Holographic security code and product and corresponding verification system

Abstract

A holographic security code comprising: a pattern of elementary cells having a predetermined shape and a predetermined relative position, said pattern comprising a two-dimensional sequence of said elementary cells; said pattern comprising a predetermined number of so-called "empty" elementary cells, i.e. such as to appear in a predetermined dark color, in particular black, and said pattern comprising a predetermined number of elementary cells that generate a diffractive effect, so-called iridescent cells, and which each comprise at least one diffractive grating having a predetermined orientation, preferably a combination of at least two diffractive gratings that differ between their orientation; said diffractive gratings being made in such a way that the light radiation emitted is visible only with an observation according to different viewing angles comprised in a predetermined range, said pattern generating, when observed according to the aforementioned viewing angles, an image consisting of the combination of said predetermined number of so-called empty cells, having a predetermined dark colour, preferably black, and of so-called iridescent cells and in particular of different colours contrasting with said dark colour of the so-called empty cells; while with viewing angles and / or illumination outside said range of viewing angles, in particular perpendicular to the surface along which said two-dimensional sequence of elementary cells extends, said empty elementary cells and said iridescent elementary cells do not have a different appearance from each other; said elementary cells having sides lengths and / or diagonals or larger diameters in the range from 50 to 300 microns. The invention also concerns a holographic security product characterized by the fact that it comprises a substrate on which said aforementioned holographic code is applied. In addition, the invention has as its object an anti-counterfeiting verification system, said system comprising: a plurality of anti-counterfeiting labels that comprise a product of the aforementioned type; at least one code reader applied to said labels, said codes being made up of at least one said holographic code; at least one processing unit comprising a memory wherein the aforementioned codes are stored and at least one program for comparing the codes transmitted by the reader and the codes contained in said database, at least one visual and / or acoustic reception and reproduction unit associated with said reader; said processing unit generating a confirmation or denial signal of the authenticity of the code depending on the outcome of said comparison, said signal being transmitted to said visual and / or acoustic reproduction unit for the emission of visual and / or acoustic information about the confirmation or denial of authenticity of said code.

Description

[0001] HOLOGRAPHIC SECURITY CODE AND PRODUCT AND CORRESPONDING VERIFICATION SYSTEM

[0002] DESCRIPTION OF PRIOR ART

[0003] Automatic identification of anti-counterfeiting elements has become increasingly important in order to recognize hidden information and make document authentication independent of human inspection. In the field of holographic security elements, numerous solutions have been developed to encode optical information in such a way as to enable automatic verification.

[0004] Patent EP0644508A1 describes a linear sequence of diffractive gratings, oriented at different angles, to contain encoded information. A specific reader consisting of a laser beam and several sensors arranged in such a way as to collect the diffracted beams, allows the encoded message to be reconstructed.

[0005] In CN1399764A patent, a phase pattern generated by a Fourier transform is associated with a label: a second phase pattern is recorded on a mask that acts as a detector element of a dedicated reader. During the label verification operation, the authenticity is proven by an optical correlation of the signals coming from the first and second phase patterns.

[0006] Patent US200208099 proposes an authentication code associated with a hologram of the "digital watermark" type, i.e. a graphic form consisting of a matrix of dots present in the hologram, containing information that can be decoded by means of a special reader.

[0007] The disadvantage of all the solutions described above is that to carry out the verification it is necessary to use dedicated readers that are not available on the market but must be developed ad hoc with development costs that are not always adequate for the areas of application.

[0008] US20190220718 and WO2019 / 21 1422 patents describe a method for creating variable encoded information by associating a QR code and / or serial code with an HSF holographic product, hot-applied on paper.

[0009] The authenticity of the label is verified using a smartphone device: after acquiring the image via a camera, the authentication SW (Software) verifies the consistency of the holographic code with the printed codes.

[0010] The solution described above is a valid anti-photocopying tool. The authentication SW is able to detect a silver shape and detect the authenticity of the code among a given set of possible codes.

[0011] However, the size of the code is such as to allow its reproduction by inkjet printing on a silver support: such reproduction is able to deceive the authentication SW, which is not able to discriminate a possible label reproduced in full by inkjet printing.

[0012] In order to overcome the problems mentioned above, a special holographic code has been designed that can be detected by the camera of a smartphone.

[0013] It consists of a two-dimensional sequence of elementary cells, detectable by means of a smartphone camera only under specific angles of observation, said cells being small enough to prevent any type of reproduction without the introduction of errors or alterations that compromise their recognizability.

