unit of the banknote is limited to a plurality of small areas (in this case, 9 sections), and the figure (Δ) shows each The first one in which the fluorescent thread 22 is contained in the banknote paper material 23 within a minute area
The figure ([1) shows a banknote as described in FIG. 2 ([1)] which does not have fluorescent threads.

Then, when each detection section is irradiated with excitation light from an excitation light source in the same manner as described above, in FIG.
/N ratio is large. On the other hand, Fig. 3(B)
The amount of fluorescence in the small area of is relatively the same as in the case of FIG. 2 CB). Once, Figure 3 (8) and Figure CB)
When comparing the amount of fluorescence between the two, there is a large difference in the absolute amount of fluorescence between the two, and from this difference in S/N ratio, a banknote with fluorescent thread 22 is compared to a banknote with fluorescent material in the paper itself (Fig. 2). (B
) It is very easy to judge from the banknotes. From this, if we limit the measurement to a minute area of a banknote, the fluorescent thread 22
It can be seen that it can be detected efficiently.

In this invention, a Selfoc lens array (hereinafter simply referred to as a Selfoc lens array) in which a large number of Selfoc lenses are arranged is used as a means for detecting the fluorescent thread 22 of the banknote 21 in a small area. The output of each SELFOC lens constituting the Fock lens array is imaged on the light receiving surface of an image sensor such as a CCD,
The image sensor outputs electrical signals corresponding to each minute area.

FIG. 4 shows a cross-sectional structure of a filamentous fluorescent substance detection device 1 which is an embodiment of the present invention, and an example in which a banknote 20 is the detection target will be described here.

The thread-like fluorescent substance detection device 1 detects fluorescent threads 22 contained in banknotes 20 that are conveyed onto a banknote passage surface 12 in the direction of the arrow shown in the figure.
The presence or absence of the fluorescent thread 22 is detected based on the fluorescent light KL emitted from the fluorescent thread 22. A support member 13 is provided above the banknote passage surface 12, and several light irradiation guide members 6 are provided on the support member 13, and surrounding external light enters the device at the upper right of the guide member 6. An excitation light source is provided, which includes a visible light leakage cut filter 5 that prevents leakage of visible light, a black light 3 that emits excitation light of a specific wavelength, and a reflector 2 attached to cover the entire black light 3. The excitation light from the black light 3 is reflected by the reflecting mirror 2, and the excitation light B is transmitted through the visible light leakage cut filter 5.
It is designed to be output as L. Further, a passage total transmission filter 7 is attached to the lower part of the guide member 6, through which excitation light BL from the excitation light source is transmitted, and the excitation light BL is transmitted to the surface of the banknote 20 conveyed on the banknote passage surface 12. It is now irradiated. Further, on the left side of the guide member 6, receiving side excitation light cut-off filters 8A and 8B are provided which cut off the excitation light BL and extract only the fluorescent light KL, and also prevent surrounding extraneous light from entering the device. , a fluorescence light receiving section is provided which is composed of a SELFOC lens array IO inserted between them and a CCD image sensor 9 as a light receiving means, and the excitation light BL irradiated onto the banknote 20 causes the banknote 20 to be The fluorescent light emitted from the fluorescent thread 22 contained in
and CC via the receiving side excitation light cutoff filter 8B.
The D image sensor 9 inputs the signal manually, and the CCD image sensor 9 converts it into an electrical signal and outputs it. Note that the excitation light cutoff filters 8A, 8[1
The reason for using two sheets is to select L more sharply for fluorescence. Furthermore, a light amount sensor 4 is provided inside the reflecting mirror 2.
is provided to measure the amount of light from the black light 3.

FIG. 5 schematically shows a schematic configuration of the thread-like fluorescent substance detection device 1, in which excitation light BL irradiated onto the banknote 20 from the black light 3 causes light emitted from the fluorescent thread 22 included in the banknote 20. Fluorescent KL is Selfoc Lens Array
irradiated by O. The SELFOC lens array IO is composed of a large number of SELFOC lenses 11, and each SELFOC lens 11 forms an image of a minute area on the banknote 20). Further, on the output side of each SELFOC lens 11, a CCD image sensor 9 is provided so as to correspond to the focal point of each SELFOC lens 11, so that L can be detected in the fluorescence from each of the microscopic areas. .

