EP1265199A2 - Device for investigating documents - Google Patents

Abstract

The arrangement has at least two detector units (1-3) for detecting light (16) emanating from a document (10) under investigation and at least one dispersion element (5) that scatters the light emanating from the document. The dispersion element(s) and detector units are arranged so that the scattered light can be detected by the detector units. The dispersion element(s) performs diffuse transmission and/or reflection.

Description

The invention relates to a device for examining documents in particular value, ID or security documents, with at least two detector units for detecting light emitted by one to be examined Document runs out.

To increase the security against counterfeiting, ID, security or Documents of value, such as Banknotes with security features or printed with suitable security printing inks.

Security features or security printing inks can be luminescent Contain substances which e.g. through light, electric fields, radiation or sound can be stimulated to glow. To check the Authenticity, the documents are made to glow and that by Luminescent substances of the document emitted luminescent light detected. Based on the intensity and / or spectral characteristics of the Luminescent light can then be used to determine whether the document is genuine or fake is.

Certain security features or security printing inks stand out also by a characteristic reflection and / or transmission behavior in certain spectral ranges. For example, becomes a document of value imitated with the help of a color copier, so you can mostly reproduce only the visible color impression of a printed area. Since commercially available color particles, however, not for security features characteristic spectral behavior in certain, in particular have invisible spectral ranges falsified documents in general by appropriate measurement their reflection and / or transmission behavior in these spectral ranges detect.

The reliability of statements about the authenticity of the checked documents is particularly dependent on the accuracy with which is the spectral characteristic, i.e. the color of a document outgoing light is analyzed. Such an analysis can, for example done by spectrometers, which however are relatively high require technical effort and high manufacturing costs.

Individual detector units, e.g. Photodiodes or photomultipliers, each with different spectral Sensitivity. Depending on the spectral characteristics of the document outgoing light, the detector units deliver different detector signals, which are then used for the spectral analysis of light can be. However, devices of this type have the disadvantage that the light detected by the individual detector units on the basis of Parallax errors are generally not from the exact same area of the Of the document. This makes a reliable assessment of the color properties the originating from a certain part of the document Light impossible. This is particularly disadvantageous if Areas with small dimensions, e.g. individual lines of a printed image, to be examined for their spectral properties, because here already slight parallax errors to particularly large inaccuracies in the spectral analysis of the originating from the document Can lead light.

It is an object of the invention to provide a device which has a higher Reliability in the study of luminescence, reflection and / or Transmission properties of documents, especially of Valuable, ID or security documents allowed.

This object is achieved according to claim 1 in that a scattering element is provided on which the document to be examined outgoing light is scattered, the scattering element and the detector units are arranged so that the scattered light from the detector units can be detected.

The invention is based on the idea that the different Part of the document outgoing light by means of a diffuser is scattered, taking into account the individual areas Mix components of the light. Individual, side by side Detector units can thereby detect light, which in each case Shares from the different sub-areas of the document. The scattering element creates a spatial mix and homogenization of the light emanating from the document.

It is achieved by the invention that the detector units that one common area of the document capture outgoing light equally can. Any parallax errors that occur with a laterally offset arrangement of detector units would occur by the invention intended scatter element greatly weakened. From the of the spectral components of the individual detector units recorded by the document outgoing light can then make statements about the spectral characteristics the luminescence, reflection and / or transmission behavior of the document can be derived with high reliability.

In a preferred embodiment of the invention, the diffusing element is for diffuse transmission and / or diffuse reflection of that from the document outgoing light trained. Under a diffuse transmission or reflection is any essentially undirected transmission or to understand reflection.

Fig. 1

eine erste Ausführungsform der Erfindung;

Fig. 2

eine zweite Ausführungsform der Erfindung;

Fig. 3

ein Beispiel für unterschiedliche spektrale Empfindlichkeiten der in den Figuren 1 und 2 verwendeten Detektoreinheiten; und

Fig. 4

ein Beispiel für eine bevorzugte elektrische Schaltung der in den Figuren 1 und 2 verwendeten Detektoreinheiten.

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the figures. Show it:

Fig. 1

a first embodiment of the invention;

Fig. 2

a second embodiment of the invention;

Fig. 3

an example of different spectral sensitivities of the detector units used in Figures 1 and 2; and

Fig. 4

an example of a preferred electrical circuit of the detector units used in Figures 1 and 2.

1 shows a first embodiment of the invention. One to be examined Document, in the example shown a banknote 10, is by means of a transport device indicated by transport rollers 40 and transport belts 41 transported past the sensor system 7. This is the banknote 10 irradiated with the light 15 of the two light sources 12. With the light sources 12 are for example fluorescent tubes, incandescent lamps, Lasers or light emitting diodes (LEDs).

