Method for verifying the authenticity of an image printed on a carrier for a security or value document

Abstract

The invention relates to a method for verifying the authenticity of a visible image (15) printed on a data carrier (20) which is encoded with detectable image-specific results (12), wherein expected image-specific results (12e) are calculated from the visible image (15) and then their agreement with image-specific results (12) encoded in the image (15) or in the area (25) of the layer (27) above the image (15) is checked.

Description

[0001] The invention relates to a method for verifying the authenticity of an image printed on a carrier for a security or valuable document.

[0002] Security documents such as ID cards or driver's licenses generally incorporate photographs as a security feature. During the production of ID documents, the data from the digital photographs is processed using the raster imaging process (RIP). The image visible in the security document is printed using colored inks in the three standardized optimal colors: cyan, magenta, yellow, and, if applicable, black.

[0003] In order to detect manipulation of the photographs, it is common practice to provide photographs with security features, which can, for example, be provided in a zone in the image to be applied.

[0004] Security documents are forged, among other things, by applying a photograph of another person over the photograph of the document holder.

[0005] The application of the other person's photograph can be done directly, for example, by printing it directly onto the card's surface using an inkjet printing process, or indirectly, by first printing it onto a transfer film and then overlaying the image onto the actual photograph. Particularly good counterfeits leave the other security features, such as luminescent underprinting or kinematic holographic structures (Identigram), largely intact, so that the document appears virtually untampered with or slightly aged.

[0006] Manipulation of photographs of genuine documents to create false identities is therefore an increasing threat.

[0007] US 2003 / 0173406 A1 teaches a security document with a visible image and a digitally enhanced ghost image visible only under UV irradiation, which can be incorporated into the same image.

[0008] Security documents with visible and personalized invisible markings that cannot be seen without the involvement of an external factor are known from DE 600 04 529 T2.

[0009] DE 696 24 400 T2 concerns security documents with a printed image and a compressed digital image encoded in the magnetic medium of the image.

[0010] DE 697 11 482 T2 teaches a certificate bearing an image engraved into an engraving foil.

[0011] US 5,421,619 discloses a security document with a photo of the holder and a dithered image of the photo inserted with a laser.

[0012] DE 10 2006 052 651 A1 relates to a data carrier with a first graphic representation and a second graphic representation which is better protected against manipulation and is designed as a reference for detecting manipulation of the first representation, wherein only partial areas of the first and second representations overlap.

[0013] EP 2 209 653 B1 discloses processes for producing polymer layer composites for security and value documents.

[0014] Furthermore, DE 10 2014 214548 A1 relates to a method for producing a document, in which the document layer is printed with an ink in a spatial area by a printing process, the ink is dried, wherein due to the drying the ink in the area takes on a random surface structure, the randomly created surface structure is optically detected, encoded and stored as a security feature.

[0015] The invention is based on the object of providing a method for detecting manipulation of security and valuable documents.

[0016] This object is achieved by the features of claim 1. In the method according to the invention for verifying the authenticity of a visible light image printed on a data carrier, which is encoded with detectable image-specific results, expected image-specific results are calculated from the visible light image and then their agreement with image-specific results encoded in the light image or in the region of the layer above the light image is verified.

[0017] Image-specific results are calculated from the data of a digital photograph, and the visible, printed photograph or an area of ​​at least one layer of the data carrier above the photograph is encoded with these results in a detectable form.

[0018] Since the visible image itself is encoded with the image-specific results or the area of ​​a layer above the image and the coding is detectable, the authenticity of the image can be verified solely on the basis of the image and, if applicable, the layer area of ​​the data carrier above the image.

[0019] The coding can be either visible in visible light or invisible. Invisible coding has the advantage that it is not easily detectable by a counterfeiter. The coding can generally be applied to the visible light image at the same time as the visible light image is printed, but can also be applied before or after the visible light image is printed.

[0020] If the coding is not carried out in the photograph itself, but in an area in one or more layers above, i.e. above the photograph, i.e. either in an area of ​​a layer of the data carrier between the photograph and the visible side of the data carrier or in the visible side of the data carrier itself above the photograph, the photograph is printed first and then the coding is carried out in the area in one or more layers above the photograph.

