DE102016001464A1 - Verification of an item provided with a security element - Google Patents

Abstract

The invention relates to a method for verifying an object (10) provided with a security element, in which the security element is produced in a multi-step process with register fluctuations and in a test field (12) an individual characteristic feature of the security element in the form of an overlay of at least two points. or line scraps (14-B, 16-B) produced in the production of the security element in different manufacturing steps with register fluctuations, and whose screen widths differ and / or which are rotated against each other, wherein in the method, the test field (12) of the Security elements with a camera (30) is detected optically, the positions of maxima and / or minima of the superposition of the at least two dot or line grids (14-B, 16-B) resulting Moiré grid (20) are determined and therefrom a test value for the individual characteristic of safety element is formed, the test value formed is compared with a reference check value, and based on the comparison result, a Verifikationsresultat for the object provided with the security element is created. The invention also relates to an associated computer program product, a verification system for carrying out the method, a security element or a checking device for such a verification system, and an article provided with such a security element.

Description

The invention relates to the verification of an object provided with a security element, and relates in particular to a verification method together with associated computer program product, a verification system for carrying out the method, a security element or a checking device for such a verification system and an object provided with such a security element.

Data carriers, such as valuables or identity documents, but also other valuables, such as branded goods, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data carrier and at the same time serve as protection against unauthorized reproduction.

For reliable authentication of such security elements often expensive inspection devices are used, for example, in cash deposit machines or banknote processing machines in commercial banks. In many cases, however, such complex devices are not available, for example, when testing a security element "in the field" or when used to secure an extended or bulky item security element that can not be easily brought together with the object in a tester. In this case, a hundred percent authenticity check is often not necessary, but it is sufficient to be able to recognize or exclude a readjustment or transfer of the security element to another object with high probability.

Proceeding from this, the object of the invention is to provide methods and associated devices with which an article provided with a security element can be verified easily and nevertheless with high reliability. In particular, verification using a smartphone as a test device should also be possible in the field.

• – das Prüffeld des Sicherheitselements mit einer Kamera optisch erfasst wird,
• – die Positionen von Maxima und/oder Minima der durch die Überlagerung der zumindest zwei Punkt- oder Linienraster entstehenden Moiré-Raster bestimmt werden und daraus ein Prüfwert für das individuelle charakteristische Merkmal des Sicherheitselements gebildet wird,
• – der gebildete Prüfwert mit einem Referenzprüfwert verglichen wird, und
• – auf Grundlage des Vergleichsergebnisses ein Verifikationsresultat für den mit dem Sicherheitselement versehenen Gegenstand erstellt wird.

The invention therefore includes a method for verifying an article provided with a security element, in which the security element is produced in a multi-step process with register fluctuations and contains in a test field an individual characteristic feature of the security element in the form of an overlay of at least two dot or line grids produced in the production of the security element in different manufacturing steps with register fluctuations, and whose screen widths differ and / or which are rotated against each other, wherein the method

• - the test field of the security element is optically detected with a camera,
• The positions of maxima and / or minima of the moire grid resulting from the superimposition of the at least two dot or line grids are determined and from this a test value for the individual characteristic feature of the security element is formed,
• - the test value formed is compared with a reference test value, and
• - Based on the comparison result, a Verifikationsresultat for the provided with the security element object is created.

Although in the following, for the sake of simplicity, the majority of the moire fringes resulting from the superimposition will be discussed in the majority, it is understood that the overlaying can also produce only a single moiré raster and that this is often even preferred in many designs.

In the method, the reference check value is advantageously formed during or after the production of the security element or during or after the article has been provided with the security element, by the positions of maxima and / or minima of the moire arising from the superposition of the at least two point or line grids -Raster be determined and from the reference check value is formed.

The reference check value can be stored together with an individual identification of the security element and / or the object in a database and queried for comparison with the test value formed from the database.

Alternatively or additionally, the reference check value, in particular in encrypted or coded form, can be present on the security element or on the object provided with the security element and read in for comparison with the formed check value. A reference test value applied to the security element or article is advantageously applied using pressure-free methods, for example in the form of a laser marking, by means of ink-jet or toner-based methods. In this case, it is also possible to dispense with storing the reference check value in a database, so that an expensive database with short access times and a very large dataset can be dispensed with.

The code containing the reference check value may be proprietary to this method or may be based on standard methods such as Data Matrix or other 2D codes, with the data contained in the code advantageously encrypted and / or signed. For encryption and decryption standard methods can be used, advantageous are asymmetric procedures with public and private keys, whereby also proprietary derivations of these procedures can be used, as long as the necessary safety standards are kept.

In addition, prior to the comparison of the test value and the reference test value, further tests may be performed to confirm the use of printing methods from the security print, thus excluding copies based on always pixelated scans. Advantageously, the typically quite high resolution of smartphone cameras is exploited. In addition, a simple plausibility check can check whether the same test field has already been read in unusual time or space. Made field checks can not only be recorded for this purpose and so foci with many counterfeits can be determined. When using banknotes, a central bank is simultaneously enabled by access to the check data to observe the circulation behavior of their notes and to derive therefor plan data that helps to avoid unnecessarily high or too small volumes in printing and also in stockpiling.

