BR112018074908B1 - IMAGE GENERATION SYSTEM AND METHOD TO GENERATE AN OBJECT AUTHENTICITY MEASUREMENT - Google Patents

Abstract

The invention relates to an imaging system (200) for generating a measure of authenticity of an object (10) comprising a dispersive imaging array (30) and an image sensor array (60). These are positioned so that when electromagnetic radiation (20) from the object (10) illuminates the dispersive imaging array (30), the electromagnetic radiation is scattered and the image is generated by means of the dispersive imaging array (30). image (60). The image generation system (200) is configured to then generate an authenticity measure of the object (10) depending on at least one relationship between the image generated by the scattered electromagnetic radiation and the reference spectral information. The invention also relates to imaging methods, computer programs, computer program products and storage media.

Description

Technical Field

[0001] The present invention relates to systems for generating an authenticity measure of an object. The invention also relates to methods, computer programs, computer program products and storage media for the same purposes.

Fundamentals

[0002] The supply of counterfeit goods in a particular Market causes a loss of revenue for the manufacturers of the corresponding authentic goods, as well as for the government when these goods are subject to taxation. End users are adversely affected by counterfeit goods because they are supplied with inferior quality products, which can be dangerous even for the health of the end user of certain products, such as when medicines are subject to counterfeiting. The manufacturer of high-quality authentic products will consequently suffer a loss of clientele.

[0003] Various anti-counterfeiting measures have been proposed in the prior art with respect, for example, to alcoholic and non-alcoholic beverages (beer, wine, liquor, soft drinks, etc.), tobacco products (cigarettes, cigars, loose tobacco , etc.), medicinal products, perfumes and normally products subject to special taxes. It is known to use sophisticated printing techniques to make the package design as difficult as possible to reproduce.

[0004] It is also known to make use of fluorescent items that look one way under ambient light and look a different way under ultraviolet (UV) radiation. Holographic images of varying degrees of complexity are also used. Other popular techniques include watermarking technology, printed gravure lines, and marks that change color depending on the heat applied to the mark.

[0005] Document CN 202533362 U relates to a device for identifying the authenticity of printed matter based on a multispectral imaging technology. The device comprises a multispectral imager for performing multispectral scanning on a test sample (the multispectral imager comprising a light source, a grid and an image detector), a spectral data processor for comparing spectral data obtained from the scan with spectral data from a standard sample, and a data server used to store the spectral data from the standard sample. If the difference between the spectral data obtained from the scan and the spectral data of a standard sample exceeds a defined threshold value, the test sample will be judged as false. Otherwise, it is judged as authentic.

[0006] The prior art also includes several imaging spectrometers used for scientific observations. These systems generally aim to obtain high-resolution spatial and spectral information about all regions of a scene or object. In particular, image spectrometers are image generators that allow the extraction of the three-dimensional spectral irradiance map of a planar object (spatial spectral data cube) l(x, y, À) through the use of two-dimensional array detectors, such as such as CCD (ie, charge-coupled device) or CMOS (ie, complementary metal oxide semiconductor) sensors. One dimension is wavelength and the other two comprise spatial information.

[0007] There are two main categories of spectral imagers: spectral raster imagers and instantaneous spectral imagers. A review of the multi- and hyperspectral imager can be found, for example, in Hagen et al, “Snapshot advantage: a review of the light collection improvement for parallel high-dimensional measurement systems”, Optical Engineering 51(11),111702 ( 2012), and Hagen et al, “Review of snapshot spectral imaging technologies”, Optical Engineering 52(9), 090901(September, 2013).

[0008] One way to acquire three-dimensional information through a two-dimensional sensor is the sequential acquisition of images through a mechanically digitized wheel or array of optical filters installed in front of an image generator. Another possibility is to adjust the central transmission band of a filter, such as a multistage liquid crystal filter, an acoustic-optical filter or a Fabry-Perot interferometer. These two examples fall under the category of spectral raster imagers.

