Classifications

• • G—PHYSICS
  • G07—CHECKING-DEVICES
  • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
  • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
  • G07D7/06—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using wave or particle radiation
  • G07D7/12—Visible light, infrared or ultraviolet radiation
  • G07D7/121—Apparatus characterised by sensor details
• • G—PHYSICS
  • G07—CHECKING-DEVICES
  • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
  • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
  • G07D7/181—Testing mechanical properties or condition, e.g. wear or tear
  • G07D7/187—Detecting defacement or contamination, e.g. dirt

Definitions

• the invention relates to a method for checking documents of value, in particular banknotes, and a corresponding checking device according to the preamble of claims 1 and 13, respectively.
• Generic methods and test devices are used, among other things, to check banknotes for their condition, in particular with regard to soiling and stains.
• the amount of light transmitted by a bank note to be checked and / or the light reflected by the bank note is used to determine the degree of contamination of the bank note to be checked. Since the reflection and transmission behavior varies greatly with the thickness of the banknote paper, changes in the thickness of the banknote, for example due to batch-related thickness fluctuations and / or in the area of watermarks, stains or other soiling, can no longer be detected with sufficient reliability.
• the inventive method is characterized in that the intensities of the transmitted and reflected light are recorded separately for the different measuring locations each form the sum of the intensities of the transmitted and reflected light and the sum is compared with a predetermined standard value.
• the test device further develops the known devices in that the lighting system and the detector system are designed for separate detection of the intensity of the transmitted and the reflected light, an evaluation unit for forming the sum of the intensities of the transmitted and reflected light for the different measuring locations and is provided for comparing the sum with a predetermined standard value.
• the detected reflected light is in particular diffusely reflected, i.e. remitted, light.
• the invention is based on the idea of designing the lighting system and the detector system in such a way that on the one hand the intensity of the transmitted light and on the other hand the intensity of the reflected light can be detected separately.
• the intensities of the transmitted and reflected light are added up in an evaluation unit for each individual measurement location, so that exactly one sum intensity value is obtained for each measurement location.
• the individual total intensity values are then compared in each case with a predetermined standard value in order to infer the presence of contamination from any deviations.
• the intensity values recorded at the different measuring locations are corrected before the formation of the sum to compensate for locally different measuring conditions.
• a corresponding correction unit can be used as well as one for the Addition of the corrected intensity values trained addition unit can be realized in the form of hardware.
• these units in the form of software on a microprocessor or the like, which is used, for example, to control the test device.
• these can also be software implementations on a conventional computer to which the Raw data are transmitted from the detector system for correction.
• the correction takes into account, in particular, local fluctuations in the intensity of the lighting given during the measurement.
• the fluctuations in measured values caused by fluctuations in the illumination profile can be greatly reduced in this way, which further increases the reliability of the method. A special effort in the construction of the lighting system is not necessary.
• each measured intensity value is preferably reduced by a dark current measured value determined for the relevant measurement location before the sum is formed.
• each intensity value is additionally multiplied by a correction factor determined for the respective measurement location.
• the test device preferably has a memory in which dark current measurement values and correction factors are stored for the various measurement locations. These data are e.g. B. during assembly or commissioning of the test facility as well as NEN later determined in special adjustment measurements and then stored in the non-volatile memory.
• the dark current measurement values are determined by intensity measurements with the lighting switched off. These dark currents are deviations of the individual detector elements of the detector system from zero. It is therefore sufficient if such a dark current value is measured for each individual detector element, which then applies to all measuring locations that were measured with this detector element.
• the correction factors serve on the one hand to compensate for the different lighting intensities and on the other hand to compensate for the sensitivities of the individual detector elements with which the measurements are carried out at the individual measuring locations.
• Different, location-dependent correction factors are required for the transmission measurement and the reflection measurement. Since each detector element observes exactly one point within the illumination profile, it is also sufficient here if a correction factor for the transmission and for the reflection is determined for each detector element and these correction factors are then used for all measurement locations measured with this detector element.
