JPH0816942B2 - Paper sheet inspection device with built-in thread - Google Patents

Description

Description: [Industrial field of use] The present invention relates to an apparatus for inspecting a paper sheet with a built-in thread, which is for judging the authenticity of a paper sheet with a built-in thread.

[Conventional technology]

In the Middle East and countries of the former British colonies, so-called thread-embedded bills, in which metal or plastic is inserted between papers, are in circulation.

In these countries, it is determined whether the bill is a genuine bill or a counterfeit bill by detecting the presence or absence of a thread of bills. As an apparatus for automatically determining the authenticity, for example, a magnetic sensor is used. It has been known. This device has a magnetic sensor placed in the bill passage of a money changer or an automatic ticket vending machine, and detects a magnetic change that occurs when a metal thread of a magnetic material contained in a bill passes through the magnetic sensor to detect a thread. The presence or absence of the bill is discriminated, and the authenticity of the bill is judged.

[Problems to be Solved by the Invention]

As mentioned above, it is possible to judge the authenticity of banknotes fairly accurately for banknotes with a built-in metal thread, but for banknotes with a built-in plastic thread, use a magnetic sensor. However, there is a situation in which it is not possible to accurately detect the authenticity because no powerful automatic machine for authenticity can be found at present. Under such circumstances, it has been considered that an inspection device for a paper sheet with a built-in thread, which can handle both a bill with a metal thread and a bill with a plastic thread, is almost impossible.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is a paper sheet containing any of a metal thread and a plastic thread,
An object of the present invention is to provide an inspection device for a paper sheet with a built-in thread, which can accurately determine the presence or absence of the thread.

[Means for solving the problem]

The present invention is configured as follows to achieve the above object. That is, the device of the present invention includes, firstly, a detection electrode arranged in a passage path of a paper sheet in which a thread is incorporated; an oscillation circuit that outputs a fixed oscillation frequency signal; and a resonator of this oscillation circuit. Has a separate and independent resonator and changes the resonance frequency tuning point with respect to the fixed oscillation frequency signal in response to a change in capacitance detected by the detection electrode, and responds to the change in the tuning point. An electrostatic sensor circuit having a tuning circuit that outputs a detection signal; and an authenticity determination circuit that analyzes the signal from the electrostatic sensor circuit and determines the presence or absence of a thread on the paper sheet. Secondly, the device of the present invention secondly includes at least first and second detection electrodes which are arranged in front of and behind the passage path of the sheet in which the sled is incorporated; The output oscillator circuit The resonator has a resonator independent of the resonator of the oscillation circuit, and changes the tuning point of the resonance frequency with respect to the fixed oscillation frequency signal in response to a change in capacitance detected by the first detection electrode. A first electrostatic sensor circuit having a tuning circuit that outputs a detection signal corresponding to a change in the tuning point; and a second electrostatic electrode having the same configuration as that of the first electrostatic sensor circuit. A second electrostatic sensor circuit that outputs a detection signal corresponding to a change in the tuning point in response to a change in the electrostatic capacitance detected by; and a signal from the first electrostatic sensor circuit and a second electrostatic sensor An output circuit that outputs a signal of the difference between the signals from the circuit; and an authenticity determination circuit that analyzes the signal from the output circuit and determines the presence or absence of a thread of the paper sheet;

[Action]

