Method and device for checking a security element

Abstract

A method and a device check a security element of a security document. The security element contains at least one particulate substance with electroluminescent properties and at least one field suppression element. The method includes applying an electric excitation field to the security element, generating an optical image of at least one region of the security element after or during the production of the electric excitation field, and detecting local intensity maxima in the optical image. The security element is verified if a number of local intensity maxima present at different image positions is greater than or equal to a specified number, the number being at least two.

Claims

1. A method for checking a security element of a security document, the security element containing at least one particulate substance having electroluminescent properties and at least one field displacement element, which method comprises the following steps of: applying an electric excitation field to the security element; generating an optical image of at least a region of the security element after or during a generation of the electric excitation field; detecting local intensity maxima in the optical image, a local intensity maximum designating image points or an image region containing a plurality of the image points in the optical image; verifying the security element if a number of the local intensity maxima present at different image positions is greater than or equal to a predetermined number, the number being at least two, wherein: a spatial size of a region of the local intensity maxima is determined, with the spatial size being the number of contiguous image points of an image region that forms a local intensity maximum, and the security element is verified if predetermined size properties are satisfied.

2. The method according to claim 1, which further comprises determining an intensity value of at least one of the local intensity maxima, and verifying the security element if at least one predetermined intensity condition is satisfied.

3. The method according to claim 1, which further comprises determining a total intensity of luminescence radiation captured during a generation of the optical image, and verifying the security element if the total intensity is less than or greater than a predetermined intensity value or is within a predetermined intensity interval.

4. The method according to claim 1, which further comprises: additionally illuminating at least a first partial region of the security element with white light radiation at a first angle of incidence and illuminated with the white light radiation at a second angle of incidence, wherein the white light radiation reflected by the first partial region is captured, wherein color hues of reflected white light radiation are determined, wherein the security element is verified if two wavelength and angle-specific color hues are detected; or additionally illuminating at least the first partial region of the security element with the white light radiation at a first angle of incidence and additionally illuminating a second partial region with the white light radiation at the second angle of incidence, wherein the white light radiation reflected by the first and the second partial regions is captured, wherein a color hue of the white light radiation reflected by the first partial region and a color hue of the white light radiation reflected by the second partial region are determined, wherein the security element is verified if the color hue of the white light radiation reflected by the first partial region corresponds to the color hue specified by a first wavelength and a first angle of incidence, and the color hue of the white light radiation reflected by the second partial region corresponds to the color hue specified by a second wavelength and a second angle of incidence.

5. The method according to claim 1, which further comprises: additionally illuminating at least a first partial region of the security element with first radiation at a first angle of incidence and with further radiation at a second angle of incidence, wherein the first radiation has a first wavelength or a first spectral range, wherein the further radiation has a further wavelength or a further spectral range, wherein the radiation reflected by the first partial region is captured, wherein intensities of reflected radiation are determined, wherein the security element is verified if an intensity is greater than a predetermined intensity; or additionally illuminating at least the first partial region of the security element with the first radiation at the first angle of incidence, and the second partial region is additionally illuminated with the further radiation at the second angle of incidence, wherein the radiation reflected by the first and second partial regions is captured, wherein the intensity of the radiation reflected by the first partial region and the intensity of the radiation reflected by the second partial region are determined, wherein the security element is verified if the intensity of the radiation reflected by the first partial region is greater than the predetermined intensity, and the intensity of the radiation reflected by the second partial region is greater than a predetermined intensity.

6. The method according to claim 4, which further comprises effecting the illumination with the white light radiation or the radiation at a first wavelength and the radiation at a second wavelength with a time delay with respect to an application of an electric excitation field.

7. The method according to claim 5, which further comprises effecting the illumination with the white light radiation or the radiation at a first wavelength and the radiation at a second wavelength with a time delay with respect to an application of an electric excitation field.

8. The method according to claim 6, which further comprises effecting the illumination with the white light radiation or with the radiation at the first wavelength and the second wavelength if a voltage of the electric excitation field is less than a predetermined value.

9. The method according to claim 7, which further comprises effecting the illumination with the white light radiation or with the radiation at the first wavelength and the second wavelength if a voltage of the electric excitation field is less than a predetermined value.

10. An apparatus for checking a security element of a security document, the apparatus comprising: at least one electric excitation field generator; at least one image capture device; and at least one hardware processor configured as an evaluation device; wherein by way of said generator for generating the electric excitation field, the electric excitation field being generated and applied to the security element; wherein by way of said image capture device, an optical image of at least one region of the security element after or during a generation of the electric excitation field can be generated; wherein by way of said evaluation device, local intensity maxima in the optical image are detected, a local intensity maximum designating image points or an image region containing a plurality of the image points in the optical image, the security element being verified by way of said evaluator if a number of the local intensity maxima present at different image positions is greater than or equal to a predetermined number, the number being at least two, wherein: a spatial size of a region of the local intensity maxima is determined, with the spatial size being the number of contiguous image points of an image region that forms a local intensity maximum, and the security element is verified if predetermined size properties are satisfied.