• the correction factors are obtained on the basis of intensity values, which are measured under ideal conditions when comparing measurements on standardized sample documents, for example on homogeneous white foils.
• a particularly effective test device which is able to check documents of value over a large area with a high throughput, has a transport device in which the documents of value are guided past the lighting system and a detector system suitably positioned for measurement in a transport direction.
• the lighting system generates a lighting profile that extends transversely to the transport direction. This can be achieved with an illumination device consisting of a row of light-emitting diodes or also by means of a field with a plurality of rows of light-emitting diodes extending transversely to the transport direction.
• the detector system preferably has one or more detector devices which comprise a plurality of detector elements which are positioned in a row transversely to the direction of transport in a manner suitable for the illumination profile.
• This can e.g. are a row of photodiodes or a plurality of rows of photodiodes arranged one behind the other.
• the invention allows simple and inexpensive checking of banknotes and other documents of value for signs of wear. Another advantage of this method is that the separately measured reflection and transmission intensities can be evaluated to derive statements regarding further properties of the value documents. For example, the measured reflection intensities can be used for authenticity testing.
• the transmission intensity values can be used to detect holes and cracks.
• FIG. 1 shows a schematic illustration of the arrangement of a lighting system and a detector system for a test device according to a first exemplary embodiment
• FIG. 2 shows a schematic illustration of the arrangement of an illumination system and a detector system for a test device according to a second exemplary embodiment
• FIG. 3 shows an example of the thickness curve in the area of a watermark on a banknote
• FIG. 4 shows a typical course of the reflection and transmission intensities along a measurement track in the case of a non-soiled banknote without absorption.
• the lighting system consists only of one lighting device which illuminates the document of value, here a bank note 1, from one side 13 in the area around a specific measuring location 2.
• the bank notes 1 are drawn past the lighting device 7 for measurement in a transport direction R.
• the lighting device 7 is a light-emitting diode line which extends across the entire width of the bank note 1 transversely to the transport direction R and which thus produces a wide illumination profile running transversely to the transport direction R.
• the light is slanted in Direction of transport R is emitted onto bank note 1 and is focused as homogeneously as possible over the entire lighting profile onto a narrow area around measuring point 2 f. This can be achieved, for example, with the aid of suitable, in particular cylindrical, lenses.
• the lighting device 7 can also have a plurality of rows of light-emitting diodes arranged parallel to one another, ie an entire array of light-emitting diodes.
• This detector system 4 here consists of two detector devices 8 and 9.
• the first detector device 8 is arranged on the same side of the bank note 1 as the lighting device 7 and detects the intensity IR of the reflected, in particular remitted, light component.
• the second detector device 9 is located directly in the beam direction of the light emitted by the illuminating device 7 on the opposite side 14 of the bank note 1. This detector device 9 detects the intensity Ir of the light component transmitted by the bank note 1.
• the two detector devices 8 and 9 each have a plurality of detector elements which are arranged next to one another in a row transverse to the transport direction. For example, this is a row of photodiodes. Alternatively, several rows of such detector elements can also be arranged in parallel next to one another, i.e. it can be a whole field of detector elements.
• the distance between the individual detector elements determines the local resolution in the direction of the banknote width running transversely to the transport direction R.
• a detector device can usually have between 200 and 600 sensor elements in a row, so that accordingly between 200 and 600 measurement tracks are measured side by side on a bank note 1.
• the resolution in the transport direction R is given by the transport speed and the measuring rate.
• the spatial resolution in the transport direction R is between 0.1 and 1 mm, although experience has shown that the spatial resolution is 7/16 mm
• IR (X) and I ⁇ (x) along the measurement tracks are processed as follows; where x is the position of a pixel, i.e. the location coordinate in the transport direction R:
• IRK (x) and I ⁇ (x) are the corrected intensity values.
• the values a (x) and b (x) are location-dependent correction factors for the reflection or the transmission to compensate for fluctuations in the illumination profile generated by the illumination device 7 and to compensate for the sensitivities of the individual detector elements at the different locations x.