[0014] This size is also chosen so that it can be acquired by means of a smartphone camera. The elementary cells are distributed in such a way as to form a code that, acquired by a camera, can be verified with a dedicated algorithm.

[0015] The specific pattern allows to store information that cannot be displayed with perpendicular lighting and therefore cannot be photocopied.

[0016] In addition, the shape and size of the elementary cells is chosen in such a way as to prevent reproduction by printing technologies.

[0017] DESCRIPTION OF THE INVENTION

[0018] The object of the present invention is the creation of a holographic security code consisting of patterns of cells of diffractive structures alternating with "empty" elementary cells, suitable to be associated with a holographic image as an element for verifying authenticity. The "empty" elementary cells, black in color, are well distinguished from the iridescent holographic image of the diffractive structures.

[0019] According to a first, more general aspect, the present invention has as its object a holographic security code comprising: • a pattern of elementary cells having a predetermined shape and a predetermined relative position,

[0020] • said pattern comprising a two-dimensional sequence of said elementary cells;

[0021] • said pattern comprising a predetermined number of so-called "empty" elementary cells, i.e. such as to appear in a predetermined dark color, in particular black, and said pattern comprising a predetermined number of elementary cells that generate a diffractive effect, so-called iridescent cells, and which each comprise at least one diffractive grating having a predetermined orientation, preferably a combination of at least two diffractive gratings that differ each other by their orientation; said diffractive gratings being made in such a way that the light radiation emitted is visible only with an observation according to different viewing angles comprised in a predetermined range, said pattern generating, when observed according to the aforementioned viewing angles, an image consisting of the combination of said predetermined number of so-called empty cells, having a predetermined dark colour, preferably black, and of so-called iridescent cells and in particular of different colours contrasting with said dark colour of the so-called empty cells; while with viewing angles and / or illumination outside said range of viewing angles, in particular perpendicular to the surface along which said two-dimensional sequence of elementary cells extends, said empty elementary cells and said iridescent elementary cells do not have a different appearance from each other; said elementary cells having side lengths and / or diagonals or larger diameters in the range from 50 to 300 microns.

[0022] Dependent claims 2 to 10 relate to specific forms and executive embodiments of said holographic code.

[0023] The present invention also concerns a holographic security product characterized by the fact that it comprises a substrate on which the holographic code is applied according to one or more of the forms and executive embodiments provided for above and in the dependent claims 2 to 10.

[0024] Dependent claims 12 to 15 define further refinements or variants of the holographic product. The present invention also concerns an anti-counterfeiting verification system, said system comprising:

[0025] - a plurality of anti-counterfeiting labels made according to one or more of claims 1 1 to 15.

[0026] Claims 17 to 20 relate to possible executive embodiments and / or improvements to said system.

[0027] On yet another side, the present invention concerns a method of verifying the authenticity of security verification codes which involves the use of a holographic code according to one or more of the forms and executive embodiments described in claims 1 to 10 and a holographic product according to one or more of the forms and executive embodiments described in claims 1 1 to 15.

[0028] This method may be implemented by a system according to one or more of the executive embodiments of claims 16 to 20.

[0029] In particular, according to a first embodiment, the method involves the following steps: a) defining a first element of information; b) generating a second element of information by processing the transformation of said first element of information c) representing said second element of information in the form of a map of cells having two different aspects according to two contrasting colors; reproducing on a holographic product such as a label or similar one or more pre-established parts of said map by means of two-dimensional sequences of so-called empty and so-called iridescent elementary cells, i.e. through one or more holographic codes according to one or more of claims 1 to 10; applying said holographic product to an object subject to authenticity check; storing the information and / or characteristics of the coding map of said second element of information; reading the two-dimensional coding sequence(s) of said coding map of the second element of information from the holographic product and reconstructing from them the parts of said coding map from said two-dimensional sequences and / or extracting from them the characteristics relating to the size, shape and position of said cells of the coding map; comparing said information and characteristics reconstructed or extracted with the information and / or characteristics relating to said map and / or to said first and / or second element of information previously stored; defining the holographic product, i.e. the label, as authentic when there is a correspondence between the information and / or the reconstructed characteristics and those stored within pre-established tolerances.

[0030] In this description and in the claims, the definition of contrasting colours is used to indicate colours that correspond to different intensities of reflection or refraction of light energy, such as in particular the colour black for so-called empty cells and other colours for iridescent cells.

[0031] Furthermore, in the present invention, the term viewing angle refers to a direction of view with a predetermined orientation that refers to the two-dimensional plane over which the sequence of two-dimensional elementary cells extends.

