EP2777027A1 - Procédé et dispositif pour détecter un matériau transparent ou semi-transparent appliqué sur un matériau absorbant et/ou de diffusion - Google Patents

Procédé et dispositif pour détecter un matériau transparent ou semi-transparent appliqué sur un matériau absorbant et/ou de diffusion

Info

Publication number
EP2777027A1
EP2777027A1 EP12784724.2A EP12784724A EP2777027A1 EP 2777027 A1 EP2777027 A1 EP 2777027A1 EP 12784724 A EP12784724 A EP 12784724A EP 2777027 A1 EP2777027 A1 EP 2777027A1
Authority
EP
European Patent Office
Prior art keywords
optical
receiver
source
area
optical source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12784724.2A
Other languages
German (de)
English (en)
Inventor
Elena Biagi
Leonardo Masotti
Enrico VANNACCI
Stefano FROSINI
Marco Calzolai
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Actis Active Sensors Srl
Original Assignee
Actis Active Sensors Srl
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Actis Active Sensors Srl filed Critical Actis Active Sensors Srl
Publication of EP2777027A1 publication Critical patent/EP2777027A1/fr
Withdrawn legal-status Critical Current

Links

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

Definitions

  • the present invention relates to methods and devices for detecting a material, for instance a sheet or web material, applied onto a base material or substrate, wherein these two materials have different optical characteristics.
  • the method relates in particular to the detection of a transparent or semi-transparent and/or semi- reflective material on an opaque material, i.e. on an absorbent material with scattering surface. More in particular, but not exclusively, the invention relates to a method and a device for detecting a transparent or semi-transparent adhesive tape applied on paper sheets, for example on banknotes, checks or other paper documents.
  • US-A-2009/0133502 discloses a system using ultrasonic sensors for detecting adhesive tape on a banknote. These sensors are expensive and sensitive to air movements. They are therefore particularly critical when applied to devices, inside which banknotes move very quickly; in fact, the fast motion creates an air flow interfering with the ultrasonic sensor detection.
  • US-A-2010/0117295 describes an apparatus using capacitance sensors for detecting adhesive tape on banknotes. In this case again, the sensors are expensive and not very reliable.
  • Optical devices have been also developed for detecting transparent or semi- transparent adhesive tape applied on the banknotes.
  • US-A-2011/0052082 discloses an example thereof.
  • This known device, as well as other optical devices, is substantially based upon the different reflection features of the adhesive tape with respect to the paper material of the banknote.
  • an optical receiver is provided in combination with at least two optical sources; these sources are inclined by different angles with respect to the banknote advancing plane. Both the sources fall, each by its incidence angle, on the same area of the banknote, and light it. The area lit by these two sources is framed by the receiver.
  • the change in the scattering and reflection signal generated by the two different sources which are differently inclined with respect to the banknote advancing path, is used for detecting the presence of adhesive tape.
  • the adhesive tape is shinier than the opaque surface of the banknote, and hence causes a change in the signal detected by the receiver, thus indicating the presence thereof.
  • These optical detection systems have several drawbacks; among other things, more optical sources with different angles are required, and this entails difficulties in the mechanical arrangement.
  • the detection system is very sensitive to the presence of folds on the base material, a banknote for instance.
  • two opposite systems shall be provided to check both the banknote sides, with consequently increased costs and bulk.
  • US-A-2009/0310126 discloses an optical system based again on using a light source and an optical receiver, wherein this latter is arranged in front of the area lit by the light source.
  • the source is strongly inclined with respect to the banknote advancing plane.
  • the adhesive tape presence is detected thanks to the reflection of its reflective surface and the shadow it generates on the banknote because of the strong inclination of the light source.
  • the used sources are strongly inclined with respect to the banknote advancing plane; therefore, the signal largely depends upon the height of the raised surface; moreover, folds or other irregularities on the base material surface may result in a false positive signal.
  • this system requires two groups arranged on the two banknote sides to examine both the document sides.
  • US 2003/0234362 discloses a thermal technique for detecting the presence of a foreign material, in particular adhesive tape, applied on a banknote.
  • This technique is based upon the thermal features of the adhesive tape, which are different than in the other banknote areas.
  • this technique uses the thermal radiation emitted by the banknote when there is a thermal gradient between banknote and detector.
  • the detected radiation is comprised between 3 and 12 micrometers.
  • the banknote may be heated or cooled, and the emitted radiation is detected after a certain time interval after heating or cooling.
  • a time interval occurs between the source application and the emitted radiation detection, because of the banknote transport speed.
  • the adhesive tape detection is based upon the fact that the areas with the adhesive tape have a greater thermal inertia.
  • the mutual position of heater and detector depends upon the banknote transport speed.
  • the radiation must be detected after a certain time interval after heating.
  • the object of the invention is to provide a method and a device for detecting a first material, for instance an adhesive tape or other transparent or semi-transparent material, such as paint, lacquer or the like, randomly or accidentally applied on a substrate constituted by a second material with different optical characteristics, for instance a scattering material such as a paper sheet and, more in particular, a banknote or the like, the method and the device being particularly efficient, reliable and inexpensive.
  • a first material for instance an adhesive tape or other transparent or semi-transparent material, such as paint, lacquer or the like
  • a second material with different optical characteristics for instance a scattering material such as a paper sheet and, more in particular, a banknote or the like
  • the invention is based on the fact that the transparent or semi-transparent and/or semi-reflective material, for instance an adhesive tape, acts as a light pipe with losses, that can be used to transfer an optical signal from a first area, lit by an optical source, towards a second area, framed by an optical receiver.
  • the object to be examined for instance a paper sheet, a note or the like, is optically opaque and scattering, so that substantially no light energy is transferred between the first and the second area.
  • a portion of a semi-transparent and/or semi-reflective material when arranged between these two areas and thus acting as a light pipe with losses, transfers an optical signal, that can be detected by the receiver, from the first area, lighted by the source, to the second area, framed by the receiver.
  • the optical signal detected by the receiver therefore indicates the presence of semi-reflective and/or semi-transparent material applied on the scattering and opaque base material of the object under examination.
  • Anti-counterfeiting security systems are currently used, using light pipes built into the paper forming the banknote.
  • the position and optical features of these light pipes, usually in the form of optical fibers, are known a priori.