• the values IRD (X) and ITD (X) are dark current intensities. These are measured intensity components which are caused by dark currents from the respective detector elements at the individual locations x. According to formulas (1) and (2), the dark current intensities are first subtracted from the measured intensities IR (X) and I ⁇ (x) before a correction with the correction factors takes place.
• the dark current intensities and the correction factors are determined in separate adjustment measurements during the manufacture of the test device and / or at later times.
• the intensities IRD (X) and ITD (X) due to the dark currents at the individual locations x are determined by a measurement with the light source switched off. Measurements are then carried out on a standard sample, for example a homogeneous white film, to determine the correction factors.
• the intensity IR S (X) of the reflected portion of the light and the intensity I ⁇ s (x) of the transmitted portion of the light are measured with the light source switched on, ie exactly as in the measuring mode.
• the correction factors a (x) and b (x) according to the formulas
• the corrected intensity values are added for each position x
• I s (x) is worth the sum intensity.
• the total intensity value I s (x) of a clean banknote is equal to 1 at all positions x (with appropriate normalization) or another constant standard value. In the case of soiled banknotes, this value deviates from the normal value in the areas of soiling.
• FIG 2 shows a second embodiment of a test device according to the invention.
• the lighting system 5 has two lighting devices 10 and 11.
• the lighting device 10 is here how the lighting device 7 is constructed in the first exemplary embodiment and also aligned accordingly.
• the lighting device 11 arranged on the other side 14 of the bank note 1 is also constructed in the same way as the first lighting device 10.
• the second lighting device 11 which is realized via a corresponding control of the two lighting devices 10 and 11.
• the detector system 6 now has only one detector device 12, which is constructed and positioned identically to the first detector device 8 in the exemplary embodiment according to FIG. 1.
• This detector device 12 now measures the radiation emitted by the first lighting device 10 onto the bank note 1 and light reflected by the banknote 1 and times the light emitted by the second lighting device 11 on the opposite side 14 onto the banknote 1 and transmitted by the banknote 1.
• the lighting cycle is preferably selected so fast relative to the measuring cycle that both an intensity signal IR for the reflection and an intensity signal I ⁇ for the transmission are measured at each measurement location along a measurement track. That there are again full-area images of the intensity values IR and I ⁇ with respect to the reflection and the transmission for each individual banknote. This data is processed in exactly the same way as in the first-mentioned exemplary embodiment.
• essentially certain areas in the white field, ie in unprinted areas, of the bank note 1 are preferably selected in order to use the intensity values measured there to determine the amount of dirt to determine degree of efficiency. Typical dimensions of such areas are between 10 and 40 mm. Frequently, however, it is precisely these areas of the banknotes in which there are watermarks and large fluctuations in thickness occur.
• FIG. 3 shows a course of the thickness of a banknote.
• the thickness d is plotted over the location x on the bank note 1 along the transport direction R.
• the paper of the banknote has a nominal thickness ds of 80 ⁇ m, which is shown by the dashed line.
• the average thickness dM of the banknote is around 50 ⁇ m. It is only in the area w of a bar watermark that there are markedly large fluctuations in thickness, in which in some areas the thickness d comes close to the target thickness d s of 80 ⁇ m.
• FIG. 4 shows the detected intensities I ⁇ and IR for the transmitted or reflected portion of the light above the location x on the bank note 1 with bar watermarks described in connection with FIG. 3.
• the intensities I R and I ⁇ are plotted in the form of proportions of the total radiation normalized to 1. Accordingly, the total intensity value Is, ⁇ consisting of the sum of the transmitted and reflected intensity, is exactly 1. This is shown in FIG. 4 by the dashed line.
• the sum Is, in particular in the area w of the bar watermark is 1, which indicates very good compensation of the Influence of the thickness variations is due.
• particularly good compensation can be achieved by corresponding corrections of the detected intensity values IR or I ⁇ , in particular on the basis of dark current measurement values and / or correction factors.
• the sum signal in the region of the contamination lies on a value which deviates from 1, usually a lower value, so that this can be recognized by a simple comparison of the sum signal with the expected standard value.

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Inspection Of Paper Currency And Valuable Securities (AREA)
• Length Measuring Devices By Optical Means (AREA)

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• 2002
  • 2002-09-17 DE DE10243051A patent/DE10243051A1/de not_active Withdrawn
• 2003
  • 2003-09-15 CN CNB038218720A patent/CN100440260C/zh not_active Expired - Lifetime
  • 2003-09-15 US US10/528,118 patent/US8107712B2/en active Active
  • 2003-09-15 EP EP03750545A patent/EP1602083A1/de not_active Ceased
  • 2003-09-15 WO PCT/EP2003/010237 patent/WO2004027718A1/de not_active Application Discontinuation
  • 2003-09-15 AU AU2003270195A patent/AU2003270195A1/en not_active Abandoned

Non-Patent Citations (1)

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