According to the present invention, when a paper sheet with a built-in thread passes through the detection electrode, when the position of the paper sheet facing the detection electrode moves from the part without the thread to the part with the built-in thread, Due to the difference in the dielectric constant of the portion, the electrostatic capacitance detected by the detection electrode changes significantly, and this change in electrostatic capacitance is added to the tuning circuit of the electrostatic sensor circuit. The tuning circuit changes the tuning point of the fixed oscillation frequency signal from the oscillation circuit and the resonance frequency in response to the change of the electrostatic capacitance, and outputs the voltage signal corresponding to the change of the tuning point. Then, the signal output from the electrostatic sensor is added to the authenticity determination circuit. The authenticity determination circuit determines, for example, whether or not the change width of the capacitance matches the width of the thread to determine the authenticity of the paper sheet.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of a first embodiment of the present invention. The device according to the present embodiment includes an electrode detection unit 1, an electrostatic sensor circuit 2, an A / D conversion circuit 3, and an authenticity determination circuit 4. The electrode detection unit 1 is composed of a detection electrode 14 formed of a conductor plate or a conductor needle and a ground electrode 15 of the conductor plate. The ground electrode 15 and the detection electrode 14 pass through a paper sheet passage 30 containing a metal or plastic thread 29. In the upper and lower position across, that is, the paper sheet
They are opposed to each other with a passage gap of 30. In this specification, "paper leaf" includes not only banknotes but also securities such as checks and tickets, and the "paper" of paper leaf is used in a broad concept including not only pulp but also films such as plastics. ing.

As shown in FIG. 2, the electrostatic sensor circuit 2 includes an oscillation circuit 6, a tuning circuit 7, a detection circuit 11, an amplification circuit 5, and
And an AFC (Automatic Frequeny Control) circuit 9.

The oscillation circuit 6 uses a ceramic resonator 10 that oscillates at a fixed and constant ultra-high frequency oscillation frequency within the range of 1 GHz to 10 GHz, and in this embodiment, an oscillation frequency of 1 GHz. The oscillating circuit 6 oscillates the high-frequency oscillating frequency signal and applies it to the tuning circuit 7 via the high impedance converting circuit 6a. The tuning circuit 7 is composed of a ceramic resonator 12, and the detection electrode 14 of the electrode detection unit 1 is connected to the output electrode side of the ceramic resonator 12. In addition,
The ground electrode 15 is connected to the ground side (ground side) of the ceramic resonator 12.

The ceramic resonator 12 has a resonance frequency characteristic as shown in FIG. 3, and the fixed oscillation frequency f _OSC of the oscillation circuit 6 is slightly displaced from the resonance frequency f ₂ of the ceramic resonator 12. Is set. The resonance frequency f ₂ of the ceramic resonator 12 is the electrodes 14, 1 detected by the electrode detector 1.
The capacitance fluctuates in accordance with the change in the electrostatic capacitance between 5 and, for example, when the capacitance C changes by ΔC, the resonance frequency f ₂ is biased to f ₁ . Since the oscillation frequency of the oscillation circuit 6 is fixed to f _OSC , the output voltage of V _{2 at} the tuning point A ₂ is sent from the ceramic resonator 12 when there is no capacitance change, but the capacitance change is ΔC. Then, the resonance frequency deviates to f ₁ , the tuning point changes from A ₂ to A ₁ , and the ceramic resonator 12 outputs the output voltage of V ₁ . Thus, the electrodes 14,15
The resonance frequency of the ceramic resonator 12 is deviated in accordance with the change in the capacitance between them, and the output voltage V corresponding to the change in the capacitance is transmitted from the ceramic resonator 12 accordingly.

The detection circuit 11 is connected to the ceramic resonator 12 via a coupling capacitor 25, and this detection circuit 11 is composed of an inductance element 21, a diode 22, a capacitor 23, and a resistor 24, and the ceramic Resonator
The output signal from 12 is detected via the coupling capacitor 25.
It is supposed to be added to 11. The diode 22
The capacitor 23 and the resistor 24 form a detection unit of the detection circuit 11, and the inductance element 21 and the capacitor 25 function as a high impedance circuit. This detection circuit 11 envelope-detects an ultrahigh frequency output signal (image signal) output from the ceramic resonator 12, converts it into a signal in a signal band for thread detection, and applies it to the amplifier circuit 5 and the AFC circuit 9.

