JPS62111376A - Optical identification system for paper money - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an optical identification method for banknotes, etc., which optically identifies whether or not an object to be inspected, such as a banknote, securities, or bond, is genuine. [Prior Art] Conventionally, methods for optically identifying banknotes in banknote identification devices include methods that detect minute patterns on banknotes, methods that detect transmittance of specific parts of banknotes, etc. . However, with the spread of copy materials in recent years, it has become easier to obtain highly accurate copies of counterfeit bills, and there is a tendency for mischief using this type of counterfeit bills to increase. In general, banknote identification devices not only use optical identification, but also
Magnetic identification, which detects magnetic ink on banknotes, is also used, but depending on the copying material, it may be difficult to determine authenticity using only magnetic identification. For the above reasons, methods for optically identifying banknotes have become increasingly complex, and methods that detect the spectral characteristics of specific portions of banknotes are becoming mainstream. [Problems to be Solved by the Invention] However, in order to detect spectral characteristics, the optical system of the detection unit in particular becomes complicated and expensive, which is one of the factors that prevents the miniaturization and cost reduction of banknote identification devices. . A conventional detection method for detecting the spectral characteristics of banknotes will be discussed below. Figure 2 shows the spectral characteristics of the transmittance of a characteristic part of a genuine note against the wavelength of the light source (b), the spectral characteristic of the transmittance of the same part of a color copy of a counterfeit note (a), and the transmittance of the same part of a black and white copy of a counterfeit note. This shows the spectral characteristics (C) of . Basically, these three types of absorbance (reflectance or transmittance) are measured at two wavelengths λ1. Discrimination is performed using a λ2 light source. ■Conventional example 1 As the first conventional example, the difference in the spectral characteristics of transmittance between genuine and counterfeit notes shown in Figure 2 is the transmittance for visible light with wavelength λ and the transmittance for infrared light with wavelength λ2. There is a system in which the authenticity of banknotes is determined based on the ratio or difference between the two banknotes (Special Publication No. 197, No.
FIG. 3 shows a schematic configuration of a detection system of this method. As shown in this figure, in this method, a visible light-emitting element 1 and an infrared light-emitting element 2 are used to illuminate the inspected portion of the banknote 6 with low brightness and saturation, and these light-emitting elements 1.2 are turned on alternately. An alternating lighting circuit 3 for lighting, a light receiving element 5 for receiving reflected light or transmitted light from a part to be inspected such as a banknote, and an output photoelectrically converted by the light receiving element 5 as an output when visible light is irradiated. a signal processing circuit 4 which separates the output from the infrared light irradiation, calculates the ratio or difference between the two outputs, and detects whether the value of the ratio or difference is within a predetermined range; has. According to this conventional method, the number of light receiving elements 5 is one, but λ
1. Two independent light emitting elements (for example LEDs) 1.2 are required as light sources with a wavelength of λ2. In general, this type of light-emitting element is expensive because it requires a type with high volatility and high sensitivity, and therefore, the need for a light source of 2 fffi is important for bill identification, both in terms of installation space and price. This is disadvantageous from the perspective of the entire device. Also, since two light emitting elements 1.2 are required, aligning the optical axis with the light receiving element 5 is as follows:
This is impossible without special measures (for example, the use of optical fibers, etc.), which makes it extremely difficult to design the spatial arrangement of the light-emitting element and light-receiving element in order to obtain the sensitivity required for the detection system. There is a point. ■Conventional example 2 As a second conventional example, as shown in FIG.
The banknote 6 is identified by an optical system and a signal processing circuit 4 including a light emitting element 2 that supplies infrared light with a wavelength of λ and two light receiving elements 5.5 corresponding to each of these light emitting elements. There is a method to identify the authenticity of banknotes by detecting the spectral characteristics of the absorbance of ink at certain points (Japanese Patent Laid-Open No. 51-6241).