In one embodiment of the invention it is provided that that of the respective Light sources 12 emitted excitation light 15 at different Wavelengths or wavelength ranges. This enables more precise Statements about the properties of the banknote 10 Light 16. It can in particular be provided that the light sources 12 illuminate the banknote 10 either individually or in combination and that detected in each case with individually or combined illuminated banknote 10 Light 16 is evaluated. First in the example shown in FIG illuminated with only one light source 12, then the detector units detect 1 to 3 three first intensity values. With subsequent lighting With the other light source 12, three second intensity values are generated. With simultaneous illumination with both light sources 12 finally got three third intensity values. By comparison and / or arithmetical linkage of the i.a. different, intensity values will be a particularly thorough study of the properties of the light 16 emanating from the examined banknote 10.

In the event that 10 luminescent light is excited in or on the banknote to be, the light sources 12 emit light which is used to excite Luminescent light in or on the bank note 10 is suitable. Preferably it is ultraviolet (UV) light. To eliminate spectral components at higher wavelengths, i.e. for example in the visible or infrared spectral range, appropriate filters (not shown) are arranged in front of the light sources 12.

For the application that the banknote 10 in certain spectral ranges remitted, i.e. diffusely reflected, light can be examined should be, the light sources 12 for emitting light 15 with spectral components formed in these spectral ranges.

In the example shown, luminescent light 16 in is excited or on the bank note 10 by the light 15 of the light sources 12. A corresponding one Luminescence is therefore referred to as photoluminescence. Alternatively or additionally, electrical fields, Radiation or sound other types of luminescence phenomena, such as e.g. Electro-, radio- or sonoluminescence stimulated in or on the banknote 10 become. The excitation takes place through appropriate excitation devices, such as B. electrical contacts or field plates, radiation sources for cathode, ion or x-rays, ultrasound sources or antennas. Depending on the temporal decay behavior, there can be between A distinction is made between phosphorescent and fluorescent light.

The luminescent light 16 excited in or on the bank note 10 or the Light reflected by the bank note 10 strikes the juxtaposed ones Detector units 1 to 3 and is detected by them. The detector units 1 to 3 have different spectral sensitivities and thereby detect different spectral components of the banknote 10 outgoing light 16. Accordingly, the differ from the Detector units 1 to 3 generated detector signals S, which for evaluation and analysis of an evaluation device 9 are supplied.

Between the bank note 10 and the detector devices 1 to 3 is in the illustrated example, a first device 13 is provided, which the the bank note 10 directs outgoing light 16 onto the detector units 1 to 3, especially focused. This can be an imaging optic act, which a portion 11 of the banknote 10 on the detector devices Depicts 1 to 3. For this purpose, preferably self-focusing Lenses, so-called Selfoc lenses, are used. In the case of self-focusing lenses it is cylindrical optical elements made of a material which one decreasing from the optical axis of the cylinder towards its jacket Has refractive index. By using Selfoc lenses one of the distance between the bank note 10 and the detector units 1 up to 3 independent and adjustment-free 1: 1 images of the patient to be examined Partial area 11 of the banknote 10 reached on the detector units 1 to 3.

Alternatively or additionally, the first device 13 can also be a light guide element, e.g. one or more glass and / or plastic fibers, exhibit. This has the advantage that the detector units 1 to 3 on any Locations can be arranged, which is a particularly compact integration such devices allowed in banknote processing systems.

According to the invention, an as is in front of the individual detector units 1 to 3 Diffuser 5 formed scattering element is provided, on which the the banknote 10 outgoing light 16 is scattered. The scatter results in the example shown, of a diffuse transmission of light 16 through the lens 5. This process is in the figure by a variety small arrows 8 indicated.

There is a second one between the bank note 10 and the detector units 1 to 3 Device for limiting the aperture, and thus the size of the on the Banknote 10 examined portion 11, provided. An aperture limitation is particularly advantageous if the spectral properties of small sections of the banknote 19, such as thin lines or details of a printed image to be examined. The second In the example shown, the device has an aperture 4, in particular an aperture Perforated or slit diaphragm. Together with the selfoc lens first device 13 becomes a particularly simple and precise aperture limitation reached. In principle, there are several alternative configurations possible to limit the aperture, for example by combining the Aperture 4 with a light guide element, e.g. based on glass and / or Plastic fibers, or by combining a light guide with a imaging optics, which the portion 11 of the bank note to be examined 10 on the light guide, in particular in a glass and / or Plastic fiber inside, maps.