The amplifier circuit 5 is configured by using elements such as a transistor 27 and a resistor, and the amplifier circuit 5 amplifies the signal applied from the detection circuit 11 and sends it to the A / D converter 3.

The AFC circuit 9 prevents the tuning point of the tuning circuit 7 from deviating from the setting region due to the influence of environmental changes and the like, and optimizes the resonance frequency of the ceramic resonator 12.

The A / D conversion circuit 3 converts the analog signal applied from the amplifier circuit 5 into a digital signal and applies it to the authenticity determination circuit 4. The authenticity determination circuit 4 is composed of a logic circuit,
The signal applied from the A / D conversion circuit 3 is analyzed to determine the authenticity of the paper sheet 30 passing through the electrode detection unit 1. For example,
When the paper sheet 30 passes through the electrode detection unit 1, the paper sheet portion without the thread 29 passes through the thread 29 portion more than when the paper sheet portion passes between the detection electrode 14 and the ground electrode 15. The permittivity between the electrodes 14 and 15 is increased, and a large change in capacitance appears in the thread 29, and a signal corresponding to the change in capacitance is applied to the authenticity determination circuit 4. The authenticity determination circuit 4 outputs a genuine bill signal when the variation width of the electrostatic capacitance falls within an allowable setting range which is a criterion for determining the width of the thread 29, and outputs a suspicious bill signal when the variation range deviates from the allowable setting range. Output.

The first embodiment is configured as described above,
The operation will be described below.

First, as shown in FIG. 3, the detection electrode 14 and the ground electrode 15
With no paper sheet 30 passing between
The fixed oscillation frequency f _OSC of the oscillation circuit 6 is set at a position slightly deviated from the 12 resonance frequencies (tuning frequency) f ₂ . At this time, the ceramic resonator 12 outputs a constant voltage of V ₂ . In this state, the paper sheet 30 is placed on the passage 8 of the paper sheet 30.
When a sheet of paper is sent between the electrodes 14 and 15 without the thread 29, the dielectric constant between the detection electrode 14 and the ground electrode 15 increases, and the capacitance changes. Due to this slight change in capacitance, the resonance frequency of the ceramic resonator 12 is deviated from f ₂ to f ₁ with respect to the oscillation frequency f _OSC of the oscillation circuit 6,
The tuning point moves from A ₂ to A ₁ and the ceramic resonator 12 to V ₁
Is output. In this state, when the thread 29 portion enters between the electrodes 14 and 15, the dielectric constant between the electrodes 14 and 15 further increases, the electrostatic capacitance between the electrodes 14 and 15 further changes, and the ceramic resonator 12 The resonance frequency deviates to f ₀ , the tuning point shifts from A ₁ to A ₀ , and the ceramic resonator 12 outputs a voltage of V ₀ .

The ceramic resonator 12 produces an AM (Amplitude Modulation) modulated wave based on these changes in the output voltage, and applies this to the detection circuit 11 as a detection signal. That is, the ceramic resonator 12 multiplies the oscillation frequency f _OSC by the resonance frequency change component Δf detected by the detection electrode 14 to obtain an AM modulated wave. In this embodiment, since the oscillation frequency f _OSC is 1 GHz, the detection signal as the modulated wave is centered at 1 GHz and becomes an ultra-high frequency signal having a bandwidth corresponding to the presence or absence of the thread 29. A high frequency signal is applied to the detection circuit 11.

The detection circuit 11 performs envelope detection on this ultrahigh frequency signal to convert it into a signal band for thread detection. A part of the band-converted signal is sent to the next amplifier circuit 5, and another part of the signal is branched and supplied to the AFC circuit 9. The amplifier circuit 5 amplifies the detected output and adds it to the A / D conversion circuit 3. Further, the AFC circuit 9 corrects that the tuning point of the ceramic resonator 12 deviates from the set range due to disturbance such as environmental change, and adjusts the tuning point to the optimum position in the linear region where the gain of the resonance frequency curve is high.

