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
  • G07D7/1205—Testing spectral properties
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
  • H04N23/10—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths
  • H04N23/11—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from different wavelengths for generating image signals from visible and infrared light wavelengths

Definitions

• the invention relates to a device for checking banknotes, which scans the banknotes to be checked by means of a semiconductor array.
• Such a device is known for example from DE 195 17194 AI.
• a CCD array is provided, which is formed by four individual, parallel, row-shaped CCD arrays which are arranged at a constant distance from one another.
• Each of the CCD arrays has a filter with a certain filter characteristic, so that a CCD array the area of blue light, a CCD array the area of green light, a CCD array the area of red light and a CCD array the range of infrared light is detected. If the bank notes to be checked are moved past the sensor, pixels of the respective bank note are recorded by the cell-shaped CCD arrays and stored for further processing.
• an image of the respective bank note can be generated in a cell-like manner from the stored pixels.
• a colored image of the banknotes can be generated by means of the CCD arrays for the blue, green and red areas of light.
• an image of normally invisible properties of the banknotes e.g. B. from their printing inks.
• the known device has the disadvantage that the CCD array used is complex since a large number of filters have to be used so that the individual line-shaped CCD arrays can detect the desired color ranges.
• problems with the composition of the colored image of the respective banknote can arise from the image points of the blue, green and red CCD arrays result because their spaced arrangement can cause parallax errors if the geometric imaging scale and the line frequency are not adapted accordingly. This can lead to so-called moire effects, particularly at light-dark transitions.
• a color image sensor is known from US Pat. No. 5,965,875, which is formed by a semiconductor array which has three layers lying one behind the other, each of the three layers being sensitive to a certain proportion of light.
• the well-known property of silicon is exploited here that the depth of penetration of the light depends on the wavelength of the light. Longer wavelength light penetrates deeper into the silicon before it is absorbed. This results in a first very thin layer from the light entry side, which mainly detects blue light, a second thicker layer, which primarily detects green light, and a third layer, which detects red and infrared light. Since the layers, or the respective pixels, which are sensitive to the different light areas lie one behind the other, they always form the same image point of the banknote to be checked in each case. Problems with parallax errors between the three signals can therefore no longer arise.
• a suitable (mostly linear) combination of the three signals of each pixel gives its blue, green and red signals.
• the known color sensor has the disadvantage that only three wavelength ranges can be detected, which are in the sensitivity range of the silicon from approximately 380 to approximately 1100 nm.
• the sensor is equipped with an infrared block filter that cuts off wavelengths above approx. 680 nm. Wavelength ranges that are important in particular for checking banknotes and that lie in the non-visible (infrared) range of light cannot then be detected.
• An extension of the known color sensor by at least one further layer, which is used, for example, for the detection of the infrared range, is in principle conceivable and possible, but such sensors are not freely available and would therefore first have to be developed in their structure and produced as a special production. With the known effort in the field of the production of semiconductor products, however, such custom-made products are very complex.
• the invention is based on a device for checking banknotes which scans the banknotes to be checked by means of a semiconductor array, the semiconductor array being formed by at least two cell-shaped semiconductor arrays spaced in parallel and the banknotes for the check moved past the semiconductor array and illuminated by a light source, in which the cellular semiconductor arrays are formed by at least three layers which are sensitive to light of different wavelengths, a first row-shaped semiconductor array being the banknotes in one scans the defined spectral range of light within the spectral sensitivity of the semiconductor and a second cellular semiconductor array scans the banknotes in a different range, for which purpose at least the second cellular semiconductor array has a filter.
• Three cases can be distinguished as configurations.
• the first semiconductor array has no filter, the second a filter that only allows invisible light to pass through.
• the first semiconductor array has no filter, the second a filter that blocks invisible light.
• the first semiconductor array has a filter that blocks invisible light, the second a filter that only allows invisible light to pass through.
• the invisible light let through the filter includes not only the infrared but also the ultraviolet part of the spectrum below approx. 390 nm. Because of the extremely short penetration depth of the ultraviolet light into the semiconductor of the array, this will only contribute to the signal of the top layer of the array. If the visible part of the spectrum (between about 390 and 700 nm) is blocked, the infrared signal of the top layer can be derived from the signal of the two layers below it and with a suitable weight defined by the sensitivity and the illumination spectrum Correction of the signal of the first layer can be used so that the signal in the ultraviolet range can also be obtained as the fifth.
• the device according to the invention has the advantage that it can be implemented simply and inexpensively using existing technology and, because of the reduction in image errors which can be caused, for example, by parallax sensors, delivers good test results.
• par- the manufacture of the filters is greatly simplified; some of them can even be designed as organic plastic filters and can be applied directly to the substrate of the detector arrays, for example by so-called spin coating.
• a control and evaluation device which processes and evaluates signals of the semiconductor array in order to convert the signals of the layers of the two cellular semiconductor arrays into a colored image and an image in the region of the generate invisible light for each banknote to be checked.
• the function of the control and evaluation device for the three cases described above is then as follows.
• the first array delivers signals from the entire spectrum, the second only from the invisible range.
• the three signals of the second array can easily be summed here. They then supply the image in the invisible area. This is used with suitable weights to correct the color signals in the visible range of the spectrum.