[0032] The term flat is not to be understood in a limited sense but also comprises slightly curved surfaces.

[0033] According to an embodiment, said reader may consist of a device comprising a reading unit and a transmission and reception communication unit and optionally a display and / or sound diffusion unit, while the processing of the codes acquired by the reader is carried out only by a processing unit of a remote unit. Said remote unit comprises a communication unit with said reader for the reception of the signals generated by the reader itself and for the transmission to said reader of the signals confirming or denying the correctness of the code.

[0034] In an alternative embodiment, said reader is associated or integrated with a processing unit, such as a smartphone, a PDA, a tablet, or similar wherein a software containing the instructions to perform the steps according to the previous claims is loaded, said steps comprising the reading of the codes and the transmission to the remote unit and the reception and display or acoustic diffusion of the signals confirming or denying the authenticity of the code and said software optionally also comprising instructions to perform at least part of the functions provided for the processing unit of said remote unit.

[0035] Brief of the fi

[0036] The characteristics and advantages of the invention will be more evident from the following description of its embodiments made by way of example and not limiting to the accompanying drawings wherein:

[0037] • Figure 1 represents a multiplicity of diffractive gratings;

[0038] • Figure 2 shows the observation mode of the iridescent hologram;

[0039] • Figure 3 shows a schematization of the pattern of elementary cells;

[0040] • Figure 4 shows the observation methods of the holographic code;

[0041] • Figure 5 represents an amplitude spectrum calculated by the FFT algorithm;

[0042] • Figure 6 shows the extraction of n portions from the amplitude spectrum of Fig. 5a;

[0043] • Figure 7 shows two examples of codes;

[0044] • Figure 8 shows a schematization of a succession of holographic labels with encoded information;

[0045] • Figure 9 shows a schematization of a succession of labels with an encoded holographic stripe;

[0046] • Figure 10 represents a flow diagram of the stand-alone verification process;

[0047] • Figure 11 represents information encoded by a stochastic algorithm;

[0048] • Figure 12 represents a preferred configuration of holographic stripe labels encoded with the pattern shown in Fig. 10;

[0049] • Figure 13 shows the sequence of operations of the stand-alone verification process;

[0050] • Figure 14 shows a sequence of codes generated with a stochastic algorithm;

[0051] • Figure 15 represents a preferred configuration of holographic stripe labels encoded with the sequence of codes illustrated in Fig, 13;

[0052] • Figure 16 shows the sequence of operations of the verification process for instance exemplary embodiment 1 ; • Figure 17 shows the sequence of operations of the verification process for instance exemplary embodiment 2;

[0053] • Figure 18 shows the sequence of operations of the verification process carried out partly in off-line mode and partly in on-line mode.

[0054] Detailed Description of the Invention

[0055] A holographic master is generally composed of a multiplicity of diffractive gratings with pitch in the range of 0.4 - 1 .5 pm, depth of the order of 200-400 nm and oriented differently according to a predetermined array, as in the example outlined in Fig.1.

[0056] By means of a thermo-pressure process (a known technique) it is possible to reproduce the array of diffractive gratings 100 on a thermoformable plastic material which, metallized, reproduces the sequence of colours of the rainbow as the angle of observation varies. Fig. 2 shows an element 101 of the array 100 and the observation at different angles, in the indicated range 200. It is also possible to obtain holographic or pseudo-holographic lattices by means of a drawing process on plastic materials that can be formed by UV drying.

[0057] The holographic code object of the present invention consists of patterns of cells 1 10 filled with diffractive gratings orthogonal to each other, alternating with the "empty" elementary cells 120 (see Fig. 3), suitable to be associated with an iridescent holographic image and to act as an element of authenticity (or "fingerprint") of the hologram itself. The specific array of structures 1 10 represented in Fig. 3 will be visible both to an observation in the angular range 250, shown in Fig. 4a, and to an observation in the angular range 251 (by rotating the sample by 90°) shown in Fig. 4b: since the pitch of the gratings of cell 1 10 is in the range 0.4 - 1 .5 pm, the angular range 250 (and 251 ) is comprised in the range 200 of Fig. 2.

[0058] The combination of the iridescent holographic cells alternating with the "empty" cells generates a succession of coloured pixels alternating with black pixels, when captured by a camera with non-perpendicular lighting.

[0059] In order to obtain an image suitable for processing by means of a black pixel recognition algorithm, it is advisable to use cells in the size range 50-200 microns.

[0060] It is also advisable to use square or rectangular cells or other forms with accentuated edges to prevent counterfeiting attempts by printing techniques.