Publication No. 8). In other words, this method

[
Light-emitting element that can be used! Find the ratio of the absorbance for visible light of 6° optical element 2 and the absorbance for infrared light of 6° optical element 2. In this particular conventional method, the authenticity of the banknote 6 is determined by checking whether the absorbance ratio of the banknotes 6 is within a predetermined range. Since they can be matched, the spatial arrangement of each element can be easily designed. However, since a total of four elements (light-emitting element and light-receiving element) are required, it is more disadvantageous than the above-mentioned conventional example 1 in terms of space and cost when looking at the entire banknote identification device, and the number of elements used increases. There is a problem that the reliability of the detection system is further reduced. Therefore, the present invention solves the above-mentioned problems and makes it possible to detect the absorbance (reflectance or transmittance) of a specific part of a banknote using an optical system with a simple configuration. The purpose is to provide an optical identification system for banknotes, etc. with high performance and reliability. Means for Solving Problem E] To achieve this object, the present invention provides a value corresponding to the ratio or difference between the absorbance for visible light and the absorbance for infrared light at a specific location of an object to be inspected such as a banknote. In an optical identification method that determines the authenticity of a metal object by detecting the detected value and checking whether the detected value is within a predetermined range, visible light and the infrared light are simultaneously used. Absorbance is detected by combining a single light-emitting element that can emit light and a single light-receiving element that has two or more types of spectral sensitivities and can almost independently photoelectrically convert visible light and infrared light and output them to the outside. It is characterized by having an optical system configured to do so. Furthermore, the present invention is characterized in that the light emitting device is provided with an adjusting means that independently and variably adjusts the visible light and infrared light emission intensities of the light emitting element. [Function] The present invention provides at least i
It has one light-emitting element that can simultaneously emit visible light and infrared light of the fffl class, has a spectral sensitivity of at least 2 fffi class or higher, can photoelectrically convert the above-mentioned plurality of lights almost independently, and each The present invention is characterized in that an optical system is constructed by combining a single light-receiving element that can independently output the conversion result to the outside. FIG. 5 shows an example of the optical system of the present invention. 11 is visible light λ
This light-emitting element is capable of emitting mixed light of visible light λ and infrared light λ2 with one element by emitting light of visible light λ and infrared light λ2 using micro elements GPI and CP2, respectively. In addition, depending on the manufacturing method of the light emitting chip, some types of LED (light emitting diodes) emit infrared light with an intensity of several percent in addition to red light with one chip, as shown in Figure 6. Since it is known that the light emitting element 11 emits light, such an element can also be used as the light emitting element 11. Furthermore, as shown in FIG. 7, λ1. Independent micro elements P)IDI each having spectral sensitivity characteristics with a peak near the wavelength of λ2
, PH02 is one light-receiving element, and is similar to a commercially available color sensor, for example. In such an optical system configuration consisting of the light emitting element 11 and the light receiving element 12, one of the micro elements P) of the light receiving element 12
It is possible to create a light reception situation in which the light photoelectrically converted by [ID] is dominated by wavelength light of λ1, and the light photoelectrically converted by the other microelement PH02 is dominated by wavelength light of λ2. . As a result, one microchord P II 0
From the output current (or voltage) of 1, t'f is approximately equal to the absorbance (reflectance or transmittance) near the wavelength λ1 of a specific part of the banknote 6, and the other micro element PIID2 output 'Iri current (or voltage)
Therefore, it is possible to obtain a value approximately equal to the absorbance (curvature J -4' or transmittance) near the wavelength λ2 at the same specific location on the banknote 6 described above. Therefore, λ1. It is now possible to calculate a value approximately equal to the absorbance (reflectance or transmittance) ratio around the wavelength λ2, and the spectroscopic time of the absorbance (reflectance or transmittance) of a specific point on a genuine note shown in Figure 2 can be calculated. It is possible to distinguish between the spectral characteristics of absorbance (reflectance or transmittance) at the same specific point on the counterfeit counterfeit banknote, or to arrange one light-emitting element and one light-receiving element facing each other as shown in Figure 5. This can be achieved with a very simple optical system configuration. [Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the basic circuit 4 of the embodiment of the present invention. ? +Shows an outline of the construction. Here, the light emitting element 11 and the light receiving element 12 are the fifth element described above.