[0021] In a further embodiment, the photograph is printed and, independently of this, the coding is carried out with the image-specific results of the photograph in a carrier layer film, which is then positioned and fixed above the photograph.

[0022] Within the scope of the invention, the image-specific results calculated from the digital photograph are understood to mean contours or positions of individual, specific points of a face (landmarks) determined from the respective portrait, thus all specific results that can be clearly calculated from the digital photograph by means of a specific algorithm.

[0023] The calculation of image contours from the visible light image can be done, for example, using Canny edge detection (Canny or Canny edge algorithm). Canny edge detection (or Canny) is a robust edge detection algorithm widely used in digital image processing. It is divided into various convolution operations and produces a light image that ideally contains only the edges of the original image.

[0024] Using Canny edge detection, specific, i.e., unique, algorithm-based contours or support contours can be extracted from a portrait and output as a separate contour image. Of course, other algorithms can also be used to extract a contour image from the visible light image.

[0025] When calculating image-specific results with landmark detection, the positions of individual, specific points of a face are calculated and the calculated landmark image is then encoded in the printed photograph, for example using transparent luminescent ink.

[0026] In order to verify the correspondence of the visible light image with the image-specific results encoded in the light image, the image-specific results must be detectable. To detect these image-specific results encoded in the light image, i.e., to observe, recognize, measure, or see them, the image-specific results can be printed into the visible light image, in particular using a luminescent ink, or incorporated into the layer above the visible light image in the form of a hologram, barcode, or milling, or in another form that can be visually or haptically perceived or measured.

[0027] The authenticity of a photograph printed on a data storage medium can be verified visually if it has a visible coding, such as a hologram or a milled mark. Furthermore, the expected image-specific results can be calculated from the visible image and then verified for their consistency with the image-specific results encoded in the image or in the layer above the image.

[0028] If the expected image-specific results calculated from the printed photograph agree with the coded image-specific results, the photograph is genuine and was produced using the process.

[0029] If no match is achieved, the printed visible photograph is a forgery because either no image-specific results are encoded in the printed visible photograph at all or because the image-specific results encoded in the photograph do not match the photograph because, for example, the original photograph was overprinted.

[0030] For a reliable verification of the authenticity of the photograph, if the verification is carried out by calculating the expected image-specific results from the visible photograph, the calculation should be carried out using the same algorithm as the original calculation of the image-specific results from the data of the digital photograph.

[0031] Preferably, the verification of the authenticity of the coded visible photograph is carried out automatically.

[0032] In addition to the automated verification or alternatively, the verification of the coding can also be carried out visually, insofar as it is visible or can be made visible by irradiation with electromagnetic radiation, such as UV radiation.

[0033] After the image-specific results, which were calculated from image-specific data of the photograph, are stored in the photograph itself or are incorporated into an area of ​​the layer above the photograph, it can be determined whether the photograph has been manipulated or not simply by checking the photograph and, if applicable, the layer area above the image, because if the image-specific results stored in the photograph do not match the photograph, it is a forgery.

[0034] Thus, the verification of the authenticity of the document can be carried out solely by checking the photograph as such and, if applicable, the area above it, and preferably in an automated manner, which allows for secure and rapid verification.

[0035] The image-specific results are the image contours or landmarks (positions of individual specific points of the face) calculated from the image-specific data.

[0036] The image-specific results can be stored in the photograph in various ways, for example by printing the image contours or landmarks into the photograph using luminescent transparent ink, so that the image contours or landmarks are only visible under UV light and thus the correspondence of the image contours or landmarks with the photograph can only be checked under UV light.

[0037] However, the image contours can also be provided as a hologram or volume hologram, whereby a carrier layer film, such as a holographic film, is exposed with the image-specific results, in particular the contours, and this is then precisely applied to the photograph, glued and sealed.

[0038] In a further embodiment, the image-specific results are removed from a layer area above the photograph, particularly on the visible side of the data carrier, for example by laser ablation. The result is a data carrier card with a photograph, in which the contours milled into the visible side, as tactile indentations, precisely match the contour of the underlying photograph in a genuine document.