[0061] The holographic security code object of the present invention is generated, in a first preferred configuration, by means of a mathematical function that calculates the distribution in the frequency space of a graphic pattern (FFT algorithms) in order to link the holographic security code to a graphic element printed on a label or a product. The verification process involves the acquisition of both elements using the camera of a smartphone device and the authentication of the code in "stand-alone" mode through an app based on FFT algorithms, as better specified below.

[0062] Fig. 5 shows an example of a graphic element A and its Fourier transform of 1024x1024 pixels (amplitude spectrum). Fig. 6 shows (220) the extraction of "N" portions of Fig. 5b of 40x40 pixels each, which will constitute codes 1 , 2, ... N. Fig. 7 shows the enlarged images of codes 1 and 2.

[0063] By extracting "N" different portions from Fig. 5b, multiple sets of codes can be obtained that can be used, in a preferred configuration, on a plurality of labels.

[0064] Each code, such as 1 , 2, ... N of Fig. 7, can be transformed into the cell pattern of Fig. 3 by filling the white pixels with the grids 1 10 and the black pixels with the "empty" elementary cells 120; this pattern can also be inserted, as part of the graphic layout, within an iridescent holographic image. This pattern is suitable for use in the creation of holographic products in self-adhesive label format (as a product authentication element) or in holographic strip format applied on paper or plastic support (as an anti-photocopy element of security cards).

[0065] Figure 8 shows a holographic product in self-adhesive label format, in particular two self-adhesive holographic labels 300 (on silicone support 301 ), containing respectively the holographic security code 320 (code 1 ) and 321 (code 2). Each code is provided, on the left side and on the top side, with a "position code" consisting of two sequences of black and white cells, respectively 310 and 31 1 , which encode in binary form, respectively, the coordinates of the top left vertex 210 of the holographic code 320 and 321 with respect to the distribution of Fig. 5b and its size. The 300 label also contains a 330 graphic or logo that is printed using inkjet.

[0066] Fig. 9 shows a holographic product in paper label format 350 with a holographic strip 360 containing a sequence of "N" holographic codes with their respective position codes: in this case some codes of the sequence 1 , 2, ..., N positioned along the edge of the holographic strip will be contained inside the paper label 350 (preferably 2 or 3). The paper label, similarly to what is described above for the self-adhesive label, also contains a graphic element or logo 330 printed by inkjet, useful for the purposes of the verification process detailed below.

[0067] The verification of the consistency of the elements present in the label is carried out through the acquisition of the position code 310 (or 31 1 ), the holographic code 320 (or 321 ) and the graphic element or logo 330 through the camera of a smartphone.

[0068] Fig. 10 shows the sequence of operations of the verification process that involves the acquisition of the photo of the label (350) using the camera of a smartphone, with a shooting angle such as to visualize the pattern of black and iridescent elementary cells that form the holographic code (with non-perpendicular lighting).

[0069] The image of the Logo acquired by the camera is searched in the set of predefined images contained in a Database (355). If the search is successful, the image contained in the Database is transformed by the FFT algorithm into a matrix containing the frequency space distribution of the Logo (360). The information extracted from the position code (365) allows the portion relating to the holographic security code (370) to be obtained from the matrix.

[0070] The verification of the authenticity of the holographic code (375) will be positive in the event of consistency between the pattern extracted by the authentication algorithm and the code acquired by the camera.

[0071] To take into account the wearing of the label and the possible defectiveness of the elements being checked, redundancy can be comprised in the information for the correction of errors or an acceptance threshold in the range of 85%-95% (percentage of consistency between the images) can be established.

[0072] In the case of verification in off-line mode, all activities are delegated to the App, which also contains the set of predefined information.

[0073] In the case of on-line verification, the Database and the functions necessary for the verification of consistency are located in a remote server while the image acquisition and interface between the server and the operator are delegated to the App. Other preferred configurations may comprise the use of algebraic, trigonometric functions, Laplace transforms, stochastic functions, etc.

[0074] In a second preferred configuration, the security holographic code consists of a non-uniform sequence of black elementary cells 410 alternating with iridescent elementary cells 420, as shown in the executive simplification of Fig. 11 . A stochastic algorithm is used to generate pseudorandom sequences, with elementary cells of discrete and predefined sizes.

[0075] With reference to Fig. 1 1 , the black elementary cells 410 are alternated with the iridescent cells 420, both of variable size in the range 80-300 microns.

[0076] The 400 pattern is used in the 520 holographic strip product in Fig. 12, applied on the 500 paper support.