  • Machines for verifying authenticity of the banknotes are designed to inject an optical radiation in a position, for instance an end, of these light pipes and to detect the optical signal in a different position, for instance at the opposite end.
  • the concepts upon which these systems are based differ from those upon which the present invention is based.
  • the light pipes are expressly embedded in the banknote structure, and their presence is verified knowing a priori their position on the banknote.
  • the system according to the present invention is designed to verify the accidental and completely random presence of an object or foreign material applied on the banknote in an unknown position.
  • the invention is substantially based upon the fact that the foreign material is more transparent than the substrate onto which it is accidentally applied.
  • the features of semi-transparency or transparency, scattering and opacity of the materials in question shall be intended as relative. This means that the foreign material feature of being transparent or semi-transparent and/or reflective or semi- reflective is relative to the lower transparency and greater opacity of the material of the substrate or object on which this foreign material is applied.
  • the method therefore comprises the steps of:
  • optical receiver framing a second area of the object by means of an optical receiver; said optical receiver and said optical source being designed and arranged so that the first area, lit by the optical source, is not directly framed by the optical receiver;
  • the materials may be sheet or web materials, i.e., generally speaking, substantially two-dimensional materials.
  • the method according to the invention may be also used to examine three-dimensional objects and materials, i.e. objects and materials provided with a non-negligible thickness with respect to the other two dimensions.
  • the material forming the object under examination and the material that is applied on it and must be detected through the optical analysis differ from one another as far as the capability of reflecting or scattering the optical radiation and/or of guiding the optical radiation through the thickness thereof are concerned.
  • the method according to the invention may be integrated in a more complex system designed also to acquire a (transparent or reflective) image of the object under examination.
  • the method may comprise the steps of:
  • the method may comprise the steps of:
  • the optical characteristic of transmittance and reflectance used to detect the material applied on the object vary according to the wavelength. This means that the characteristic of the material of being transparent or semi-transparent and/or reflective or semi-reflective is referred to the wavelength of the optical radiation used.
  • Usual adhesive tape is a semi-transparent and semi-reflective material in the visible and infrared spectrum. As the adhesive tape thickness is nearly 50 micrometers, the adhesive tape is:
  • Paper in particular paper used for banknotes, is less transparent and more scattering, i.e. it has a more diffuse reflectance than the adhesive tape, both in the visible and the infrared spectrum.
  • adhesive tape is semi-transparent and semi-reflective in the visible and infrared spectrum; as the wavelength increases, transparency increases and reflectance decreases.
  • Banknote is an opaque, i.e. absorbent and scattering material in the visible and infrared spectrum: the absorption capacity increases as the wavelength decreases, the scattering increases as the wavelength increases until the ratio between thickness and wavelength is lower than about 0.1. For values above this limit, the banknote reflects and refracts. For high wavelengths, i.e. for thickness/wavelength ratios lower than 10 "3 - 10 "4 the banknote is transparent.
  • the optical source may therefore emit in the visible and/or infrared spectrum.
  • the invention also relates to a device for detecting a first material (for instance adhesive tape) having at least one first optical characteristic and applied on a second support material (for instance a banknote) having at least one second optical characteristic, different from the first optical characteristic, the device comprising a first optical source and a first optical receiver.
  • the first optical source and the first optical receiver are designed and arranged so that the optical source lights a first area of the object under examination, and the optical receiver frames a second area of the object, wherein the second area and the first area are different and spaced from each other, said first area being not directly framed by the optical receiver.
  • figure 1 shows a diagram of a usual arrangement of light source and receiver in a reflection imaging device
  • figure 2 schematically shows a usual arrangement of light source and receiver in a transmission imaging device
  • figure 3 shows a diagram of a first embodiment of a device according to the invention
  • figure 4 shows a diagram of a second embodiment of the device according to the invention.
  • figure 5 shows a diagram of a third embodiment of the device according to the invention.
  • figure 6 shows a diagram of a fourth embodiment of the device according to the invention.
  • FIGS 7, 8, 9, 10, and 11 show diagrams illustrating the optical principle upon which the invention is based, in different configurations and use conditions;
  • figures 12A, 12B; 13A, 13B; 14A, 14B show diagrams illustrating the image acquisition method by means of a device according to the invention;
  • figure 15 schematically illustrates the acquisition of two types of image of the same banknote according to an embodiment of the invention
  • figure 16 shows an arrangement of the main mechanical members of a device according to the invention in a possible embodiment
  • figure 17 shows a perspective view of the arrangement of figure 16 with some parts removed.
  • FIGS 18 to 23 show diagrams of further embodiments of the device according to the invention.
  • the invention will be described below with specific reference to the detection of pieces of adhesive tape applied on banknotes, the adhesive tape being transparent or semi-transparent to the wavelength used for the detection. It should be however understood that the invention may be also used for detecting transparent or semi- transparent adhesive tape applied on other documents or products, for instance cheques or the like. More in general, it should be also understood that the invention may be applied every time it is necessary to detect a first material applied on a second material, wherein the two material differ in terms of optical transparency and reflection.
  • the device comprises light sources and receivers. Particular reference will be made below always to a single source and a single receiver, even if they can be replaced by linear arrays of sources and receivers.
  • Figure 1 schematically shows a traditional arrangement used to acquire images of a sheet material, for instance a banknote, in a known device by means of a reflection or scattering system.
  • BA schematically indicates a banknote advancing along an advancing path according to the arrow FA.
  • each portion of the banknote BA passes through an image acquisition area Z.
  • the area Z is lit by a source S.
  • the light beam Fl generated by the source S lights the area Z.
  • the banknote reflects and scatters the incident radiation by the angle ⁇ .
  • Figure 1 shows the reflection 9R and scattering 9DI , 9D 2 angles.
  • a receiver R is provided to frame the same area Z; it is positioned according to the reflection direction 9R to acquire the reflected image of the banknote B A, or according to the scattering direction 9DI or 9D 2 to acquire the scattered image of the banknote BA.
  • the banknote BA By advancing the banknote BA along the advancing path according to FA, it is possible to acquire subsequent images of the banknote by means of the light source S and the receiver R, each of these images corresponding to a thin strip of the banknote orthogonal to the advancing direction FA.
