ES3013238T3 - Method for verifying the authenticity of an image printed on a carrier for a security or value document - Google Patents

Abstract

The invention relates to a method for checking the authenticity of a visible image (15) printed on a data carrier (20) encoded with detectable image-specific results (12), wherein the expected image-specific results (12e) are calculated from the visible image (15) and then checked for consistency with the image-specific results (12) encoded in the image (15) or in the region (25) of the layer (27) above the image (15). (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Procedure for verifying the authenticity of a printed image on a support for a security or valuable document

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

Security documents, such as ID cards or driver's licenses, often contain photographs as a security feature. When producing ID cards, the digital photo data is processed using the Raster Imaging Process (RIP). The image visible on the security document is printed with colored inks in the three standardized optimal colors: cyan, magenta, yellow, and, if necessary, black.

To detect photo manipulation, a common practice is to add security features to the photos, which can be provided, for example, in an area of the image to be tampered with.

Security documents are falsified, among other things, by applying a photograph of another person over the photograph of the document holder.

The application of the other person's photograph can be done, for example, directly using an inkjet printing process to print the actual photograph directly onto the card surface, or indirectly by first printing on a transfer film and then laminating the image over the actual photograph. Particularly good forgeries leave other security features, such as luminescent background printing or kinematic holographic structures (Identigram), virtually intact, so that the document appears virtually intact or slightly aged.

Therefore, manipulation of photographs of real documents to create false identities is an increasing threat.

Document US 2003/0173406 A1 shows 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.

Document DE 600 04 529 T2 describes security documents with personalized visible and invisible markings that cannot be seen without the intervention of an external factor.

Document DE 69624400 T2 refers to security documents that have a printed image and a compressed digital image encoded on the magnetic image medium.

Document DE 697 11482 T2 shows a certificate bearing an image engraved on an engraving plate.

Document US 5,421,619 is known as a security document with a photograph of the holder and an interpolated image of the photograph applied with a laser.

Document DE 102006052651 A1 relates to a data carrier with a first graphical representation and a second graphical representation, which is better protected against manipulation and is designed as a reference to detect manipulations of the first representation, with only partial areas of the first and second representations overlapping.

EP 2209653 B1 discloses processes for producing polymer layer composites for security and valuable documents.

Furthermore, document DE 102014214548 A1 relates to a method for producing a document, in which the document layer is printed with a color in a spatial area by means of a printing process, the color dries, the color in the area assumes a random surface structure due to drying, the randomly created surface structure is optically recorded, encoded and stored as a security feature.

The invention is based on the objective of indicating a method for detecting manipulation of security and valuable documents.

This object is solved by the features stated in claim 1. In the method according to the invention for verifying the authenticity of a visible photograph printed on a data carrier, which is encoded with image-specific detectable results, the image-specific expected results are calculated from the visible photograph and then their coincidence with the image-specific results encoded in the photograph or in the area of the upper layer of the photograph is verified.

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 manner.

Since the visible photograph itself is encoded with the specific results of the image or the area of a layer above the photograph and the encoding is detectable, the authenticity of the image can be verified based solely on the photograph and, where appropriate, on the layer area of the data carrier above the photograph.

The coding can be visible or invisible under visible light. Invisible coding has the advantage that it is not easily recognized by a counterfeiter. The coding can, in principle, be performed on the visible photograph at the same time as the printing of the visible photograph, but also before or after the printing of the visible photograph.

To the extent that the coding is not carried out on the photograph itself, but in an area of one or more layers above it, i.e. on 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 on the visible side of the data carrier itself above the photograph, the photograph is first printed and then the coding is carried out in the area in one or more layers above the photograph.

In another embodiment, the photograph is printed and, independently of this, the coding is performed with the specific results of the photograph image on a support layer film, which is then positioned and fixed above the photograph.

Within the scope of the invention, specific image results calculated from the digital photograph are understood to mean contours or positions of individual, specific points of a face (reference points) determined from the respective portrait, i.e. all specific results that can be unambiguously calculated from the digital photograph by calculation using a specific algorithm.