11. The apparatus according to claim 10, further comprising: white light radiation arranged relative to a section such that light is radiated onto the section illuminating a first partial region with white light radiation at a first angle of incidence; white light radiation arranged relative to the section such that white light is radiated onto the section at a second angle of incidence; or wherein the first partial region or a second partial region can be illuminated with white light radiation at the second angle of incidence.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) The invention is explained in more detail using an exemplary embodiment. In the figures:

(2) FIG. 1 is a schematic overview of an apparatus according to the invention,

(3) FIG. 2 illustrates an exemplary signal profile of an electric excitation field and an illumination, and

(4) FIG. 3 is a schematic optical image of the security element.

DESCRIPTION OF THE INVENTION

(5) FIG. 1 illustrates a schematic overview of an apparatus 1 according to the invention. The apparatus 1 comprises an electrode 2 for generating an alternating electric field, which serves as an excitation field. Furthermore, the apparatus 1 comprises an image capturing device, which is represented by a CCD chip 3. Furthermore, the apparatus 1 comprises an evaluation device 4, which is signal-connected to the CCD chip 3. Furthermore, the apparatus 1 comprises a lens 5, which can be embodied as a Fresnel lens, for example. A security document 6 has a strip-shaped section 7 which forms a security element. The security element includes at least one particulate substance having electroluminescent properties and at least one field displacement element in a predetermined mixing ratio. The field displacement elements here are embodied as optically variable effect pigments.

(6) By way of the electrode 2, an alternating electric field with a predetermined amplitude and frequency is generated. This excitation field interacts with the electroluminescent pigments and generates luminescence radiation. This radiation is imaged by the lens 5 on the CCD chip 3 with a predetermined resolution. The evaluation device 4 then detects image point-based local intensity maxima in the optical image and determines, in particular exclusively, the number of these local intensity maxima. If this number of the local intensity maxima present at different image point positions is greater than or equal to a predetermined number, said number being at least two, then the security element can be verified.

(7) Furthermore, the apparatus 1 comprises a first white light source 8, and a second white light source 9. The first white light source 8 is in this case arranged relative to the section 7 in such a way that white light 10 is radiated onto the section 7 at a predetermined first angle of incidence by way of the first white light source 8. The light reflected by the section 7 is also imaged on the CCD chip 3 by way of the lens 5. The evaluation device 4 can then determine a color hue of the reflected light. The second white light source 9 is correspondingly arranged in relation to the section 7 such that white light 11 is radiated onto the section 7 at a predetermined second angle of incidence by means of the second white light source 9, wherein the first angle of incidence differs from the second angle of incidence. The light reflected by the section 7 is also imaged onto the CCD chip 3 by way of the lens 5. The evaluation device 4 can then determine a color hue or a spectral frequency of the reflected light.

(8) If predetermined color hues, which are defined by the properties of the optically variable pigment and the angle of incidence, are detected, the security element can be verified.

(9) FIG. 2 illustrates an exemplary signal profile of an electric excitation field and an illumination over time t. A voltage profile 12 of the electric excitation field has a predetermined frequency and a predetermined amplitude. Likewise illustrated is an intensity profile 13 of a luminescence radiation caused by the excitation field. This luminescence radiation also has an intensity dependent on the properties of the electroluminescent particles, the frequency and the intensity of the excitation field and the mixing ratio of electroluminescent particles to field displacement elements. A spectral range of the luminescence radiation depends on properties of the electroluminescent particles and a frequency of the electric excitation field.

(10) Also illustrated is a time profile 14 of an activation signal for the first white-light source 8 illustrated in FIG. 1 and/or the second white light source 9. The white light sources 8, 9 are only activated and thus only emit white light 10, 11 onto the section 7 if the voltage of the electric excitation field is less than or greater than a predetermined threshold value. As a result, a disturbing influence of the image of the luminescence radiation on the CCD chip 3 (see FIG. 1) by the white light 10, 11 can be avoided.

(11) FIG. 3 shows a schematic optical image 16 of the strip-shaped section 7 illustrated in FIG. 3. Here, the optical image 16 has a plurality of local intensity maxima 15. The local intensity maxima 15 here are spatially distributed and have different sizes. In addition to the number of local intensity maxima 15, it is also possible to evaluate a spatial distribution, in particular distances between the local intensity maxima 15, and the size of the local intensity maxima 15 for verification of the security element.