CN114341874A - Object marking, generating and authenticating method - Google Patents

Abstract

An object marker (9) comprising a first security element (3) and at least a second security element (4), wherein each security element (3, 4) is associated with a set of data segments (6, 7) and each security element (3, 4) presents a code segment, depending on a capture condition, in particular a viewing angle (10) and/or a lighting direction, which is an opto-electronically readable representation of one of the data segments (5) in the set associated with the respective security element (3, 4), wherein different distinct data segments are represented by different code segments (5) and the set associated with the first security element (3) and the set associated with the second security element (4) differ in at least one data segment; a method for generating an object marker and a method for authenticating an object marker.

Description

Object marking, generating and authenticating method

The present disclosure relates to an object marker comprising a first security element and at least a second security element, wherein each security element is associated with a set of data segments and each security element presents a code segment which is an opto-electronically readable representation of one of the data segments in the set associated with the respective security element depending on a capture condition, in particular a viewing angle and/or an illumination direction. Furthermore, the present disclosure relates to a set of object markers.

Furthermore, the present disclosure relates to a base material for producing an object marking comprising a first security element and at least a second security element, wherein each security element is associated with a set of data segments and each security element presents a code segment which is an opto-electrically readable representation of one of the data segments in the set associated with the respective security element depending on a capture condition, in particular a viewing angle and/or an illumination direction. The disclosure also relates to a method for authenticating an object marker and a method for generating an object marker.

Various types of object markers for authentication or verification and base materials from which they can be produced and methods for authenticating or verifying them have been proposed in the prior art. For example, WO 2018/046746 a1 shows a sheet-like product comprising indicia and a security feature. The indicia is a machine readable code. The security feature is implemented by a security device separate from the indicia. The security device comprises two Optically Variable Devices (OVDs) placed side by side, for example different diffraction gratings exhibiting different colour variations that can be perceived, for example, by a camera or the naked eye. Thus, by ensuring that the two OVDs appear different, the presence of the security feature can be readily identified and verified using a programmable device comprising a camera. The security features all present substantially the same optically variable image, however with different starting angles. The sheet product has a plurality of different indicia, each indicia being flanked by a randomly selected security element.

The optical diffraction effect, i.e. the image that the optically variable device "emits" or appears to present, depends on the lighting conditions and the viewing angle. In a typical setup, a point-like light source is assumed, and the characteristics of the diffraction grating forming the security feature are designed for this particular lighting scene. In the design process, the physical structure is developed in such a way that it diffracts the incident light in the desired way, i.e. presents a certain image at a certain (azimuthal) angle. More specifically, a point-like light source at a specific position is assumed, and the diffraction grating is designed to present a specific image, for example, a specific color or shape, at different specific viewing angles. The known behavior of the security element is therefore limited to this specific lighting scene. Since the rendered image of an optically diffractive security device is inherently dependent on the illumination conditions and viewing angle, reading the actual content of the security feature becomes an inherent difficult problem in practice when defined environmental conditions cannot be ensured. Thus, an optically diffractive security element will, at least to some extent, react unpredictably under uncontrolled conditions. A typical way to overcome this problem is to provide some kind of equipment or other means (e.g., user guidance, special actions, training … …) to ensure that the conditions are at least similar to the environmental conditions used during the design process. The subject of the present invention is to overcome the limitations of a controlled environment for authentication.

The sheet product introduced in WO 2018/046746 a1 is specifically optimized for authentication by a programmable device comprising a camera, wherein the marking is used to determine the desired behavior of the surrounding security features. However, in practical uncontrolled settings, there are few instances where a defined lighting situation can be established during the verification process. Thus, the response of the safety device will be different than expected during the design process. Therefore, one is forced to extract illumination invariant features from illumination related optically variable security devices. Not surprisingly, this is an inherently difficult problem to solve and there is always a need to trade off between the stringency or accuracy and robustness of verification/authentication to account for uncontrolled lighting conditions and the effects of external unforeseen factors. This becomes particularly difficult if more than one point-like light source is present in the authentication setting. Furthermore, diffuse illumination may be understood as an indefinite number of (weak) point-like light sources. In such a multi-light-source setup, due to the lack of collimated incident light, different diffracted beams are inevitably superimposed onto the programmable device comprising the camera, eventually generating multiple superimposed images visible at a single angle. There is no reliable way to filter and distinguish the superimposed reflections, and therefore it is a significant challenge to verify a correctly emitted image at a particular angle.

Traditionally, optically variable devices have been designed primarily for the purpose of providing a satisfactory optical effect. The security of such devices is mainly due to the use of structures that others cannot produce, even if copying becomes difficult. To verify, expert knowledge is required, and the micro-and nanostructures are usually evaluated under laboratory conditions to verify the correct physical structure of the grating. Automatic verification on a macroscopic scale, for example based on a rendered image, for example by computer vision means, is generally not taken into account at all. Prominent examples of prior art optically variable devices are rainbow holograms (zero order/first order diffraction gratings, typically with colored reflections) or animations of geometrical shapes, such as rotating or moving objects, zooming effects (typically produced by nanostructures, micromirrors, etc.), etc. Because of the main goal of such OVDs, i.e., visually pleasing and verifiable under laboratory conditions, they are often attempted to create seamless animations and continuous color changes. In the ideal case considered in this way, conventional optically variable devices are designed with an indefinite number of images to provide a smooth optically variable effect, these indefinite number of images being provided as individual areas of mutually colored colors when the viewing angle is changed. This is achieved physically, especially for rainbow holograms, because the incident white light is only diffracted at the grating. Since rainbow holograms contain only one "pixel" that exhibits a smooth color transition, these OVDs cannot store or encode any form of distinct or distinctive data segment.

US 2012/0211567 a1, on the other hand, shows an animated bar code encoding a string of information, in particular a series of consecutive bar codes. The optical layer is arranged to affect the display of different barcodes at different viewing angles such that each barcode is displayed at a different viewing angle. The aim of this solution is to increase the data capacity stored in a single barcode area. To achieve this, ideal lighting conditions are implicitly assumed and indeed required. However, as mentioned above, such lighting conditions, while potentially acceptable for data storage applications, are not acceptable for security marking applications where reliable and convenient authentication is critical for user acceptance and ultimately necessary to reveal fraud and counterfeiting.

It is an object of the present invention to overcome the problems inherent in unpredictable images in an uncontrolled authentication environment. In particular, the present disclosure will provide a special design of an optically variable security element of an object marker that allows for more robust authentication using a programmable device comprising a camera, while making less compromise in authentication accuracy and precision.

The invention proposes an object marker as mentioned at the outset, wherein different distinct data sections are represented by different code sections, and wherein the set associated with the first secure element and the set associated with the second secure element differ in at least one data section. Thus, each security element presents (i.e. displays according to its light reflection properties) at least two different code segments depending on the capture conditions. The capture conditions may include viewing angle and/or illumination direction, where a change in either or both is necessary to reveal different code segments. Each code segment is an electro-optically readable representation of a data segment. The same data segment may be represented by one or more code segments. Each code segment represents exactly one data segment. The data segments represented by the code segments belong to a limited set of data segments associated with the respective secure element. The first secure element is associated with a first set of data segments. The second secure element is associated with a second set of data segments. Each set may include at least two data segments. The first set of data segments is different from the second set of data segments. For example, there may be at least one data segment located in the first set or the second set, but not in both sets. Thus, the code segments presented by the secure element and ultimately the secure element itself are different. The object marker may comprise more than two security elements that differ in the same sense; that is, the object marker may include three or more secure elements associated with a respective number of sets of data segments, where each set pair differs according to the above definition. In this group of security elements, each security element can therefore be distinguished from every other security element. Depending on the degree of similarity between the sets of interest (e.g., the number or ratio of data segments in more than one set), any two secure elements in such a group may be distinguished by reading one or more of the code segments of the sets of interest under a corresponding number of capture conditions. Each secure element may present a predefined maximum number of code segments so that they can be distinguished at least when the number of code segments is read from any two secure elements.