The calculation of image contours from the visible photograph can be performed, for example, using Canny Edge Detection (Canny algorithm). Canny Edge Detection (or Canny) is a robust edge detection algorithm widely used in digital image processing. It is divided into several convolution operations and provides a photograph that, ideally, only contains the edges of the original image.

With Canny Edge detection, specific, i.e., unambiguous contours or support contours can be extracted from a portrait based on the algorithm and generated as a separate contour image. Of course, other algorithms can also be used to extract a contour image from the visible photograph.

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

In order to verify the match of the visible photograph with the specific image results encoded in the photograph, the specific image results must be detectable. In order to be able to detect, i.e., observe, recognize, measure, or see, these specific image results encoded in the photograph, the specific image results can be printed on the visible photograph, in particular by means of a luminescent ink, or can be introduced into the layer area above the visible photograph, for example in the form of a hologram, barcode, milling, or in another visually or haptically perceptible or measurable form.

The authenticity of a photograph printed on a data carrier can be visually verified using visible encoding, such as a hologram or milling. Furthermore, image-specific expected results can be calculated from the visible photograph and then verified to match the image-specific results encoded in the photograph or in the layer area above it.

If the image-specific expected results calculated from the printed photograph match the image-specific coded results, the photograph is genuine and has been produced using the procedure.

If no match is achieved, the printed visible photograph is a forgery, since there is no specific image result encoded in the printed visible photograph or the specific image results encoded in the photograph do not match the photograph, since, for example, the original photograph has been overprinted.

For 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 must be performed using the same algorithm as the original calculation of the image-specific results from the digital photograph data.

The authenticity of the visible light encoded image is preferably verified automatically.

In addition to automated verification or as an alternative to it, the coding can also be verified visually, to the extent that it is visible or can be made visible by irradiation with electromagnetic radiation, such as UV radiation.

Once the image-specific results, which have been calculated from specific image data of the photograph, are deposited on the photograph itself or entered into an area of the layer above the photograph, it can be determined by checking only the photograph and, where appropriate, the area of the layer above the image, whether the photograph has been manipulated or not, because if the image-specific results deposited on the photograph do not match the photograph, it is a forgery.

Therefore, the authenticity of the document can be verified by checking only the photograph itself and, if applicable, the area above it, preferably automatically, allowing for secure and rapid verification.

Image-specific results are image contours or reference points (positions of individual specific points on the face) calculated from the specific image data.

Specific image results can be deposited on the photograph in various ways, for example by printing the contours or reference points of the image onto the photograph using luminescent transparent ink, so that the contours or reference points of the image are only visible under UV light and therefore the matching of the contours or reference points of the image with the photograph can only be verified under UV light.

However, the image contours can also be provided as a hologram or volume hologram, where a carrier layer film, such as a holographic film, is exposed to light with the specific image results, in particular the contours, and then applied, glued and sealed onto the photograph with a precise fit.

In another embodiment, image-specific effects are removed from an area of the layer 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 depressions exactly match the contour of the underlying photograph on a real document.

According to a preferred embodiment, the data carrier comprises one or more layers made of the following plastics or their derivatives, in particular 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), 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, polyimides or thermoplastic elastomers (TPE), in particular thermoplastic polyurethane (TPU).

A particularly preferred configuration with a luminescent ink is explained in detail below.

In this configuration, in addition to the visible photograph, the photograph also features an invisible luminescent contour image, which can be made visible under a UV source. This allows the contour image to be verified as matching the visible photograph. The visible photograph is therefore overprinted with its own invisible contour image.

Because the contour image is generated using a luminescent dye that is only visible under UV irradiation, manipulation of the image (photograph) by gluing a film onto it or by superimposing it becomes visible under UV light, since the unambiguous contour, calculated from the visible original photograph and in particular its supporting structures, coincides exclusively with the original photograph. If the photograph were manipulated visibly, the contour would no longer match the manipulated photograph, and the forgery would be exposed.