[0077] According to an embodiment, in order to create labels with holographic security code with maximum variability, a development of the die-cutting layout is chosen that is not commensurable with the distance 530 so that, by die-cutting the paper support in the final 510 format of the labels, different patterns of elementary cells are obtained on the individual labels.

[0078] This preferred configuration is suitable for insertion in holographic strips widely used as an anti-counterfeiting element of security cards such as product authentication labels, tobacco dowels, revenue stamps, banknotes, etc.

[0079] The verification process is carried out by acquiring and processing, with a dedicated App, the image of the holographic strip, acquired with the camera of a smartphone: the geometric characteristics of the elementary cells and the sequence of the cells are extracted from the image. The authenticity check will be positive in the event of consistency between the values detected and those predicted by a data set or by a pre-established function both in terms of size and sequence of the dimensions of the elementary cells.

[0080] Fig. 13 shows the sequence of operations of the verification process: acquisition of the photo of the holographic strip (650) using the camera of a smartphone, with a shooting angle such as to visualize the pattern of black and iridescent elementary cells that form the holographic code (with nonperpendicular lighting); image processing to verify the size and distance of the black elementary cells (655); comparison with the information stored in the verification app (data set or specific functions) (660); consistency of the information extracted from the photo with the dataset or with the values of the specific function (665), within an acceptance value in the range of 85%-95% (percentage of consistency between the images).

[0081] The operations described above for verification can be carried out directly from the app in off-line mode or, in a more secure way, they can be performed on a remote server, while the image acquisition and interface between the server and the operator are delegated to the app.

[0082] In another preferred configuration, the security holographic code consists of multiple patterns of elementary, black, iridescent cells, randomly placed within a holographic strip.

[0083] Fig. 14 shows the patterns of elementary cells 601 , 602, 603 and 604 that are added with random steps in the holographic strips 410 of Fig. 15.

[0084] The 510 labels, obtained by die-cutting the 500 paper support, will contain patterns of elementary cells located in different positions within the portion of the holographic strip present on the label itself.

[0085] This positioning information, together with the recognition of the code, allows verification to be carried out in the way illustrated below.

[0086] The verification is carried out with a dedicated app, which acquires and processes the image of the label: the information encoded in the patterns and the relative distances between the patterns present in the holographic strip of the individual label are extracted from the image.

[0087] In a first exemplary representation of this configuration, all the elementary cells have the same size and are uniformly positioned in a chessboard pattern to form a pattern. The information contained in the patterns is binary codes obtained by means of a pseudo-random number generator: the codes are represented in the patterns, attributing the logical value 1 to the black elementary cells and the logical value 0 to the iridescent elementary cells. The patterns may also contain information from, for instance, logical or mathematical operations carried out on the binary codes represented in the patterns, to be used in the verification phase of the holographic security code as detailed below.

[0088] Redundancy systems (control and / or correction) are inserted in each pattern to overcome reading errors or slight wearing of the elementary cells.

[0089] The following are examples of the types of information encoded in the patterns:

[0090] • In each pattern there is information that follows a sequentiality rule established by a specific function;

[0091] • In each pattern 3 pieces of information are encoded: two are binary codes obtained through the pseudo-random number generator and the third is obtained through an operation performed on the two codes (for instance an XOR operation)

[0092] • In each pattern, a binary code obtained through the pseudo-random number generator is represented in the first half and the same code but encrypted in the second half.

[0093] Fig. 16 shows the sequence of operations of the verification process:

[0094] • acquisition of the photo of the holographic strip (750) by means of a smartphone camera, with a shooting angle such as to visualize the pattern of black and iridescent elementary cells that form the holographic code (with nonperpendicular lighting);

[0095] • extraction of elementary cell patterns (755);

[0096] • extraction of distances between patterns (760);

[0097] • logical / mathematical operations on the information extracted from the patterns (765).

[0098] The authenticity check (770) will be positive in case of consistency with the pre- established rules in the coding of information in the patterns, namely:

[0099] • if the information (binary codes) encoded in the patterns on each label comply with a sequentiality rule established by the specific function used; • if the third piece of information encoded in the pattern is the correct result of the pre-established logical / mathematical operation;

[0100] • if the decrypted code present in the second half of the pattern coincides with the code present in the first half.

[0101] In all 3 cases above, the verification will be completed with the consistency of the distance between the patterns established by the data set or by the specific function.