Without limiting the scope of the present disclosure, an object marker may additionally include similar secure elements, i.e., two or more secure elements associated with the same set of data segments. In the case of more than one group of similar security elements, the groups may differ in their size (i.e. the number of their security elements) and/or the relative arrangement between their members (e.g. the distance between security elements from the same group or the direction of the nearest neighbouring security element from the same group). These features and measures provide: distinct but similar security elements may be distinguished by their respective adjacent (or contiguous) dissimilar security elements. In other words, if adjacent (or consecutive) dissimilar security elements can be read, even similar security elements can generally be distinguished from each other. Essentially, what happens is that two or more sets of data segments are combined based on the geometric distance of their associated secure elements. The set of first combinations and the set of second combinations are then different on at least one data segment. In this case, for easier understanding, we refer to different "neighborhoods" of the security element.

Differentiating between different security elements or different neighborhoods may be used to increase the variety of object markers that may be generated from a given base material. Increased diversity means that the probability that any two real objects are labeled the same or even similar is reduced. The effort to counterfeit an object mark is proportional to the number of different instances that must be forged, since copying the same instance typically requires relatively little effort. In a preferred arrangement this can be achieved by observing the relative frequencies of verified object markers having the same indistinguishable pattern, and thus essentially being physically authentic replicas. This observation may be made by capturing all verifications from a single verification device that includes the camera or from a database, where verification data for multiple programmable devices that include the camera is captured. Since the probability of a genuine duplicate is low, the threshold for the frequency of the duplicate may be low, and thus a counterfeit may be easily detected if it is used to produce a higher than average number of duplicates. Thus, greater diversity makes counterfeiting more expensive and ultimately less attractive without a negligible risk of detection.

The invention also proposes a set of object markers, wherein the set comprises a plurality of object markers as defined above. For example, the set includes object tags of two or more of the above-defined types. The set of object markers, in particular when it contains more than 100, more than 1000 or more than 10000 object markers, exhibits statistical properties of a single object marker. In particular, for example, the average repetition rate of a secure element having any particular set of data segments, or the repetition rate of any particular neighborhood or combined set of data segments, may be determined from the set of object markers, or otherwise the set size determines the upper bound of such repetition frequency. In other words, the statistical properties of the collection are quantitative and measurable expressions of the diversity described above.

Furthermore, the invention proposes a base material as mentioned at the outset, wherein different distinct data sections are represented by different code sections, and the set associated with the first secure element and the set associated with the second secure element differ in at least one data section. A base material is provided for generating an object marker. Optionally, the base material comprises a sufficient number of security elements to produce at least two object markers or at least three object markers or more object markers. For example, the base material may comprise a two-dimensional array of security elements having significantly more than two security elements, for example an array of at least 5x5 security elements or an array of at least 10x10 elements or an array of at least 20x20 security elements. Without limiting the scope of the present disclosure, the base material, as explained above for a single object marker, may additionally include similar secure elements, i.e., two or more secure elements associated with the same set of data segments. All the above explained for a single object marker regarding distinguishable "neighborhoods" apply as similar possibilities to the base material. Furthermore, again without limiting the scope of the present disclosure, the base material may have a repeating sequence of security elements, wherein the period of repetition, i.e. the distance between repeating instances of the security element, is significantly larger than the size of a single object mark, e.g. at least ten times larger or at least one hundred times larger.

Furthermore, without limiting the scope of the present disclosure, the present invention proposes a method of generating an object mark by randomly or pseudo-randomly combining at least two different secure elements. The random combination may be achieved by changing the "neighborhood" configuration of the distinguishable security devices, i.e. arranging the "neighborhood" configuration differently for different object markers. In order to produce a security device comprising at least two different security elements by the method, the following apparatus can be used: the device is configured to randomly or pseudo-randomly select the at least two different secure elements from a limited set of distinguishable secure elements and place the at least two different secure elements in a particular geometric arrangement in a random or pseudo-random manner. More specifically, the security element may be pre-generated using any means suitable for generating an optically variable device. Furthermore, any registered transfer process suitable for transferring the pre-generated security element to a carrier material (forming an object marking) or to the object itself may be used. For example, registered hot or cold stamping, digital cold foil transfer or the like may be used to transfer at least two OVD-like security elements to a carrier material or object to produce a security device and an object marking according to the invention.

The invention also proposes a corresponding method for authenticating an object marker comprising an optoelectronically distinguishable delimited region of a base material (for example optionally forming the object marker on a carrier material or directly on an object), wherein the base material is a base material as described above, wherein the region comprises a first security element and at least a second security element, the method comprising the steps of:

capturing a first image of the object marker from a first angle or under a first illumination direction;

identifying a first code segment presented in a first image by a first secure element;

decoding the first code segment to obtain a first data segment;

capturing a second image of the object marker from a second angle and/or under a second illumination direction;

identifying a second code segment presented by the first secure element in the second image;

decoding the second code segment to obtain a second data segment;

a determination is made as to whether a set of data segments including a first data segment and a second data segment exists according to a model that stores a set of data segments associated with a secure element of a base material.

The above method essentially checks whether a combination of data segments contained in the first secure element has a corresponding set of data segments according to a defined storage model containing all valid sets of data segments. If no match is found, i.e. no corresponding set is found, the security element is likely to belong to a counterfeit object mark.

For authentication purposes of a particular secure element, it may be sufficient to observe only a subset of at least two code segments of all possible code segments of the particular secure element. In a preferred arrangement, an authentication method may be set up to confirm authenticity when observing N of the M possible code segments (known from the model) of the particular security element from different angles or under different capture conditions (e.g. lighting). Examples of parameters N and M are: n ═ 2(N must be greater than or equal to 2), M ═ 5(M must be greater than or equal to N, for example, M ═ N +1, M ═ N +2, M ═ N +3, M ═ N + 4). Since all code segments are independent, it is not important to decode N-2 out of M-5. Any combination is sufficient.

In general, it is sufficient for two or more different code segments for viewing a particular security element to be possible to change the viewing angle while keeping the illumination direction (e.g. the arrangement of the light source and the security element) unchanged.

Finally, the invention proposes a method for generating an object marker, comprising the steps of:

randomly, pseudo-randomly or deterministically selecting an area of a base material, wherein the base material is a base material as disclosed herein, the selected area comprises a first security element and at least a second security element, an

The selected regions are defined electro-optically discernably from the non-selected portions of the base material.

The method for selecting regions of the base material may contribute to the diversity of the resulting object markers. The random as well as pseudo-random selection ensures that no unintentional repetition with a reasonably high repetition rate is caused. Thus, these measures also increase the diversity. The selected shape, size or any other opto-electronically readable characteristic may vary. The selection may be done by cutting or punching from the base material, combining a plurality of security elements directly on the object or partially overprinting the base material and using a negative selection mask such that the base material is only visible in this mask area.