In the case of mechanical or chemical erasure, in which the luminescent contour image is also altered, there is no longer any match to either the original photograph or the manipulated image, so the counterfeit can also be recognized. Of course, this also applies to the mechanical or chemical erasure of holograms or milled contours.

The photograph can therefore be invisibly encoded and thus protected by characteristic spatial image elements.

Preferably, the printing of the contour image or reference points with the transparent luminescent ink occurs simultaneously with the printing of the visible photograph with the colored inks. In a preferred configuration, in addition to the color channels for the various colors (CMYK), the printer provides another color channel (Spotcolour) for the luminescent ink, so that all inks can be printed simultaneously.

This creates 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 reference points of the photograph become visible as luminescent lines.

In addition, the contour or reference point image can also be printed first with the luminescent transparent ink and only then can the visible photograph be printed on the contour or reference point image, or the visible photograph can be generated first and then the contour or reference point image printed on the visible photograph.

In another embodiment, the contour or reference point image is printed with the luminescent transparent ink on a first support layer, for example, based on polycarbonate, and the visible photograph is printed with the colored inks on a second support layer, preferably also based on polycarbonate. The support layers are then positioned and then bonded together, in particular laminated with increasing temperature and pressure, as described in DE 102007052947 A1.

In principle, transparent luminescent inks can be used that contain the desired UV-absorbing, luminescent, and visibly transparent soluble dyes suitable for printing on the respective data carriers. The proportion of luminescent dye is preferably up to 10% by weight.

For printing data carriers based on polycarbonate polymer layers, the inks known from DE 102007052947 A1 are preferably used. Such inks contain up to 20% by weight of a binder with a polycarbonate based on a disubstituted geminal dihydroxydiphenylcycloalkane, at least 30% by weight of an organic solvent, up to 10% by weight, based on the dry mass, of a dye or dye mixture, and, where appropriate, functional materials, additives and/or auxiliaries. Preferred solvents are organic hydrocarbons and/or ketones and/or esters.

These inks can be printed onto polycarbonate polymer layers using inkjet printers and then laminated into a composite with compelling optical properties.

In luminescent transparent ink, the dyes or mixtures of dyes are luminescent dyes. Luminescent dyes are substances that are fluorescent, phosphorescent, or glow.

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

The luminescent dye can be a pure substance or a mixture of luminescent dyes. 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 ink's respective solvent. The luminescent dye(s) can emit various colors in the visible spectrum, such as yellow, red, green, but also in mixed colors or even near-white.

Through the specific selection, composition, and, where appropriate, the concentration ratios of one or more luminescent dyes and their excitation and emission wavelengths, special luminescences can also be generated. These can be detected visually under a UV lamp, but also spectroscopically, and can represent another safety feature. If several luminescent dyes are provided that differ in their excitation and emission wavelengths, different luminescence colors can also be generated with different UV excitation wavelengths.

The selection and, where appropriate, combination of special luminescent dyes therefore provides an additional security feature, as 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 (or mixture of luminescent dyes).

During verification, a digital recording of the printed color photograph can be made on the security document to calculate the expected contours or reference points of the printed photograph from the digital data of the printed image. The expected contours are then compared to the luminescent contour or reference point image measured under UV irradiation. If the contours match, the photograph is authentic.

In order to be able to compare the contours calculated from the registered printed photograph, and therefore expected in the photograph, with the contours originally calculated and invisibly printed on the color photograph, the digital registration of the printed photograph on the security document must 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.

Both the calculation of the contour or reference point image from the original digital photograph and the calculation of the contour or reference point image from the recorded printed photograph are performed using the same algorithm. Therefore, the luminescent contour or reference point image recorded under UV irradiation can be compared with the contour or reference point image calculated from the printed photograph.

Since ultraviolet light penetrates deeper layers of the security document during irradiation, the luminescent dye can also absorb UV radiation below the surface of the security document and also below a counterfeit superimposed photograph, converting it into luminescent light. The contour image created in the original image layer after the absorption of UV radiation by the luminescent dye is visible on the surface of the security document even if the original image is covered by a counterfeit photograph, since a large portion of the luminescent radiation passes through the counterfeit image layer.