  • the whole image of the banknote, of a sufficiently high resolution, can be therefore reproduced through subsequent acquisition steps controlled by a central control unit.
  • the source S and the receiver R may be practically constituted by a series of optical emitters and receivers respectively.
  • CIS contact image sensors
  • a linear matrix of light emitters typically LEDs, forming the light source
  • the housing in which source and receiver are arranged, is provided with a window, usually into contact with the sheet, whose image shall be acquired.
  • source and receiver are shown spaced with respect to the object plane for the sake of simplicity and clarity of the drawings.
  • Figure 2 shows a similar arrangement for transparency imaging.
  • the same numbers indicate identical or equivalent parts to those in figure 1.
  • the optical source S is arranged in a half plane and the receiver R in the opposite half plane, said half planes being defined by and separated from the plane whereon the banknote BA is placed or advances.
  • Z indicates again the area under examination.
  • the banknote BA advances along the advancing path according to the arrow FA.
  • the light radiation Fl emitted by the source S passes across the banknote BA. A part of the radiation is directly transmitted to the receiver R, whilst a part is scattered according to the angles QDI and ⁇ 2 .
  • the image acquisition systems currently used have therefore source and receiver framing the same portion of the object under examination.
  • the receiver is aligned according to the direction of propagation of the central ray of the beam of optical radiation coming from the source or according to any one of the possible scattering directions.
  • Figure 3 shows the diagram of one embodiment of the invention, only as regards the general arrangement of the main components forming the detection device. Further details about the operation and the optical principles used will be explained below with particular reference to figure 7 and the following.
  • B A indicates again a banknote advancing according to the arrow FA along an advancing path P.
  • an optical or light source 1 and a receiver 3 are arranged on a same side of the advancing path P.
  • Optical source means any source of electromagnetic radiation in a useful spectrum comprised between IR and UV.
  • the optical source 1 is advantageously a linear source, able to emit a light beam whose height, orthogonal to the figure plane, is equal at least to one of the maximal dimensions (height or width) of the banknote BA.
  • the optical source 1 can be constituted by a light bar or by a linear array or matrix of LEDs or laser sources.
  • the light bar may be a light pipe made of glass or other suitable material, for instance a synthetic resin, transparent to the used wavelength.
  • the bar has a diffusing strip along its longitudinal development on the lateral surface thereof, allowing the optical radiation to exit, to form an optical radiation barrier.
  • a source of this kind is described for instance in WO-A-00/77447, to which reference is made for further details on the light pipe structure.
  • the optical receiver 3 may be constituted by a linear array or matrix of optical sensors, of the type commonly used in scanners, copiers and the like.
  • the receiver may be formed by a light pipe constituted for instance by a bar in a material transparent to the used wavelength.
  • the bar may be worked along a longitudinal line or strip to collect the optical radiation.
  • the optical radiation is collected by a single optical sensor or by a pair of optical sensors arranged at the ends of the bar forming the light pipe.
  • this solution has some limits as it does not allow to obtain an image of the banknote; it only allows to collect a single optical signal that may be modulated by the presence of a piece of adhesive tape, as it will be more apparent below.
  • a bar of this type for collecting the optical radiation is described in WO-A-00/77447.
  • the optical source 1 is arranged at a certain distance from the receiver 3 in the advancing direction FA of the banknote BA.
  • the light beam Fl generated by the optical source 1 lights an area Zl of the banknote BA.
  • the area Zl is separate and spaced from an area Z2 framed by the receiver 3. This separate arrangement of the lit area Zl and of the framed area Z2 is an important feature of the present invention, distinguishing the method and the device according to the invention from the optical devices and methods of the prior art.
  • the distance between the areas Zl and Z2 shall be compatible with the dimension of the foreign material, for instance adhesive tape, that is applied on the banknote BA and shall be detected by the device.
  • the distance shall be for instance equal to, or lower than, the minimum width the adhesive tape may have, typically in the order of one centimeter.
  • the device has also a barrier 5 with a first aperture 5A and a second aperture 5B.
  • the first aperture 5A allows the passage of the light beam Fl lighting the area Zl from the source 1.
  • the second aperture 5B allows the area Z2 to be framed by the receiver 3, thus allowing the optical radiation to pass from the surface of the area Z2 to the receiver 3.
  • the radiation lobe of the beam Fl extends orthogonally to the plane of the figure for a length equal at least to the height or the length of the banknote BA; therefore, also the apertures 5A and 5B shall be elongated.
  • These apertures are, practically, slots preferably orthogonal to the advancing direction FA of the banknote BA.
  • directional sources for instance laser sources, having the intrinsic feature of generating a directed beam without the need for shields or optical barriers.
  • the barrier 5 with the apertures or slots 5A and 5B allows reducing or eliminating the radiation generated by the source 1 that can be directly detected by the receiver 3.
  • the barrier 5 may be advantageously provided with a strongly absorbent surface at the wavelength used for the detection.
  • the barrier may have a reflective surface, so as to reflect the optical radiation falling on the barrier surface towards a useful path.
  • the barrier may have a scattering surface. It is only important that it does not allow the incident radiation from the source to pass across the barrier thickness and reach the receiver.
  • the receiver 3 may be constituted by a contact image sensor (CIS), the source of which has been adequately deactivated and no longer lights the same area framed by the receiver, as usually occurs in these sensors.
  • CIS contact image sensor
  • the inner source of the CIS is used in combination with the optical source 1 outside the receiver to obtain further functions.
  • the suggested solution is useful both when arranging receiver and source into contact with the object plane, defined by the advancing plane of the banknote BA, as well as when arranging them, or one of them, spaced from the plane.
  • the figures refer to the configuration in which receiver and source are arranged spaced from the object plane, only for the sake of clarity of the drawings.
  • Figure 4 shows the diagram of a different embodiment of the invention.
  • the same numbers indicate identical or equivalent parts to those in figure 3.
  • the barrier 5 instead of being nearly parallel to the advancing plane of the banknote BA, is arranged orthogonal to said plane and interposed between the optical source 1 and the optical receiver 3.
  • the front edge 5C of the barrier 5 is arranged directly adjacent to the banknote BA, preferably at a distance just sufficient to allow the banknote, which could be provided with an adhesive tape strip, to pass without interference. In this way the possibility is significantly reduced that the optical radiation generated by the optical source 1 directly reaches the receiver 3.
  • FIG. 5 schematically shows a third embodiment of the device according to the invention.