[0039] According to a preferred embodiment, the data carrier comprises one or more layers made of the following plastics or their derivatives, namely polycarbonate, bisphenol A polycarbonate, carboxy-modified PC, polyesters such as polyethylene terephthalate (PET), its derivatives such as glycol-modified PET (PETG), carboxy-modified PET, polyethylene naphthalate (PEN), vinylic polymers such as polyvinyl chloride (PVC), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polystyrene (PS), polyvinylphenol (PVP), polypropylene (PP), polyethylene (PE), polyacrylonitrile butadiene styrene, polyamides, polyurethanes, polyureas, polyimides or thermoplastic elastomers (TPE), in particular thermoplastic polyurethane (TPU).

[0040] A particularly preferred embodiment with a luminescent ink is explained in detail below.

[0041] In this embodiment, the light image features not only the visible light image but also an invisible luminescent contour image, which can be made visible under a UV source, allowing the correspondence of the contour image with the visible light image to be verified. The visible light image is thus overprinted with its own invisible contour image.

[0042] By providing a contour image using a luminescent dye that only becomes visible under UV irradiation, any manipulation of the image (or photo) through over-gluing or overprinting under UV light becomes visible, since the unique contour calculated from the visually visible original photo, and especially its supporting structures, only matches the original photo. If the photo were manipulated in the visible range, the contour would no longer match the manipulated photo, thus revealing the forgery.

[0043] With a mechanical or chemical shave, which also alters the luminescent contour image, there is no longer any correspondence, either with the original photograph or with the manipulated image, making the forgery recognizable. This, of course, also applies to mechanical or chemical shaving of holograms or milled contours.

[0044] Thus, the photograph can be invisibly coded and thus secured using characteristic spatial image elements in this design.

[0045] Preferably, the contour or landmark image is printed with the luminescent transparent ink, while the visible light image is printed with the colored inks. In a preferred embodiment, the printer provides an additional color channel (spot color) for the luminescent ink in addition to the color channels for the chromatic colors (CMYK), so that all inks can be printed simultaneously.

[0046] The result is a photograph that is a "normal" image of the document holder in daylight or when irradiated with white visible light, but under UV excitation only the relevant contours or landmarks of the photograph are visible as luminescent lines.

[0047] In addition, the contour or landmark image can be printed first with the luminescent transparent ink and only then can the visible light image be printed into the contour or landmark image, or the visible light image can be created first and then the contour or landmark image can be printed into the visible light image.

[0048] In a further embodiment, the contour or landmark image is printed with the luminescent transparent ink onto a first carrier layer, for example, a polycarbonate-based one, and the visible light image is printed with the colored inks onto a second carrier layer, preferably also a polycarbonate-based one. The carrier layers are then positioned relative to one another and then joined, in particular laminated under increased temperature and pressure, as described in DE 10 2007 052 ​​947 A1.

[0049] In principle, any ink containing the desired UV-absorbing and visible-luminescent, transparent, soluble dyes suitable for printing on the respective data carriers can be used as luminescent transparent inks. The proportion of the luminescent dye is preferably up to 10% by weight.

[0050] For printing on data storage media based on polycarbonate polymer layers, the inks known from DE 10 2007 052 ​​947 A1 are preferably used. Such inks contain up to 20 wt.% of a binder with a polycarbonate based on a geminal disubstituted dihydroxydiphenylcycloalkane, at least 30 wt.% of an organic solvent, up to 10 wt.% based on the dry mass of a colorant or colorant mixture, and optionally functional materials, additives, and / or auxiliaries. Preferred solvents are hydrocarbons and / or ketones and / or organic esters.

[0051] These inks can be printed onto polycarbonate polymer layers using inkjet printers and then laminated to form a composite with convincing optical properties.

[0052] In luminescent transparent inks, the colorants or colorant mixtures are luminescent dyes. Luminescent dyes are substances that fluoresce, phosphorescent, or luminescent.

[0053] In order for the contour image printed with the ink containing the luminescent dye to be invisible when illuminated in the visible spectral range and thus transparent, the luminescent dye should not absorb or only very slightly absorb in the visible spectral range.