In an advantageous embodiment, the test field of the security element is detected optically with a smartphone camera and the determination of the positions of maxima and / or minima of the moiré raster and the formation of the test value by a software program running on the smartphone, also referred to below as App.

In order to have a large number of register fluctuation combinations, the verification method is advantageously performed on a test field containing a superposition of three, four or more dot or line grids generated in different production steps with register fluctuations in the production of the security element, and whose screen widths differ and / or are rotated against each other.

The verification method is advantageously carried out on a test field whose dot or line raster are generated at least partially by printing processes, in particular offset printing, indirect high-pressure, gravure gravure, screen printing, letterpress printing, stamp printing or flexographic printing. Also advantageously, the verification method is performed on a test field, the point or line grid are at least partially formed by applications, in particular applied film elements, or by elements or windows on the applications. Further advantageously, the verification method is carried out on a test field whose dot or line patterns are at least partially formed by laser cuts, perforations, watermarks, laser markings, ink-jet labels or toner-based methods. For printing inks, glazing colors are an advantage, but opaque colors can also be used. The inks can have the same hue or different hues, so that in the superimposed dot or line areas mixed colors.

With regard to the achievable resolution, the finest line on banknote substrates in the background printing (indirect high-pressure) is typically positive 30 μm, negative 50 μm, usually 40 μm or 80 μm wide; is in offset printing the finest line on banknote substrates typically positive 25 microns, negative 35 microns, usually 30 microns and 50 microns wide; In intaglio printing, the finest line on banknote substrates is positive 15 μm, negative 10 μm, usually 50 μm or 30 μm wide; is in screen printing the finest line positive 250 microns, negative 500 microns, usually 400 microns or 900 microns wide; and is in the stamp printing (imprinting the numbering) the finest line usual 700 microns wide. If the aforementioned dot or line patterns are printed, in particular indirect high-pressure, offset printing and / or intaglio printing are used because of the high resolution.

With pressure-free process, a variation of the dot or line grid can also already generated in a single pass and thereby additional information is introduced into the test field. For example, the spacing of the dot or line grids generated in a manufacturing step may be varied and the local distribution stored in a database along with an individual tag, such as a serial number.

In the verification method, the positions of maxima and / or minima of the moiré rasters in two orthogonal spatial directions are preferably determined and taken into account in the formation of the test value. This is particularly useful when using dot screens whose screen widths differ in two spatial directions in different ways.

In an advantageous variant of the method, at least two of the dot or line grids are in different colors and the optical detection takes place in several color channels. In this case, the resulting moiré rasters can only be recognizable or easily recognizable in a part of the color channels, so that imitations can be more easily identified.

In order to enable a particularly reliable test value determination, the test field can have several subregions, in each of which there are different superimpositions of dot or line grids, in order to improve accuracy and accuracy Reliability of detection of maxima and minima of moiré rasters and determination of the test value increase. In this case, a partial test value can first be formed for each partial area and the partial test values then combined to form a total test value, for example by summing, multiplying, dividing or correlating, or by a combination with other evaluation methods such as pattern recognition. The subdivision into subregions can be carried out, for example, in the form of fields, rows or columns.

With particular advantage, the verification process is performed on a security element that is integrated into the article. For example, the security element may be part of a banknote or another value document. In this case, the test field is advantageously smaller than the object and, for example, expediently occupies at most half the area of the value document in the case of a document of value. The test field is further advantageously arranged close to a serial number, identification number or other code of the security element or object to be detected in order to easily detect both with the camera.

• – einem mit einem Sicherheitselement versehenen Gegenstand, bei dem das Sicherheitselement in einem Mehrschrittverfahren mit Registerschwankungen hergestellt ist und in einem Prüffeld ein individuelles charakteristisches Merkmal des Sicherheitselements in Form einer Überlagerung von zumindest zwei Punkt- oder Linienrastern enthält, die bei der Herstellung des Sicherheitselements in unterschiedlichen Herstellungsschritten mit Registerschwankungen erzeugt sind, und deren Rasterweiten sich unterscheiden und/oder die gegeneinander gedreht sind, und
• – einer Prüfvorrichtung für die Verifikation des Gegenstands, mit
• – einer Kamera für die optische Erfassung des Prüffelds des Sicherheitselements,
• – einer Auswerteeinheit zum Bestimmen der Positionen von Maxima und/oder Minima der durch die Überlagerung der zumindest zwei Punkt- oder Linienraster entstehenden Moiré-Raster und zum Bilden eines Prüfwert für das individuelle charakteristische Merkmal des Sicherheitselements daraus, und
• – Mitteln zum Vergleichen des gebildeten Prüfwerts mit einem Referenzprüfwert und zur Erstellung eines Verifikationsresultats auf Grundlage des Vergleichsergebnisses.