In a further preferred arrangement, the proposed base material is particularly suitable for producing a safety device as proposed in WO 2015/079014 a1 and/or for a safety system as introduced, for example, in WO 2013/188897 a1, since the selected position in the base material is known by the model. In such a specific setup, the randomness introduced by the selection process (e.g. due to manufacturing tolerances) is combined with a priori known geometric information from the model, which essentially maps the base material.

By providing a security element presenting a code segment representing the data segment electro-optically instead of e.g. a security element with a rainbow effect, i.e. smooth color variations, the authentication of the object marking is more robust. The reason for this is that it can be determined whether a code segment actually represents a valid data segment. Random or diffuse lighting conditions will result in the likelihood that an invalid security element will accidentally render a code segment representing a valid data segment much less likely than an invalid color-shifted image or a simple geometric shape will accidentally display a valid image. Furthermore, by presenting a secure element of a code segment representing a data segment, by scanning the code segment, the location (or one of a few valid locations) of the code segment in the original base material can be determined and the validity of the code segment can be verified by a model that associates a set (or neighborhood) of data segments with a location. In other words, the security element is used as a landmark in the model (e.g. a base material from which the object marker is generated by mapping). Since the secure element differs in at least one data segment, the location can be determined by varying the capture conditions. Alternatively or additionally, depending on the set, the position may also be determined by capturing the first and second secure elements under only a single capture condition and looking for corresponding combinations of adjacent sets (of adjacent or abutting secure elements). In this case, the "neighborhood" may be used as a landmark in the model. Notably, in order to authenticate at least one secure element in this arrangement, at least the second code segment (and corresponding data segment) needs to be viewed from at least a second, different capture environment to ensure that an OVD is indeed present (rather than representing a printed copy of the OVD, for example, in a single capture environment). It is also noteworthy that the object markers disclosed herein, particularly the secure elements, do not allow for the use of animated barcodes to encode more information than conventional barcodes. Rather, it allows authentication using animated bar codes.

In case of rendering according to capture conditions, a code segment is understood as a corresponding code segment that is physically displayed in at least some form. In particular, for each code segment there is at least one capture condition under which the code segment can be distinguished from other code segments of the security element and/or can be identified electro-optically from the code segments representing the data segments in the set of security elements. The viewing angle refers to the viewing angle of the object marking, more particularly to the viewing angle of the corresponding security element. For practical applications, it is important to mention: strictly speaking, the viewing angle and the capture conditions have been slightly different for adjacent security elements. This is a problem that is difficult to solve using the conventional optically variable device. One can design optically variable devices with features that are so robust that geometric offsets can be neglected. Alternatively, it is impractical from our experience that the capture conditions can be estimated from an observed rendered image from a first code segment and a mathematical model used to infer an expected rendered image of a second adjacent code segment.

An advantage that can be achieved using the present disclosure is that authentication is essentially checking whether a particular data segment belongs to a set of data segments for a particular secure element. The authentication method is very robust and no longer needs to take into account the diversity of capture conditions that occur within a single captured image due to geometric distortions across the security device or more specifically across the object marker.

The code segments of the second secure element preferably do not overlap at least partially, more preferably completely, with the code segments of the first secure element. The code segment representing the data segment from the set associated with the first secure element preferably does not at least partially, more preferably completely, overlap with the code segment representing the data segment from the set associated with the second secure element. Furthermore, the security elements themselves, i.e. the first security element and the second security element, may be at least partially non-overlapping or (completely) non-overlapping. That is, the first security element and the second security element may be arranged without overlap between the first security element and the second security element. The first security element and the second security element may for example be arranged adjacent, abutting or at a distance from each other.

Optionally, the set of data segments associated with each secure element is an aggregation of data segments represented in an opto-electronically readable manner by an aggregation of code segments presented under overall capture conditions. Optionally, for each data segment of the set of data segments associated with each secure element there is at least one code segment representing the data segment in an opto-electronically readable manner under at least one defined capture condition. That is, each code segment representing in an electro-optically readable manner a data segment of the set of data segments associated with each secure element is presented by the secure element under at least one defined capture condition.

According to a particular embodiment of the present object marker, for a fixed lighting direction, each data segment in the set associated with the security element (and therefore each code segment rendered by the respective security element) is associated with a distinct viewing angle region in which the contrast of the code segment representing the respective data segment is higher than the contrast of the code segments representing all other data segments from the same set. In other words, the code segments are associated with a range of viewing angles or regions from which they can be read. Instead, each view is attributed to only one particular code segment (and thus, data segment), but each code segment can be visible from multiple different views. The viewing angle range is usually dependent on the actual illumination and indeed may overlap in case of multiple distributed light sources. It is also worth noting that in practical applications, a particular data segment may be associated with a plurality of distinct views or view angle regions, where each view angle or view angle region may be due to just one data segment, i.e., there may be mutually exclusive distributions of views or view angle regions between particular sets of data segments associated with the secure element.

In this context, there may optionally be at least one view region associated with a data segment of the set of first secure elements that is different from each of the view regions associated with data segments of the set of second secure elements. Thus, there may be at least one of the following viewing angles: at the perspective, the first secure element changes the presented code segment while the second secure element does not change the presented code segment. More generally, the switching characteristics may be different between the first security element and the second security element. For example, due to the different sizes of the first set of data segments and the second set of data segments, the switching characteristics may be different: for example, a first set of data segments may consist of nine data segments and a second set of data segments may consist of 18 data segments, wherein the first secure element presents a different code segment (i.e. switching) every 20 ° between 0 ° and 180 ° views and the second secure element presents a different code segment (i.e. switching) every 10 ° between 0 ° and 180 ° views.

Each code segment may be a structured image, in particular a barcode-like structure, preferably a two-dimensional code, more preferably a two-dimensional array code. These types of images are relatively easy to read out electro-optically. In particular, the structured image may provide sufficient contrast to distinguish structures under different illumination conditions.

More specifically, each code segment may be a two-dimensional array code, wherein each code segment is an array of tiles, and the data segments are represented by the code segments by selecting one of at least two optically distinguishable states (e.g., dark or light, black or white) by each of the tiles of the code segment, wherein the code segment presented by the first secure element is arranged adjacent to the code segment presented by the second secure element. Two-dimensional array codes may have no delimitations and/or no look-up patterns between tiles of adjoining code segments.

According to an embodiment of the present disclosure, each code segment may represent a respective data segment in a predefined code, wherein the predefined code preferably comprises information for error detection or error correction.

Optionally, the predefined encoding may allow for a maximum number of possible distinct data segments, and the number of data segments in the set of data segments of each secure element may be less than 1/100, preferably less than 1/1000, more preferably less than 1/10000, of the maximum number of possible distinct data segments. In other words, only a small fraction of the possible data segments (and thus code segments) may actually be used. This may be used to detect read errors, which are likely to result in unused segments of read data, assuming that the read errors will be approximately equally related to all parts of the code segment. In this respect, the data sections used may be selected such that, for example, the code sections representing the data sections used differ over more than one tile (in the case of a tile-like two-dimensional array code), preferably more than two tiles, such that a single flipped tile will lead to unused data sections and thus to detectable read errors.

The position of the security elements relative to each other may be predetermined. These locations may be stored in the model, for example, and used to identify and distinguish neighborhoods of otherwise (at least partially) similar security devices, thereby increasing the diversity of distinguishable object labels.