Fig. 2 shows a second embodiment of the invention, in which in the difference to the embodiment shown in Fig. 1 instead of one Diffuser 5 a reflector 6 is used as a diffuser. That from the Banknote 10 outgoing light 16 is on the reflector 6, for example one matt or roughened mirror, diffusely reflected and then from the individual detector units 1 to 3 arranged next to one another. The functionality of all other components of the device is analogous to the example described in Fig. 1.

As an alternative to the diffusing elements 5 or reflector 6 can be used to scatter the emanating from the banknote 10 Light 16 can also be used as an integrating sphere. This is what it is about is a hollow sphere, the interior of which is diffusely reflective Paint, for example made of magnesium oxide, barium sulfate or Teflon is. The light 16 emanating from the banknote 10 occurs in a first Opening in the Ulbricht sphere, becomes several times diffuse inside reflects and exits through another opening. The passage of incoming light directly to the outlet opening is by appropriate additional means inside the sphere, e.g. Reflectors, prevented. The diffuse light emerging from the Ulbricht sphere can then emanate from the Detector units 1 to 3 can be detected.

Another possibility for spatial mixing of the banknote 10 outgoing light 16 represents a scattering element designed as a hologram in which light rays emanating from the banknote 10 in a large number of light beams split in different directions and in this way before hitting the detector units be mixed.

An optical filter (not shown) can be placed in front of the scattering element 5 or 6. be arranged which e.g. only for those spectral components of the from the banknote 10 outgoing light 16 is transparent, which of the behind the scattering element 5 or 5 arranged detector units 1 to 3 detected should be.

In a further alternative embodiment of the invention, that the scattering element the first device 13 and / or the second device, in particular the aperture 4 comprises. Preferably the first contains or second device light-scattering particles, on which the Banknote 10 outgoing light 16 is scattered. In this configuration the scattering element can be formed by the first and / or second device be, so that on a separate scattering element 5 or 6, if necessary can be dispensed with.

The detector units 1 to 3 are preferably designed as photodiodes, which can be integrated on a common semiconductor substrate. This results in a particularly dense arrangement of the detector units 1 to 3 reached side by side, so that any parallax errors are greatly reduced can be. Particularly suitable and commercially available Three-color sensors (e.g. types MCS3AT / BT or MCSi from MAZeT GmbH, D-07745 Jena) are made up of three Si-PIN photodiodes, which integrated on a chip and as segments of a circle or hexagons typical diameters between approx. 0.07 mm and 3 mm. In order to achieve low crosstalk between the photodiodes, the individual segments are separated from each other by additional structures. Each of the photodiodes has a corresponding dielectric color filter sensitized to a different color range, especially to the primary colors Red, green and blue.

Alternatively, the detector units 1 to 3 can be along a line or on be arranged on a surface so that it is a one- or two-dimensional Form detector array, in particular photodiode array (PDA).

In addition to photodiodes, other types of detectors, e.g. photomultiplier, suitable for detecting the light 16.

FIG. 3 shows an example for different spectral sensitivities E. of the detector units 1 to 3 used in FIGS. 1 and 3. The sensitivities E are plotted against the wavelength λ. How from The spectral sensitivities are shown in the diagram E1, E2 and E3 of the individual detector units in essentially separate Spectral regions. Depending on the type of analysis of the spectral characteristics The light emanating from a document can change the spectral position as well the spectral course of the individual sensitivities E1 to E3 accordingly to get voted. The spectral sensitivities are preferably E1, E2 or E3 in the blue, green or red spectral range. Depending on Individual sensitivities E1 to E3 can also be used in invisible applications Spectral ranges, e.g. in the infrared or ultraviolet. Of course, the sensitivity curves E1 to E3 of the individual detector units 1 to 3 at least partially overlap and color values from the output signals S1 to S3 of the detector units investigating document can be determined.

In a further embodiment of the invention, the sensitivity profiles overlap E1 to E3 of the individual detector units 1 to 3 via a wide spectral range, in particular over the entire examined Spectral range, the maxima or mean values of the respective sensitivities E1 to E3 at different wavelengths or wavelength ranges lie. This can be easily done e.g. by realizing that the detector units 1 to 3 examined three over the entire Spectral range sensitive photodiodes with preferably the same sensitivity curve have, wherein at least two of the photodiodes with optical filters are provided, which in a wide spectral range are differently permeable. The individual photodiodes thereby capture the intensity of the light 16 emanating from the bank note 10 at different Wavelengths or wavelength ranges. From the captured Intensities can then make statements about the spectral properties of the light 16 detected. The spectral ones are preferred Transmission profiles of the filters chosen so that in particular you Ratio in the relevant, i.e. examined, spectral range a clear Function of the wavelength is.