[0054] A pure substance or a mixture of luminescent dyes can be used as the luminescent dye. In principle, the luminescent dye can be an inorganic or organic substance, with organic luminescent dyes being preferred. The luminescent dye must be excitable by UV radiation and soluble in the respective ink solvent. The luminescent dye(s) can emit in the visible spectral range in various colors such as yellow, red, and green, but also in mixed colors or even nearly white.

[0055] Through the specific selection, combination, and, if necessary, concentration ratios of one or more luminescent dyes and their excitation and emission wavelengths, special luminescence can be generated that can be detected visually under a UV lamp, but also spectroscopically, and can represent an additional security feature. If multiple luminescent dyes are used that differ in their excitation and emission wavelengths, different luminescence colors can also be generated using different excitation wavelengths in the UV.

[0056] The selection and, if necessary, combination of special luminescent dyes thus enables an additional security feature, because counterfeiters would not only have to completely suppress the luminescence of the original contour image and integrate the contour image applied with luminescent ink into the counterfeit photograph, but would also have to use the same luminescent dye (mixture).

[0057] During verification, a digital image of the printed color photograph in the security document can be taken to calculate the expected contours or landmarks for the printed photograph from the digital data of the printed image. The expected contours are then compared with the luminescence contour image or landmark image of the printed image measured under UV irradiation. If the contours match, the photograph is authentic.

[0058] In order to be able to compare the contours calculated from the recorded printed photograph and thus to be expected in the photograph with the contours originally calculated and invisibly printed in the colour photograph, the digital recording of the printed photograph in the security document should be carried out under the same conditions as the production of the original digital image, i.e. under white light, preferably with an RGB camera.

[0059] Both the calculation of the contour or landmark image from the original digital image and the calculation of the contour or landmark image from the captured printed image are performed using the same algorithm. Thus, the luminescence contour or landmark image captured under UV irradiation can be compared with the contour or landmark image calculated from the printed image.

[0060] Because the UV light penetrates the deeper layers of the security document during irradiation, the luminescent dye can absorb the UV radiation and convert it into luminescent light, even beneath the surface of the security document and beneath a forged overprinted photograph. The contour image created in the layer of the original image when UV radiation is absorbed by the luminescent dye is visible on the surface of the security document even if the original image is covered by a forged photograph, since a large portion of the luminescent radiation passes through the layer of the forged image.

[0061] Security documents in the form of book-like documents such as passports include, in addition to the laminated data carrier, a book cover and a book block that encloses the data carrier.

[0062] The invention and further advantageous embodiments and developments thereof are described and explained in more detail below with reference to the examples shown in the drawings. They show: Figure 1 the falsification of the photograph of a document holder by overprinting, Figure 2 a digital photograph, a contour calculated from it and the superposition of the calculated contour with two different photographs, Figure 3 the production of a printed photograph with an overprinted contour image, Figure 4 the verification of the contours, Figure 5 the production of contours in the visible side of a data carrier with a laser, and Figure 6 the production of contours in a data carrier with a light image in the form of a (volume) hologram

[0063] Figure 1The photograph of a document holder shows "original," the photograph of another person shows "overprint," and the falsification of the original by overprinting the photograph of the other person. As long as the security features of the original remain intact during the falsification, the forgery cannot be detected.

[0064] In Figure 2 A digital image 10 ("Image 1") and the contour image 13 of this image 10 ("Contour 1") calculated using Canny Edge Detection are shown. When the contour image 13 (Contour 1) is superimposed on the image 10 (Image 1), the contours match; Contour 1 "matches" Image 1.

[0065] However, if you overlay the contour image 13 "Contour 1" with the light image 10' (Image 2), which deviates from Image 1, you can see, for example, in the chin and eyebrow area, that the portrait in Image 2 deviates from Contour 1.

[0066] Since different people have different contours and the contours are image-specific, these can be used for verification.

[0067] The contour image 13 (contour 1) printed with the luminescent ink 24 is preferably only visible under UV irradiation.

