EP3810432B1

EP3810432B1 - A method for providing an object with a unique mark

Info

Publication number: EP3810432B1
Application number: EP19752554.6A
Authority: EP
Inventors: Nuno Miguel MENDONÇA DA SILVA GONÇALVES; Bruno André SANTOS PATRÃO; Leandro MORAES VALLE CRUZ; Ricardo Jorge DIAS BARATA; João Pedro DE ALMEIDA BARRETO; João Pedro FREIRE DUARTE; Renato PAULO MONTEIRO; João Paulo FERREIRA SARAIVA DA MOUTA DIAS; Albano Augusto CAVALEIRO RODRIGUES DE CARVALHO
Original assignee: Incm Imprensa Nacional Casa Da Moeda SA; Universidade de Coimbra
Current assignee: Incm Imprensa Nacional Casa Da Moeda SA; Universidade de Coimbra
Priority date: 2018-06-22
Filing date: 2019-06-19
Publication date: 2023-10-18
Anticipated expiration: 2039-06-19
Also published as: EP3810432A1; WO2019244081A1; PL3810432T3; RS65087B1; EP3810432C0

Description

FIELD OF THE INVENTION

The present invention is enclosed in the area of unique marking of objects, for instance authenticity in assay or uniquely identifying and tracking an object.

PRIOR ART

Prior art solutions exist where a marking is applied to an object.
Document DE 10 2008 015466 discloses a security marking for objects, comprising particles randomly distributed on or at the surface or, in the case of a material transparent to optical radiation, in the volume of an object, wherein the particles reflect light depending on an angle and change a phase or polarization or spectral formation of the light. The particles have a disk-shaped geometry, preferably with a layer thickness of 0.1 to 10 µm and an extent of 1 to 1000 µm. It is also disclosed a device for identifying an object and a method for identifying an object.
In document US 2016/376674 , a method for marking an article is disclosed which includes providing an article including a substrate, the substrate including a surface and a surface material, and forming a design on the surface of the substrate by applying a marking material to the surface wherein applying the marking material includes an additive manufacturing technique. A second method for marking an article is disclosed, further including the surface having a first surface and second surface, the second surface defining a depression relative to the first surface, and forming a design on the surface of the substrate by applying a marking material to the second surface, the marking material forming a marking surface which is substantially flush with the first surface. The marked article formed by the methods includes a microstructure derived from the additive manufacturing technique.
Document US 2018/029304 refers to a method for preparing a composite body comprising a support body and at least one decorative element, preferably a gemstone, the support body comprising a thermoplastic material, the method being characterized by the steps of: arranging the decorative element on the support body, heating the support body, pressing the decorative element into the support body by using a stamp consisting of an elastically deformable material, the material of the stamp being selected from the group of elastomers.
In the area of assurance of authenticity, the object is typically a valuable object, the marking providing assurance of authenticity of the object by visual analysis, indicating that the object contains a certain degree of purity (in the case of gemstones and precious metals) or which has a certain provenance (in the case of food products, such as wine bottles). Examples of provenance or guarantee authenticity consist of security documents (for identification, such as passports, national citizens' cards, driving licenses, visas, residence documents, etc.), certificates of authenticity (diplomas, certificates of formal qualifications, official stamps, etc.) and certificates of authenticity of products or trademarks (products of protected origin, trade marks, or others).
In the first case of gemstones stones and precious metals, the marking is applied by punching the object. In the case food products, a guarantee seal with certain visual characteristics is applied, typically further comprising a numbering. In both cases, the marking that is intended to be unique is recognizable and the security against copy of the marking is dependent on access to the puncture and associated equipment or the equipment producing the said seals, or the ability to reproduce them.
On the other hand, and outside the area of guarantee of authenticity (although the solutions described below are equally applicable to this area), in order to validate, identify and trace a product, marking solutions are also known, such as codes with n-dimensions (bar codes, QR code, or others) or solutions with electronic components, such as RFID or other electronic-based solutions of greater constructive complexity.
The development of technology, in particular computing, makes these solutions less effective, since the ability of a machine to fully identify and hence reproduce/mimic such codes or devices is increasingly higher.
The present invention aims to address all of these problems by providing a solution that guarantees authenticity to an object and also allows validation, identification and tracking of the object, by introducing intrinsically unique techniques in the object marking process and consequently in the object itself.