[0102] In a second exemplary representation of this configuration, deformations are introduced into the chessboard, constituting the pattern, by modifying one or more elementary cells (for instance the size or shape, for instance trapezoidal instead of square). The position of the "deformed and / or translated" elementary cell or the type of deformation / translation is established by the information encoded in the pattern itself. This correlation will be used in the security holographic code verification phase.

[0103] The patterns, as mentioned, are distributed within the label with a random step. This conformation, together with the previous correlation, will be used in the verification phase. By way of example and without limitation, the following two situations will be considered:

[0104] • The relative distance values between the patterns are stored in a dataset

[0105] • The values of the relative distances between the patterns respect the sequentiality rules established by a specific function.

[0106] Figure 17 shows the sequence of operations of the verification process:

[0107] • acquisition of the photo of the holographic strip (850) using the camera of a smartphone, with a shooting angle such as to visualize the pattern of black and iridescent elementary cells that form the holographic code (with nonperpendicular lighting);

[0108] • extraction of elementary cell patterns (855);

[0109] • extraction of distances between patterns (860);

[0110] • processing of deformations and translations of elementary cells according to the information encoded in the pattern (865).

[0111] The authenticity check (870) will be positive in the event of consistency with the pre-established rules, namely:

[0112] • If the position of the "deformed and / or translated" elementary cell agrees with the information encoded in the pattern

[0113] • If the relative distance values between the patterns match the predefined values (dataset in the app)

[0114] • If the sequentiality is respected with regard to the values of the relative distances between the patterns according to the specific function used.

[0115] The verification processes described above can be carried out in off-line mode, in on-line mode or in mixed mode.

[0116] In the case of verification in off-line mode, all activities are delegated to the App, which also contains the set of predefined information.

[0117] In the case of remote verification, the App performs the function of image acquisition and interfacing between the user and the remote server, which performs the functions of recognition and consistency.

[0118] In the case of mixed mode, part of the comparison and verification operations will be carried out with the set of information stored in the remote server and the rest directly from the App.

[0119] Reference is made to the first executive representation of Fig. 16, to describe, by way of example and without limitation, a verification process in mixed mode wherein, in off-line mode, the values of the positions of the elements of the patterns and of the sequences of pre-established values are verified, allowing an initial verification even in the absence of a network signal, while the control over logical-mathematical operations is carried out remotely.

[0120] The sequence of operations of the verification process, as outlined in Fig. 18, is shown below:

[0121] • The photo of the holographic strip is acquired by the App, in off-line mode, using the camera of a smartphone;

[0122] • The verification of consistency between the values of the positions of the elements of the patterns and the sequences of pre-established values is carried out by the App, in off-line mode; • In the event of a positive outcome of the off-line verification, the App connects with the remote server;

[0123] • The remote server verifies the logical / mathematical operations on the information extracted from the patterns and produces a positive or negative outcome in case of consistency or inconsistency with the expected values.

Claims

CLAIMS1. A holographic security code comprising: a pattern of elementary cells having a predetermined shape and a predetermined relative position, said pattern comprising a two-dimensional sequence of said elementary cells; said pattern comprising a predetermined number of so-called “empty” elementary cells appearing in a predetermined dark color, particularly black, and said pattern comprising a predetermined number of elementary cells generating a diffractive effect, called iridescent cells, each comprising at least one diffractive grating with a predetermined orientation, preferably a combination of at least two diffractive gratings differing in orientation; said diffractive gratings being configured so that the emitted light radiation is visible only when viewed at different angles within a predetermined range, said pattern generating, when viewed at said viewing angles, an image formed by the combination of said predetermined number of so-called empty cells with a predetermined dark color, preferably black, and so-called iridescent cells with various contrasting colors to said dark color of the so-called empty cells; wherein at viewing and / or illumination angles outside said range of viewing angles, particularly perpendicular to the surface along which said two-dimensional sequence of elementary cells extends, the so-called empty elementary cells and the so-called iridescent elementary cells do not show a different appearance from each other; said elementary cells having side lengths and / or diagonals or larger diameters within the range of 50 to 300 microns.

2. The holographic Security Code according to claim 1 , wherein two types of diffractive gratings are present in the so-called iridescent cells, which gratings have orientations perpendicular to each other.

3. The Holographic Security Code according to claims 1 or 2, wherein said cells have a polygonal shape with sharp edges, preferably a quadrangular shape, i.e., square or rectangular.