[0009] There are instantaneous spectral imagers capable of simultaneous acquisition of images in different spectral bands through an array of filters and an example is the camera with multi-aperture filters (MAFC), using matrices of lenses with a focal plane detector.

[0010] Transmission diffraction gratings based on instantaneous spectral imaging systems also exist. One example is the Computed Tomography Imaging Spectrometer (CTIS), which uses multiple cross-transmission gratings or specifically designed Kinoform gratings capable of dispersing multiple spectral orders around a zero order. Computed tomography algorithms must be used to reconstruct the spectral radiance of the object.

[0011] Another example with transmission diffraction grating is the aperture coded instantaneous spectral image generator (CASSI), which uses complex masks to shade some parts of the object image in order to facilitate spectrum extraction.

[0012] The integral field image spectrometers also have diffraction gratings to disperse the light. In these configurations, the image is sliced by different methods to fit into an entrance slit of a conventional spectrometer to extract spectra. Image slicing can be achieved by using the fiber bundle and distributing individual fibers into an entrance slit, or by splitting the aperture using a lense array.

[0013] Fourier transform imaging spectrometers also exist in a separate category.

[0014] An interferometer is scanned to obtain images at different optical path differences and the spectra are reconstructed by Fourier transform. Some settings rely on the lense array to do aperture splitting and analyze averaged spectra in different parts of the image/object. One example is the multiple-image Fourier transform spectrometer (MIFTS) based on a Michelson interferometer. Another distinct example is the Instantaneous Hyperspectral Imaging (SHIFT) Fourier Transform spectrometer, which uses the pair of birefringent prisms to obtain different optical path lengths.

[0015] In view of the above, there is a need to provide fast, simple, inexpensive, compact and robust equipment for authentication purposes, particularly, but not only, for incorporation into portable auditing devices.

summary

[0016] To meet or at least partially meet the objectives mentioned above, systems, methods, systems, computer programs, computer program products and storage media according to the invention are defined in the independent claims. Particular embodiments are defined in the dependent claims.

[0017] In one embodiment, an image generation system is provided for generating a measure of authenticity of an object. The imaging system comprises one or more optical elements, the one or more image sensors being referred to hereinafter as "image sensor array", and one or more optical elements, the one or more optical elements being referred to below as "dispersive imaging arrangement". The dispersive imaging arrangement is realized such that when electromagnetic radiation from the object illuminates the dispersive imaging arrangement, at least part of the electromagnetic radiation is scattered. Furthermore, the dispersive imaging array is positioned with respect to the imaging sensor array in a manner to allow the imaging sensor array to image said scattered electromagnetic radiation. The image generation system is configured so that, after the image sensor arrangement generates an image of the scattered electromagnetic radiation in at least one image generation period, it generates a measure of authenticity of the object depending on at least one relationship between the generated image by scattered electromagnetic radiation and reference spectral information.

[0018] Such an image generation system allows efficient verification of whether, and/or to what extent, the relationship between the image generated by the scattered electromagnetic radiation and the reference spectral information, which represents the expected spectral composition of the electromagnetic radiation from the object, corresponds to predicted physics, in a situation in which some information about the electromagnetic radiation before scattering, i.e. some spatial information about the source of the radiation, is known or assumed (such as spatial information about the type brand, sign or code that the image generated by the object carries). If the relationship matches the predicted physics, the object is probably authentic. Otherwise, the object is more likely to be faked.