SUMMARY OF THE INVENTION

The present invention is defined by the claims and any subject-matter falling outside the scope of the claims is provided for information purposes only.
It is an object of the present invention a method for providing an object with a unique marking, comprising marking such object with a physical chaotic marking process on the surface of a portion of said object, such physical chaotic marking process consisting of:

i) random deposition of particles over the surface and further incrustation, wherein said portion of the object consists of a incrustation portion made of a material with hardness and ductility which provide accommodation of incrusted particles, the material consisting of a metal, a polymer or a resin, said physical chaotic marking process consisting of incrustation of particles in the incrustation portion, such incrustation being performed by a) puncturing or b) application of a laser beam, on the surface of the incrustation portion, said particles being deposited on the surface prior to incrustation and therein incrusted after incrustation, and wherein such particles consist of diamond particles, approximately spherical, and wherein said particles covers an average area of 0.7-3.2 % of the area of the incrustation portion, the particles having a diameter between 50-100 µm and the surface of the incrustation portion having an area of 1-4 mm², such surface of the incrustation portion consisting of a square with 1-2 mm sides;
or
ii) printing with a bondable fluid enriched with glitter particles, thereby providing a marking on such surface, wherein said bondable fluid consists of ink, glue, a resin or varnish, wherein the glitter particles have a diameter between 50-100 µm, wherein the glitter particles consist of metal particles non solvent in the bondable fluid, such particles being spherical or discoidal; wherein the glitter particles are randomly organised within the bondable fluid, and the glitter particles are dispersed in a low density along the marking and the amount of glitter particles range from 10 to 1000 glitter particles along the making for a common label.

The used processes, intrinsically chaotic, provide a unique character to the resulting object which is, thus, unique. In the case of process i), the incrustation of particles in an object provides the uniqueness of the marking, since the particles are randomly deposited over the surface and subsequently incrusted. The resulting marking is thus not reproducible, since a reproduction of the deposition and incrustation steps would render a different result. This is also true for the case of process ii), since glitter particles in a fluid are mobile, and thus provide a random organization, which is stabilized after printing. The printing of the surface with the bondable fluid enriched with such particles (i.e. a mixture of a bondable fluid with glitter particles) even promotes the random organization of particles within the fluid, therefore leading to a unique marking. Thus, and unlike prior art solutions, the present invention provides for truly unique marking of an object, while being constructively simple. The physical chaotic marking thus provides a random result.
In an advantageous configuration of the method of the present invention, the portion of the object consists of a incrustation portion made of a material with hardness and ductility which provide accommodation of incrusted particles, in particular the material consisting of a metal, a polymer or a resin, said physical chaotic marking process specifically consisting of i) incrustation of particles in the incrustation portion, such incrustation being performed by a) puncturing or b) application of a laser beam, on the surface of the incrustation portion, said particles being deposited on the surface prior to incrustation and therein incrusted after incrustation. Incrustation of particles are more efficiently performed a) by puncturing (with a punch) of the particles into the object, which in the present case is a metal object, or b) by applying a laser beam on the surface of the incrustation portion, thereby fusing such area and providing incrustation of the particles into the surface. The incrustation portion material consists of a metal, thus providing a metal portion. Where the incrustation portion material consists of a polymer, such polymer consists of acrylic.
In another, alternative, advantageous mode of the method of the present invention, the physical chaotic marking process specifically consists of ii) printing with a bondable fluid enriched with glitter particles, where said printing being performed by one of the following methods: serigraphy, flexography, rotogravure, carving, typography, offset, spray painting or direct printing with a brush embedded in said bondable fluid. Printing of a bondable fluid enriched with glitter particles are efficiently performed on the surface of the portion of the object by one of the described methods.
It is also an object of the present invention an object which is obtained from the method for providing an object with a unique marking of the present invention, such object comprising:

a incrustation portion, the physical chaotic marking process being applied by i) incrustation of particles on the surface of such incrustation portion,
- wherein the incrustation portion is made of a material with hardness and ductility which provide accommodation of incrusted particles, wherein said material consists of a metal, a polymer or a resin; and
- wherein such particles consist of diamond particles, approximately spherical, and wherein said particles covers an average area of 0.7-3.2 % of the area of the incrustation portion and such particles have a diameter between 50-100 µm and the surface of the incrustation portion has an area of 1-4 mm², such surface of the incrustation portion consisting of a square with 1-2 mm sides;
  or
a portion, the physical chaotic marking process being applied by ii) printing with a bondable fluid enriched with glitter particles on the surface of such portion and thereby providing a marking on the surface of the portion of the object;
- wherein said bondable fluid consists of ink, glue, a resin or varnish;
- wherein the glitter particles have a diameter between 50-100 µm;
- wherein the glitter particles consist of metal particles non solvent in the bondable fluid, such particles being spherical or discoidal; wherein the glitter particles are randomly organised within the bondable fluid, and the glitter particles are dispersed in a low density along the marking and the amount of glitter particles range from 10 to 1000 glitter particles along the making for a common label,

Furthermore, it is an object of the present invention the use of particles, in particular:

diamond particles, approximately spherical, wherein said diamond particles covers an average area of 0.7-3.2 % of the area of the incrustation portion and such diamond particles have a diameter between 50-100 µm; or
glitter particles, preferably of a mixture of a bondable fluid with such glitter particles, thereby providing a bondable fluid enriched with glitter particles, for providing an unique mark by random deposition of such particles;

Such unique marking being provided in the object, which consists of a stamp or the object to be marked itself.
It is yet an object of the present invention a machine for manufacturing an object with a unique marking, the machine being configured to implement the method for providing an object with a unique marking of the present invention, the machine comprising:

i) means for random deposition of particles over a surface of an object and further incrustation of such particles in the surface or
ii) means for printing a surface of an object with a bondable fluid enriched with glitter particles, thereby providing a marking on such surface of the object.