As shown in the figure, the element according to the present invention has a similar configuration, and an optical system (sensor system) 13 is constituted by pixel elements 11 and 12. The object to be inspected (banknote) 6 is inserted between the pixel elements 11 and 12, and is sent in the direction of the arrow X in this figure by a transport mechanism (not shown). 14 is a lighting circuit for lighting the light emitting element 11. It is preferable that the lighting circuit 14 includes a supply current adjusting means such as a variable resistor that can simultaneously emit at least one type of visible light and infrared light from the light emitting element 11 and can independently vary the emission intensity of each. . 15 is a logarithmic conversion circuit that converts each of the outputs of the light receiving elements 12 into logarithms, and 16 is a storage circuit that stores the conversion results of the logarithmic conversion circuit 15. 17 divides or subtracts the data stored in the memory circuit 16 to determine the difference between the absorbance of the ink to visible light and the absorbance of the ink to infrared light of at least iffi class at a specific location of the object to be inspected 6 such as a banknote. This is an arithmetic circuit that calculates a value corresponding to a ratio. Reference numeral 18 denotes a comparison circuit that determines whether the detected value, which is the calculation result of the calculation circuit 17, is within a predetermined range. Determine whether 6 is true or false. FIG. 8 shows a detailed circuit configuration of a banknote identification device according to an embodiment of the present invention. Figure 9 shows the first
The equivalent circuit of the above-mentioned light-receiving element 12 shown in FIG. P II 02 are photodiodes each having different spectral sensitivity characteristics, as shown in FIG. λ1. The spectral sensitivity of each of the micro elements PH01 and PH02 with a wavelength of λ2 is a
II+ a 12* a2I* a22 Also, the output current of the light receiving element 12 in FIG. 9 is 110.120
is the minute cord PIID1 when there is no inspection object 6. PH0
2, and the output current of I Il+ I 12 is the micro element P) 101. when there is an object to be inspected 6. P) is the output current of ID2. In addition, as a parameter indicating the characteristics of the light emitting element 11, the emission intensity ratio of light of 2 fffi is expressed as U (wavelength λ2
Emission intensity α2 ÷ wavelength λ, emission intensity αI). 2 as a parameter indicating the characteristics of the inspected object 6.
The transmittance ratio with respect to the wavelength of the seed is expressed as K (transmittance T1 for wavelength λ1 ÷ transmittance λ2 for length λ2). In the optical system with the above configuration, the output operation of the light receiving element 12 when there is no object to be inspected 6 is shown in the following equation (1), and the output operation of the light receiving element 12 when there is an object to be inspected is shown as follows. It is shown in formula (2). t is a constant for converting into an absolute output current of the light receiving element 12. Here, as a parameter indicating the characteristics of the light receiving element 12, X=a+++a+2+ A=(a2□÷82
2) ÷X 2f! Define class 1, microchord P II D
The output current ratio (Iz÷I +o) with and without the test object 6 regarding I, and the output current ratio (Iz÷I +o) with and without the test object 6 regarding the micro element P 1102.