[0068] Figure 3 shows the advanced processing of image data in the context of personalizing a security or valuable document. In addition to processing the digital photograph 10 in a raster imaging process (RIP) for color printing of the photograph 15 with the colored inks 16, 17, 18, 19, the contours of the digital photograph 10 are extracted using Canny edge detection. Specific contours or support structures are calculated from the portrait and output as a separate contour image ("Canny contour").

[0069] This contour image 13 is prepared as a separate color channel (spot color) during printing and is printed simultaneously with the color colors (cyan, magenta, yellow, key (CMYK)) using transparent luminescent ink 24, which is only visible under UV irradiation ("spot").

[0070] As a result, a printed photograph 15, 13 is produced, which in the visible range is a "normal" image 15 of the document holder in the printing colors YMYK, in which the contours are encoded, since these are only visible as luminescent lines under UV excitation.

[0071] In order to prove the verifiability of the authenticity of a photograph using the Canny contours, Figure 4 The original photograph 10 (top) and the forgery 10' (bottom), from which the respective Canny contour images 13, 13' were calculated. The overlay of the Canny contour images 13, 13' from the original 10 and the forgery 10' shows that they do not match.

[0072] During verification, the visible light image 15 is captured with an RGB camera under white light, and the expected contours are calculated using the Canny Edge method. Verification should be performed using the same method as the image data preparation.

[0073] The document is then excited with UV radiation, for example, at a wavelength of 365 nm, and the luminescence image of the contour image 13 is recorded and compared with the image of the calculated expected contours. Matches between the measured contour image 13 printed with the luminescent ink 24 and the contours calculated from the RGB image verify the light image 15, or, if there is a discrepancy, indicate tampering.

[0074] Figure 5shows on the left side schematically the structure of a data carrier 20 of a security document, which consists of several layers 27 and a printed photograph 15, which are laminated together to form a composite. The printed photograph 15 is located within the layer composite. The area 25 of the layer 27, which extends above or over the photograph 15 in the direction of the visible side 28, is transparent and thus allows a view of the photograph 15. In this area 25 of the layer 27 located above the photograph 15, in the example of the Figure 5 into the visible side 28 in the area 25 of the layer 27, the contours 13 (support contours) or landmarks 14 are now produced by laser ablation in a precise fit into the finished data carrier 20 with a suitable laser 40, for example a CO 2 laser (wavelength 10 micrometers) or a CO laser (wavelength 5 micrometers).

[0075] The result is a data carrier in which the contours 13, 14 are milled precisely above the printed image 15, whereby the contours 13, 14 represent more or less tactile depressions.

[0076] In Figure 6 On the left side, a holographic film 26, i.e., a carrier layer film 26, is shown, into which the calculated contours are exposed by means of a laser 40 to produce a hologram 13. Subsequently, the holographic film 26 is precisely applied to the data carrier 20 above the printed image 15, bonded to the data carrier 20 by means of an adhesive layer 29, and the surface is subsequently sealed with a scratch-resistant varnish 30.

[0077] The result is a data carrier with a light image 15 and precisely fitting holographic contours above the light image 15. List of reference symbols

[0078] 10Digital image 13Contour image 14Landmarks image 15Printed visible image 16Color ink 17Color ink 18Color ink 19Color ink 20Data carrier 24Luminescent transparent ink 25Area of ​​the data carrier above the image 15 26Film 27Layer of the data carrier 28Visible side of the data carrier 29Adhesive layer 30Scratch-resistant varnish 40Laser

Claims

1. A method for verifying the authenticity of a visible photographic image (15) printed on a data carrier (20), which is encoded with detectable image-specific results, wherein the data carrier has several layers (27, 29), characterized in that image-specific results to be expected from the visible photographic image (15) are calculated and then the correspondence between the calculated image-specific results and the image-specific results (12) encoded in the photographic image (15) or in an area (25) of a layer (27) above the photographic image (15) is checked, the image-specific results calculated from the visible light image being contours or positions of individual specific points of a face.

2. Method according to claim 1, in particular for a security or value document, characterized in that the calculation of the image-specific results from the visible photographic image (15) is carried out by producing a digital recording of the printed visible photographic image (15) and calculating from this the image-specific results to be expected.