• the first array delivers signals from the entire spectrum, the second only signals from the visible range. These can be used directly without further correction.
• the image in the non-visible area is obtained from the signals of the first array by reducing the signals by the corresponding signals of the second array and then summing them.
• both arrays are provided with filters whose passband areas are mutually exclusive, so that the first array provides the colored image and the second array by summing the invisible image.
• the device according to the invention has the particular advantage that the lower sensitivity of semiconductor arrays in the invisible range is improved by summing the signals of the three layers, which means that better test results can be achieved.
• FIG. 1 shows a schematic view of a device for checking banknotes, which scans the banknotes to be checked by means of a semiconductor array 4, 5,
• Figure 2 shows a further schematic view of the device of Figure 1, from a different angle
• FIG. 3 shows a representation of the spectral sensitivities of the three layers of a semiconductor array according to FIG. 1, for layer thicknesses which result in approximately the same sensitivity for the three layers.
• the apparatus 1 shown in FIG. 1 for checking banknotes BN has a semiconductor array 4, 5 with which the banknotes BN to be checked are scanned when they are transported from the transport device T, not shown, to the semiconductor array 4, 5 is moved past.
• the semiconductor array 4, 5 consists of two parallel, cellular arrays 4 and 5, which have three successive layers b, g, r, which are sensitive to light of different wavelengths.
• the cellular arrays 4, 5 can be separate components, but they can also be arranged on a single component, in particular on a single component Semiconductor substrate.
• the semiconductor arrays 4, 5 can, for. B. consist of silicon and be built in CMOS technology.
• the sensitivity of the layers b, g, r is shown in FIG. 3.
• the top layer b is blue light
• the middle layer g is green light
• the bottom layer r is maximally sensitive to red light.
• the exact relationships of such layered CMOS arrays can be found, for example, in US Pat. No. 5,965,875 mentioned at the beginning.
• the layer thicknesses have different thicknesses, so that there is approximately the same sensitivity for the three views b, g, r in accordance with the wavelength-dependent absorption of the silicon.
• a light source 2 illuminates the bank note BN to be checked. Using an aperture 3 or suitable optics, an illuminated area is generated on the bank note BN, which corresponds approximately to the image of the CMOS array 4, 5.
• the light from the light source comprises 2 wavelength ranges, which are required for checking the bank note BN, in particular thus the range of visible light and the range of infrared or ultraviolet light.
• the intensity of the light source 2 is preferably the same over the entire relevant wavelength range or the spectral profile of the intensity of the light source 2 is adapted to the profile of the overall sensitivity of the CMOS array, as is shown, for example, in FIG. B. in the unpublished German patent application . 10239225.0 of the applicant.
• the bank note BN is scanned pixel by pixel over its entire width, as shown in FIG. If the scanning is carried out synchronously with the transport speed of the bank note BN, a complete colored and infrared image of the bank note BN can be generated.
• the necessary procedure in particular especially for synchronization to the transport speed of the banknotes BN, reference is made to the aforementioned DE 195 17194 AI.
• the colored image of the bank note BN is generated by a control and evaluation device 7 by means of the signals of the first cellular CMOS array 4.
• the signals of the blue layer b, the green layer g and the red layer r of the respective pixels of the CMOS array 4 are present at the control and evaluation device 7 in order to generate a component color image (eg RGB).
• a filter can be attached in front of the array 4, which blocks the light of longer (infrared) wavelengths. Then no correction with the signals of the array 2 is necessary. This only has to be done if the filter is missing and the array 4 is also sensitive in the non-visible area.
• the infrared image of the bank note BN is generated by the control and evaluation device 7 by means of the signals of the second cellular CMOS array 5.
• a filter 6 is provided in front of the CMOS array 5, which only the infrared range of light, for. B. with a wavelength greater than 850 nm.
• the signals of the blue layer b, the green layer g and the red layer r of the respective pixels of the CMOS array 5 are on the control and evaluation device 7, which evaluates the signals and combines them to form the infrared image. It is particularly advantageous if the signals of the blue, green and red layers b, g, and r of the CMOS array 5 are summed by the control and evaluation device 7.
• the distance between the two CMOS arrays 4 and 5 is chosen to be as small as possible. It can thereby be achieved that the colored image originating from the CMOS array 4 and the infrared image originating from the CMOS array 5 can be generated almost without parallax errors.
• the CMOS array used in the device 1 can be constructed from individual cellular CMOS arrays, but it is also possible to use a CMOS array which provides the required lines on a common substrate.
• a diaphragm or optics is also provided in front of the CMOS array 4, 5 in order to implement certain imaging properties.
• the filter 6 z. B. is replaced by a filter that only or additionally short-wave light, for. B. UV light can happen.
• another third CMOS array provided with a corresponding filter can be used.
• the device 1 can also be designed in such a way that light or instead of or additionally reflected light from the banknotes BN is evaluated, for which purpose CMOS array 4, 5 and the light source 2 are arranged on one side of the bank note BN. It is also obvious that instead of the transport of the bank notes BN along their long sides shown in the figures, a transport along the short sides of the bank notes BN can also take place. In this case, the dimensions of the CMOS array 4, 5 and the light source 2 or its diaphragm 3 or possibly existing optics must be adjusted accordingly.

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• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Inspection Of Paper Currency And Valuable Securities (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)

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• 2003
  • 2003-05-23 DE DE10323410A patent/DE10323410A1/de not_active Withdrawn
• 2004
  • 2004-05-21 US US10/557,825 patent/US7504632B2/en not_active Expired - Fee Related
  • 2004-05-21 WO PCT/EP2004/005515 patent/WO2004104947A2/fr active Application Filing
  • 2004-05-21 RU RU2005140061/09A patent/RU2318240C2/ru not_active IP Right Cessation
  • 2004-05-21 EP EP04734246A patent/EP1629440B1/fr not_active Not-in-force
  • 2004-05-21 DE DE502004008733T patent/DE502004008733D1/de active Active
  • 2004-05-21 AT AT04734246T patent/ATE418771T1/de active

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