The ratio F of I it: I 1Lo) is defined as in the following equation (3). This F is the detection amount of the tree method. (+), as shown in the following equation (4) from equation (2) [2< 41
4 is a function of the variation of the class. The right side of equation (4) is the 4-pass ratio for each of the two types of light at wavelengths λ1 and λ, which is necessary to distinguish the spectral characteristics of the transmittance of the afn class as shown in Figure 2. The reciprocal of I/
It is clear from the following that it is approximately equal to K. That is, assuming that the light receiving element 12 has ideal spectral sensitivity characteristics as shown in Figure 1O, (1)
, In formula (2), 812 = 821 = O, and (3)
F defined by the formula is as shown in the following formula (5). F = I / K -45) a 1
2=821" O is A-0, X-ω when considered using equation (4)
It is clear from the following equation (6) that equation (5) holds true. In other words, the smaller the parameter A and the larger the parameter X in the light receiving element 12, the closer the detection amount F defined by equation (3) becomes to l/. Therefore, when F is adopted as the detected quantity, the ratio of the transmittance (or reflectance) TI of the object to be inspected to visible light with wavelength λI and the transmittance (or reflectance) I2 of infrared light with wavelength λ2 is This is an identification method (first method) that distinguishes between three basic types of inspection objects 6 as shown in FIG. 2 using an amount approximately equal to . In addition, when the natural logarithm log of F, F, is adopted as the detection power, from the following equation (7), the absorbance of the test object 6 for visible light with wavelength λ1 and the absorbance of infrared light with wavelength λ2 are calculated. This is an identification method (second method) that optically identifies the authenticity of banknotes based on an amount approximately equal to the difference. j20gaF = j20g+oF
... (7) βoglOa In the present embodiment shown in FIG. converted to
Since it is subsequently amplified by the differential amplifier 25, the eighth
The voltage V at the 0 point in the diagram is Jl! oga(120/r
+o) or It oga(f 21/ I z
). a of II og is a scale factor determined by the amplification degree of the differential amplifier 25. Therefore, this embodiment corresponds to the second method of identifying banknotes and the like based on the above-described difference in absorbance. Hereinafter, the operating state for actually identifying banknotes will be specifically described. In FIG. 8, the light emitting element! 1 is λ1=fi80nm
, 2ff1i type light with wavelength λ2=890 nm is emitted with an appropriately adjusted intensity ratio U. Now, the object to be inspected such as banknotes 6
is being transported in the direction of arrow X by a transport mechanism 35 (details not shown). The output terminal of the logarithmic converter 20 is also connected to a comparator 24 via an anti-logarithmic converter 22, and a voltage inversely proportional to the output current of the micro element PIIDI is inputted to the comparator 24. On the other hand, the reference voltage generated by the reference generator 23 is also input to the comparator 24, and when the inspected object 6 interrupts the gap between the light emitting element 11 and the light receiving element 12, an output is generated in the comparator 24. Furthermore, while the object to be inspected 6 is being transported, the synchronous clock generator 27 generates a clock that is synchronized with the transport. The output of the comparator 24 and the clock of the synchronous clock generator 27 are input to the control section 26. First, while the object to be inspected 6 is being transported, the control section 26 controls A1 at an appropriate timing until the comparator 24 outputs an output.
0 (analog-digital) converter 28 and storage means 29 to control the differential amplifier 25 when the light emitting element 11 and the light receiving element 12 are not cut off by the object to be inspected 6.
The output data xoga (I 20/I 1°) is converted into digital data and stored in the storage means 29. Next, the control unit 26 counts the clocks input from the synchronous clock generator 27 from the time when the output is generated in the comparator 24, and the specific point p of the inspected object 6 shown in FIG. The timing of the position between the light emitting element 11 and the light receiving element 12 is detected, and at the time of detection, the A/D converter 28 and the recording (
9 means 29 to output data 11 oga(121/i++
) is converted into digital data and stored in the storage means 29. After memorizing these data,! l, 1J13 [1 means 26
waits for the output of the comparator 24 to disappear, and when the output disappears, controls the storage means 29 and the calculation means 30 to calculate the following equation (8), and stores the calculation result f in the register 31. Store in. f x Il, oga(h+/I++3-110ga
(r2o/I+o) - (8) This calculation result f is approximately equal to the difference between the absorbance for visible light at wavelength λ and the absorbance for infrared light at wavelength λ2 at point p of the inspection object 6. be. After that, the control unit 26 controls the register 31 and the subsequent comparator 32.
and the reference value supply means 33 to check whether the value of f in equation (8) is within a predetermined reference range,
If the value of f is within the reference range, a genuine note signal indicating that the bill is genuine is sent to the genuine note signal output terminal 34, and the conveyance mechanism 35 is controlled to transfer the object 6 to be inspected outside the bill recognition device. ,
For example, it is carried out into a fee delivery box. Further, if the value of f is outside the reference range, the control unit 26 controls the transport mechanism by 35 degrees.