FIG. 6 (8) shows the state of the ray locus of the SELFOC lens 11, and the SELFOC lens 11 is shown in the same figure (tl
), it is made of a glass rod in which the refractive index distribution n changes approximately parabolically from the central axis X toward the periphery. The principle of the SELFOC lens array 10 is as shown in FIG.
, L, and A). The SELFOC lens array IO has the same focal length 1ffiffL on the input end and output side. It is designed to maintain and be used. Selfoc lens array 1 like this
The feature of 0 is that the distance between object images I T c can be short, and a homogeneous image can be obtained over the entire width.

On the other hand, FIG. 8 shows the block configuration of the circuit system of the filamentous fluorescent substance detection device 1, in which 11 W of high-frequency power is supplied from the high-frequency power source 30 to the black light 3 inside the thickness with excitation light, and the black light 3 It will be lit. Then, the light amount of the black light 3 that is turned on at a high frequency is measured by the light amount sensor 4 in the reflecting mirror 2, and a light amount signal is input to the amplifier circuit 36 via S4. The light amount signal KS5 amplified by the amplifier circuit 36 is input to the A/D converter 37, and the 8/D converted digital light amount signal DSL is input to the CPU circuit 38. The CPU circuit 38 is composed of a microprocessor, etc., and controls the black light 3 based on the digital light amount signal O51.
The change in light amount due to deterioration of the display signal II is output as a digital signal DS2 and a display signal H5.
s is manually input to the external display device 39, and the black light 3
Information such as when to replace the battery is displayed on the outside. In addition, CPU circuit 3
The digital signal DS2 from 8 is input to the D/A converter 4o, and the analog change signal ASI converted to D/8 is input to the comparator 33.

On the other hand, the detection signal 51 from the CCD image sensor 9 is input to the amplifier circuit 31, the amplified detection signal KS2 is inputted to the filter circuit 32, and the filtered signal S
3 is manually input to the comparator 33. Comparator 33
A threshold for detecting the fluorescent thread 22 is set in advance, and the peak value of S3 is compared with the manually generated filtered signal based on this threshold, the presence or absence of the fluorescent thread 22 is detected, and the detection signal C5I is generated. Output. In this invention, the comparator 33 has an S
The comparator 33 automatically changes the above threshold based on the SI to the analog change signal, and even if the light intensity of the black light 3 changes due to deterioration or replacement of the black light 3, the detection signal C5I is now reliably output. Then, the detection signal C5I from the comparator 33 is input to the counter 34.

The counter 34 sequentially counts the detection signal C5I and outputs a count signal C52 when it reaches a preset value. The count signal C52 is input manually to the CPU circuit 35, and the CPI
The J circuit 35 determines the authenticity of the banknote 20 by determining the count signal C52, and outputs the result as a determination signal C53.

Next, the operation of the filamentous fluorescent substance detection device 1 having the above-described configuration will be explained.

11 W of high frequency power is supplied from the high frequency power supply 30 to the black light 3, and the black light 3 is turned on at high frequency.

Then, the banknote 20 is conveyed to the banknote passage surface 12 by a conveyance device (not shown), and the excitation light BL is irradiated onto the banknote 20, so that the fluorescent thread 22 contained in the banknote paper material 23 of the banknote 2o fluoresces. KL is emitted and manually applied to the fluorescent light receiving section. Here, since each self-focus lens 11 of the SELFOC lens array 10 is imaged within a minute area of the banknote 20, the fluorescent thread 22 has a good S/N ratio as described above.
L is detected in the fluorescence of L is CCD for detected fluorescence
It is converted into a detection signal KSI by the image sensor 9, and then sent to the amplifier circuit 31. A filtered signal S3 is input to a comparator 33 via a filter circuit 32.