The A / D conversion circuit 3 converts the analog signal applied from the amplifier circuit 5 into a digital signal and applies it to the authenticity determination circuit 4. The authenticity judgment circuit 4 is based on the signal added from the A / D conversion circuit 3 and is true when the detection signal width of the thread 29 is included in a preset allowable range which is a judgment criterion of the presence or absence of the thread. It is determined that the bill is a bill, a genuine bill signal is output, and when the bill is out of the allowable setting range, the bill is determined to be a suspicious bill, and a suspicious bill signal is output.

According to this embodiment, the thread 29 with a built-in paper sheet is detected by the electrode detection unit 1 as a change in capacitance, and the change in tuning point of the ceramic resonator 12 is utilized in response to the change in capacitance. Since a detection signal is obtained, it is possible to detect an extremely small change in capacitance of 1 × 10 ^-5 PF with high sensitivity, and whether the thread 29 is made of metal or plastic is used. Whether it is a thread or not, it is possible to accurately detect the presence or absence of the thread 29, and it becomes possible to accurately determine the authenticity of the paper sheet of the metal thread and the paper sheet of the plastic thread with one device. It is very convenient.

FIG. 4 shows a second embodiment of this embodiment.
In the second embodiment, a pair of electrode detecting portions 1a and 1b and a pair of electrostatic sensor circuits 2a and 2b are provided in front of and behind the passage 8 of the paper sheet 30 with built-in sled, and the first electrode detecting portion is provided. The first electrostatic sensor circuit 2a processes the change in the electrostatic capacitance of 1a, and the second electrostatic sensor circuit 2b processes the change in the electrostatic capacitance detected by the second electrode detection unit 1b. It is composed. And
The output signal of the first electrostatic sensor circuit 2a and the output signal of the second electrostatic sensor circuit 2b are guided to a differential amplifier 17 as an output circuit, and the differential amplifier 17 obtains the difference between both output signals.
This is amplified and added to the A / D conversion circuit 3, and other configurations are the same as those in the first embodiment.
In the second embodiment, the distance between the electrode detectors 1a and 1b is set smaller than the width of the thread 29, and the thread material is also taken into consideration so that an appropriate detection signal can be obtained. .

In the second embodiment, when the paper sheet 30 with the built-in sled is sent along the passage route 8, when the tip A of the sled 29 comes directly below the first detection electrode 14a, The change in capacitance between the detection electrode 14a and the ground electrode 15 is the first
Since the change in the capacitance is not detected in the electrode detection unit 1b, the differential output of the detection signals from both the detection electrodes 14a and 14b is negative as shown in FIG. Appears as a peak S ₁ protruding at. Next, when the tip A of the thread 29 comes directly under the second detection electrode 14b, similarly,
The change in capacitance is detected by the second detection electrode 14b. Since the component of change in capacitance is the same as the capacitance detected by the first detection electrode 14a, its differential output is 0, and the pulse S ₁ falls in the positive direction. further,
When the sheet 30 moves in the traveling direction and the rear end B of the sled 29 passes the detection electrode 14a, the electrostatic capacitance detected by the first detection electrode 14a changes, and the differential output of the differential amplifier 17 Is the fifth
The pulse waveform S ₂ rises up in the figure, and the pulse waveform S rises when the rear end B of the thread 29 passes by the second detection electrode 14b.
_{It is} a fall of ₂ . By analyzing the peak voltage and the peak interval of S ₁ and S ₂ of this pulse waveform, the presence or absence of the thread 29 can be accurately obtained.

According to the second embodiment, the capacitance change component due to the environmental change detected by the first detection electrode 14a and the capacitance change due to the environmental change detected by the second detection electrode 14b. The difference between the component and the component is canceled when the signal difference is obtained by the differential amplifier 17, and the presence or absence of the thread can be detected more accurately without being affected by the environmental change.