8 control, the object to be inspected 6 is returned to the bill insertion slot and returned to the suppressor (user). In addition, in this example, explanation will be given. 'J@, we have illustrated the case of one point p as a specific location on the object 6 to be inspected, but normally the spectral characteristics of transmittance (or reflectance or absorbance) at each location on the banknote are investigated in advance. Then, a plurality of positions unique to the banknote are found, and the calculation of equation (8) is repeated to determine whether the banknote is genuine or false. Moreover, if the differential amplifier 25 is replaced with a signal switching means in FIG. 8, I IO+ I II+ I 20
Since the logarithmically converted value of each of , it is possible to optically identify the authenticity of banknotes. ,...=L 蒀肚二り姐辻二 ,...(9)11
0gal 110gal+a Also, each micro element CPI of the light emitting element 11 in FIG. If the lighting circuit 14 is configured so that the current value supplied to CF2 can be independently and variably adjusted using a variable resistor or the like, the light emission intensity of each micro element (:Pl, (:P2) can be independently and variably adjusted. Therefore, by adjusting the light emitting element 11
The mixing ratio of the plurality of mixed lights emitted from the light emitting element 1
It becomes possible to always maintain a constant value regardless of changes over time or variations in characteristics of the banknote, even in a plurality of banknote identification devices. Thereby, it is possible to provide an optical identification device for banknotes and the like in which the influence of variations in light emitting elements is eliminated using an extremely simple optical system. That is, as the light emitting element 11, one such as an LED is used which emits visible light having a wavelength λ and infrared light having a wavelength λ having an intensity ratio of about several %. Therefore, since U in equation (4) has a certain band, the detection fiF
Also, a corresponding band is generated. This relationship is shown in FIG. In FIG. 12, P2 is the relationship between F and U at a specific location of a genuine note, and Pl+P3 is the relationship between F and U of a color copy fake note and a black and white copy fake note, respectively. ΔU is the variation in the light emitting elements, and ΔN is the color copy counterfeit note (P
ΔF2 is the band of detection iF for the genuine note (P
2) is the band of the detected amount F for the specific location,
ΔF3 is the band of the detection amount F for the black and white copy counterfeit note (P3). In order to determine the authenticity of banknotes, etc., a predetermined range of Fs is set by taking into account the above-mentioned ΔF2 to the dispersion of detected fiF at a specific location of a genuine banknote, but the upper limit of the range of ΔU is Among a plurality of banknote identification devices using light-emitting elements 11 located at the lower limit value, there are cases where the banknotes deviate from the predetermined range Fs in FIG. There will be a difference in probability. This is the above-mentioned F
The circumstances are the same regardless of whether 11 ogaF or 11 ogaF is used, and when using the light emitting element 11 as described above, it is necessary to electrically control visible light with wavelength λ and infrared light with wavelength λ2. Since this is not possible, there are some unavoidable problems. Therefore, as described above, the mixing ratio of the mixed light of the visible light λ1 and the infrared light λ2 of the light emitting element 11 is made variable by the lighting circuit I4. For example, if an object with a suitable chromatic color (test vapor) is used as a mask and the optical system is adjusted so as to always obtain a constant detection -mFc with respect to this mask, the two types of light from the light emitting element 11 It becomes possible to ensure that the emission intensity ratio is always at the position Us in FIG. This makes it possible to optically identify banknotes and the like using a simple optical system with one light-emitting element 11 and one light-receiving element 12, and which is not affected by variations in the light-emitting elements. [Effects of the Invention] As explained above, according to the present invention, in a detection system for spectral characteristics of absorbance (reflectance or transmittance) of an object to be inspected such as a banknote, a single unit that can simultaneously emit light of a plurality of wavelengths is used. The optical system is composed of a light-emitting element and a light-receiving element that has multiple spectral sensitivity characteristics and whose outputs can be taken out independently. An optical system consisting of a plurality of light-emitting elements, a plurality of optical filters, or a plurality of light-receiving elements required for this is the purest optical system with one light-emitting element and one light-receiving element, and therefore In addition to making it extremely easy to design the spatial arrangement of the optical system, there are also advantages in terms of space. Furthermore, according to the present invention, the price of the above-mentioned light-emitting element and light-receiving element used in the present invention is almost the same as the price of conventionally used elements, so the detection system can be provided at a lower price than in the past. At the same time, the reliability of the detection system is improved by using fewer elements. Furthermore, in the present invention, by making it possible to adjust the sensitivity of the optical system consisting of a light emitting element and a light receiving element, it is possible to eliminate the influence of element variations on authenticity identification.