4. The Holographic Security Code according to one or more of the preceding claims, wherein said two-dimensional sequence of elementary cells is in the form of a chessboard with a predetermined extension in two orthogonal directions and said distribution ofthe so-called empty cells with respect to the so-called iridescent cells within said two-dimensional sequence is defined by a transformation function of a first information element into a second information element encoded as a graphic coding map comprising cells with two different aspects in two contrasting colors, wherein cells of one type are represented by so-called empty elementary cells while cells of the other type are represented by said so-called iridescent cells.

5. The Holographic Security Code according to claim 4, wherein said graphic coding map has more cells than the elementary cells in said two-dimensional sequence, said elementary cells of said two-dimensional sequence being defined as corresponding to cells of a predetermined region of said graphic coding map of said second information element, said two-dimensional sequence of elementary cells being associated with an identification code of the position of an elementary cell being the start the two-dimensional sequence with reference to said graphic coding map, which identification code is a binary code and comprises at least an additional coding distribution of the position comprising a predetermined number of empty cells and iridescent cells having a predetermined position within said two- dimensional sequence of elementary cells and a smaller size than said two- dimensional sequence, said position coding distribution being optionally a linear distribution and / or a combination of at least two linear distributions along two different directions.

6. The Holographic Security Code according to claim 5, wherein said code comprises two or more different two-dimensional sequences of elementary cells, said two or more two-dimensional sequences differing in that said two-dimensional sequences are defined by said two different aspects of the cells of said graphic coding map of respectively different parts of said graphic coding map, each two-dimensional sequence being associated with the binary position coding graph of the part of said coding map represented by said two-dimensional sequence.

7. The Holographic Security Code according to one or more of the preceding claims, wherein the elementary cells of a two-dimensional sequence alternatively exhibit:a) all substantially the same dimensions, said second information element being encoded by the pattern distribution of the so-called empty cells and the so-called iridescent cells within said two-dimensional sequence; b) different dimensions, said dimensions constituting an additional encoding function of said second information element or a predetermined part thereof in combination with the encoding by said pattern of the so-called empty cells and the so-called iridescent cells; c) alternatively or in combination with points a) or b) a two-dimensional distribution of two or more different two-dimensional sequences according to claim 6 characterized by a specific selection of said different two or more two- dimensional sequences and / or their relative arrangement within the two- dimensional extension of said two-dimensional distribution relative to a predetermined order of succession and / or their distance; d) alternatively or in combination with points a) to c) predetermined variations of the perimeter shape of a predetermined number of so-called empty and / or so- called iridescent elementary cells.

8. The Holographic Security Code according to one or more of the preceding claims, wherein the transformation function of said first information element into said second information element can alternatively or in combination be constituted by one or more of the following functions: a mathematical function such as one or more transforms, preferably a Fourier transform, a Laplace transform, one or more trigonometric functions, one or more algebraic functions, one or more stochastic functions.

9. The Holographic Security Code according to one or more of the preceding claims, characterized in that it is provided in combination with an additional information element, optionally holographic, in an overlapped and / or side-by-side form.10.The Holographic Security Code according to one or more of the preceding claims, wherein one or more of said two-dimensional sequences comprises a combination of so-called empty and so-called iridescent elementary cells configured to encode information correctness verification strings.

11. A Holographic Security Product characterized in that it comprises a substrate on which the holographic code according to one or more of the preceding claims is applied.12.The Holographic Security Product according to claim 1 1 , wherein said holographic code is provided in combination with a graphic and / or alphanumeric information element, optionally represented by a hologram, and wherein said information element constitutes said first information element, while said second information element is constituted by a processing of said first information element by one or a combination of said transformation functions.13.The Holographic Security Product according to claim 12, wherein said holographic code is constituted by a holographic code according to one or more of claims 5 to 7.14.The Holographic Security Product according to claim 1 1 , wherein the holographic code is applied to said substrate in the form of a continuous holographic strip on which one, two, or more of said different two-dimensional sequences are represented in a predetermined sequence alternatively: a) a cyclic repetition of one, two, or more of said different two-dimensional sequences; b) a random repetition of two or more of said different two-dimensional sequences; c) a repetition according to point a) or point b) wherein in said strip the relative position of said one or two or more two-dimensional sequences differs along its longitudinal extension and is defined by a function, preferably a random function.15.The Holographic Security Product according to one or more of claims 1 1 to 14, characterized in that it is in the form of a label comprising one, two, or more of said two-dimensional sequences or at least one of said two-dimensional sequences and at least a part of one, two, or more of said two-dimensional sequences.