3. Method according to claim 1 or 2, characterized in that the verification of the correspondence between the expected image-specific results and the coded image-specific results is carried out by comparing the calculated, expected image-specific results with a luminescence contour image or luminescence image of specific points of the face in the printed photographic image (15), measured under UV irradiation.

4. Method according to claim 2 or 3, characterized in that the digital recording of the printed photographic image (13, 14, 15) in the security or value document is carried out under white light with an RGB camera.

5. Method according to one of claims 1 to 4, characterized in that the verification of the authenticity of the coded visible photographic image (15) is carried out in an automated manner.

6. Method according to claim 2 or 3, characterized in that the calculation of the expected image-specific results from the visible photographic image (15) is carried out using the same algorithm as the original calculation of the image-specific results from the data of a digital photograph.

7. Method according to one of the claims 1 to 6, characterized in that the visible photographic image (15) is printed with coloured inks (16, 17, 18, 19) based on data from a digital photographic image, image-specific results are calculated from the data of the digital photographic image and the visible photographic image (15) or an area (25) of at least one layer (27) of the data carrier (20) above the photographic image (15) is coded with these results in detectable form (13, 14).

8. Method according to claim 7, characterized in that the coding of the photographic image (15) is carried out simultaneously with, before or after the printing of the visible photographic image (15), or the coding of the area (25) of the layer (27) above the photographic image (15) is carried out after printing the photographic image (15) or that the coding is carried out in a supporting layer film (26) which is then positioned and fixed above the photographic image (15).

9. A method according to one of the preceding claims, characterized in that the coding is visible or invisible in visible light.

10. A method according to one of the preceding claims, characterized in that the calculation of the contours is carried out using Canny edge detection, in particular in the form of supporting contours or specific contours.

11. A method according to one of the preceding claims, characterized in that the detectable image-specific results are printed in the visible photographic image (15) or in an area (25) of the layer (27) above the photographic image (15) by means of a luminescent transparent ink (24), or in the form of a hologram, barcode or milling or in another visually, haptically or otherwise perceptible or measurable form in an area (25) of the layer (27) above the photographic image (15).

12. Method according to claim 11, characterized in that the milling is carried out by laser ablation or in that the hologram is introduced into the layer region (25) above the photographic image (15) by exposing a holographic carrier layer film (26) with the image-specific results and then positioning this on the printed photographic image (15) and sealing it if necessary.

13. A method according to any of the preceding claims, characterized in that the data carrier (20) has one or more layers (25, 26) made of the following plastics or their derivatives, namely polycarbonate, bisphenol-A-polycarbonate, carboxy-modified PC, polyesters, polyethylene terephthalate (PET), glycol-modified PET (PETG), carboxy-modified PET, polyethylene naphthalate (PEN), vinyl polymers such as polyvinyl chloride (PVC), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polystyrene (PS), polyvinylphenol (PVP), polypropylene (PP), polyethylene (PE), polyacrylonitrile butadiene styrene, polyamides, polyurethanes, polyurea, yrene (PS), polyvinylphenol (PVP), polypropylene (PP), polyethylene (PE), polyacrylonitrile butadiene styrene, polyamides, polyurethanes, polyurea, polyimides or thermoplastic elastomers (TPE), in particular thermoplastic polyurethane (TPU).

14. A method according to any one of the preceding claims 3 to 13, characterized in that the printing of the printed photographic image (15) encoded with image-specific results has been carried out by means of luminescent transparent ink (24) and the luminescent transparent ink (24) comprises up to 10 % by weight of at least one soluble luminescent dye that can be excited by UV radiation and emits in the visible spectral range, or that the printing of the printed photographic image (15) coded with image-specific results is carried out with inks (16, 17, 18, 19, 24) which comprise up to 20% by weight of binders having a polycarbonate based on a geminally disubstituted dihydroxydiphenylcycloalkane and at least 30% by weight of organic solvents, in particular hydrocarbons and / or ketones and / or organic esters.

15. A method according to one of the preceding claims, characterized in that the detectable coding can be made visible in the visible spectral range or under electromagnetic irradiation and the verification of the correspondence of the visible visible photographic image (15) with the detectable coding is carried out visually in daylight or under electromagnetic irradiation.

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