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the basic circuit configuration of an embodiment of the present invention, Fig. 2 is a waveform diagram showing the spectral characteristics of transmittance at specific points in genuine notes and counterfeit notes, and Fig. 3 is a diagram of the conventional detection system. FIG. 4 is a schematic diagram showing the configuration of another conventional detection system. FIG. 5 is a schematic diagram showing the configuration of an optical system according to an embodiment of the present invention. FIG. FIG. 7 is a waveform diagram showing an example of the emission spectrum of the light emitting element; FIG. 7 is a waveform diagram showing an example of the spectral sensitivity characteristics of the light receiving element of the embodiment shown in FIG. 5; FIG. FIG. 9 is an equivalent circuit showing the output current of the light receiving element of the embodiment of the present invention, FIG. 10 is a waveform diagram showing the ideal spectral sensitivity characteristics of the light receiving element of FIG. 9, and FIG. 11 is the main FIG. 12 is a front view showing an example of the inspection point of the object to be inspected in the embodiment of the invention. FIG. 12 is a waveform diagram showing an example of the FU characteristics of genuine notes and counterfeit notes. 6... Detected object (banknote), 11... Light emitting element 12... Light receiving element 13... Optical system (sensor system), 14... Lighting circuit 15... Logarithmic conversion circuit 16. ...Storage circuit 17...Arithmetic circuit 18...Comparison circuit 19...Signal processing circuit (detection system) 20.21...Logarithmic converter 22...Anti-logarithm converter 23...Reference generation 24... Comparator 25... Differential amplifier 26... Control section 27... Synchronous clock generator 28... /D converter 29... Storage means 30... (countable means 31...Register, 32...Comparator, 33...Reference value supply means 34...Genuine bill signal output terminal long distance (yon) Fig. 2 Conventional diagram showing spectral properties and tits of specific points Figure 3: The insects that make up the seven detection systems of Cong. Figure 5: Prize of Shisuke 11, Kabuto Heji's Empress, Su Duke 7, Child 11's death, father Figure 6, Unshi I 1, Girl child, Motoko's child support 4, Slipperiness Waveform diagram of 911 Figure 7 ★ Shiiku 1 ('s Uke Motoko's etc. 4 verses Figure 9 Broken length (1m) Prize dissection of the girl Motoko's theory 1.!, target y, Bunji Hachihiq thousand r1
Figure 1 θ Diagram 1 of the 4 skins of the Unkari Formation fil. Figure 12 of the 3 good forms for special 1st graders

Claims (1)

[Claims] 1) a) A value corresponding to the ratio or difference between the absorbance for visible light and the absorbance for infrared light at a specific location of an object to be inspected such as a banknote is detected, and this detected value is set in advance. In an optical identification method that determines the authenticity of the object by checking whether the object is within a predetermined range, b) a single light emitting device capable of emitting the visible light and the infrared light simultaneously; and c) a single light-receiving element that has two or more types of spectral sensitivities and photoelectrically converts the visible light and the infrared light almost independently and outputs the same to the outside to detect the absorbance. An optical identification method for banknotes, etc., characterized by comprising an optical system. 2) A banknote, etc. according to the method described in claim 1, characterized in that the method includes an adjusting means for independently and variably adjusting the emission intensity of the visible light and the infrared light of the light emitting element. optical identification method. 3) The method according to claim 1 or 2, comprising: a logarithmic conversion circuit that converts the output of the light receiving element into a logarithm; a storage circuit that stores output data of the conversion circuit; and the storage. The detection system is characterized by comprising a calculation circuit that calculates the detected value based on data stored in the circuit, and a comparison circuit that determines whether the calculation result of the calculation circuit is within the predetermined range. Optical identification method for banknotes, etc.