Such machine therefore uniquely marks objects, due to the chaotic/random properties of the means it comprises, therefore providing the advantages of the method for providing an object with a unique marking of the present invention.
Furthermore, another object of the present invention is a method for capturing a marking, such marking being obtained by the method for providing an object with a unique marking of the present invention or being present in the object with a marking of the present invention, the method for capturing the marking comprising the following steps:

obtaining at least one digital image of the marking, preferably through a digital camera or microscope,
segmenting particles on said digital image by means of image processing,
determine a digital descriptor based on identified particles, the digital descriptor comprising information on visual, geometrical and/or morphological aspects of the particles in the marking, and
compare such digital descriptor with a plurality of digital descriptors in a database, and thereby obtaining further information associated with a corresponding digital descriptor in the database.

Such method for capturing a marking therefore provides an efficient way to capture and obtain relevant information from an object with a marking as obtained from the method for providing an object with a unique marking of the present invention, or an object obtained from such method for providing an object with a unique marking. A computational apparatus comprising digital image acquiring means, preferably a digital camera or microscope, configured to implement the method for capturing a marking of the present invention, and a computer-readable non-transitory storage media comprising program instructions executable to carry out the method for capturing a marking of the present invention are also objects of the present invention.

DESCRIPTION OF FIGURES

Figure 1 - images of a surface with a marking, in an object, obtained from the method for providing an object with a unique marking consisting of i) random deposition of particles over the surface and further incrustation, disclosed in the present invention. Particles are visible. Such images consist of the digital images of the method for capturing a marking of the present invention. The incrustation portion is of gold (thus, a metal portion) in the image on the left and silver in the image on the right. The image was obtained with 200x zoom.
Figure 2 - image of a surface with a marking, in an object, obtained from the method for providing an object with a unique marking consisting of ii) printing with a bondable fluid enriched with glitter particles, disclosed in the present invention. Particles are visible. Such images consist of the digital images of the method for capturing a marking of the present invention. Resolution is of 1080p and the bondable fluid is ink, in which glitter particles were mixed. Printing was performed through serigraphy.
Figure 3 - several digital images relevant for the method for capturing a marking of the present invention. Fig. 3 a) consists of a digital image of a marking obtained by incrustation. Fig. 3 b) consists of the same image, in which rectification was applied. Fig. 3 c) consists of the same as Fig. 3 b), after identification of particles. Fig. 3 d) consists of the same image as Fig. 3 c), in which geometrical properties (distances and angles between particles) were identified.
Figure 4 - several digital images relevant for the method for capturing a marking of the present invention. Fig. 4 a) consists of a digital image of a marking obtained by incrustation of diamond particles in the surface of a gold portion. Fig. 4 b) consists of the same image, in which classification / mask produced by a convolutional neural network (CNN) was applied. Fig. 4 c) consists of the same image as Fig. 4 b), after selection of a region of interest with the mask, Fig. 4 d) consists of the same image as Fig. 4 c), after cut of the region of interest.
Figure 5 - several digital images relevant for the method for capturing a marking of the present invention. Fig. 5 a) consists of a digital image of a marking obtained by incrustation of diamond particles in the surface of a gold portion. Fig 5 b) consists of the same image, after manual identification of particles by a human operator, for training purposes, as described below. Fig 5 c) consists of the same image, after identification of particles by means of the method for capturing a marking of the present invention.
Figure 6 - example of an embodiment of the method for capturing a marking of the present invention, with registration steps.
Figure 7 - example of an embodiment of the method for capturing a marking of the present invention, with verification steps.