Thus, with respect to the base material, the positions of the security elements relative to each other on the base material may be predetermined according to the model, and the data segments of the set associated with the security elements may be predetermined according to the model.

Thus, when the object marker is generated by randomly, pseudo-randomly or deterministically placing the secure element in a geometric arrangement, the location of the secure element may be recorded in a model or database. This information may be accessed during authentication.

Optionally, each code segment may represent a respective data segment in a predefined code, wherein the predefined code preferably comprises information for error detection or error correction. Error detection is particularly useful for triggering re-reading (i.e. repeated read attempts) of the relevant code segment, wherein such re-reading will typically advantageously be performed under different lighting conditions, thereby increasing the chance that the same read error is not repeated any more. Error correction provides a more robust optoelectronic readout of a code segment, where read errors of small parts of the code segment can usually be tolerated. Thus, both error detection and error correction contribute to the robustness of the read-out. This reduces the likelihood that the true object tag will be rejected (false rejection). It is worth mentioning that especially the use of well known error correction coding such as Reed-Solomon is considered to be susceptible to error decoding when used for very small data segments, e.g. 16 bits, but with high error correction capability.

As an extension of what was discussed above for single object marking, the predefined encoding may allow for a maximum number of possible distinct data segments, and the number of distinct data segments in the set of data segments for all secure elements (i.e., on the base material) may be less than 1/100, preferably less than 1/1000, more preferably less than 1/10000, of the maximum number of possible distinct data segments. As mentioned above, this sparse use of data segments can be exploited to further minimize the number of false rejects for known bugs with very small data segments in the error correction code.

With respect to the method for authenticating an object identification, the method may further comprise the steps of:

identifying a third code segment presented in the first image or the second image by the second secure element;

decoding the third code segment to obtain a third data segment;

determining whether a second security element positioned relative to the first security element is associated with a set of data segments containing a third data segment according to a model storing a set of data segments associated with the security elements of the base material and storing the relative positions of the security elements of the base material with respect to each other. In this case, the optically variable property of the second security element is verified, and in addition, the contained information is used to increase the diversity of the object marking.

According to a particular embodiment of the method for authentication, the security elements of the base material may be arranged in a tiled manner, wherein the object mark comprises a part of the security element and each code segment presented by the security element is an array of tiles, and the code segments presented by one security element are arranged to be malleable to the code segments presented by the other security elements such that a larger array of tiles is formed, wherein the method further comprises the steps of:

a) identifying a first sample tile in a first image;

b) decoding a first segment of sample data in a first image to obtain a first segment of sample data, the first segment of sample data formed from a first array of sample tiles including the first sample tile at a predefined location;

c) determining, from a model storing a set of data segments associated with a secure element of a base material, whether there is at least one set of data segments containing the first sample data segment;

d) if such a set cannot be determined in step c), repeating steps a) to c) using a different first sample tile until such a set is found in step c); and

l) identifying the current first sample code section as the first code section.

Optionally, more specifically, the method may further comprise, before step l), the steps of:

e) identifying a first sample tile in a second image;

f) decoding a second sample code segment formed by the first sample tile array in the second image to obtain a second sample data segment;

g) determining, from a model storing sets of data segments associated with a secure element of a base material, whether at least one of the at least one set including the first sample data segment includes the second sample data segment;

h) if such a set cannot be determined in step g), repeating steps a) to g) until such a set is found in step g); and

m) identifying the current second sample code segment as the second code segment.

Finally, to optionally further refine the method for authentication, the method may further comprise, before step l) -and, if applicable, before step m) -the steps of:

i) decoding a third sample code segment formed of a second sample tile array positioned relative to the first sample tile array to obtain a third sample data segment;

j) determining, from a model storing a set of data segments associated with the secure element of the base material and storing the relative positions of the secure elements of the base material with respect to each other, whether a third sample data segment is contained in a set of data segments belonging to secure elements respectively positioned with respect to the secure element to which the set preliminarily identified in step e) belongs;

k) if such a set cannot be determined in step j), repeating steps a) to d) and i) to j) and preferably e) to h) until such a set is found in step j);

n) identifies the current third sample code segment as the third code segment.

Reference is now made to the drawings, which are for the purpose of illustrating the disclosure and not for the purpose of limiting the same.

Fig. 1a schematically shows a first embodiment of a base material for generating an object marker with six complete security elements according to the present disclosure, and visually indicates two sets of data segments associated with two of the security elements below the object marker;

FIG. 1b schematically shows an object marker and indicates the code segments of a presentation at three different view angles;

fig. 2 schematically shows a second embodiment of a base material for generating an object marker with sixteen security devices presenting a two-dimensional array code as code segments, wherein the code segments at different viewing angles are indicated, according to the present disclosure; and

fig. 3a to 3c schematically show a method for authenticating an object tag according to the present disclosure.

As a basic building block of the base material 1 and the resulting object marker 8 according to the present disclosure, a security element 2 optimized to be able to authenticate using a programmable device comprising a camera is proposed in a first embodiment. The security elements 2 of the base material 1 can each only display a very limited, discrete set of distinguishable images. This means that: due to the possible combination of illumination settings and an indefinite number of viewing angles, each image in the limited set will be visible from multiple viewing angles. In practice, such a security device 2 may be designed by creating an optical element that presents a specific picture over a range of (azimuthal) angles, i.e. displays the same picture over a range of +/-5 degrees. This can be achieved by lenticular lenses, diffraction gratings, micromirrors and micro-lenses, nanostructures, etc.

The displayed image of the security element may be an image in the "traditional" sense, such as a geometric shape, a combination of shapes, different colors, a pixilated image, etc. In the present disclosure, these images are also referred to as code segments. We will then show different possible configurations of the base material (typically a sheet product) and different embodiments of the present disclosure.

For purposes of summarizing the main functions of the present disclosure, we assume in fig. 1a for illustrative purposes the following settings: in this setup, the set of available images consists of images from the lower case characters of the Latin alphabet, i.e. { a … … z }. Fig. 1a also exemplarily presents a part of the proposed base material 1 comprising a plurality of security elements 2. For easier understanding, we will focus the explanation on the first security element 3 and the second security element 4. The first secure element 3 is configured to: one image (or generally code segment) 5 of a first set of images 6 (or generally code segments representing data segments from a first set of data segments) is rendered according to the viewing angle. The second secure element 4 is configured to: one image (or typically a code segment) 5 of the second set of images 7 (or typically a code segment representing a data segment from the second set of data segments) is rendered according to the viewing angle. The number of images in the two sets 6, 7 and the angular coherence may be different, i.e. the images in the first set 6 may have different switching characteristics than the images in the set 7. Furthermore, some images may appear in multiple sets, e.g., 6 and 7, as long as the sets themselves are distinguishable, i.e., not all elements are equal.

As previously mentioned, various production processes may produce selection or object markers 9 from the base material 1.

Fig. 1b shows an exemplary object marking 9 after selection from the base material 1, which object marking 9 contains the first security element 3 and the second security element 5. Fig. 1b also shows the selected presented image (or code segment) 5 when viewed from a different angle 10. The first secure element 3 displays an image (or code) "a" which is a member of the set of images 6 corresponding to the first secure element 3, when viewed from a first angle 10 α. At the same viewing angle, the second secure element 4 displays an image (or code) "z", which is a member of the set of images 7 corresponding to the second secure element 4.