  • the same numbers indicate parts identical or equivalent to those in figures 3 and 4.
  • the optical source 1 is arranged on one side of the path P, and the optical receiver 3 on the opposite side.
  • the optical source 1 and the receiver 3 are in two distinct half planes, said half planes being separated by the advancing plane of the banknote B A.
  • Zl and Z2 indicate again respectively the area lit by the optical source 1 and the area framed by the optical receiver 3.
  • Fl is the light beam of the source 1 lighting the area Zl .
  • the diagram of figure 5 there are two barriers 6 and 8 respectively, provided with a first aperture or slot 6A and with a second aperture or slot 8A respectively.
  • the barrier 6 with the aperture 6A allows the passage of the beam Fl
  • the barrier 8 with the aperture 8 A allows the passage of the optical radiation coming from the area Z2 and collected by the receiver 3.
  • the two barriers 6 and 8, similarly to the barrier 5 of figure 3, prevent the optical radiation generated by the source 1 from directly reaching the receiver 3, or anyway they reduce the quantity of radiation that can directly reach the receiver 3.
  • Figure 6 shows the diagram of a further embodiment of the device according to the invention. Equal numbers indicate the same or equivalent parts to those of the previous embodiments.
  • the optical source 1 is arranged on one side of the advancing path P of the banknote BA, and the receiver 3 is arranged on the opposite side.
  • Fl indicates the optical beam with which the source 1 lights the area Zl, whilst the area Z2 framed by the receiver 3 is spatially separated from the area Zl, similarly to figures 3, 4, and 5.
  • 6 and 8 indicate two barriers arranged on the two sides of the advancing path
  • the two barriers 6 and 8 are orthogonal to the banknote advancing plane and have the same purposes described in connection with figure 5. Only the barrier 6 may be provided in this configuration.
  • FIG 7 shows a schematic enlargement of the lighted and framed area of the banknote BA in the embodiment of figure 4.
  • BA indicates the banknote that, as in the other figures, is shown in a sectional view.
  • the banknote BA is devoid of transparent or semi- transparent adhesive tape.
  • the wave vector is illustrated of a single light ray R emitted by the optical source 1. Below it will be described how this ray is used to generate a signal useful to detect the presence of transparent or semi- transparent adhesive tape. It should be understood that what is described with reference to the wave vector of a single ray R applies to each wave vector of each ray of optical radiation generated by the optical source 1, lighting the area Zl of the banknote BA advancing along the path P.
  • Figure 7 shows how the ray R is partially scattered by the outer surface of the side Bl of the banknote facing the optical source 1.
  • the barrier 5 preferably absorbent or specular at the used wavelength, prevents the radiation scattered or reflected by the side Bl from reaching the receiver 3 arranged on the opposite side of the barrier 5 with respect to the optical source 1.
  • a part of the optical radiation of the ray R scattered in the point A propagates and diffuses through the thickness of the banknote BA.
  • a part of this radiation is reflected by the inner surface of the side B2 of the banknote BA facing the opposite side with respect to the optical source 1.
  • Another part of the radiation propagating through the thickness of the banknote BA exits from the side B2.
  • A indicates the point of incidence of the ray R on the surface Bl .
  • B indicates a generic point of the inner surface of the side B2 on which a ray, propagating from the point A through the thickness of the banknote B A, falls. This ray is reflected at B and reaches the point C, which is again arranged on the side Bl in the area Z2 framed by the receiver 3. A part of the radiation falling in C is scattered towards the outside. This part of optical radiation scattered towards the outside is very small, and a part thereof is collected by the receiver 3.
  • Figure 8 shows the same diagram of figure 7, but in this case a piece of semi- transparent and semi-reflective material, for instance adhesive tape, indicated with N, is applied on the banknote BA.
  • a piece of semi- transparent and semi-reflective material for instance adhesive tape, indicated with N, is applied on the banknote BA.
  • the path A, B, C is indicated again, followed by a part of the optical radiation of the ray R that is scattered through the thickness of the banknote BA, reaches the point C on the outer surface of the side Bl and is scattered outside the banknote BA in the area Z2 framed by the receiver 3.
  • a further optical path is indicated, extending within the thickness of the adhesive tape N. This optical path is defined by the points A, E, C, and D.
  • the point E is on the face Nl of the adhesive tape N opposite to the face N2 of the adhesive tape applied to the side Bl of the banknote.
  • the adhesive tape N has a more reflective surface than the banknote BA, and the material of which it is made is more transparent than the paper forming the banknote BA.
  • a significant part of the optical energy contained in the ray R is conveyed along the path A, E, C, D.
  • a further path AG is also shown that, through the presence of the adhesive tape N, is conveyed through the path AGHLCD to the area Z2 framed by the receiver 3.
  • the point D arranged in the area Z2 framed by the receiver 3, it diffuses towards the receiver 3 a significantly greater quantity of optical energy than that in the point C framed by the receiver 3 in the situation of figure 7, where there is no adhesive tape N.
  • the receiver 3 sees the adhesive tape N as an area that is brighter than the substantially dark background defined by the banknote BA.
  • the arrangement of the optical source 1 and of the receiver 3, arranged so as to light and frame different areas Zl and Z2 of the banknote, allows to detect the adhesive tape N thanks to the optical characteristics of this latter, that differ from the optical characteristics of the banknote BA.
  • the adhesive tape N is used like a light pipe with losses, conveying a part of the optical radiation incident on the area Zl, lighted by the optical source 1, towards the area Z2, framed by the receiver 3.
  • Figure 9 shows again the optical path A, B, C of the part of light radiation of the ray R, which is scattered through the thickness of the banknote BA, is reflected in the point B, falls in the point C and partially exits in the area Z2 framed by the receiver 3.
  • a part of the light radiation falls in the point D on the side B2 of the banknote BA, passes across the thickness of the adhesive tape N and is reflected in the point E on the face Nl of the adhesive tape N.
  • the part of radiation that from the point E is reflected again towards the inside of the adhesive tape N falls on the banknote side B2 in the point F, passes through the thickness of the banknote BA and falls in the point C framed by the receiver 3.
  • the small quantity of optical energy following the path A, B, C is added therefore to the greater quantity of optical energy following the path A, D, E, F, C, allowing again the detection of the adhesive tape N through the signal of the receiver 3.
  • Figure 10 shows a diagram of the device in the configuration of figure 6, where the optical paths of the radiation of a single ray R generated by the optical source 1 are represented, to show the operation of the method according to the invention in the case of detection in transmission instead of reflection.
  • the adhesive tape N is applied on the side Bl of the banknote BA facing the optical source 1.