The invention also includes a verification system for carrying out the method of the type described above, with

• A security element provided article in which the security element is manufactured in a multi-step process with register fluctuations and contains in a test field an individual characteristic feature of the security element in the form of an overlay of at least two dot or line grids, in the production of the security element in different Manufacturing steps are generated with register fluctuations, and whose screen widths differ and / or are rotated against each other, and
• - a verification device for the verification of the article, with
• A camera for the optical detection of the test field of the security element,
• An evaluation unit for determining the positions of maxima and / or minima of the moiré raster arising from the superposition of the at least two dot or line grids and for forming a test value for the individual characteristic feature of the security element thereof, and
• - Means for comparing the formed test value with a reference test value and for generating a Verifikationsresultats based on the comparison result.

The test apparatus advantageously contains means for detecting a coded reference test value, for decoding the detected reference test value and for comparing the test value formed with the decoded reference test value.

The point and line grids, in particular the extent and the distance of the points or lines can be adapted to the requirements, for example, the resolution of the test apparatus.

• – das Verifikationssystem eine Datenbank umfasst, in der für die Sicherheitselemente jeweils ein Referenzprüfwert zusammen mit einer individuellen Kennzeichnung des Sicherheitselements und/oder des Gegenstands abgelegt sind, und dass
• – die Prüfvorrichtung Mittel zum Abfragen des Referenzprüfwerts oder des Vergleichsergebnisses von Prüfwert und Referenzprüfwerts aus der Datenbank auf Grundlage der individuellen Kennzeichnung des Sicherheitselements und/oder des Gegenstands enthält.

In an advantageous development, it is further provided that

• The verification system comprises a database in which for each of the security elements a reference check value is stored together with an individual identification of the security element and / or the object, and in that
• The test device contains means for interrogating the reference test value or the comparison result of test value and reference test value from the database on the basis of the individual marking of the security element and / or the object.

The test apparatus can be in particular a bank note processing machine or a smartphone. The camera of the test apparatus is set up in particular for optical detection in a plurality of color channels.

The invention also includes a security element for a verification system of the type described above, which is manufactured in a multi-step method with register fluctuations and contains in a test field an individual characteristic feature of the security element in the form of an overlay of at least two dot or line grids, which in the manufacture of Security elements are produced in different manufacturing steps with register fluctuations, and whose screen widths differ and / or which are rotated against each other, and the use of such a security element for verification of an article provided with the security element. The invention further includes an article, in particular value document, security paper, identity card or branded article with such a security element.

• – einer Kamera für die optische Erfassung des Prüffelds des Sicherheitselements,
• – einer Auswerteeinheit zum Bestimmen der Positionen von Maxima und/oder Minima der durch die Überlagerung der zumindest zwei Punkt- oder Linienraster entstehenden Moiré-Raster und zum Bilden eines Prüfwert für das individuelle charakteristische Merkmal des Sicherheitselements daraus, und
• – Mitteln zum Vergleichen des gebildeten Prüfwerts mit einem Referenzprüfwert und zum Erstellen eines Verifikationsresultats auf Grundlage des Vergleichsergebnisses.

The invention further includes a verification device for a verification system of the type described above

• A camera for the optical detection of the test field of the security element,
• An evaluation unit for determining the positions of maxima and / or minima of the moiré raster arising from the superposition of the at least two dot or line grids and for forming a test value for the individual characteristic feature of the security element thereof, and
• - means for comparing the generated check value with a reference check value and for generating a verification result based on the comparison result.

Finally, the invention also includes a computer program product having machine-readable program instructions for a control unit of a data-processing device, in particular a smartphone, which causes it to carry out a method of the type described above.

In further variants of the invention, individual codes or markings of the security element can be used, which are integrated into the design of the test field. On the one hand, these can serve to recognize the individual security element or the object and to identify it for a database query, and can also ensure that each individual security element remains distinguishable even with a coarser scan.

The individualization can consist in particular of characters, graphic elements, bar codes or 2D codes or the like and can either be recognizable as such or integrated into the design. Codes preferably have a redundancy of the useful contents or error correction elements. Preferably, the individualization is part of the data that gives the above test value.

For example, a numbering can overlay the test field and thus contribute to the test value. Since, for example, banknotes or other documents of value do not resemble each other's serial numbers, this contribution is always individual. If only a portion of the index is superimposed, it is advisable, on the basis of the usual numerical schemes, to use the rear characters of a digit changing from note to note in order to achieve a good distinction between the sheets; the front characters, on the other hand, to achieve a good distinction between the individual benefits within an arc. The test value can either be calculated purely according to the methods mentioned above or supplemented by an OCR reading of the numbering. For example, it is possible to use the letterpress numbering customary in banknote printing, but also printing-free methods such as laser marking or inkjet methods.

As a further example, color, color components or metallization of film elements can be removed or a color impression can be produced with a laser marking. Accordingly, prints in the test field can be individually modified by changing color fields by removing the color, by removing the absorbing color components, or by removing metallizations from film elements; but it can also be added by blackening of the substrate or color change another color impression. If a laser-absorbing ink is used for at least some of the prints, mixed forms of removal and addition may also occur.

In a particularly advantageous embodiment of a laser marking, the laser is only used to individually remove or lighten color for each security element. Although this may be visible in the test field recognizable to the user, it may also extend over a larger area of the object provided with the security element. These markings are expediently in areas produced with different steps and have for each banknote an individual position whose coordinates or relative position to each other also represent a test value. Advantageously, a film application is also included, ie demetallized by the laser approximately in areas.