Similarly, at an angle 10 β, the first security element 3 appears "s", while the second security element 4 appears "v", both "s" and "v" being members of the respective image sets 6, 7. We note that due to the very limited set of available images and the varying number of possible illumination/perspective scenes, different combinations or all combinations of images may be possible. For example, at a viewing angle of 10 γ, the first security element 3 again displays an image "a" 5 (similar to the angle 10 α), while the second security element 4 displays an image "b" 5. This scenario may also occur: if different switching characteristics, i.e. different optical elements and characteristics, are used for different security elements 2 in the design of the base material 1. The first security element 3 may have, in addition to a different set of images, a different switching characteristic/switching angle than the second security element 4.

As a symbolic annotation, we will use the capital letter a … … P to denote the different security elements 2 for the sake of clarity in the subsequent figures. We will use the letter "a" to denote the first secure element 3, and the letter "B" to denote the second secure element 4, etc. The first image (or code segment) 5 in the image collection 6 will then be denoted a _1, the second image (or code segment) 5 will be denoted a _2, etc. Similarly, the image (or code segment) 5 of the second secure element 4 of the corresponding second set of images 7 will be denoted B _1, the second image (or code segment) 5 will be denoted B _2, etc. In the simplest case, each code segment has a 1:1 relationship with the corresponding data segment. However, the scope of the present disclosure extends to the case where multiple code segments (e.g., A _1.1, A _1.2, etc.) may represent the same data segment (e.g., A _ 1). Associated with the collection are data segments. For simplicity, we will use the terms image, code segment, and data segment synonymously and labeled 5 in connection with the description of the subsequent figures.

In practical applications, when using computer vision means to verify or read certain images on programmable devices including cameras, the correctness of the reading/decoding of the images themselves is always an issue. Although the aforementioned example of color-shifted images sounds fairly simple, reading and classifying (absolute and even relative) colors remains a very difficult problem in the field of computer vision. Thus, it is not recommended to select different colors as different images to be presented. Geometric or structured images in general with good contrast are more reliable to read and decode, but it is still almost impossible to completely avoid decoding errors without taking any additional measures. Thus, in practical applications, the use of generic images or even alphabetic images (as used in fig. 1) poses no minor problems, however, in practice requires almost error-free reading. This is indeed desirable for the present purposes as we need a reliable method to determine from the decoded image whether its data segment representation is a member of the set of data segments for that particular secure element. Of course, we do not want to reject the actual object tag due to read errors to discourage consumer adoption.

In a preferred embodiment, the images 5 are designed in such a way that they can be read easily and almost error-free in an automated manner by a programmable device comprising a camera. One possible measure to ensure correct readability is to embed a parity-like and/or parity-like structure in each of the possible images. This concept is well known in the field of telecommunications; the image is structured into at least two separately readable/decodable portions and there is a relationship between these portions. In the field of information technology, these parts are commonly referred to as "codewords" -payload "and parity", respectively. The codewords/parts are read and decoded separately and then the decoding results are matched to each other. If the decoding results match, then a correct read is confirmed. Prominent methods implemented in the field of information technology are checksums, cyclic redundancy check codes (CRC) or Error Correction (EC) codes. In the field of visually decodable barcodes, especially Reed-Solomon coding, an example of EC codes, is popular.

Thus, as one possible embodiment of the present disclosure, we propose to use an image 5, which image 5 is optimized for robust readability/decodability using a programmable device comprising a camera. An intuitive option is to use a barcode-like structure, such as a two-dimensional code or a pixel-level structure, which represents codewords encoded using an EC code, such as Reed-Solomon encoding.

Such encoding provides the possibility of encoding any type of digital data segment (e.g. numeric, alphanumeric, binary, etc.). In a preferred arrangement, numeric or alphanumeric identifiers may be encoded in a 2D-like structure, and the set of possible images corresponds to the set of encoded identifiers.

While standard barcode structures such as DataMatrix-Codes, QR-Codes, etc. may be used, we propose to use codeword arrangements and custom structures using error correction coding, e.g., Reed-Solomon coding. This is more efficient in terms of space and data capacity, i.e. increases the number of possible images. This is due to the fact that: these standard barcode structures use special structures or patterns to encode version information, a Finder pattern to locate and size the code in the image, etc. We propose in the remainder of this document a method of locating and decoding such structures without the need for the normally used finder pattern or the like.

It is known from e.g. US 2012/0211567 a1 to use an optically diffractive layer to display different spatially overlapping linked barcode structures depending on the viewing angle. US 2012/0211567 a1 suggests the use of an optical layer which functions in such a way that when viewed from different angles, different barcodes are displayed. They also propose to use coding to link these at least two view-dependent codes together and determine their order. The main object of the present invention seems to be to increase the data storage capacity, and therefore efforts are made to establish links to recombine data into one data segment when reading different codes.

It is to be understood that in the present invention, the view-dependent images/code segments/data segments are independent of each other. Furthermore, in contrast to data storage applications, the present invention is designed to require only a small portion of a data segment from a particular set of data segments to be decoded. The order of decoding is irrelevant, as only the membership of the decoded data segment to a particular set of data segments identifying a particular secure element is important. Finally, the subject of the invention is the identification of the position of the security element within the base material by: the identity of a particular secure element and the location within the base material are determined by decoding at least one data segment from at least one view, preferably taking into account the decoding of other code segments under different capture conditions and determining their corresponding set membership, by using a priori knowledge of a model storing a set of data segments identifying the secure elements and their geometric relationship to each other. Thus, in strong contrast to e.g. US 2012/0211567 a1, instead of (physically) encoding the linking information and the order information within the data segments/code segments themselves, the relationship between the different data segments/code segments is determined by a predetermined model.

Fig. 2 shows a preferred embodiment of the present disclosure. The range of possible pictures is limited by 6 x 6 pixels, which may be black or white. The base material 1 comprises a plurality of security elements 2 arranged in a tiled manner. For example, a first secure element 3, identified as secure element a, is placed adjacent (or directly adjacent) to a second secure element 4, identified as secure element B. Each of the security elements 2 implements an optically variable element which displays one of N different images when viewed from different angles or illumination conditions. Thus, the first secure element 3 identified as secure element a may switch between N different images a _1, a _2, … … a _ N (5) of the set of possible images 6 for that particular secure element under different capture conditions α, β, … … ω. A similar second set of images 7 with available images B _1, B _2, … … B _ N is defined for the second secure element 4.

It is worth mentioning that in a practical setting, a trade-off needs to be made between the sensitivity of the switching, i.e. the "speed" and robustness of the switching effect. In particular, if there is diffuse illumination or a plurality of point-like light sources with similar intensities, crosstalk between the plurality of images may occur, i.e. two or more of the N images in the set of M possible images may be superimposed with different intensities. In this case, the error correction function becomes particularly useful because the error correction function allows filtering between superimposed images to some extent, or at least determines that an image cannot be reliably read under the current conditions.

In a practical setup, there is usually more than one illumination (light) source during readout. For example, there may be a dedicated light source linked to the authentication device comprising the camera. When operating in real-world conditions there is always some residual of ambient light, or even a point-like light source (lamp, sun … …) superimposed with a dedicated light source may be present. In another practical setup, there may not be a dedicated light source, but a superposition of multiple "natural" light sources. Furthermore, it may be beneficial to equip the authentication device comprising a camera with a plurality of dedicated light sources, which may be switched on and off one at a time, or in a preferred arrangement simultaneously, creating a mix of different, more or less directional light sources.