[0019] The invention also relates, in one embodiment, to an image generation method for generating an authenticity measure of an object. The imaging method makes use of: one or more optical elements, the one or more image sensors being referred to as mentioned above as the "image sensor array", and one or more optical elements, the one or more more optical elements being referred to, as mentioned above, as "dispersive imaging array". The dispersive imaging arrangement is realized such that when electromagnetic radiation from the object illuminates the dispersive imaging arrangement, at least part of the electromagnetic radiation is scattered. Furthermore, the dispersive imaging array is positioned with respect to the imaging sensor array in a manner to allow the imaging sensor array to image said scattered electromagnetic radiation. The imaging method comprises: imaging, through the array of the image sensor, the electromagnetic radiation scattered over at least one imaging period, and generating a measure of authenticity of the object depending on at least one relationship between the image generated by scattered electromagnetic radiation and reference spectral information.

[0020] The invention also relates, in some embodiments, to a computer program or a set of computer programs for performing an image generation method, as described above, for a computer program product or a set of products of a computer program for storing a computer program or a set of computer programs as described above, and for a storage medium for storing a computer program or a set of computer programs as described above.

Brief description of figures

[0021] Embodiments of the present invention will now be described, together with the attached figures, in which: Fig. 1 schematically illustrates an object to be imaged and an image generation system in an embodiment of the invention; Fig. 2 schematically illustrates an object to be imaged and a system in an embodiment of the invention, wherein the system comprises both an image generation system and a lighting arrangement; Fig. 3 schematically illustrates an imaged object and a system in an embodiment of the invention, wherein the system notably comprises lighting elements arranged around a dispersive imaging arrangement; Figs. 4 to 6 schematically illustrate three imaging systems and objects to be imaged, respectively in three embodiments of the invention; Figs. 7 and 8 schematically represent, using a fine lens grid approximation, two imaging systems and marks to be imaged, respectively in two embodiments of the invention; Fig. 9a schematically illustrates an imaging system in an embodiment of the invention, wherein the imaging system is an imaging device; Fig. 9b schematically illustrates a system in one embodiment of the invention, wherein the system comprises both an imaging system and a lighting arrangement, and wherein the system is an imaging device; Fig. 10a schematically illustrates an imaging system in an embodiment of the invention, wherein the imaging system comprises an imaging device and said imaging device comprises an image sensor arrangement and a imaging arrangement. of dispersive imaging, but said imaging device is not configured to actually generate the authenticity measure; Fig. 10b schematically illustrates a system in an embodiment of the invention, wherein the system comprises an imaging device and said imaging device comprises an image sensor array, a dispersive imaging array, and an illumination array , but said imaging device is not configured to actually generate the authenticity measure; Fig. 11 is a flowchart of an imaging method according to an embodiment of the invention; Fig. 12 is a flowchart of an imaging method in an embodiment of the invention, wherein generating the authenticity measure comprises decoding scattered electromagnetic radiation through reference spectral information. Fig. 13 is a flowchart of an imaging method in an embodiment of the invention, including an evaluation of whether a deconvolution result is decodable; Fig. 14 schematically illustrates the image processing generated by scattered electromagnetic radiation for authentication purposes, in an embodiment of the invention, in which the object bears a two-dimensional matrix bar code; Fig. 15 schematically illustrates the image processing generated by scattered electromagnetic radiation for authentication purposes, in an embodiment of the invention, in which the object bears a printed pattern (being a star-shaped logo); Fig. 16 schematically illustrates image processing generated by different scattered electromagnetic radiation for authentication purposes, in an embodiment of the invention; Fig. 17 shows calculated authentication parameters, or authentication measures, corresponding to the five spectrum profiles of Fig. 16, in an embodiment of the invention; Figs. 18 to 21 provide further explanation regarding some embodiments of the invention; Fig. 22a schematically illustrates an imaging system in an embodiment of the invention when applied, by simulation, to a single point of a two-dimensional matrix bar code; Fig. 22b schematically illustrates an imaging system in an embodiment of the invention when applied, by simulation, to a two-dimensional matrix bar code; Figs. 23 to 24 schematically illustrate two image generation systems, respectively in two embodiments of the invention; Figs. 25 and 26 schematically illustrate the generation of an authenticity measure of an object, in two embodiments of the invention, in which the image sensor arrangement generates an image of electromagnetic radiation scattered in a plurality of periods of illumination; Figs. 27 and 28 are flowcharts of imaging methods in two embodiments of the invention, wherein the generation of the authenticity measure of an object follows the arrangement of the image sensor generating image of scattered electromagnetic radiation in a plurality of illumination periods; Figs. 29a and 29b show images of a soda can lid without (Fig. 29a) and with a mask (Fig. 29b) acquired using an imaging system in an embodiment of the invention; Fig. 30 shows example images of a soda can lid acquired without a physical mask, but excited in two different lighting periods by blue light (left image) and green light (right image), in an embodiment of the invention; Fig. 31 shows examples of background subtracted images using two different linear combinations, in one embodiment of the invention; Fig. 32 shows the spectral reflectivity of two different color pigments; Fig. 33 shows the typical relative spectral distribution of a white LED; Fig. 34 shows the typical relative spectral distribution of an incandescent lamp at a temperature of 3000 K compared to that of the sun; Fig. 35 shows the excitation spectrum and emission spectrum of an exemplary fluorescent dye; Figs. 36 and 37 show the emission and excitation spectra for exemplary phosphorescent phosphor pigments; Fig. 38 is a schematic diagram of an exemplary implementation of a computing unit in accordance with an embodiment of the invention; Fig. 39 schematically illustrates an example of an imaging period and illumination period, in an embodiment of the invention; and Fig. 40 schematically illustrates an imaging system comprising, on the one hand, an imaging device comprising an image sensor arrangement, wherein the imaging device is a mobile phone with a camera, and, on the other hand , an imaging accessory comprising a dispersive imaging arrangement.