In the case of a banknote, this check value can be assigned to the banknote identified by the serial number and an encrypted code can be applied to the banknote from the serial number, check value and, if applicable, signature of the issuing point, in particular once again using a pressure-free method, for example the same laser marking unit. In the latter case, the code with its relative position may also belong to the test value. All data may be advantageous, but need not be stored in a database for later tracking of the note.

The test value can be determined in the field and simultaneously read from the code with a public key and compared. For this method, the register fluctuations during printing and in the field need not be measured, since the position of the markings alone is of importance. Even a database query is not essential, but still beneficial.

In customization, ink-jet printers can be used primarily to print individual graphic elements or codes. In most cases, you can only add color, if necessary bleached by solvents or other substance combinations, but also color.

For example, the security element or check box may also contain links to consumer information, such as provided by QR (Quick Response) codes, or data matrix codes. Such codes may or may not be integrated into the design of the test field but may or may not contribute to the test value.

For the evaluation of an optically recorded test field, the image acquired by the smartphone camera can first be preprocessed in a manner known per se, for example by transformations in the spatial or frequency domain, for example by Fourier transformation or wavelet analysis, by projections, interpolations, for example between different ones Scattering, resolutions or coordinate systems, scaling, rotations, filtering, both isotropic and anisotropic, morphological methods, segmentation and feature extraction methods, pattern recognition, entropy measurement, or averaging.

In order to improve the results, a one-time calibration of the used camera of the tester in field may be required, for example by a white balance or the recording of a test pattern. The evaluation can be facilitated by registration marks, which can also result from distinctive points of the design, and thus improve the alignment and / or scaling of the image in the preprocessing. Even codes can advantageously serve as registration marks.

The evaluation can be facilitated and improved in the field and possibly also in the production by the recording of several images, possibly from different angles and distances (hereinafter referred to as video mode). In this case, security features in the test field can also be verified, which offer different impressions depending on the viewing angle.

Codes used within the scope of the invention may be visually recognizable as such and thus encourage use or may be integrated in the design of the test field and possibly even hidden. While hidden codes are advantageously two-dimensional in structure, the recognizable codes are advantageously 1d codes, such as bar codes EAN, 2 / 5i, UPC, Code128, and stacked 1d codes, such as PDF417, 2d codes , such as QR codes or data matrix or mixed forms.

In the present case, 2d codes in particular offer themselves, since the readout is advantageously carried out with cameras, ie 2d sensors. But there are also applications with bar code readers into consideration. The presentation must follow not known standards, but can also be proprietary. For example, it can be achieved that the content can only be read by a specific app on a smartphone.

The content of the code or codes on a security element may include a unique signature of the issuing office. The content may contain real or pseudo-random data. The content may also contain hashed test data for later comparison. For an application with mobile devices, in particular a smartphone, the use of asymmetric encryption methods is advantageous.

Since, as in biometrics, the actual measured quantities are analogue in nature, similar procedures are recommended for the storage in the production and the verification in the field: For example, a "fuzzy vault" can be used. For this purpose, additional error correction data (auxiliary data) can be applied to the security element or object or stored in a database, which ensure sufficient redundancy. The error correction and the elements to be read are advantageously closely matched. However, it is also possible to use standard biometric methods with a template read once and the definition of maximum allowed deviations in the measurement in the field.

Furthermore, the so-called Biometric Template Protection can be used in which instead of the test data protected reference data are stored, which allow a comparison, but no retroactive accounting on the original data. Again, a fuzzy vault can be used. Often, the fault tolerance can also be achieved by quantizing the analog input values.

For example, in order to compare similar data and determine the degree of correspondence, the method of "context triggered piecewise hashes (CTPH)", also known as "fuzzy hashing", can be exploited. Also statistical methods, such as the "Principal Component Analysis (PCA)" can be used or contribute to the storage and evaluation. Furthermore, the code can contain not only the optionally encrypted and signed check value, but also the possible range of variation. The fluctuation can also be included in an extra code. The fluctuation can also be encrypted and / or signed. During verification, the fluctuation range can then be measured, even with a different resolution, and compared with the specified value. Thus, it can be determined whether the test result is within a precision determined both in the first test and in the field. Depending on the resolution of the camera of the tester so increases the security of the verification. Simultaneous verification of a signature further increases security.

The security element or test field can be combined with other security features, in particular with security features that can only be identified by means of aids, as long as they have the evaluation the beneficial information lying in the visible range of the light does not affect or even contribute to this information. In this way, the test field can help to use the limited area, for example, on banknotes for other security elements, and / or it may indicate the actual function of the test field in the test with the help of additional devices.

For example, a fluorescent pressure over the test field in the form of a smartphone or in the form of a QR code may indicate that information is available for smartphones when the note is held at about a cash register under a UV lamp. An IR cut can also be provided in the test field, for example, without impairing its function.

Due to their register fluctuation, effect colors can contribute to the other printing processes on the one hand for information in the test field, on the other hand, for example, by color-shift effects allow testing without aids. If a code is checked from several directions, the color-shift effect can also be checked with the smartphone. This can be done for example by using the video mode described above when recording the test field.