Crosstalk between multiple images caused by multiple light sources or diffuse light may be exploited during readout. Based on the information learned from the model and with the error correction function, the superimposed image can be decomposed and a plurality of code segments can be decoded. This allows that in some cases a security element can be verified from a single captured image if the superimposed image can be successfully decomposed into at least two different code segments belonging to the set of available code segments for the particular security element. A very simple way to achieve such decomposition is as follows:

determining the intensity of the main code segment in the superimposed image from the superimposed image (e.g. by grey value and histogram analysis)

-filtering all other intensities to separate highlighted code segments

-decoding the separated highlighted code segment

-determining the respective secure element and thus the set of available code segments for the particular secure element.

Continue with other possible strengths and attempt decoding as well.

A secure element may be considered valid and authentic if there is a second code segment that can be decoded and matched with the set of available code segments for that secure element.

In another preferred arrangement, one may not attempt to find the strengths of the major code segments, but simply iterate over all possible strengths. For each intensity, the "possible" code segments are separated. If the "likely" code segment is decodable, i.e., error correction and error detection are successful, then the code segment is assumed to be a valid code segment and the corresponding secure element is determined. Iterations are then performed on the remaining possible intensities, filtering for each intensity and attempting to decode the possible code segments at those intensities. A secure element may be considered authentic if there is at least a second strength in which a code segment may be decoded and the code segment is a member of a set of available code segments for the secure element.

In each of these cases, the authenticity of the security element (and thus at least a part of the security device) can be verified from a single captured image, provided that the lighting environment comprises a suitable superposition of light sources adapted to separate and filter different code segments.

In the current 6 x 6 pixel example, the number of distinguishable pictures is theoretically 2^ 36. In a simple setup this would mean that we can encode 2^36 different identifiers. However, in this case, there is no room for error correction and correct decoding cannot be ensured. If error correction coding is used, for example we can use 12 bits for error correction and 24 bits as payload, then the number of distinguishable images can be reduced to 2^ 24.

If we choose a small number, for example N-5 images, this allows, for each set 6, 7 of images for the first 3 and second 4 security elements, to "code" a considerable area of the sheet product by simply placing the security elements in a tiled manner on the sheet product. However, practical applications require more robust error correction capabilities, especially when smartphones or tablets with poor capture quality are used as authentication programmable devices including cameras. With such a fault tolerance and high redundancy setup (e.g. 16-bit payload, 20-bit error correction), a considerable amount of "corrupted" data (e.g. due to poor capture quality, erroneous binarization and classification, etc.) can be corrected. This comes at the cost of erroneous reads-i.e., decoding of erroneous identifiers-becoming more likely or more likely.

In an authentication setting, one may then benefit from making a model of the sheet product, i.e. a set of possible images of each security element, available to an authentication programmable device comprising a camera. This model is known a priori because it is brought out as a blueprint for designing sheet products. While one false read may have occurred unsuitably in a high redundancy setting as described above with a fairly low probability, the second decoding again results in a very small probability of false reads, especially two image members of the same set of N ═ 5 images (of, for example, 2^16 available images) that are corresponding to the two false reads. Thus, by using two images from different angles of the same secure element and checking whether the two identifiers are part of the set of images defining that particular secure element, erroneous readings can be further reduced or virtually eliminated.

Alternatively or additionally, one may use the spatial relationship of different security elements with respect to each other. Thus, for example, if an erroneous picture, e.g., P _2, is decoded in a first secure element (having a modeled set of available pictures A _1 … … A _ N (6)) and B _2 is correctly decoded in a neighboring second secure element (having a set of 7: B _1 … … B _ N), then it will be apparent from the model that one of the two must be an erroneous decoding. If the first region 3 is decoded to set 6: picture 5 in a _1 … … a _ N and the second region 4 is decoded as set 7: image 5 in B1 … … B _ N, this can safely be assumed to be two correct reads. We want to understand that such geometric relationships embedded in the model may be particularly useful for minimizing the chance of erroneous decoding when using images without error detection/correction capabilities.

Typically, for example for standard 2D code formats, there are no small codes like 6 x 6 elements, just because the risk of erroneous decoding using such a short payload is often too high to be practical. Nonetheless, and similar to that outlined above, the present disclosure allows for the use of such small codes in a nearly error-free reading setting by utilizing the angular and/or spatial relationship of the images. This is made possible by: decoding correctness is increased by using a priori knowledge available from a predetermined model of the sheet product in a programmable device comprising a camera. The advantage of using such small codes compared to more suitable code sizes (e.g. 10x10 and higher) is that the security device that needs to contain at least one security element can be made smaller and still be decoded almost error-free.

In such an arrangement, even with the decoding of at least two secure elements and using a model of the base material to confirm correct decoding, it is virtually impossible for erroneous decoding to occur.

Having a nearly error-free picture decoding approach or rather determining the appropriate set of possible pictures enables two beneficial settings:

a security element characterized by its set of possible images can act as an identifier (unique or almost unique) due to the absolute position within the base material. It is noted that not all N images need to be decoded to determine the set of possible images and to identify the corresponding secure element. For example, it is sufficient if two images from different angles are decoded and a set containing the two images can be determined from the available models of the sheet product. The following facts are assumed: the sets are structured in such a way that no set can contain the same image pairs as any other set/such that in this hypothetical embodiment the image pairs are unique among all sets in the base material.

No two-dimensional code typical structures, such as finder patterns, frequency patterns or any other segmentation/localization measures, are required for encoding in the security element. The security elements may be placed adjacent to each other in a tiled manner without any indicator as to where one security element ends and the next security element begins. High specificity (low probability of false reads) allows sliding the window pixel by pixel on the currently presented image. Each possible position is decoded. If the possible locations can be decoded (i.e., the identifiers extracted), all possible sets containing that particular image/identifier are predetermined according to the model. In a second step, spatially or angularly different images are decoded. In the case of angularly different images (i.e. from the second captured image), all predetermined sets are searched for the second decoding identifier. All sets that do not contain the second image, the identifier, are no longer candidates. By performing this operation iteratively, only one set will remain which identifies the secure element and at the same time allows the boundaries of this secure element to be defined for subsequent reading in other captured images. In the case of using spatially different images, the same captured image may be used. Assume a 6 × 6 code: for each candidate location where the identifier may be decoded, the programmable device including the camera is also configured to attempt to decode the adjacent 6 x 6 region. If any of these regions is decodable, all possible sets of the regions are determined, leaving us with a set of potentially identifiable secure elements. By using the spatial relationship of two observed security elements to each other and matching the spatial relationship to the set of identifiers and the relationship of the predetermined model, one can find a matching combination (e.g. a pair of adjacent sets) and again identify two adjacent security elements and the boundaries of the security elements because they are arranged in a tiled manner. Naturally, if coding allows, the unused bits can be set to a specific bit pattern that can be used to design heuristics and speed up the process of finding decodable areas, i.e. secure element locations and boundaries.

The present disclosure is in no way limited to relatively small image sizes, i.e., 6 x 6 pixels. The above-mentioned identification strategy may not be necessary for larger images, since the error correction code is specific enough to prevent erroneous reads that are initially made forward from a particular size (i.e., Nr bits). In the case of larger codes with more capacity, one may not need an additional strategy to avoid erroneous decoding by using a priori knowledge from a predefined model. In such an arrangement with a larger code, the sheet product may be encoded in such a way that each identifier appears only once or not twice in a certain local neighborhood, provided that the adjacent code pair is used to identify a location in the base material. Thus, due to the high specificity/almost error-free decoding provided by codes with considerable capacity/size and the fact that each identifier can be maximally included. A successful decoding of a set of possible images is sufficient to determine the boundaries of the security element and to identify the specific security element (and therefore the exact absolute position within the sheet product).