DETAILED DESCRIPTION

The more general and advantageous configurations of the present invention are described in the Summary of the invention. Such configurations are detailed below in accordance with other advantageous and/or preferred embodiments of implementation of the present invention.
Subsequently described advantageous embodiments of the method of the present invention are within the scope of physically marking by i) random deposition of particles over the surface and further incrustation.
In an advantageous configuration of the method of the present invention, incrustation of particles is specifically performed by a) puncturing on the surface of the incrustation portion by means of a metal punch over said pre-deposited particles on the surface.
In another advantageous of the method of the present invention, incrustation of particles is specifically performed by b) application of a laser beam on the surface of the incrustation portion and, prior to such incrustation, particles being pre-crimped on said surface. Therefore, a random organisation of particles is provided as in alternative process a), of puncturing, although particles are not truly incrusted but only partially fixed to the surface. It is the application of a laser beam that incrusts the particles, already randomly organised by the pre-crimping.
In another inventive aspect, the particles consist of diamond particles, approximately spherical, therefore providing resistance to the impact of puncturing or the effect of laser, and also providing evenness of particles, with a generally spherical form.
Said particles of have an average area of 0.7-3.2 % of the area of the incrustation portion, the particles having a diameter between 50-100 pm and the surface of the incrustation portion having an area of 1-4 mm², the surface of the incrustation portion consisting of a square with 1-2 mm sides. Such relation between areas provides for a good visual organization of particles in the metal, thereby enhancing optical or visual reading methods.
The particles have a high contrast with the incrustation portion, preferably having a colour which provides high contrast with such incrustation portion. The incrustation portion comprises or consists of a precious metal, preferably one or more of the following: gold, silver, platinum or palladium. It is - although in no way necessary - that the whole object is made of the same material or materials as the incrustation portion.
We define the incrustation of diamond particles in metal artefacts, usually precious metals (gold, silver, platinum and palladium). The application process is performed by punching or through a laser beam. The size of the particles varies depending on the intended applications, namely, the particles are of 50 to 100 pm in 1mm side markings.
Variables consist of:

Particle Material: diamond
Particle size: 50 to 100 micrometers
Particle Format: roughly spherical
Dimension of the mark, surface of the portion: approximately quadrangular with 1mm of side, the objective being to provide an unique assay marking on precious metals.

Process described as a) comprises placement of the particles, by deposition on the metal surface, and crimping the particles by puncturing using a metal punch, over the pre-deposition of particles.
Process described as b) comprises placement of the particles, by deposition on the metal surface, and particle crimping by incidence of a laser beam, with or without pre-crimping of the particles for initial fixation.
Subsequently described advantageous embodiments of the method of the present invention are within the scope of physically marking by ii) printing with a bondable fluid enriched with glitter particles.
In an inventive aspect of the method of the present invention, the bondable fluid enriched with glitter particles is obtained by mixing glitter particles into a bondable fluid, prior to printing. Such mixing enhances the random organisation of glitter particles within the bondable fluid.
Printing is specifically performed by serigraphy with a net, the net being such it provides passing of the glitter particles through it.
For evenness, the glitter particles have a diameter between 50-100 pm and consist of metal particles non solvent in the bondable fluid, such particles being spherical or discoidal. The bondable fluid consists of ink, glue, a resin or varnish.
In another inventive aspect, said glitter particles are such that have high contrast with said bondable fluid, the bondable fluid said bondable fluid preferably having transparency. More preferably, the fluid is transparent. Thus, the glitter particles will be even more visible, in their contrast with the bondable fluid.
Variables consist of:

Particle Material: metal glitter particles
Particle size: 50 to 100 micrometers
Particle Format: roughly spherical or discoidal
Density of the material: as desired
Dimension of the mark, on the surface of the portion: as desired, the objective being to provide an unique printed marking with the desired dimension and format.

The process comprises placement of the particles, by mixing the powder particles with the bondable glue, such as ink, to be applied, and printing using screen print technique with a net wide enough to allow the passage of glitter particles, other printing processes also being suitable.
The printing of glitter-mixed inks is applied to almost all printing processes, which means they generate unique images by instantiation. Each of these processes is fine-tuned by defining the variables mentioned above. Some of the processes applied are:

Flexography
Rotogravure
Carving
Typography
Offset
free manual painting with the use of a conventional brush.

With regard to both methods, certain options provide enhanced results, as above described.
Contrast: existence of high visual contrast between the particles and the carrier material where the marking is created. In the examples used, it is desirable that the colour of the glitter particles be differentiated from the colour of the paint and / or colour of the carrier material (paper, polymer, PVC, polycarbonate, wood, among other carrier materials) when applied with inks or transparent glues or with a high transparency index. On the other hand, in the case of precious metal marks, given the hardness of the carrier, it is desirable that the colour of the particles be differentiated from the colour of the metal.
Particle resistance: high particle resistance in terms of physical and chemical integrity to the process of marking creation. Depending on the marking process, the particles suffer a physical shock that fractures or destroys them partially or completely. For this reason, it is desirable that the particle be of a material resistant to the physical process. In the case of marking in metals, one of the most suitable materials for the marking process is the diamond (carbon element), given its high physical strength. From the chemical point of view, it is also desirable that the particles maintain their physical integrity and chemical composition, and be stable throughout the life cycle of the marking. In the case of glitter-enriched inks, one of the suitable materials is non-soluble metal particles in the solvents, glues, resins and paints where they will be mixed.
Density: existence of low density and non-high amount of particles along the marking. The amount of particles range from 10 to 1000 along the making for a common label, although it is desirable that the number of particles be between 30 and 200. A higher or lower particle value does not compromise the marking, but reduces the ability of a system to identify it. As to density, it is desirable that there be no particle agglomeration, for this purpose the use of a low density dispersion is desirable.
With regard to the object obtained by the method of the present invention, it consists of:

a metal piece of a precious metal such as gold, silver, platinum or palladium, thereby consisting of a precious piece, such as a jewellery piece, a precious metal piece, an ingot, a precious piece which is used in the mechanism of machinery or a piece of art and the unique marking consisting of a mint mark, the incrustation portion consisting of a portion of such metal piece, and the physical chaotic marking process being applied by i) incrustation of particles, or
a cellulose or polymer based piece such as polycarbonate (PC), polyvinyl chloride (PVC), wood or paper, the portion consisting of a portion of the surface of such piece, and the physical chaotic marking process being applied by ii) printing the surface with a bondable fluid enriched with glitter particles.

With regard to the method for capturing a marking of the present invention, also advantageous aspects exist, as subsequently described. The method for capturing a marking further comprises rectifying the digital image, prior to particle segmentation, such rectifying comprising:

detecting a region containing a marking in the image, through feature search and identification, detection of such region comprising:
- ∘ implementation of a convolutional neural network on the region of the image, such network having been trained over pre-acquired data relating to other markings,
applying a transformation in such region, such transformation comprising removing perspective effects and/or a desired orientation.

Such rectification provides a more suitable image to analyse, i.e., to in which particles and further details are detected.
The particle segmentation of the method for capturing a marking also further comprises implementing a convolutional neuronal network on the image, such network having been trained over the image and a mask containing already identified particles.
The method for capturing a marking also further comprises associating a digital descriptor with additional information and storing both the digital descriptor and additional information in a relational database, thereby registering such digital descriptor where no corresponding digital descriptor from the plurality of digital descriptors in a database was identified, the additional information comprising one or more of the following: date, time, localisation, owner reference, manufacturer reference, information on each sale / transition of ownership of the piece, information on remodelling or any procedure implemented on the piece.

EMBODIMENTS

Specific embodiment details relative to both capturing and analysing digital images according to the method for capturing a marking of the present invention, as well as the apparatus that implements such method, are subsequently described.
For objects with incrustation marking, given the reduced size of the marking, the most suitable reading system would most suitably have a magnification capability for the particles to be individually detected. This system could be a microscope (with enlargements of IOOx, 200x or higher) or a conventional chamber of great magnification. Another suitable reading system is the camera of a smartphone or tablet with a lens attached.
The image acquisition process should be optimized to collect one or more images under predefined lighting, positioning and magnification conditions. Ideally the equipment should be capable of capturing 5 megapixel images in the case of magnifications greater than 200x and 12 megapixels in case the equipment is a smartphone or tablet, with or without magnifying accessory lenses, and the marking must be completely visible, without occlusions or cuts. Figure 1 illustrates two examples of markings captured with a microscope. These resolution values are indicative of solutions with high robustness, however, the reading system has a lower resolution, which does not compromise the robustness of the solution in most cases.
For objects with printing marking, depending on the size of the glitter particles and the area of the mark, the reading system could be a conventional camera or the camera of a mobile device, or even a microscope, but it is not usually necessary to use the latter.
The image acquisition process must be able to capture all the particles of a marking. The acquisition equipment is a mobile phone with a common camera attached. The capture is done preferably, but not exclusively, with resolution equal to or greater than 1080p. Since the interaction of the particles with light differs according to the direction of incidence of the latter and from the point of view of the acquisition, it is preferable to capture more than one image and to identify the particles in all of them and subsequently to compose the description of the marking (as described in Section 3: Image Descriptor). Figure 2 shows a glitter marking captured with the camera of a mobile phone.
As above described, a digital descriptor that combines visual aspects, geometric characteristics and/or morphological characteristics is used. The function of a digital descriptor is to enable the marking validation operation, without recourse to the original image, which is available or not at the time of validation and, consequently, to improve the speed of obtaining a validation result.
The visual aspects of a marking are described through image characterization methods, such as: descriptors of local characteristics, textures, hue, minutiae, among others. Two images of the same marking are compared through local (pixel-by-pixel) or global (general structure from image) relationships. In order to better perform a local comparison it is necessary to perform a correct alignment between two images captured from the same mark, through rectification.
The computation of local characteristics is carried out by the implementation of corner and edge detection algorithms such as ORB [Oriented Features from Accelerated Segment Test (FAST) and Rooted BRIEF (Binary Robust Independent Elementary Features)], among other possible methods. These methods allow to detect and compare small sections (typically 5x5 pixels) in order to find matches.
The detection and characterization of the surfaces of the marking and of the pieces comprising it is supported by extraction of data through the filtering of the images with filters of Local Binary Markings (LBP), allowing to distinguish surfaces with different attributes.
The gathering of information of hue is relevant, since it allows to identify the type of material on which the marking is applied. By analysing the RGB channels of the image it is possible to identify the type of metal being analysed, or the type of pigment in which the glitter is immersed.
Minutiae detection refers to implemented mechanisms capable of identifying and characterizing imperfections or indentations created by the marking on the surface on which the marking was applied or created by the particles themselves that make up the marking.
Since the elements in the marking consist of particles that are detected, their relative and absolute positions in the marking and their shape being known, it is possible to characterize the marking also on the basis of this information. From the mask identifying the particles (Fig. Be)), characteristics describing their morphology are calculated namely, size, circularity, aspect ratio, particle density, distance to the centre of the marking, between others. Once these characteristics are calculated, their distribution in a histogram is studied and values are collected at specific frequencies of the histogram which then constitute the morphological aspects of the marking in question.
The geometric aspects of a marking are described by histograms of characteristics associated with the sequence or sets of particles (a marking is composed of several particles). Among these aspects, we firstly use the distance between sets (the order of points does not matter) of two particles and the angle formed by the sequence (points chosen in a specific order) of three particles (Fig. 3d)).
Such a histogram consists of a vector of integers that account for the occurrence of value ranges of a given characteristic among all sets / sequences of points associated with the particles. Figure 3d illustrates the calculation of the distance between two pairs of points, as well as the angle formed by a sequence of three other points.
Assuming that the image is properly rectified (as explained in Section 4.1), and the particles have been properly identified (as explained in Section 4.2), the calculation of the histogram consists of the following steps:

∘ For each region associated with a particle identify a representative point (this point is the centre of this region)
∘ Normalize (according to the marking region) the coordinates of the representative points of the particles between two values, namely, 0 and 100
∘ Initialize the histogram (with 141 elements in the case of distance, and 181 elements in case of angles)
∘ For each sequence of points (a pair in the case of distance, and a trio in the case of angles) calculate the geometric characteristic of the points (angle or distance)
∘ Calculate the histogram index relative to such characteristic (integer value approximation of the characteristic)
∘ Increment a unit on the histogram element for such calculated index.

With regard to rectification, a marking is photographed at different distances and from different points of view. Thus, in order to calculate the descriptors of a marking (visual, morphological and geometric) it is necessary to initially transform the image so that the marking appears integrally, without perspective, and with the same orientation in all the images. This phase is called rectification. To do this, it is necessary to (i) detect the marking through a characteristic identification that allows it to be recognized in the image, (ii) apply a transformation in the marking region to leave such a region without the initially mentioned deformations.
Marking image detection aims at extracting the region of interest for further processing. The extraction of the zone of interest allows the system to operate only on a part of the image, reducing the computational effort required, as well as increase the chances of success with particle detection and segmentation. In addition, it also allows a more efficient management of the information that is stored in the database, due to the smaller size of the image that needs to be retained.
The process of marking detection is achieved at the expense of the implementation of a convolutional neural network (CNN), called U-Net. This neural network is an algorithm capable of recognizing which zones of the image that contain the marking that is the zone of interest. This network is trained on a set of data acquired during the system building process and is updated and re-trained as the amount of information available in the database increases.
With regard to particle identification, a possible algorithm is based on the use of a U-Net convolutional neural network (CNN), trained directly on the image and its mask with the identified particles. For each marking used in the training of this network, the image of the marking is presented, the true segmentation of the particles (carried out manually).
With regard to registration of a marking, its respective digital descriptor is created and added to a database. The database record contains, in addition to the original captured image, its geometric and visual descriptors as well as other additional information (namely: date, time, location, observations, owner, manufacturer). The set of stored information will later be used by the system to confirm the authenticity of the marking.
With regard to validation of a marking, it is performed by two different operations, with different objectives and purposes: verification and identification. On the one hand, given an image of a marking, a set of characteristics of this marking are determined (targeting masks, particle position, random marking descriptors, etc.), which are evaluated by the model in the sense of identifying which marking which is sufficiently similar to the standard presented, in the case of identification. This validation process, called identification, is a 1-to-many search. On the other hand, the validation process is performed as a verification process. In the case of verification, this set of characteristics is compared only with the characteristics of the marking whose identity is known or suggested, becoming, therefore, a 1-to-1 search.
Fig. 6 shows an example of the complete registration process in a database of a diamond-on-metal particle dispersion marking.
With regard to verification - when verifying the authenticity of a marking - its image must be captured by any reading system similar to the system used for marking registration. Once the image is acquired, it will be processed. The processing (Fig. 7 (a) to (d)) generally includes the following operations: marking detection, identification of the carrier material, identification of the standard material, rectification and standardization of the marking for standard scale and orientation, detection of the particles forming the randomness and the calculation of the digital descriptors that characterize it, as above described.
Next, the descriptor of the marking to be checked will be purchased with the descriptor of the marking with which the comparison is intended, stored in database. In order for the descriptors of a given marking to correspond, even when the reading processes are performed at different times and by similar but different acquisition systems, the two marks are subjected to the same standardization operations described above (Fig. 7 e)). If this comparison, measured by a sufficiently effective likelihood measurement model, returning a sufficiently high score, then the marking is validated as being the same marking stored.
With regard to identification of the authenticity of a marking, its image must be captured by any reading system similar to the system used for marking registration. Once the image is acquired, it will be processed. The processing (Fig. 8 (a) to (d)) generally includes the following operations: marking detection, identification of the carrier material, identification of the material constituting the standard, rectification and standardization of the marking for standard scale and orientation, detection of the particles forming the random marking and calculation of the descriptors that characterize it, as described above (Fig. 8 a) to d)).
After the descriptor of the marking to be identified has been calculated, it will be compared to the descriptors stored in the database, which contains all the marking to be searched. The research process is not simple and its complexity depends on the size of the database, among other factors. The comparison is made using a cost metric between descriptors, producing a comparison value. In addition, the process is accelerated through an indexed search and hypothesis elimination system (Fig. 8 e). From this comparison will appear a list of the candidate markings, that is, those whose descriptors are more similar to the marking under verification.
The identification process includes several passages through this process of successively reducing the number of candidate markings until a comparison with a degree of confidence sufficient to generate a final response appears.
The identification process is structured at several levels, so that when one level generates more than one candidate marking, then the next level will initiate a new identification process with this list of candidate markings. New descriptors relating to this level should be calculated from this list.
Some of the operations that are used for the second level of research include processes of image alignment by homography techniques, comparison of marking geometry, and measurement of similarity of descriptors. If one of these comparisons returns a sufficiently high score, the marking identity is confirmed.
Of course, the preferred embodiments shown above are combinable, in different possible forms, within the scope of the appended claims.