Even paints, threads or foils with hard or soft magnetic pigments or vapor depositions can contribute to machine readability without disturbing the principle of the test field. The same applies to colors that show piezo, photo or thermochromic effects, which can also be electrically excited.

The test described the test field can be combined in the field with other methods that allow verification of the authenticity of the bill. These include, for example, an examination of the printing methods used, an examination of security features such as holograms or effect colors on angle-dependent correct image or color data, an examination of the interaction of printing ink and substrate in high-resolution images; a plausibility check with respect to the query times and locations of the same serial number, or a check for the presence of the serial number in a database of banknotes in circulation. Such supplementary procedures can easily preclude forgery of impressions in advance.

In addition to smartphones, stationary devices at banknote processing companies, stationary devices at points of sale and machines that collect banknotes, especially at commercial banks, as well as mobile devices, especially for checking the test areas for law enforcement authorities, Outlets, or offices and other authorities.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.

Show it:

1 a schematic representation of a banknote with a security element in the form of a printed on the banknote test field,

2 a detailed view of the test field of 1 .

3 a schematic representation of the verification of the banknote of 1 involved components,

4 further variants of test fields with dot screens and with mutually rotated point or line screens,

5 a test panel integrated in the graphic design of a banknote, and

6 a design in which a test field is present in a separate security element which is applied to a cash box to be secured.

The invention will now be explained first using the example of the verification of a banknote with the aid of a smartphone. 1 shows a schematic representation of a banknote 10 with a security element in the form of a on the banknote 10 printed test field 12 , This in 2 Test field shown in detail 12 is part of the banknote 10 and was used in the production of the banknote 10 generated along with the other printing elements on the banknote substrate. In other configurations, however, the test field can also be present on a separate security element, for example a transfer element, which is applied to a banknote or another article to be protected.

For authentication, the banknote 10 with the test field 12 in the manner described below, optically detected with a smartphone camera and verified using a test app installed on the smartphone.

The banknote 10 and the test field 12 are generated in a multi-step process with register fluctuations. For example, was on the banknote 10 in offset printing the value number 14-A , in engraving gravure a portrait 16-A and in book printing a serial number 18 applied. Simultaneously with the value number 14-A was in the test field 12 a line grid 14-B generated with a screen width of w ₁ = 200 microns in offset printing, as in the detailed representation of the test field 12 in the 2 shown in more detail. In a separate printing step was simultaneously with the portrait 16-A in the test field 12 a second line grid 16-B with the same orientation, but the slightly larger screen width of w ₂ = 220 microns generated.

As in 2 can be seen, arises from the superposition of the two line grid 14-B . 16-B a slightly different screen ruling (or equivalent: slightly different frequency) a moiré raster 20 with significantly larger screen width w _M (or equivalent: much smaller frequency). In 2 are the two line grids 14-B and 16-B For better visibility, also with non-overlapping areas drawn in a real test field 12 However, such non-overlapping areas are not required.

To explain the magnifying effect, the two line grid 14-B . 16-B for example, each black and white (unprinted) lines, each with the same width. Are the black lines of the first grid 14-B exactly at the place of the black lines of the second grid 16-B , the moire grid is bright in this area (minima of the moiré grid), since locally only about half of the area is still printed. Are the lines of the two grids 14-B . 16-B on the other hand exactly half a grid spacing apart, in this area practically the entire area is dark (maxima of the moiré grid), since the lines of the second grid 16-B straight into the spaces between the first grid 14-B fall.

Becomes the first line grid 14-B by half a pitch width w _1/2 from the second line grid 16-B shifted, the brightness ratios in the moiré grid are reversed 20 just around, so that results in the big moiré grid 20 has shifted by half the grid width w _M / 2. Since the distances of the moiré grid are much larger than the distances of the generating line grid, a small shift results in one of the two line screens 14-B . 16-B to a big shift in the moiré grid 20 , The measurement of the maxima and minima of the large moiré grid 20 requires a much lower resolution than the measurement of small line grid shifts 14-B . 16-B ,

Such small shifts of the line grid 14-B . 16-B against each other result from Passerschwankungen, due to the generation of the elements 14-A / 14-B respectively. 16-A / 16-B in each case separate operations with different manufacturing processes are inevitable.

The present inventors have now recognized that these inevitable registry variations of the various manufacturing processes may serve as a kind of fingerprint for identifying a particular security item or bill.

For estimation one can assume, for example, that the generation of the test field 12 involved manufacturing steps each register fluctuations of ± 1 mm in mutually orthogonal directions (hereinafter referred to as x and y direction) have. The maximum permitted variation is, for example, ± 1.5 mm. A typical smartphone camera with a nominal 6 megapixels has a resolution of 2848 × 2136 pixels. Is taken with such a camera an area that at least the test field 12 and the serial number 18 contains, for example, with a recording area of 120 mm × 90 mm, the result is a dot density of about 600 dpi or a resolution of 42 microns.