FIG. 6 shows a third embodiment of the present invention. The third embodiment differs from the second embodiment in that a pair of electrode detectors 1c and 1d are provided in a direction orthogonal to the traveling direction of the paper sheet 30, and the third electrode detector 1c is provided. Third detection electrode
The third electrostatic sensor circuit 2c processes the change in the electrostatic capacitance detected by 14c so that the change in the electrostatic capacitance detected by the fourth detection electrode 14d of the fourth electrode detection unit 1d is changed to the first value. 4 is configured to be processed by the electrostatic sensor circuit 2d. Then, similarly to the case where the differential output of the first and second electrostatic sensor circuits 2a and 2b is obtained by the differential amplifier 17a, the differential amplifier 1
At 7b, the difference between the signals from the third and fourth electrostatic sensor circuits 2c and 2d is obtained, amplified, and added to the authenticity determination circuit 4 via the A / D conversion circuit 3.

In the third embodiment, information such as wrinkles and tears formed on the paper sheet 30 is detected by the detection electrodes 14c and 14d, and the difference is obtained after passing through the third and fourth electrostatic sensor circuits 2c and 2d. This is obtained as a dynamic output, and the A / D conversion signal of this differential output is added to the authenticity judgment circuit 4. The authenticity determination circuit 4 receives the information such as wrinkles and tears to detect the detection electrodes 14a and 14a.
It is possible to ensure its accuracy in making the authenticity judgment based on the signal applied from the b side. For example, when there is no factor such as wrinkles or tears in the paper sheet 30, changes in capacitance detected by the detection electrodes 14c and 14d are the same, and the signal output from the differential amplifier 17b is 0. On the other hand, if the paper sheet 30 has wrinkles or tears, the electrostatic capacitances detected by the detection electrodes 14c and 14d are different from each other, and the signal corresponding to the difference is converted into a digital signal to the authenticity determination circuit 4. Added. The authenticity determination circuit 4 analyzes the magnitude of the input signal and the temporal change of the signal, detects that the paper sheet 30 has wrinkles or tears, and detects this wrinkle or tear information from the detection electrodes 14a, 14b series. In addition to the determination element for the presence or absence of the thread 29 based on the signal, it is possible to accurately determine the presence or absence of the thread without being disturbed by factors such as wrinkles and tears.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and various modes of implementation can be adopted. For example, in each of the above-described embodiments, the resonator of the oscillation circuit 6 and the resonator of the tuning circuit 7 in the electrostatic sensor circuit are made of ceramic resonators, but they may be made of other resonators such as strip lines. Good.

Further, in each of the above embodiments, the authenticity determination circuit 4 is configured by a logic circuit (logic determination circuit), but the A / D conversion circuit 3 may be omitted and the authenticity of the thread may be determined by processing an analog signal. Good.

Further, in the third embodiment, the first and second electrode detectors 1a and 1b are combined into a set, and the third and fourth electrode detectors 1c and 1d are formed.
However, the combination of the electrode detection units is arbitrary, and for example, the first and third electrode detection units 1a and 1c are set as one set, and the second and fourth electrode detection units 1b and 1d are combined. It may be a set. In the third embodiment, the third and fourth electrode detectors
Although 1c and 1d are provided in a direction orthogonal to the traveling direction of the paper sheet 30, they may be arranged obliquely with respect to the traveling direction.

Furthermore, in each of the second and third embodiments described above, the independent oscillation circuit 6 is used for each electrostatic sensor circuit.
An oscillation frequency signal may be applied to the tuning circuit 7 of each electrostatic sensor circuit from each oscillation circuit via a distributor.

〔The invention's effect〕

The present invention detects the presence or absence of a thread in a paper sheet with a built-in thread as a change in electrostatic capacitance using a detection electrode, and this change in electrostatic capacitance tunes the resonance frequency of the tuning circuit with respect to the fixed oscillation frequency of the oscillation circuit. Since it is configured to obtain, for example, an AM modulated signal based on the change of the point, it becomes possible to detect the change of the minute electrostatic capacitance with ultra-high sensitivity, and it is possible to accurately detect the presence or absence of the thread with built-in paper. Can be detected. In addition, the device of the present invention is very convenient in use because it can accurately detect both the thread made of metal and the thread made of plastic with one device.