Claims

A method for providing an object with a unique marking characterised in that it comprises marking such object with a physical chaotic marking process on the surface of a portion of said object, such physical chaotic marking process consisting of
i) random deposition of particles over the surface and further incrustation, wherein said portion of the object consists of a incrustation portion made of a material with hardness and ductility which provide accommodation of incrusted particles, the material consisting of a metal, a polymer or a resin, said physical chaotic marking process consisting of incrustation of particles in the incrustation portion, such incrustation being performed by a) puncturing or b) application of a laser beam, on the surface of the incrustation portion, said particles being deposited on the surface prior to incrustation and therein incrusted after incrustation, and wherein such particles consist of diamond particles, approximately spherical, and wherein said particles covers an average area of 0.7-3.2 % of the area of the incrustation portion, the particles having a diameter between 50-100 µm and the surface of the incrustation portion having an area of 1-4 mm², such surface of the incrustation portion consisting of a square with 1-2 mm sides;
or

ii) printing with a bondable fluid enriched with glitter particles, thereby providing a marking on such surface, wherein said bondable fluid consists of ink, glue, a resin or varnish, wherein the glitter particles have a diameter between 50-100 µm, wherein the glitter particles consist of metal particles non solvent in the bondable fluid, such particles being spherical or discoidal; wherein the glitter particles are randomly organised within the bondable fluid, and the glitter particles are dispersed in a low density along the marking and the amount of glitter particles range from 10 to 1000 glitter particles along the marking for a common label.
The method according to the previous claim wherein incrustation of particles is specifically performed by a) puncturing on the surface of the incrustation portion by means of a metal punch over said pre-deposited particles on the surface.
The method according to claim 1 wherein incrustation of particles is specifically performed by b) application of a laser beam on the surface of the incrustation portion and, prior to such incrustation, particles being pre-crimped on said surface.
The method according to any of the preceding claims wherein said particles have a high contrast with the incrustation portion, preferably having a colour which provides high contrast with such incrustation portion.
The method according to any of the claims 1-4 wherein said incrustation portion comprises or consists of a precious metal, preferably one or more of the following: gold, silver, platinum or palladium.
The method according to claim 1 wherein said physical chaotic marking process specifically consists of ii) printing with a bondable fluid enriched with glitter particles, said printing being performed by one of the following methods: serigraphy, flexography, rotogravure, carving, typography, offset or direct printing with a brush embedded in said bondable fluid.
The method according to any of the claims 1 or 6 wherein bondable fluid enriched with glitter particles is obtained by mixing glitter particles into a bondable fluid, prior to printing.
The method according to any of the claims 6-7 wherein said printing is specifically performed by serigraphy with a net, the net being such it provides passing of the glitter particles through it.
The method according to any of the claims 1 or 6-8 wherein said glitter particles are such that have high contrast with said bondable fluid, the bondable fluid said bondable fluid preferably having transparency.
An object characterised in that it is obtained from the method of any of the preceding claims, such object comprising:
- a incrustation portion, the physical chaotic marking process being applied by i) incrustation of particles on the surface of such incrustation portion, according to any of the claims 1-5; wherein the incrustation portion is made of a material with hardness and ductility which provide accommodation of incrusted particles, wherein said material consists of a metal, a polymer or a resin;
and wherein such particles consist of diamond particles, approximately spherical, and wherein said particles covers an average area of 0.7-3.2 % of the area of the incrustation portion and such particles have a diameter between 50-100 µm;

and the surface of the incrustation portion has an area of 1-4 mm², such surface of the incrustation portion consisting of a square with 1-2 mm sides;
or