Has the first line grid 14-B as in the embodiment, a grid width w ₁ = 200 microns and the second line grid 16-B a raster width of w ₂ = 220 microns, so fall the lines of the first and second grid only after a distance of 2,200 microns again with the same shift on each other, that is, the enlarged moiré grid 20 has a grid width of w _M = 2.2 mm. Shifts due to register fluctuations, the first grid 14-B against the second grid 16-B , so also the maxima and minima of the enlarged moiré grid shift 20 , After a shift of the first grid 14-B a raster width w ₁ again results in original moiré rasters 20 that is, a shift of the first grid 14-B by 200 microns causes a shift of the moiré grid 20 by 2.2 mm, so the shift is so magnified in Moiré grid by a factor of 11.

This moiré magnification makes it possible to measure significantly smaller register errors with relatively low resolution, such as that of a smartphone camera. The above-mentioned factor 11 allows, for example, at a resolution of the camera of 40 microns (based on the resolution in determining the position of the maxima or minima in the moiré grid 20 ) To measure register differences of less than 4 μm. It should, of course, be taken into consideration that this measurement takes place "modulo raster width of the line raster", ie that with a raster width of 200 μm in the evaluation of the moiré raster, for example between a register error of 4 μm and a register error of (200 μm + 4 microns) = 204 microns can be distinguished.

Thus, in the present case, 200 μm / 4 μm = 50 different register situations can be distinguished before the Moire grid repeated. If, instead of a line grid, a two-dimensional dot matrix is used, as described below, the moiré magnification can be used in two directions and 50 × 50 = 2500 different register situations can be distinguished in the example given with a camera with a resolution of 40 μm.

Coming back to the presentation of the 2 The register fluctuations of the production steps lead to offset printing (elements 14-A . 14-B ) and engraving gravure (elements 16-A . 16-B ) to an offset of the two line grids 14-B . 16-B by measuring the positions of the maxima and / or minima of the moiré grid 20 can be well quantified as explained above.

For example, in another example, the first line grid 14-B in the line with a grid width of w ₁ = 55 μm and the two line grid 16-B be generated in offset with a grid width of w ₂ = 60 microns. The raster width of the superimposed moiré raster is then w _M = 660 μm, ie the magnification factor is equal to 12. At a resolution of 40 μm, a definable resolution in the first or second line raster of 3.3 μm results. If dot patterns are used instead of the line grid, then 198 × 198 = 39,204 distinguishable register fluctuations. With a higher camera resolution of 25 μm, there are already 72,182,016 possible distinctions. The closer the two screen rulings of the two screens are to one another and the finer the resolution of the camera, the more distinctions are possible.

As can be seen from the above estimate, the number of possible register fluctuation combinations in the current resolution of smartphone cameras in two line grids is usually still too low to be able to make a clear identification of a banknote. Nevertheless, the number of possibilities is already so great that despite the simple check with a smartphone with a positive verification with high probability on a real banknote can be closed. If a larger number of manufacturing steps are included, and / or dot patterns are used, the number of register fluctuation combinations can also be sufficient for a clear identification of a banknote.

The test value derived from the positions of the maxima and minima of the moire raster may be at or immediately after the production of the banknote 10 For example, in the quality control of banknotes, first recorded and along with the serial number 18 the banknote 10 as a reference check value in a database 34 ( 3 ) are deposited. In the database 34 is then the serial number 18 associated with certain positions of maxima and / or minima of the resulting moire grid. As explained above, the assignment does not necessarily have to be unique for meaningful verification.

For verification, the banknote 10 then, as in 3 shown by a user with the camera of his smartphone 30 photographed (reference numeral 32 ) and thus the test field 12 and the serial number 18 optically recorded. One on the smartphone 30 running test app can on the one hand via an OCR module serial number 18 the banknote 10 read and on the other hand via an image processing module, the positions of the maxima and / or minima of the moire grid 20 determine and from this the check value for banknote 10 form.

The testing app then builds a connection 36 from the smartphone 30 to the database 34 on and transmits the serial number 18 and the formed test value. In the database 34 the transmitted test value becomes the serial number 18 stored reference check value and the comparison result over the connection 36 transferred back to the testing app. This shows the result of the authenticity check, for example in the display 38 and may also give an audible feedback on the successful or failed verification for reinforcement. In one variant, the database can also transmit the stored reference check value to the check app and the comparison of the formed check value with the reference check value can be made in the check app itself.

Alternatively or additionally, the reference check value can also be encrypted on the banknote after its first detection 10 themselves be applied, for example in the form of a next to the test field 12 arranged barcodes 28 , For verification, the banknote 10 then by a user with the camera of his smartphone 30 photographed and thus the test field 12 together with the barcode 28 be captured optically. The on the smartphone 30 running test app then determines the positions of maxima and / or minima of the moiré grid via the image processing module 20 in the test field 12 , forms the check value for banknote 10 , reads the barcode 28 and decrypts the thus coded reference check value.

The determined test value is compared with the decrypted reference test value and the result of the authenticity check in the display 38 displayed and possibly also issued acoustically.

In 2 For the sake of simplicity, only two lines are produced in different production steps 14-B . 16-B It is understood, however, that in practice or line grids can be used in the test field, which are generated in three, four or more different manufacturing steps.

