RU2122236C1 - Device for checking validity of bank notes - Google Patents

Abstract

FIELD: bank equipment. SUBSTANCE: device operations are based on capacitance method for detection of faked bank notes. Level of dielectric permeability of paper of tested bank note is preliminary checked against preset tolerance range for values of dielectric permeability. In addition method takes into account dielectric permeability of air in order to exclude influence of environment. Device provides optimal shape of measuring electrode of capacitance detector. EFFECT: increased reliability of detection, simplified operations in dynamic mode which involves simultaneous counting and checking of bank notes. 1 dwg

Description

 The present invention relates to the field of banknote authentication devices and can be used in banks, shops and other organizations where a solution to the problem of detecting counterfeit banknotes is required.

 The closest analogue to the claimed is a device for determining the authenticity (WO 89/08898, G 07 D 7/00, 09/21/89).

 A known banknote authentication device is based on a capacitive detection method. The essence of the method is that the capacitance sensor measures the dielectric constant of banknotes in the watermark region, compares the value of the measured value with a pre-selected threshold value and takes it as a true banknote in which the dielectric constant in the zone of the watermark is above the threshold value.

 The known device contains two measuring electrodes, a capacitive bridge and a threshold device, and a signal extraction device. In this case, the measuring electrodes are made round, in the shape of a watermark and the dimensions correspond to the dimensions of the watermark on the banknote.

 The specified device has a number of disadvantages, which may include: detection of counterfeit banknotes is not performed if the dielectric constant of the counterfeit banknote is higher than the dielectric constant of the banknote section with a watermark; the accuracy of the method is affected by external conditions - temperature, humidity, etc .; when such a device operates in dynamic mode under banknote counting conditions with simultaneous detection, it is difficult to combine watermarks on the banknote with the round electrodes of the capacitive sensor. In addition, various banknotes have watermarks in different parts of the banknote, which creates additional difficulties.

 The technical result of the invention is the creation of a device for recognizing the authenticity of banknotes, which eliminated these disadvantages of the prototype.

 The technical result is achieved by the fact that in the device for determining the authenticity of banknotes containing two electrodes, one of which is isolated from the housing and the other is electrically connected to it, a signal extraction device and a threshold device, a second threshold device, an analyzing device, and a device for determining the absence of banknotes are introduced between the electrodes, a memory device and a summing device, and the insulated electrode has the shape of a rectangle, one of whose sides is commensurate with the length of the protective thread of the banknote, the output of the device for determining the absence of banknote is connected to the input of the signal extraction device, the outputs of which are connected to the memory device and one of the inputs of the summing device, to the second input of which the output of the memory device is connected, and the output of the summing device is connected to the inputs of the first and second threshold devices, the outputs of which connected to the analyzing device.

In this case, the capacitance sensor, as in the prototype, measures the dielectric constant of the paper from which the banknote is made, but the measurements are carried out only in the area of the banknote on which a metallized dotted or solid security thread is applied. To determine the authenticity of banknotes, two threshold values of the dielectric constant are preselected - the lower threshold corresponding to the lower limit of the dielectric constant of the banknote in the section on which the thread is applied, U _lower. and upper, corresponding to the upper limit, U _top . These values are chosen empirically during experiments. The portion of the banknote on which measurements are made is selected in the region of the security thread, because it is characterized by a stable and sufficiently high level of dielectric constant.

 After measuring the dielectric constant of the banknote, the magnitude of the measured signal is compared with the values of two threshold levels and taken as a genuine banknote, the dielectric constant of which in the area of the protective thread is in the range between the first and second threshold values.

To exclude the influence of environmental parameters on the reliability of determining the authenticity of banknotes, measurements are made as follows. The time intervals when there are no banknotes in the capacitive sensor are determined. At these time intervals, the dielectric constant of the gap between the electrodes is measured and the measured signal value U _vozd.pr. Then, when the banknote is between the electrodes of the capacitive sensor, the dielectric constant of the banknote U banknote is _measured . In this case, the measured signal will consist of two components: U _air.pr , which characterizes the air gap, and U _banknote , which characterizes the banknote. Before comparing the measured signal with the threshold values U _lower and U _upper , from this measured signal subtract the U _air signal measured in the capacitive sensor when there are no banknotes in it. Because the measurement time is short, then during this time the surrounding conditions - temperature, humidity, etc. do not change. As a result of this, after subtracting the signal U _air from the measured signal for comparison with threshold values, the signal U _banknote , free from environmental influences, will be received.