  • A, B, C, D is the path followed by a part of the radiation of the ray R that, falling in the point A of the lighted area Zl, is reflected, propagates through the adhesive tape N, is reflected in the point B on the inner surface Nl, propagates again inside the adhesive tape N, exits from the point C, is scattered through the thickness of the banknote BA, and then exits from the point D in the area Z2 framed by the receiver 3.
  • Figure 11 shows the same principle, but with the adhesive tape N applied on the side B2 of the banknote B A facing the receiver 3 and not on the side B 1 facing the optical source 1.
  • the adhesive tape N generates an optical radiation path defined by the points A, B, C, D, and E. If there were no adhesive tape N, this part of optical radiation wouldn't be collected in the area framed by the receiver 3. In this case, in fact, the collected radiation would be only the radiation that from the point A, crossing the banknote BA, directly reaches the point D. In all the illustrated configurations, it is therefore possible to obtain an increase in the optical radiation collected by the receiver 3 in the framed area Z2 when a portion of banknote BA, on which an adhesive tape N is applied, passes in front of the optical source 1 and the receiver 3.
  • FIGs 12, 13, and 14 schematically show what occurs in terms of acquired image when there is no banknote BA (figure 12), when there is an undamaged banknote BA without adhesive tape (figure 13) and when there is a banknote BA with adhesive tape N applied on one of the two sides thereof (figure 14).
  • Figure 12A shows a substantially black acquired image; this indicates that in front of the receiver 3 there are no objects allowing the light radiation from the optical source 1 to reach the receiver 3.
  • Figure 12B shows a pattern of the signal acquired by the receiver 3 as a function of the time (on the x-axis). Actually, if the receiver 3 is formed by an array of optical sensors, each sensor generates a signal like that indicated in the lower part of figure 12B.
  • the image of figure 12A is completely dark as the source 1 lights an area Zl of the object plane different than the area Z2 framed by the receiver 3. As source 1 and receiver 3 are not aligned, the only signal received is the noise.
  • FIG 13 a banknote BA is moving along the advancing path P.
  • the banknote BA is undamaged, i.e. devoid of adhesive tape on both the sides Bl and B2.
  • Figure 13A schematically shows the acquired image. With respect to the situation of figure 12, here the receiver 3 receives a quantity of optical radiation - even if a small quantity; the image is therefore clearer than that of figure 12 A.
  • Figure 13B represents the signal collected by the receiver 3 as a function of time. More exactly, the figure shows the trend over time (on the x-axis) of the amplitude of the signal (on the y- axis) generated by the light collected by the single receiver 3 or by a single element of the array forming the receiver 3.
  • the signals of the single sensors will be substantially equal to one another.
  • the instants indicated with tl and t2 on the x-axis indicate the instants when the initial edge and final edge of the banknote pass in front of the sensor generating the signal indicated on the y- axis.
  • the acquired signal is greater than the signal acquired in absence of banknote, and it is due to the optical radiation, which propagates inside the paper material of the banknote BA from the area lit by the optical source 1 towards the area framed by the receiver 3, is scattered outside the banknote in said framed area, and is collected by the receiver 3 or more exactly by the single sensor forming it.
  • the banknote moves forward along the path P, through subsequent acquisitions it is possible to re-construct the whole image of the banknote.
  • FIG 14 an adhesive tape N is applied on one side or on the other side of the banknote BA.
  • FIG 14A a light rectangle is superimposed on the banknote image acquired by the receiver 3; this rectangle represents the image of the piece of adhesive tape N applied on the banknote BA.
  • the time-signal diagram of figure 14B shows the instants tl and t2 when the initial edge and the final edge of the banknote BA pass in front of the optical sensor. Within this time interval, the points t3 and t4 show the instants when the initial edge and the final edge of the adhesive tape N pass in front of this sensor.
  • the signal in the diagram is that of a single sensor or of one of the various sensors or photo-detectors that, arranged in the form of a linear matrix, form the receiver 3.
  • the position of the time instants t3 and t4 along the x-axis can vary from photo-detector to photo-detector and depends upon the inclination with which the adhesive tape N is applied on the surface of the banknote BA.
  • a central processing unit can generate the whole image that will be formed by a substantially homogeneous background, on which the light rectangle corresponding to the piece of adhesive tape N stands out.
  • the receiver is formed by a linear light pipe associated with a receiver, designed to collect on the same receiver all the radiation collected by the light pipe, only one output signal will be obtained, whose pattern nearly corresponds to that of figure 12B, 13B, or 14B depending upon the situation. In this case no image of the adhesive tape is generated on the background of the banknote.
  • the banknote surface is strongly scattering and that the semi- reflective and semi-transparent material of the adhesive tape N is both a light conveyor and a light pipe with losses
  • it is provided to convey again towards the material all the propagation directions of the optical radiation that would be scattered in the space outside the lobe, and would be therefore lost.
  • the solutions may be various.
  • the simplest solution is a distribution of specular surfaces between source and receiver on one or both the banknote sliding surfaces of the configurations of figures 8 to 11. This leads to images with a higher signal/noise ratio and a greater contrast between the situation of presence and the situation of absence of semi-reflective and semi-transparent material on the banknote.
  • the optical source or sources 1; 23, 123 may be controlled through coded signals to decrease the optical noise of the outside environment and/or the electronic noise, and increase the signal/noise ratio.
  • the device can be integrated in an equipment that besides verifying the presence of adhesive tape on the banknote or other substrate, also acquires the image of the same document and/or to perform further controls. This is useful for instance in the case of equipment used for verifying the authenticity of the banknotes and, if necessary, for identifying their nomination and the wear levels, and consequently for distributing them in a series of drawers or containers provided to this end. Equipment of this type are known per se and their methods for identifying the authenticity, the nomination and the wear level do not required to be described herein.
  • Figure 15 schematically shows a configuration of a device allowing both to acquire the banknote image and to detect the presence of adhesive tape on one or the other banknote side.
  • the same numbers indicate identical or equivalent parts to those of the previous figures.
  • one of the possible solutions is indicated for arranging a mirror surface along the feeding path P of the banknote BA .
  • a wall 21 is provided with a mirror surface 21 A, which reflects at the used wavelengths. Obviously, this feature may be omitted.
  • Number 5 indicates the absorbent or reflecting barrier separating the optical source 1 from the area in front of the optical receiver 3.
  • the wall 21 acts also as a barrier to prevent the receiver 3 from directly seeing the optical radiation coming from the source 1.
  • a further barrier may also be provided, similar to the barrier 5 orthogonal to the advancing plane of the banknote BA on the half plane containing the receiver.
  • Number 23 indicates a second optical source arranged in front of the receiver 3.