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 containing the data carrier.

The invention and other advantageous embodiments and improvements thereof are described and explained in more detail below by means of the examples shown in the drawings. In the drawings:

Figure 1 shows the falsification of a photograph of a document holder by superprinting;

Figure 2 shows a digital photograph, a contour calculated from it, and the superposition of the calculated contour with two different photographs;

Figure 3 shows the production of a printed photograph with a superimposed contour image;

Figure 4 shows the verification of the contours;

Figure 5 shows the generation of contours on the visible side of a data carrier using a laser; and

Figure 6 shows the creation of contours on a data carrier with a photograph in the form of a hologram (volume).

Figure 1 shows a photograph of a document holder "original", a photograph of another person "superimposed", and the forgery of the original by superimposing the photograph of the other person. If the security features of the original remain intact during the forgery, the forgery cannot be recognized.

A digital photograph 10 ("image 1") and the contour image 13 of this photograph 10 ("contour 1") calculated using Canny Edge detection are shown in Figure 2. When the contour image 13 (contour 1) is superimposed on the photograph 10 (image 1), the contours coincide, contour 1 "snaps" to image 1.

However, if the contour image 13 "contour 1" is superimposed with photograph 10' (image 2) which differs from image 1, it can be seen, for example in the area of the chin and eyebrows, that the portrait in image 2 is different from contour 1.

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

Preferably, the contour image 13 (contour 1) printed with the luminescent ink 24 is only visible under UV irradiation.

Figure 3 shows the extended processing of image data in the context of personalizing a security or valuable document. In addition to preparing the digital photograph 10 in a Raster Image Processor (RIP) for color printing of the photograph 15 with color inks 16, 17, 18, 19, the contours of the digital photograph 10 are extracted using Canny Edge detection. Here, specific contours or support structures are calculated from the portrait and generated as a separate contour image ("Canny Contour").

This contour image 13 is prepared during printing as a separate colour channel (Spotcolour) and at the same time with the various colours (cyan, magenta, yellow, key (CMYK)) with transparent luminescent ink 24, which is only visible under UV irradiation ("Spot").

This generates a printed photograph 15, 13, which is visible as a "normal" image 15 of the document holder in YMYK printing colors, in which the contours are coded, since these are only visible as luminescent lines under UV excitation.

To demonstrate the verifiability of the authenticity of a photograph using Canny contours, Figure 4 shows the original photograph 10 (top) and the forgery 10' (bottom), from which the respective Canny contour images 13, 13' have been calculated. Superimposing the Canny contour images 13, 13' of the original 10 and the forgery 10' shows that they do not match.

During verification, visible photograph 15 is recorded with an RGB camera under white light, and the expected contours are calculated from it using the Canny Edge method. Verification should be performed using the same procedure as for preparing the image data.

The document is then excited, for example, with UV radiation at a wavelength of 365 nm. The luminescent 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 photograph 15 or, in the event of a discrepancy, indicate tampering.

Figure 5 on the left shows a schematic representation of 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 material. The printed photograph 15 is located within the layered composite material. The area 25 of the layer 27, which extends above the photograph 15 or over it in the direction of the visible side 28, is transparent and thus allows the photograph 15 to be viewed. In this area 25 of the layer 27 located above the photograph 15, in the example of Figure 5 on the visible side 28 in the area 25 of the layer 27, the contours 13 (carrier contours) or reference points 14 are then generated precisely on the finished data carrier 20 by laser ablation with a suitable laser 40, for example a CO2 laser (wavelength 10 micrometers) or a CO laser (wavelength 5 micrometers).

The result is a data carrier in which the contours 13, 14 are precisely milled above the printed photograph 15, the contours 13, 14 representing more or less tactile depressions.

On the left side of Figure 6, a holographic film 26 is shown, i.e. a carrier layer film 26, on which the contours calculated by a laser 40 are exposed to light to generate a hologram 13. The holographic film 26 is then precisely applied onto the data carrier 20 over the printed photograph 15 and bonded to the data carrier 20 by means of an adhesive layer 29, and then the surface is sealed with a scratch-resistant varnish 30.