On the other hand, the light amount of the black light 3 is measured by the light amount sensor 4, and sent to the CPU circuit 38 as a digital light amount signal DSL via the amplifier circuit 36 and the to/D converter 37.
is input, and if the black light 3 has not deteriorated yet, the external display device 39 will not display the time to replace the black light 3. Also, if the device has deteriorated, a message indicating when to replace it will be displayed, so stop the device and turn on the black light 3.
Replace with a new one. The digital signal DS2 from the CPU circuit 38 is input to the comparator 33 via the D/A converter 40 as an analog change signal ASI.

FIG. 9(A) shows an example of the waveform of S3 in the filtered signal manually input to the comparator 33, and the waveform of the filtered signal KS3 corresponding to the fluorescent thread 22 is changed by the threshold Ll preset in the comparator 33. The image portion is binarized, and a detection signal C5l as shown in FIG. 4(B) is output. Also, the threshold L1 is connected to the analog change signal S.
For example, the analog change signal ASI serves as the threshold L1. Therefore, for example, a new black light 3 has a large amount of light, so the level increases, and as it deteriorates, the amount of light decreases and the level also decreases. When the light intensity of black light 3 decreases, the CCD
Since the overall level of the detection signal KSI of the image sensor 9 is lowered and the level of the filtered signal S3 is also lowered, the comparator 33 can always perform stable binarization regardless of the deterioration of the black light 3. Comparator 33
The detection signal C5I from is input to the counter 34, the count signal C52 is input to the CPU circuit 35, and the CPU circuit 35 outputs a discrimination signal C53. CPU circuit 3
5 compares the count signal C52 from the counter 34 with a predetermined value for each banknote to determine whether the detected banknote 20 is genuine or not.

FIG. 1O shows another example of the filamentous fluorescent substance detection device of the present invention, corresponding to FIG. 4. In the above-described thread-like fluorescent substance detection device 1, the fluorescence KL is detected by a reflection method, but in this thread-like fluorescent material detection device 50, a transmission method is used. That is, this filamentous fluorescent substance detection device 50
The LA detects the presence or absence of the fluorescent thread 22 contained in the banknote 20 being conveyed to the banknote passage surface 12 in the direction of the arrow shown in the figure, using the LA in the fluorescence transmitted from the banknote 20.

In addition, a light introduction hole 51 is provided in the banknote passage surface 12, and at the lower part of this light introduction hole 51, the excitation light BL is cut so that only the LA is not extracted as fluorescence, and the surrounding external light is allowed to enter the device. Excitation light cut-off filter 57 on the receiving side that prevents the light from entering
A, 57B, a SELFOC lens array 58 inserted between them, and a COD image sensor 59 are provided. 22 fluorescent threads included
The LA transmits the generated fluorescence from the light introduction hole 51 to the excitation light cut-off filter 57, SELFOC lens array 58, and the SELFOC lens array 58. The excitation light is input to the COD image sensor 59 via the excitation light cutoff filter 57B on the light receiving side, and is converted into an electrical signal by the COD image sensor 59 and output. Note that the block configuration of the circuit of the filamentous fluorescent substance detection device 1 shown in FIG. 8 can be used as is.

In the above embodiment, a CCD image sensor was used to detect the fluorescent threads, but instead of the CCD image sensor, a photodiode array in which a large number of photodiodes are arranged is used, and the fluorescent threads are detected using the circuit described below. You can do it like this.

FIG. 11 is a block diagram of a circuit for a filamentous fluorescent substance detection device using a photodiode array 70.
The circuit for processing the light amount signal KS4 from the light amount sensor and outputting the analog change signal ASI is the same as that explained in FIG. 8, and the description thereof will be omitted here. A detection signal KSIO from the photodiode array 70 is input to an amplifier circuit 71, where it is amplified and output as a detection signal Sit as shown in FIG. The detection signal KSII is input to the filter circuit 72, differentiated, and a differential signal 512 as shown in FIG. 13 is input to the comparator 73. A threshold L2 for detecting the fluorescent thread 22 is set in advance in the comparator 73, and 512
It binarizes and outputs a detection signal C3lO. Note that the comparator 73 receives an analog change signal ASI similar to that described above.
This is done manually to ensure stable comparisons.