Further, the device of the present invention has a simple device configuration and a small size, and it is possible to provide the device of the present invention having excellent performance at low cost. Further, at least the first and second
According to the present invention, which is configured by providing the detection electrode of No. 3, the change component of the capacitance due to the environmental change detected by the first detection electrode and the capacitance due to the environmental change detected by the second detection electrode Of the thread is canceled when the difference between the signals is obtained by the output circuit, and the presence or absence of the thread can be detected more accurately without being affected by the environmental change.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing a first embodiment of a paper sheet inspection device with a built-in thread according to the present invention, and FIG. 2 is a circuit diagram showing an example of an electrostatic sensor circuit constituting the device of the present invention. FIG. 3 is an explanatory diagram showing the operation of the tuning circuit of the circuit of FIG. 2, FIG. 4 is a structural explanatory diagram showing a second embodiment of the present invention, and FIG. 5 is an explanation of differential output waveforms in the same embodiment. FIG. 6 and FIG. 6 are configuration explanatory views showing a third embodiment of the present invention. 1,1a, 1b, 1c, 1d …… Electrode detector, 2,2a, 2b, 2c, 2d …… Electrostatic sensor circuit, 3 …… A / D conversion circuit, 4 …… Authenticity judgment circuit, 5 …… Amplification circuit, 6 ... Oscillation circuit, 6a ... High impedance conversion circuit, 7 ... Tuning circuit, 8 ... Passage path,
9 ... AFC circuit, 10 ... Ceramic resonator, 11 ... Detection circuit, 12 ... Ceramic resonator, 14, 14a, 14b, 14c, 14d ...
… Detection electrode, 15 …… Ground electrode, 17,17a, 17b …… Differential amplifier, 21 …… Inductance element, 22 …… Diode, 23
...... Capacitor, 24 ...... Resistor, 25 ...... Coupling capacitor, 27 ...... Transistor, 29 ...... Thread, 30 ...... Paper sheet.

Claims (2)

[Claims] 1. A detection electrode disposed in a passage path of a sheet containing a thread; an oscillation circuit for outputting a fixed oscillation frequency signal; and a resonator independent of the resonator of the oscillation circuit. A tuning circuit that changes the tuning point of the resonance frequency with respect to the fixed oscillation frequency signal in response to a change in capacitance detected by the detection electrode, and outputs a detection signal corresponding to the change in the tuning point. And an electrostatic sensor circuit having:
An apparatus for inspecting a paper sheet with a built-in thread, comprising: an authenticity determination circuit for analyzing the signal from the electrostatic sensor circuit to determine the presence or absence of a thread on the paper sheet. 2. At least first and second detection electrodes which are arranged in front of and behind a paper path in which a thread is built; an oscillation circuit which outputs a fixed oscillation frequency signal, and an oscillation circuit of this oscillation circuit. The resonator has a resonator independent of the resonator and changes the tuning point of the resonance frequency with respect to the fixed oscillation frequency signal in response to a change in capacitance detected by the first detection electrode, and tunes the resonance frequency. A first electrostatic sensor circuit including a tuning circuit that outputs a detection signal corresponding to a change in point;
A second electrostatic sensor which has the same configuration as the first electrostatic sensor circuit and outputs a detection signal corresponding to the change of the tuning point in response to the change of the electrostatic capacitance detected by the second detection electrode. A sensor circuit; an output circuit that outputs a signal of the difference between the signal from the first electrostatic sensor circuit and the signal from the second electrostatic sensor circuit; And an authenticity determination circuit for determining the presence or absence of a thread.