  • the receiver 3 can therefore acquire images obtained through the optical radiation generated by the optical source 1 and images generated by the optical radiation coming from the optical source 23.
  • the image obtained by the receiver 3 through the radiation generated by the optical source 1 is that for the detection of the adhesive tape on the banknote, and is acquired as described above.
  • the image obtained by the receiver 3 through the radiation generated by the optical source 23 is a normal transparent image obtained through methods known in the machines and equipment for banknote detection.
  • number 20 schematically indicates a suitable central control unit interfaced with the optical sources 1, 23 and with the receiver 3. This unit makes the receiver acquire in subsequent steps and sequentially both the two images, activating in fast sequence and repeatedly at one time the optical source 1, at another time the optical source 23.
  • the result is schematically illustrated in figure 15.
  • On the right part of figure 15 a combination CI is shown of the transparent images of the banknote BA obtained through the source 23 and of the images of the adhesive tape N obtained through the optical source 1.
  • the central unit 20 is able to re-construct on one hand the image C2 of the banknote through the optical radiation generated by the source 23 and on the other hand the image C3 of the adhesive tape N applied on the banknote BA.
  • the resolution required for acquiring the image C2 of the banknote and for acquiring the images C3 of the pieces of adhesive tape N is relatively low; it is therefore possible simultaneously to acquire the images C2 and C3 simply through a time scanning, sequentially activating the source 1, 23 in subsequent advancing steps of the banknote BA, without the need for stopping it during the motion thereof along the feeding path P.
  • the image C2 will be substantially re-constructed through the sum of sub-images spaced from one another in the banknote advancing direction FA. With the spaced sub-images forming the image C2, sub-images are alternated, acquired through the optical radiation of the source 1 , generated by the banknote and by the adhesive tape N to form the image C3.
  • the banknote, or other object under examination may be kept in position and scanned moving the source and the receiver with respect to the object. Scanning may occur according to only one direction, using for instance a linear source and a linear receiver. In other embodiments one-dimensional sources and receivers may be used, moved according to two different scan directions, for instance orthogonal to each other.
  • Figure 16 shows a section of a device according to the invention, according to a plane orthogonal to the advancing plane of the banknote BA.
  • Equal numbers indicate equal or equivalent parts to that described with reference to the previous schematic figures.
  • Number 25 indicates, generically and as a whole, a CIS containing the optical receiver 3 and the second optical source 23 described with reference to figure 15.
  • the optical source 1 is outside the CIS 25, in front of an aperture 30 formed in a wall 31 that, together with an opposite wall 33, defines the advancing path P of the banknote BA.
  • Both the walls 31 and 33 may have a suitable distribution of reflecting surfaces.
  • the wall 33 may contain a mirror 34, equivalent to the reflecting surface 21 A of the wall 21 described with reference to figure 15.
  • 35, 37, and 39 schematically indicate members for moving the banknote BA along the path P.
  • these moving members are constituted by a first pair of rollers 35, 37, at least one of which is motorized, and by a second pair of rollers 39, 41, at least one of which is motorized.
  • the arrangement of the sources 1, 23 and of the receiver 3 allows the acquisition of the images of adhesive tape N - source 1 and receiver 3 - and of the banknote BA - source 23 and receiver 3 - as described with reference to the previous figures.
  • the source 1 may be a discrete or continuous source (of the type described in WO-A-00/77447) suitably fixed to the wall 25.
  • a second CIS may be for instance used adjacent to the CIS 25 of figure 16, whose source is used together with the receiver 3 of the CIS 25 to produce images of the adhesive tape.
  • Figure 17 shows an axonometric view of some components of figure 16, to better illustrate their position in the space.
  • the arrangement of the sources 1, 23 in figure 16 is only one of the possible arrangements. Alternative arrangements are in fact also possible.
  • the source 1 may be arranged on the opposite side with respect to the receiver 3, in such a position to fall in the situations described in figures 10 and 1 1.
  • the image obtained through reflection, with source 23 and receiver 3, is useful for producing images of the banknote BA.
  • the image obtained through transparency using the source 1 and the receiver 3 represents the image for the detection of the adhesive tape N.
  • the source 1 may be a continuous source (see WO- A-00/77447) or a discrete one or it may be the inner source of a further CIS arranged on the opposite side with respect to the receiver 3.
  • Figure 18 shows a section according to a plane orthogonal to the advancing plane of the banknote BA of a device according to the invention in a different configuration.
  • the same reference numbers indicate equal or equivalent parts to those described with reference to the previous schematic figures.
  • Figure 18 shows a configuration with two CISs suitably facing each other and indicated with 25A and 25B.
  • the transparent image is obtained for the detection of the adhesive tape N.
  • the transparent image is obtained of the banknote BA.
  • Both the walls 31 and 33 defining the advancing path P of the banknote BA may have an adequate distribution of reflecting surfaces 34.
  • the two CISs 25A and 25B may be used to obtain reflection images of both the banknote sides.
  • the central unit 20 manages the timing for the acquisition of the different types of images as described with reference to the previous figures.
  • the described device may be completed with further sensors and detecting means of the known type, arranged along the path P of the banknote BA, for instance a further CIS to acquire the image of the banknote side opposite that acquired by the sensor 25, magnetic sensors, capacitive sensors and the like.
  • the barrier 5 may be omitted using strongly directional sources and receivers. These new types of devices may be also used in the mechanical arrangements described above. In this case again an adequate distribution of reflecting surfaces 34, on the walls 31 and 33 defining the advancing path P of the banknote BA, allows improving the quality of the images.
  • Figures 20 and 21 show other configurations of detection systems according to the invention.
  • a linear array of receivers 3 extends parallel to the advancing path P of the banknote BA.
  • a single source 1 is arranged in an intermediate position along the extension of the linear array of receivers 3. The arrangement may be multiplied forming a two-dimensional matrix of receivers 3 and a linear array of sources 1.
  • the adjacent receivers 3, arranged off-axis with respect to the source 1 may receive the optical radiation conveyed by the semi-transparent and semi-reflective material, if any, applied on the banknote BA, generating a corresponding signal.
  • WO-A-00/77447 is arranged in front of a single receiver 3, which is positioned in an intermediate position with respect to the linear extension of the optical source 1.
  • a shield or barrier 8 is arranged, preventing the light emitted by the source 1 from directly achieving the receiver 3.
  • the semi-transparent and semi- reflective material applied on the banknote BA advancing along the path P between the source 1 and the receiver 3 generates a signal due to the effect of the light conveyed through the semi-transparent material from the area of the uncovered source 1 (i.e. outside the shield 8) to the receiver 3.