The detection signal C3lO from the comparator 73 is sent to the counter 7
4, a count signal C3lI is output in the same manner as the counter 34 described above, and is manually input to the CPIJ circuit 75.
The CPU circuit 75 outputs a determination signal C513 indicating authenticity determination of the banknote 20.

When the photodiode 70 is used in this way,
Since the instantaneous fluorescence of the fluorescent thread is output when the bill 20 passes, there is an advantage that it can handle high-speed conveyance.

(Modified example of the invention).

In the above-mentioned embodiments, an example was explained in which the fluorescent threads contained in the banknotes emit fluorescence, but the fluorescent threads can be efficiently detected even in banknotes where the banknote paper material emits fluorescence in the same manner as in fluorescent banknotes.

Further, in the above description, the threshold of the comparator is made to correspond to the analog change signal, but this is not necessarily necessary in terms of the operating principle. Furthermore, the structures shown in FIG. 4 and FIG.
7B, etc. are not necessarily necessary.

(Effects of the Invention) According to the filamentous fluorescent substance detection device of the present invention, since the filamentous fluorescent substance is detected within a minute area such as a banknote using a SELFOC lens array, the filamentous fluorescent substance can be detected by S
It is possible to perform detection with a good /N ratio, and furthermore, the device can be further miniaturized.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged view of a banknote to which this invention is applied;
Figures (A'), (B) and Figure 3 (A), (B)
is a comparison diagram based on the detection area of the banknote, and FIG. 4 is a cross-sectional structural diagram of a filamentous fluorescent substance detection device which is an embodiment of the present invention.
Figure 5 is a diagram schematically showing the general structure of the present invention, Figure 6 (A) is a diagram showing the state of the ray locus of the SELFOC lens, and Figure 6 (B) is a diagram showing the relationship between its diameter and refractive index. Figure shown, 7th
The figure is a principle diagram of the Selfoc lens array, Figure 8 is a block diagram showing the circuit system of the filamentous fluorescent substance detection device, and Figure 9
Figures (8) and (B) are diagrams for explaining the operation of the comparator, Figure 10 is a cross-sectional structural diagram showing another filamentous fluorescent substance detection device, and Figure 11 is a filamentous fluorescent substance detection using a photodiode array. Partial block diagram of the device circuit system,
FIG. 12 is a diagram showing the waveform of the detection signal, and FIG. 13 is a diagram showing the waveform of the differential signal. 1150... Thread-like fluorescent material device, 2... Reflector, 3
...Black light, 4...Light level sensor, 6...
Guide member, 7... Total transmission filter for passage, 8A, 8
B, 578. 57B... Light receiving side excitation light cutoff filter, 9°5
9... CCO image sensor, 10.58... Selfoc lens array, 11... Selfoc lens, 12... Bill passage surface, 13... Support member, 20.
21... Banknote, 22... Fluorescent thread, 23... Banknote paper quality, 30... High frequency power supply, 31, 36.71... Amplification circuit, 33.73... Comparator, 31j, 74
...Counter, 35, 38.75-CPU circuit, 3
7...-A/D converter, 39... external display device,
40...D/Hachimbata. Ki 2 times 11] [in day Rororo (A) (B) $3 times (A) CB) Sheep 6 Figure 7 5j C3f Certain IO diagram

Claims (1)

[Claims] An excitation light source that irradiates excitation light onto a filamentous fluorescent substance contained in banknotes, etc., a SELFOC lens array that receives fluorescence from the filamentous fluorescent substance excited by the excitation light, and light output from this SELFOC lens array. What is claimed is: 1. A filamentous fluorescent substance detection device, comprising: a light receiving means for detecting the filamentous fluorescent substance, and is configured to detect the filamentous fluorescent substance within a minute area of the banknote or the like.