One main object is to use a programmable device containing a camera together with an optically variable device for the purpose of providing an automated way of verifying the presence of the optically variable device and thus its authenticity. This is typically achieved by computer vision means and computer programs configured to evaluate multiple images, i.e. video streams, captured from different angles and/or lighting conditions, without any further devices other than a camera. Alternatively, multiple simultaneously captured images from multiple cameras may be processed. The latest techniques here are to evaluate the color change (zero order/first order diffraction devices) or certain animation effects, switching contrast, etc. of the image or shape. Due to the uncontrolled environment, the trade-off between security and robustness/readability is substantial, i.e. only moderate specificity can be achieved — thus achieving security. Typically, if high security is a concern, a second evaluation line is employed in the authentication process that uses a forensics (forensics) device or a dedicated reading device to evaluate the physical structure of the OVD rather than the reflective properties.

At the same time, applications that employ standard equipment (such as programmable devices that include cameras) are often intended to enable untrained users to verify the authenticity of a security device, where the user desires a convenient (and therefore robust) authentication process. Thus, the presence of OVDs or even OVDs can only be roughly assessed at best. In the context of color changing OVDs, this means, for example, that accepting "any" color change is typically the method of at least confirming the presence of an OVD. Confirming the presence of an OVD is often necessary to distinguish the 3-dimensional OVD forming the security device from its picture/photo copy. Typically, under different kinds of adverse capture conditions (e.g., diffuse illumination), adverse changes in illumination or capture artifacts result in more variation in the captured image of the printed replica ("photo copy") of the OVD in terms of color variation, blur, etc., than the original OVD would exhibit. Therefore, the decision threshold for binary OVD presence detection (yes/no) is typically close to the following point: printed copies are accepted as OVDs under certain conditions, while authentic OVDs are rejected due to lack of significant differences in the captured image (e.g., only small color changes).

The subject of the present disclosure is also to provide a method of very reliably confirming the way in which the presence of an optically variable device is present. By capturing at least two images from different angles/lighting settings and decoding at least two images of the same security element, which naturally need to be present in the set of possible images of that particular security element, in combination with error correction, an OVD can almost certainly be present, since a photographic copy or a printed reproduction cannot exhibit this image switching behavior. Furthermore, code switching is error corrected by the encoding of the marks-which means that if changes in the image are observed, the chance of error is negligible.

Fig. 3a to 3c relate to a method for authenticating an object marking made of the base material 1 according to fig. 2. In this example, the object marker comprises a portion of the base material 1, wherein the portion is partially covered by a masking layer. The security elements 2 of the base material 1 are arranged in a tiled manner. Each code segment presented by the secure element is an array of (secondary, monochromatic) tiles. The code segments presented by one secure element are arranged to be malleable with respect to the code segments presented by other secure elements, such that a larger (secondary, monochromatic) tile array is formed overall. The mask layer retains the photo-electrically discernable delimited regions of the base material 1. The area comprises a first security element 3 and a second security element 4.

The method for authenticating the object marker includes capturing a first image 12 of the object marker from a first angle or under a first illumination direction. The first image 12 shown in fig. 3a depicts the visual appearance of a defined area that is electro-optically discernable under a first capture condition (e.g., a first viewing angle). The method comprises identifying a first sample code segment 13 presented in the first image 12 by the hypothetical first secure element (wherein a "sample" indicates that the first sample code segment is a candidate for the first code segment). The first sample code segment 13 is decoded to obtain a first sample data segment 15 for the purpose of identifying the actual first code segment. In more detail, in step a), a first sample tile 11 is identified in a first image 12. Then in step b), the first segment of sample data 13 in the first image 12 formed by the first array of sample tiles 14 comprising said first sample tile 11 at the predefined position is decoded to obtain the first segment of sample data 15. On the basis of this first sample data segment 15, it is determined in step c) from a model 16 storing a set of data segments associated with the security element of the base material 1 whether there is at least one set of data segments 6 containing said first sample data segment 15 (i.e. a data segment candidate). If such a set cannot be determined in step c), the data segment candidates are rejected and steps a) to c) are repeated using a different first block of samples until such a set is found in step c). For example, the next tile to the right of the first sample tile 11 may be identified as a new "first sample tile" and the above steps repeated. This may be repeated until a number of steps corresponding to a predetermined (known) width of the security element with respect to the tiles (here six tiles in width) are covered, then the tile immediately below the original first sample tile 11 may be identified as a new "first example tile" and the above steps repeated, and so on. Once at least one set 6 of data segments containing a first sample data segment 15 (i.e. a data segment candidate) can be found-for example, in fig. 3a, set a contains a _1, the current first sample code segment 13 is preliminarily identified as a first code segment.

Without a particular sequence or order, the method further includes capturing a second image 17 of the object marker under different capture conditions (e.g., from a second angle and/or under a second illumination direction). This is shown in fig. 3 b. The second code segment presented by the first secure element is identified in the second image 17. The second sample code segment 18 is decoded for the purpose of identifying the second code segment to obtain a second sample data segment 19. This may function similarly as for the first data segment. I.e. in step e), a first sample tile 11 (typically arbitrary, e.g. the tile closest to the upper left corner of the second image 17) is identified in the second image 17; in step f), decoding a second sample code segment 18 formed of the first sample tile array 14 in the second image 17 to obtain a second sample data segment 19; in step g), it is determined from the model 16 whether at least one of the sets in the model 16 containing the first sample data segment 15 also contains a second sample data segment 19; if such a set cannot be determined in step g), step h) indicates a loop and repeats steps a) to g) until such a set 6 is found in step g). In practice this means: if a matching second sample code segment cannot be identified, the first sample code segment is rejected, causing the two sample code segments to be dismissed, thereby scanning different tile positions and boundaries until a valid combination of sample code segments is found. On the other hand, when a set of these two sample data segments is found, the current second sample code segment 18 is identified in step m) as the second code segment. That is, the method determines from the model 16 storing a set of data segments associated with the secure element of the base material 1 whether there is a set of data segments containing the first sample data segment 15 and the second sample data segment 19. Only in the affirmative case, i.e. if such a set 6 of data segments is part of the model 16, the object marker can be determined to be authentic.

Furthermore, as shown in fig. 3c, the method comprises identifying a third sample code segment presented in the first image 12 by the hypothetical second secure element (although the second image 17 or both may be used similarly). The identified third code segment is decoded to obtain a third sample data segment. Based on the decoded third sample data segment, it is determined from the model whether there is a second secure element located relative to a first secure element (identified by the first sample data segment and the second sample data segment) associated with a set of data segments containing the third sample data segment. Thus, the model 16 stores not only the set of data segments associated with the secure elements of the base material, but also the relative positions of the secure elements of the base material to each other. Thus, before confirming the authenticity of the object marker, the method comprises: in step i), decoding a third sample code segment 20 formed of a second sample tile array 21 positioned relative to the first sample tile array 14 to obtain a third sample data segment 22; in step j), it is determined, from the model 16 comprising the sets 6, 7 of data segments associated with the secure element 2 of the base material 1 and the relative position of the secure element 2 of the base material 1 and the further secure element 23, whether a third sample data segment 22 is contained in the set 7 of data segments, which set 7 of data segments belongs to the secure element 4 located respectively relative to the secure element 3 to which the set preliminarily identified by means of searching the set with the first and second sample data segments belongs; if such a set cannot be determined, returning in step k) and repeating steps a) to j) until such a set is found; and once the set is found, the current sample code section 13, 18, 20 is identified as the valid code section in step n). Thus, the model 16 includes the following information: which sets of data segments are associated with successive security devices on the base material 1.