Regarding 4 Instead of line grid with advantage also dot matrix in a test field 40 can be used, which, as explained above, having an overlap in two spatial directions grid widths w _x and w _{y of} the resulting moiré grid, which may also be different.

In addition to dot and line screens with different screen rulings, point or line screens rotated against each other can also be used. For example, the test field shows 42 a superposition of two mutually rotated line rasters of the same screen ruling (w = 200 μm), in which the resulting moiré raster is rotated and has a significantly larger raster width wM than the original line raster. Similarly, the test field shows 44 a superimposition of two mutually rotated dot patterns of the same screen ruling (w = 200 μm), in which the resulting moiré raster is rotated and in each case has a significantly greater raster width (wA or wB) than the original dot rasters in two spatial directions.

In practice, the printing process typically does not overlay two black dot or line grids, but point or line grids of different colors. Although this reduces the brightness amplitude of the moiré raster, but as a further advantage that an obvious possibility of counterfeiting can be excluded, namely the imitation of the moiré raster by a normal halftone screen with corresponding brightness modulation. For example, in the simple case of two black line grids, a low resolution camera often can not distinguish between a true moiré raster and an imitation where the brightness modulations corresponding to the moiré raster are printed directly with only a halftone raster.

In a color print in combination with the evaluation of color images, such imitations can be recognized when the moiré screens are compared in different color channels. If, for example, a red and a green dot or line grid are printed, the red dots or lines in the red channel of the camera image are not or hardly distinguishable from the white paper, but the green dots are very dark or even barely distinguishable from black. In the red channel, the camera sees practically only the green grid and thus no moire. The situation is analogous in the green channel, where essentially only the red grid can be seen. In the blue channel, on the other hand, both the red and the green dots or lines are dark and the moire grid is clearly visible. If such a moiré raster is imitated by directly printing a correspondingly modulated halftone raster, the imitated moiré raster in all color channels is equally clearly recognizable, as a result of which the forgery can be recognized as such.

In the 4 shown test fields 40 . 42 . 44 can also be parts of a larger test field 46 in each of which there are different superimpositions of dot or line grids in order to increase the accuracy and reliability of the detection of the maxima and minima of the moire raster and the determination of the test value.

For the determination of the test value, the image captured by the camera of the smartphone is first preprocessed advantageously in the manner described above. In addition, other methods of image processing, such as edge detection can be used.

A test field does not need to exist as a separate field on the document, it can also be integrated into the graphic design of the document, as in the test field 50 of the 5 illustrated. In the embodiment shown contains a banknote 10 in a subarea a graphic 52 in the form of an angry tree whose tree trunk 54 the test field 50 is formed and provided with a grain, which in the manner described above by superposition of two applied in different printing process dot patterns as a moire raster 56 results. The dot patterns can be applied, for example, in stitch or offset printing in different printing steps. The positions of the maxima and minima of the moiré grid 56 depend on the individual characteristic register variations of the two printing steps. You can as described with the help of a smartphone camera 30 are detected and a test value derived therefrom are compared with a reference test value.

The user must be aware of the presence or location of the test field 50 in graphic design 52 not known. It suffices if the user uses the entire banknote or at least the design 52 with his smartphone camera 30 The test app records the location of the test field 50 and its properties to be tested, specifically the maxima and minima of the moiré grid used to determine the test value 56 knows. Should the recording quality not sufficient or the test field 50 not completely recorded, the test app can generate an error message and to re-recording, if necessary, with a reference to the area to be recorded.

6 shows a further embodiment in which a test field of the type described above in a separate security element 60 present on an object to be secured, such as a cashbox 62 , is applied. In the exemplary embodiment, the in 6 shown cashbox 62 filled, closed and the cover gap 64 with the security element 60 sealed. Then the test field of the security element 60 for example, with the camera of a smartphone 30 photographed (reference numeral 32 ) and from an app in the manner described above a check value for the security element 60 determined. Next is an identification number 66 the cashbox 62 either entered or captured with the camera. The app then builds a connection 36 to a database 34 and transmits the identification number 66 and the formed test value for the security element used for protection 60 , In the database 34 then the transmitted test value is the reference test value for the identification number 66 filed and thus the security element 60 with the cashbox to be backed up 62 connected.

After transporting the cashbox 62 The recipient may first check to see if the security element 60 is intact and then verify that the security element 60 actually to the identification number 66 the cashbox 62 belongs. For this he only needs the test field of the security element 60 take pictures with the camera of his smartphone and the identification number 66 the cashbox 62 enter or also photograph. The app then forms the check value for the security element 60 , if necessary, determines the identification number 66 via an OCR module, then builds a connection to the database 34 and transmits the identification number 66 and the formed test value. In the database 34 the transmitted test value is there with the identification number 66 stored comparison reference value and transferred the comparison result back to the smartphone app, which notifies the recipient of the success or failure of the verification.