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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)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

L'invention porte sur un procédé pour détecter la présence d'une première matière étrangère (N) appliquée de façon aléatoire sur un objet (BA) qui est examiné, constitué par une deuxième matière, la première matière étrangère (N) étant transparente ou semi-transparente et la deuxième matière absorbant et/ou diffusant au moins une longueur d'onde d'un rayonnement optique. Le procédé permet l'éclairage d'une première zone (Z1) de l'objet (BA) à l'aide d'au moins une source optique (1). Le procédé permet également la mise en trames d'une seconde zone (Z2) de l'objet (BA) à l'aide d'un récepteur optique (3). Le récepteur optique (3) et la source optique (1) sont conçus et agencés de telle sorte que la première zone (Z1), éclairée par la source optique (1), est différente de la seconde zone (Z2), mise en trames par le récepteur optique (3). La présence de la première matière étrangère (N) sur une surface de l'objet (BA) est détectée à l'aide d'un changement dans le signal optique sur le récepteur optique (3) du fait d'un rayonnement optique émis par la source optique (1) et transporté à travers la première matière étrangère (N) à partir de la première zone (Z1) jusqu'à la seconde zone (Z2).
EP12784724.2A 2011-10-05 2012-10-03 Procédé et dispositif pour détecter un matériau transparent ou semi-transparent appliqué sur un matériau absorbant et/ou de diffusion Withdrawn EP2777027A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT000214A ITFI20110214A1 (it) 2011-10-05 2011-10-05 "metodo e dispositivo per il rilevamento di materiale con certe caratteristiche ottiche sovrapposto a un materiale di caratteristiche ottiche diverse"
PCT/IB2012/055280 WO2013050931A1 (fr) 2011-10-05 2012-10-03 Procédé et dispositif pour détecter un matériau transparent ou semi-transparent appliqué sur un matériau absorbant et/ou de diffusion