For the purposes of the invention, the spectral properties of the detected visible or invisible light 16 in addition to its color in particular also the wavelength, e.g. the central wavelength, and / or the wavelength range to understand.

Fig. 4 shows a preferred circuit of those used in Figs. 1 and 2 Detector units 1 to 3, especially when using one of the above described commercial three-color sensors. The trained as photodiodes Detector units 1 to 3 are connected so that their cathode outputs are at a common potential 18 and their Anode outputs 19 are connected to an evaluation device 19. In the evaluation device 9 can then from the detector signals S1 to S3 of the photodiodes statements about the spectral properties, in particular over the wavelength, e.g. the central wavelength, and / or the wavelength range and / or the color of the detected light 16 become.

Claims (22)

Device for examining documents, in particular value, identification or security documents, with at least two detector units (1, 2, 3) for detecting light (16) which emanates from a document (10) to be examined,
characterized in that at least one scattering element (5, 6) is provided, on which the light (16) emanating from the document (10) is scattered, and the scattering element (5, 6) and the detector units (1, 2, 3) are arranged so that the scattered light can be detected by the detector units (1, 2, 3). Device according to claim 1, characterized in that the scattering element (5, 6) is designed for diffuse transmission and / or diffuse reflection of the light (16) emanating from the document (10). Apparatus according to claim 2, characterized in that the diffusing element (5, 6) is designed as a diffusing screen (5) on which the light (16) emanating from the document (10) is diffusely transmitted and / or diffusely reflected. Apparatus according to claim 2, characterized in that the diffusing element (5, 6) is designed as a reflector (6), in particular as a mirror with a matt surface, on which the light (16) emanating from the document (10) is reflected diffusely , Device according to one of claims 1 to 2, characterized in that the scattering element is designed as an integrating sphere. Device according to one of claims 1 to 2, characterized in that the scattering element is designed as a hologram which splits light rays emanating from the document (10) into a plurality of light rays of different directions. Device according to one of claims 1 to 6, characterized in that the detector units (1, 2, 3) have different spectral sensitivities (E1, E2, E2). Device according to one of claims 1 to 7, characterized in that the detector units (1, 2, 3) are constructed as photodiodes. Device according to one of claims 1 to 8, characterized in that the detector units (1, 2, 3) are integrated next to one another on a common semiconductor substrate. Device according to one of claims 1 to 9, characterized in that at least one detector unit (1, 2, 3) has an optical filter. Device according to one of claims 1 to 10, characterized in that an excitation device is provided which is designed to excite luminescent light in or on the document (10) to be examined, and the detector units (1, 2, 3) are designed to detect at least part of the luminescent light (16) emanating from the document (10). Apparatus according to claim 11, characterized in that the excitation device comprises at least one light source (12) for illuminating the document (10) with light (15) which is suitable for exciting luminescent light in or on the document (10). Device according to one of claims 1 to 12, characterized in that at least one light source (12) is provided for illuminating the examining document (10) and the detector units (1, 2, 3) are designed to detect at least part of the light (16) reflected, in particular remitted, and / or transmitted by the document (10). Device according to one of claims 1 to 13, characterized in that at least one first device (13) is provided for directing the light (16) emanating from the document (10) onto the detector units (1, 2, 3). Device according to claim 14, characterized in that the first device (13) comprises at least one lens, in particular a self-focusing lens, for focusing the light (16) emanating from the document (10). Device according to one of Claims 14 to 15, characterized in that the first device (13) has at least one light-guiding element, in particular based on glass and / or plastic fibers, for guiding the light (16) emanating from the document (10) ) to the detector units (1, 2, 3). Device according to one of claims 1 to 16, characterized in that a second device for limiting the aperture is arranged between the document (10) and the detector units (1, 2, 3). Apparatus according to claim 17, characterized in that the second device has an aperture (4). Device according to one of claims 1 to 18, characterized in that an evaluation device (9) is provided for deriving statements about the spectral properties, in particular about the wavelength, such as the central wavelength, and / or the wavelength range and / or the color, of the light (16) emanating from the document (10) from detector signals (S, S1, S2, S3) generated by the detector units (1, 2). Device according to one of claims 14 to 18, characterized in that the scattering element comprises the first device (13) and / or second device (4). Apparatus according to claim 20, characterized in that the first device (13) or second device (4) contains light-scattering particles, on which the light (16) emanating from the document (10) is scattered. Device according to one of claims 1 to 21, characterized in that the detector units (1, 2, 3) are arranged along a line or on a surface.

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