16. An Anti-counterfeiting Verification System, the system comprising: a plurality of anti-counterfeiting labels made according to one or more of claims 1 1 to 15;at least one code reader of the codes applied to said labels, said codes being constituted by at least one holographic code according to one or more of claims 1 to 10; at least one processing unit comprising a memory in which said codes are stored and at least one program for comparing the codes transmitted by the reader with the codes contained in said database, at least one receiving and visual and / or acoustic reproduction unit associated with said reader; said processing unit generating a confirmation or denial signal of the authenticity of the code based on the result of said comparison, said signal being transmitted to said visual and / or acoustic reproduction unit for the issuance of a visual and / or acoustic information on the confirmation or denial of the authenticity of said code. e Anti-counterfeiting Verification System according to claim 16, wherein: said codes are further constituted by at least one graphic and / or alphanumeric information element preferably applied so as to be visible on said labels; in the memory of said processing unit, or in said database, said first information elements and the generation functions of the corresponding said second information elements and the coding functions of said second information elements in a holographic code according to one or more of claims 1 to 10 are stored, which is constituted by at least one or two or more of said two- dimensional sequences of elementary cells; said at least one code reader being connected to an input of said processing unit and in said processing unit there is loaded or loadable a software comprising the instructions to receive the reading data from said reader corresponding to a holographic code and to verify the congruence of said first information elements with the corresponding second information elements reconstructed by decoding said holographic code. e System according to claim 16 or 17, wherein: said first information element is constituted by a graphic and / or alphanumeric logo;said second information element is constituted by a processing by an algorithm of said first information element, which algorithm is of the type according to claim 8;- said holographic code is constituted by a holographic code according to one or more of claims 5 to 10;- said processing software comprising the instructions to perform the following operations: i) processing of the image acquired by said reader of said first information element by applying to it the transformation function used for the generation of the second information element; ii) generation of the coding map of said second information element reconstructed from said image of said first information element; iii) determination of the position of the one or more two-dimensional sequences of elementary cells, from the position codes of the same with reference to the areas of the coding map of the second information element represented by said one or more two-dimensional sequences; iv) comparison between said one or more two-dimensional sequences reconstructed from the acquired image of the first information element with said one or more two-dimensional sequences acquired by the reader, the labels being considered authentic for which the result of said comparison indicates an identity within predetermined tolerances.

19. The System according to claim 16 or 17, wherein:- said first information element is constituted by a deterministic or random combination of dimensions and / or distances of the cells having aspects according to two types with contrasting colors, particularly black and white;- said second information element is constituted by a representation of said first information element by one, two, or more two-dimensional sequences of so- called empty and so-called iridescent elementary cells;- said processing software comprising the instructions to perform the following operations:i) acquisition of said one or more two-dimensional sequences of so-called empty and so-called iridescent cells by the reader; ii) determination of the distance and / or size of the cells of the first information element, the distances and / or sizes of the cells of said one or more two- dimensional sequences of so-called empty and so-called iridescent cells; iii) comparison between the distance and size information of the cells of the first information element stored in the memory of said processing unit with the corresponding values obtained from the processing of said one or more two- dimensional sequences, the labels being considered authentic for which the result of said comparison indicates an identity within predetermined tolerances. O.The System according to one or more of claims 16 to 18, wherein:- said first information element is constituted by a deterministic or random combination of one, two, or more of said two-dimensional sequences of so- called empty and so-called iridescent cells, said deterministic or random distribution being relative to the dimensions and / or distances of the cells having aspects according to two types with contrasting colors, particularly black and white and / or relative to the order of succession of said different two-dimensional sequences among themselves and / or relative to the variation of the perimeter shape of a predetermined number of so-called empty and / or so-called iridescent elementary cells;- said second information element is constituted by a representation of said first information element by one, two, or more two-dimensional sequences of so- called empty and so-called iridescent elementary cells;- said processing software comprising the instructions to perform the following operations: i) acquisition of said one or more two-dimensional sequences of so-called empty and so-called iridescent cells by the reader; ii) determination of the distance and / or size and / or perimeter shape of the cells of the first information element, the distances and / or sizes and / or perimeter shapes of the cells of said one or more two-dimensional sequences of so-called empty and so-called iridescent cells and / or determination of the distance of saidtwo-dimensional sequences among themselves and / or determination of the order of succession of said two-dimensional sequences among themselves; iii) comparison between the distance and size and / or perimeter shape information of the cells of the first information element and / or the distance and / or order of succession of the two-dimensional sequences among themselves stored in the memory of said processing unit with the corresponding values obtained from the processing of said one or more two-dimensional sequences, the labels being considered authentic for which the result of said comparison indicates an identity within predetermined tolerances.

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