The result is a data carrier with a 15-photo and precisely adjusted holographic contours above the 15-photo.

List of reference symbols

10 Digital photography

13 Contour image

14 Image of reference points

15 Visible printed photograph

16 Color ink

17 Color ink

18 Color ink

19 Color ink

20 Data support

24 Luminescent transparent ink

25 Data carrier area above image 15

26 Movie

27 Data carrier layer

28 Visible side of the data carrier

29 Adhesive layer

30 Scratch-resistant varnish

40 Laser

Claims (15)

1. A method for verifying the authenticity of a visible photograph (15) printed on a data carrier (20) which is encoded with image-specific detectable results, the data carrier comprising a plurality of layers (27, 29), characterized in that image-specific expected results are calculated from the visible photograph (15) and the image-specific results calculated are then checked for consistency with image-specific results (12) encoded in the photograph (15) or in an area (25) of a layer (27) above the photograph (15), the image-specific results calculated from the visible photograph being contours or positions of individual specific points of a face. 2. Method according to claim 1, in particular for a security or valuable document, characterized in that the calculation of the image-specific results from the visible photograph (15) is carried out by producing a digital record of the printed visible photograph (15) and calculating from this the expected image-specific results. 3. Method according to claim 1 or 2, characterized in that the verification of the coincidence of the expected image-specific results with the coded image-specific results is carried out by comparing the calculated expected image-specific results with a luminescence contour image or a luminescence image of specific points of the face in the printed photograph (15), measured under UV irradiation. 4. Method according to claim 2 or 3, characterized in that the digital recording of the printed photograph (13, 14, 15) on the security or valuable 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 photograph (15) takes place automatically. 6. Method according to claim 2 or 3, characterized in that the calculation of the image-specific results to be expected from the visible photograph (15) takes place 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 claims 1 to 6, characterized in that the visible photograph (15) is printed with colored inks (16, 17, 18, 19) from data of a digital photograph, image-specific results are calculated from the data of the digital photograph and the visible photograph (15) or an area (25) of at least one layer (27) of the data carrier (20) above the photograph (15) are encoded with these results in a detectable manner (13, 14). 8. Method according to claim 7, characterized in that the coding of the photograph (15) is carried out simultaneously with, before or after printing of the visible photograph (15), or the coding of the area (25) of the layer (27) above the photograph (15) is carried out after printing of the photograph (15), or in that the coding is carried out on a support layer film (26) which is then positioned and fixed above the photograph (15). 9. Method according to one of the preceding claims, characterized in that the coding is visible or invisible in visible light. 10. Method according to one of the preceding claims, characterized in that the calculation of the contours is carried out by detecting the edges with Canny-Edge-Detection, in particular in the form of support contours or specific contours. 11. Method according to one of the preceding claims, characterized in that the image-specific detectable results are printed on the visible photograph (15) or in an area (25) of the layer (27) above the photograph (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 photograph (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 area (25) above the photograph (15) by exposing a film (26) of holographic support layer with the specific image results to light and then positioning it on the printed photograph (15) and sealing it if necessary. 13. Method according to one of the preceding claims, characterized in that the data carrier (20) comprises one or more layers (25, 26) of the following plastics or derivatives thereof, 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, polyimides or thermoplastic elastomers (TPE), in particular thermoplastic polyurethane (TPU). 14. Method according to one of the preceding claims 3 to 13, characterized in that the printing of the printed photograph (15) encoded with specific image results is 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 which can be excited by UV radiation and emits in the visible spectral range, or in that the printing of the printed photograph (15) encoded with specific image results is carried out with inks (16, 17, 18, 19, 24) comprising up to 20% by weight of binder with a polycarbonate based on a disubstituted geminal dihydroxydiphenylcycloalkane and at least 30% by weight of organic solvents, in particular hydrocarbons and/or ketones and/or organic esters. 15. 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 coincidence of the visible photograph (15) with the detectable coding is carried out visually in daylight or under electromagnetic irradiation.