- a portion, the physical chaotic marking process being applied by ii) printing with a bondable fluid enriched with glitter particles on the surface of such portion, according to any of the claims 1 or 6-9, and thereby providing a marking on the surface of the portion of the object; wherein said bondable fluid consists of ink, glue, a resin or varnish;
wherein the glitter particles have a diameter between 50-100 µm; wherein the glitter particles consist of metal particles non solvent in the bondable fluid, such particles being spherical or discoidal; wherein the glitter particles are randomly organised within the bondable fluid, and the glitter particles are dispersed in a low density along the marking and the amount of glitter particles range from 10 to 1000 glitter particles along the marking for a common label.
The object according to the previous claim wherein it consists of:
- a metal piece, preferably of a precious metal such as gold, silver, platinum or palladium, thereby consisting of a precious piece, and the unique marking consisting of a mint mark, the incrustation portion consisting of a portion of such metal piece, and the physical chaotic marking process being applied by i) incrustation of particles, or

- a cellulose or polymer-based piece, preferably polycarbonate (PC), polyvinyl chloride (PVC), wood or paper, the portion consisting of a portion of the surface of such piece, and the physical chaotic marking process being applied by ii) printing the surface with a bondable fluid enriched with glitter particles.
An use of particles in a method for providing an object with a unique marking of any of the claims 1 to 9, wherein said particles consists of:
- diamond particles, approximately spherical, wherein said diamond particles covers an average area of 0.7-3.2 % of the area of the incrustation portion and such diamond particles have a diameter between 50-100 µm;
or

- glitter particles, preferably of a mixture of a bondable fluid with such glitter particles, thereby providing a bondable fluid enriched with glitter particles, for providing a unique mark by random deposition of such particles; wherein the glitter particles have a diameter between 50-100 µm, wherein the glitter particles consist of metal particles non solvent in the bondable fluid, such particles being spherical or discoidal; wherein the glitter particles are dispersed in a low density along the marking and the amount of glitter particles range from 10 to 1000 glitter particles along the marking for a common label.
A machine for manufacturing an object with a unique marking, configured to implement the method of any of the claims 1-9 and comprising:
- i) means for random deposition of the diamond particles over a surface of an object and further incrustation of such particles in the surface or

- ii) means for printing a surface of an object with a bondable fluid enriched with the glitter particles, thereby providing a marking on such surface of the object.
A method for capturing a marking, such marking being obtained by the method of any of the claims 1-9 or being present in the object of any of the claims 10-11, characterised in that it comprises the following steps:
- obtaining at least one digital image of the marking, preferably through a digital camera or microscope,

- segmenting particles on said digital image by means of image processing,

- determine a digital descriptor based on identified particles, the digital descriptor comprising information on visual, geometrical and/or morphological aspects of the particles in the marking, and

- compare such digital descriptor with a plurality of digital descriptors in a database, and thereby obtaining further information associated with a corresponding digital descriptor in the database.
The method according to the previous claim wherein it further comprises rectifying the digital image, prior to particle segmentation, such rectifying comprising:
- detecting a region containing a marking in the image, through feature search and identification, detection of such region preferably comprising:
∘ implementation of a convolutional neuronal network on the region of the image, such network having been trained over pre-acquired data relating to other markings,

- applying a transformation in such region, such transformation comprising removing perspective effects and/or a desired orientation.
The method according to any of the claims 14-15 wherein particle segmentation comprises implementing a convolutional neuronal network on the image, preferably on said region of the image, such network having been trained over the image and a mask containing already identified particles.
The method according to any of the claims 14-16 wherein it further comprises associating a digital descriptor with additional information and storing both the digital descriptor and additional information in a relational database, thereby registering such digital descriptor, preferably where no corresponding digital descriptor from the plurality of digital descriptors in a database was identified, preferably the additional information comprising one or more of the following: date, time, localisation, owner reference, manufacturer reference.
A computational apparatus comprising digital image acquiring means, preferably a digital camera or microscope, and a processor configured to implement the method of any of the claims 14-17.
A computer-readable non-transitory storage media comprising program instructions which, when executed by a computer, cause the computer to carry out the method of any of the claims 14-17.