Publications (1)

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EP2777027A1 true EP2777027A1 (fr) 2014-09-17

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EP12784724.2A Withdrawn EP2777027A1 (fr) 2011-10-05 2012-10-03 Procédé et dispositif pour détecter un matériau transparent ou semi-transparent appliqué sur un matériau absorbant et/ou de diffusion

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EP (1) EP2777027A1 (fr)
IT (2) ITFI20110214A1 (fr)
WO (1) WO2013050931A1 (fr)

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CN104297260B (zh) 2014-11-04 2017-10-10 广州广电运通金融电子股份有限公司 一种薄介质的无接触式检测方法及装置
WO2019193669A1 (fr) * 2018-04-04 2019-10-10 グローリー株式会社 Système d'examen de feuille, dispositif de réalisation d'image et procédé d'examen de feuille

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SE447516B (sv) * 1985-03-25 1986-11-17 Esselte Verdetryck Ab Forfarande for att avlesa ett verdedokument, jemte verdedokument samt anordning for dylik avlesning
IT1308286B1 (it) 1999-06-15 2001-12-10 Leonardo Masotti Sorgenti e ricevitori ottici estesi continui e barriere otticheutilizzanti dette sorgenti e detti ricevitori
DE10217586A1 (de) * 2002-04-19 2003-11-20 Giesecke & Devrient Gmbh Verfahren und Vorrichtung zur Erkennung von Fremdmaterial auf Banknoten
GB0526381D0 (en) 2005-12-23 2006-02-08 Rue De Int Ltd Transducer
WO2008020208A1 (fr) 2006-08-18 2008-02-21 De La Rue International Limited Procédé et appareil pour la détection de matière en relief
CN101754919B (zh) 2007-07-26 2011-12-07 富士通株式会社 纸张厚度检测装置
JP5367509B2 (ja) * 2009-08-27 2013-12-11 株式会社東芝 光検出装置、及びこの光検出装置を備える紙葉類処理装置
US8749767B2 (en) 2009-09-02 2014-06-10 De La Rue North America Inc. Systems and methods for detecting tape on a document
PL2512742T3 (pl) * 2009-12-18 2014-08-29 Orell Fuessli Sicherheitsdruck Ag Dokument bezpieczeństwa z falowodem optycznym

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WO2013050931A1 (fr) 2013-04-11
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