LIST OF REFERENCE NUMBERS

10

bill

12

test field

14-A

value number

14-B

first line grid

16-A

portrait

16-B

second line grid

18

serial number

20

Moire pattern

28

barcode

30

Smartphone

32

photographic capture

34

Database

36

connection

40, 42, 44

test facilities

46

test field

50

test field

52

graphic

54

Tree trunk

56

Moire pattern

60

security element

62

cashbox

64

cover gap

66

identification number

Claims (20)

A method of verifying an article provided with a security element, wherein the security element is manufactured in a multi-step process with register fluctuations and contains in a test field an individual characteristic feature of the security element in the form of an overlay of at least two dot or line grids used in the manufacture of the security element are produced in different production steps with register fluctuations, and whose screen widths differ and / or which are rotated against each other, wherein the method - the test field of the security element is optically detected with a camera, The positions of maxima and / or minima of the moire grid resulting from the superimposition of the at least two dot or line grids are determined and from this a test value for the individual characteristic feature of the security element is formed, - the test value formed is compared with a reference test value, and - Based on the comparison result, a Verifikationsresultat for the provided with the security element object is created. A method according to claim 1, characterized in that the Referenzprüfwert is formed during or after the production of the security element or during or after the provision of the object with the security element by the positions of maxima and / or minima of the overlapping of the at least two point or grid of lines resulting Moiré grid are determined and from the reference test value is formed. A method according to claim 1 or 2, characterized in that the Referenzprüfwert stored together with an individual identification of the security element and / or the object in a database and is queried for comparison with the formed test value from the database. Method according to at least one of claims 1 to 3, characterized in that the reference check value, in particular in encrypted or coded form on the security element or on the provided with the security element Subject is present and read in for comparison with the test value formed. Method according to at least one of claims 1 to 4, characterized in that the test field of the security element is detected optically with a smartphone camera and the determination of the positions of maxima and / or minima of the moiré grid and the formation of the test value by a on the Smartphone running software program done. A method according to at least one of claims 1 to 5, characterized in that the verification method is performed on a test field containing a superposition of three, four or more dot or line grids, which are generated in the production of the security element in different manufacturing steps with register fluctuations , and whose screen widths differ and / or which are rotated against each other. Method according to at least one of claims 1 to 6, characterized in that the verification process is carried out on a test field, the dot or line grid are at least partially generated by printing process, in particular offset printing, engraving gravure, screen printing, letterpress, stamp printing or flexographic printing. Method according to at least one of Claims 1 to 7, characterized in that the verification method is carried out on a test field whose dot or line grids are at least partially present on applications, in particular on applied film elements, or are formed by elements or windows on the applications. Method according to at least one of Claims 1 to 8, characterized in that the verification method is carried out on a test field whose dot or line patterns are at least partially formed by laser cuts, perforations, watermarks, laser markings, ink-jet labels or toner-based methods , Method according to at least one of Claims 1 to 9, characterized in that the positions of maxima and / or minima of the moiré screens are determined in two orthogonal spatial directions and taken into account in the formation of the test value. Method according to at least one of Claims 1 to 10, characterized in that at least two of the dot or line grids are present in different colors and the optical detection takes place in a plurality of color channels. Method according to at least one of claims 1 to 11, characterized in that the verification method is carried out on a security element which is integrated in the object. Verification system for carrying out the method according to one of claims 1 to 12, with A security element provided article in which the security element is manufactured in a multi-step process with register fluctuations and contains in a test field an individual characteristic feature of the security element in the form of an overlay of at least two dot or line grids, in the production of the security element in different Manufacturing steps are generated with register fluctuations, and whose screen widths differ and / or are rotated against each other, and - a verification device for the verification of the article, with A camera for the optical detection of the test field of the security element, An evaluation unit for determining the positions of maxima and / or minima of the moiré raster arising from the superposition of the at least two dot or line grids and for forming a test value for the individual characteristic feature of the security element thereof, and - Means for comparing the formed test value with a reference test value and for generating a Verifikationsresultats based on the comparison result. Verification system according to claim 13, characterized in that the test apparatus comprises means for detecting a coded reference test value, for decoding the detected reference test value and for comparing the formed test value with the decoded reference test value. Verification system according to claim 13 or 14, characterized in that - the verification system comprises a database in which for the security elements in each case a Referenzprüfwert are stored together with an individual identification of the security element and / or the object, and that - the testing device means for querying the Reference check value or the comparison result of check value and reference check value from the database based on the individual marking of the security element and / or the object. Verification system according to at least one of claims 13 to 15, characterized in that the test device is a bank note processing machine or a smartphone. Security element for a verification system according to one of claims 13 to 16, which is manufactured in a multi-step method with register fluctuations and contains in a test field an individual characteristic feature of the security element in the form of an overlay of at least two point or line grids, which in the production of the security element in Different manufacturing steps are generated with register fluctuations, and the screen widths differ and / or are rotated against each other. Object, in particular document of value, security paper, identity card or branded article with a security element according to claim 17. Verification system verification apparatus according to any one of claims 13 to 16, comprising A camera for the optical detection of the test field of the security element, An evaluation unit for determining the positions of maxima and / or minima of the moiré raster arising from the superposition of the at least two dot or line grids and for forming a test value for the individual characteristic feature of the security element thereof, and - means for comparing the generated check value with a reference check value and for generating a verification result based on the comparison result. Computer program product comprising machine-readable program instructions for a control unit of a data-processing device, in particular a smartphone, which cause it to carry out a method according to one of claims 1 to 12.

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