In summary, the above method scans (at least) two images 12, 17 in an array of blocks substantially as follows: starting with any tile and selecting a different tile in each pass until the data segments represented by the code segments are offset from the given tile and their respective arrangement produces a match in the model 16. If no such match is found, the object tag is rejected (i.e., authenticity cannot be confirmed).

Claims (15)

1. Object marker (9) comprising a first security element (3) and at least a second security element (4), wherein each security element (3, 4) is associated with a set of data segments (6, 7) and each security element (3, 4) presents a code segment which is an opto-electronically readable representation of one of the data segments (5) in the set associated with the respective security element (3, 4) depending on a capture condition, in particular a viewing angle (10) and/or an illumination direction,

the object marker is characterized in that it is,

different distinct data segments are represented by different code segments (5), and the set associated with the first secure element (3) and the set associated with the second secure element (4) differ in at least one data segment.

2. Object marker (9) according to claim 1, characterized in that for a fixed illumination direction each data segment of the set associated with the security element (3, 4) is associated with a distinct viewing angle region within which the contrast of the code segment (5) representing the respective data segment is higher than the contrast of the code segments representing all other data segments from the same set.

3. The object marker (9) according to claim 2, characterized in that there is at least one view area associated with a data segment in the set of the first secure element (3) different from each of the view areas associated with data segments in the set of the second secure element (4).

4. Object marker (9) according to any one of claims 1 to 3, characterized in that each code segment (5) represents the respective data segment in a predefined coding, wherein the predefined coding allows a maximum number of potentially distinguishable data segments and the number of data segments in the set of data segments of each security element (3, 4) is less than 1/100, preferably less than 1/1000, more preferably less than 1/10000.

5. A set of object markers, characterized by a plurality of object markers (9) according to any one of claims 1 to 4.

6. A base material (1) for producing an object marking (9) comprising a first security element (3) and at least a second security element (4), wherein each security element (3, 4) is associated with a set of data segments and each security element (3, 4) presents a code segment (5) which is an opto-electronically readable representation of one of the data segments in the set associated with the respective security element (3, 4) depending on a capture condition, in particular a viewing angle (10) and/or an illumination direction,

the object marker is characterized in that it is,

different distinct data segments are represented by different code segments (5), and the set associated with the first secure element (3) and the set associated with the second secure element (4) differ in at least one data segment.

7. The base material (1) according to claim 6, characterized in that the positions of the security elements (2) on the base material (1) are predetermined with respect to each other according to a model, and the data segments in the set associated with the security elements (2) are predetermined according to the model (16).

8. The base material (1) according to any one of claims 6 or 7, characterized in that each code segment (5) represents a respective data segment in a predefined code, wherein the predefined code preferably comprises information for error detection or error correction.

9. The base material (1) according to claim 8, characterized in that the predefined encoding allows a maximum number of potentially distinguishable data segments, and the number of distinct data segments in the set of data segments of all security elements is less than 1/100, preferably less than 1/1000, more preferably less than 1/10000.

10. A method for authenticating an object marker (9), the object marker (9) comprising an optoelectronically distinguishable delimited region of a base material (1) according to any one of claims 6 to 9, wherein the region comprises a first security element (3) and at least a second security element (4), the method comprising the steps of:

capturing a first image (12) of the object marker (9) from a first angle (10) or under a first illumination direction;

-identifying a first code segment presented in the first image (12) by a first secure element (3);

decoding the first code segment to obtain a first data segment;

capturing a second image (17) of the object marker (9) from a second angle (10) and/or under a second illumination direction;

-identifying a second code segment presented by the first secure element (3) in the second image (17);

decoding the second code segment to obtain a second data segment;

determining whether a set of data segments comprising the first data segment and the second data segment is present from a model (16) storing the set of data segments (6, 7) associated with a secure element (3, 4) of the base material (1).

11. The method of claim 10, further comprising the steps of:

-identifying a third code segment presented by a second secure element (4) in the first image (12) or the second image (17);

decoding the third code segment to obtain a third data segment;

determining whether the second security element (4) positioned relative to the first security element (3) is associated with a set of data segments comprising the third data segment according to a model (16) storing the set of data segments associated with the security elements (2) of the base material (1) and storing the relative positions of the security elements (2) of the base material (1) with respect to each other.

12. The method according to any of claims 10 or 11, wherein the security elements (2) of the base material (1) that are comprised in part by the object marking (9) are arranged in a tiled manner, and each code segment (5) presented by the security elements (2) is a tile array, and the code segment (5) presented by one security element is arranged to be malleable to the code segments presented by the other security elements such that a larger tile array is formed, the method being characterized in that it further comprises the steps of:

a) identifying a first sample tile (11) in the first image;

b) decoding a first segment of sample data (13) in the first image (12) to obtain a first segment of sample data (15), the first segment of sample data (13) being formed by a first array of sample tiles comprising the first sample tile (11) at a predefined location;

c) determining, from a model (16) storing the set of data segments associated with a secure element (2) of the base material (1), whether there is at least one set of data segments comprising the first sample data segment (15);

d) if such a set cannot be determined in step c), repeating steps a) to c) using a different first sample tile until such a set is found in step c); and

l) identifying a current first code segment (13) as said first code segment.

13. The method according to claim 12, characterized in that it further comprises, before step i), the steps of:

e) identifying the first sample tile (11) in the second image (17);

f) decoding a second sample code segment (18) formed by the first sample tile array in the second image (17) to obtain a second sample data segment (19);

g) determining, from a model (16) storing the set of data segments associated with a secure element (2) of the base material (1), whether at least one of at least one set including the first sample data segment (15) includes the second sample data segment (19);

h) if such a set cannot be determined in step g), repeating steps a) to g) until such a set is found in step g); and

m) identifying a current second sample code segment as the second code segment.

14. Method according to claim 12 or 13, characterized in that it further comprises, before step l) and preferably before step m), the steps of:

i) decoding a third sample code segment (20) formed of a second sample tile array located relative to the first sample tile array to obtain a third sample data segment (22);

j) determining, from a model (16) storing the set of data segments associated with the secure element (2) of the base material (1) and storing the relative positions of the secure elements (2) of the base material (1) to each other, whether the third sample data segment (22) is contained in a set of data segments belonging to secure elements respectively positioned with respect to the secure element to which the set preliminarily identified in step e) belongs;

k) if such a set cannot be determined in step j), repeating steps a) to d) and i) to j) and preferably e) to h) until such a set is found in step j);

n) identifying a current third sample code segment as the third code segment.

15. A method for generating an object marker (9), the method comprising the steps of:

randomly, pseudo-randomly or deterministically selecting a region of the base material (1) according to any of claims 6 to 9, said region comprising a first security element (3) and at least a second security element (4), and

-photo-electrically discernably defining said selected regions with non-selected portions of said base material (1).

Images