 A device for implementing the method of determining the authenticity of banknotes is shown in the drawing and contains a measuring electrode 1 isolated from the housing (earth), a grounded electrode 2, a signal extraction device 3, a first threshold device 4, a second threshold device 5, an analyzing device 6, an intermittent or solid protective thread 7, banknote 8, a device for determining the absence of banknotes 9, a memory device 10, a summing device 11.

 The device consists of two rigidly fixed electrodes 1 and 2 located with an air gap above each other. The upper measuring electrode 1 is isolated from the housing, and the lower 2 is connected to the housing (ground). The device also includes a signal isolation device 3, two threshold devices 4 and 5, and an analysis device 6. The upper measuring electrode 1 has the shape of a rectangle, one of whose sides is comparable with the length of the security thread 7 of banknote 8, and a device for determining the absence of banknotes 9 between the electrodes 1 and 2, a memory device 10 and an adder 11.

 The operation of the device is as follows.

 Banknotes 8 with a security thread 7, one by one, enter the gap between the electrodes 1 and 2, which together with the signal extraction unit 3 form a capacitive sensor. In the initial state, the capacitive circuit is balanced. When money ticket 8 passes between the electrodes 1, 2, the dielectric constant of the banknote section is measured, on which a protective dotted or solid thread 7 is applied and which is characterized by a stable and fairly high level of dielectric constant. An imbalance signal is supplied to the signal isolation device 3 from the electrodes, the amplitude of which is proportional to the change in capacitance formed by the electrodes 1, 2. Depending on the quality of the banknote being checked, the capacitance and, accordingly, the amplitude of the signal arriving at block 3 are changed.

 To facilitate the measurement of the dielectric constant of the banknote 8 in the area of the security thread 7 and increase the reliability of detection of banknotes, the insulated electrode 1 is structurally made in the form of a rectangle, one of whose sides is comparable with the length of the security thread.

 From the signal extraction device 3, the measuring signal is fed to the inputs of threshold devices 4, 5, tuned to two different threshold signal levels. The dielectric constant of the paper from which genuine banknotes are made, measured in the area of the security thread, is enclosed in a certain range of values. One threshold device is set to a threshold signal level corresponding to the lower boundary of the specified range, and the other to a threshold value corresponding to the upper limit of the range. The measuring signal through the threshold devices 4, 5 enters the analyzing device 6, which compares the signal of the capacitive sensor with the first and second threshold values. If the value of the signal from the checked banknote falls into the range between the upper and lower threshold levels, then the banknote is considered genuine, otherwise - false. The device for determining the authenticity of banknotes introduced a device for determining the absence of banknotes 9, a memory device 10, a summing device 11.

 The moment of absence of banknotes in the gap between the electrodes 4, 5 is fixed by the device 9, the signal of which measures the dielectric constant of the air gap of the capacitive sensor. The measuring signal from the signal isolation device 3 is supplied to the memory device 10, which stores it. At the moment of passing the banknote through the electrodes 1, 2, the dielectric constant of the banknote is measured in the area of the security thread 7. The measuring signal is sent from the signal extraction device 3 of the capacitive sensor to the summing device 11, where a signal proportional to the dielectric constant of the air gap of the capacitive sensor is subtracted. coming from the memory device 10 to another input of the summing device 11. As a result, the threshold devices 4, 5 and further analyzing device Property 6, a signal is received characterizing the dielectric constant of the banknote itself in the area of the protective thread and free from environmental influences. Further, the operation of the device is similar to that described above.

 The advantages of the described method and device for determining the authenticity of banknotes include the following.

 By introducing a range of variation in the possible dielectric constant of genuine banknotes in the area of the security thread location, the detection reliability is increased.

 Due to the exclusion of the influence of environmental parameters increases the reliability of detection of counterfeit banknotes.

 Due to the execution of the measuring electrode of the capacitive sensor in the form of a rectangle, one of whose sides is commensurate with the length of the protective thread, the process of measuring the dielectric constant of banknotes is facilitated, the reliability of the device in dynamic mode is increased while counting and detecting banknotes.

Claims (1)

 A device for determining the authenticity of banknotes containing two electrodes, one of which is isolated from the housing, and the other is electrically connected to it, a signal extraction device and a first threshold device, characterized in that a second threshold device, an analysis device, and an absence determination device are included in it banknotes between the electrodes, a memory device and a summing device, and the insulated electrode has the shape of a rectangle, one of whose sides is commensurate with the length of the protective thread of the banknote, at m the output of the device for determining the absence of banknote is connected to the input of the signal extraction device, the outputs of which are connected to the memory device and one of the inputs of the summing device, to the second input of which the output of the memory device is connected, and the output of the summing device is connected to the inputs of the first and second threshold devices, the outputs of which connected to the analyzing device.