Detailed Description

[0022] The present invention will now be described in conjunction with specific embodiments. These specific embodiments serve to provide the person skilled in the art with a better understanding, but are not intended to restrict the scope of the invention, which is defined by the appended claims. A list of abbreviations and their meaning is provided at the end of the detailed description.

[0023] Fig. 1 schematically illustrates an imaging system 200 in an embodiment of the invention. The system 200 aims to generate a measure of authenticity for an object 10, i.e., an article. The object 10 may be, for example, without being limited to, a bottle or can of beer, wine, alcoholic beverages or soft drinks, a package, pack or box of cigarettes or cigars, a package of medicine, a bottle of perfume or any other taxable goods, a banknote, a paper of value, an identity document, a card, ticket, label, tag, security strip, security thread or the like. The object 10 has at least one part, surface or side bearing a visible or invisible mark, logo, sign, image or pattern, for example printed with an ink and/or printing coating, either printed on a label attached to the object 10 or printed directly on the object 10 (such as on a lid, capsule or the like of the object 10, where the lid or capsule may, for example, have a colored background). The expected spectral response of said part, surface or side, and possibly of the paint thereon (which may or may not have, for example, photoluminescent properties), when subjected to particular lighting conditions, is known and constitutes the reference spectral information. Some spatial information about the visible or invisible brand, logo, sign, image or pattern that the object 10 bears is also known or assumed to be known, as will be explained below.

[0024] System 200 comprises an array 60, hereinafter referred to as "image sensor array" 60, consisting of one or more image sensors. System 200 also comprises another array 30, referred to hereinafter as a "dispersive imaging array" 30, consisting of one or more optical elements.

[0025] In one embodiment, the image sensor array 60 comprises one or more arrays of CCD or CMOS detectors for recording the intensity distribution of incident electromagnetic energy. The dispersive imaging array 30 not only scatters electromagnetic energy, but can also collect electromagnetic energy from the object 10 and focus the rays of electromagnetic energy to produce a scattered image of the object 10 in an imaging plane where the sensor array of image 60 is positioned. In one embodiment, the dispersive imaging arrangement 30 comprises, on the one hand, at least one of a diffractive element, a refractive element, one or more lenses, and an objective, for producing a dispersed image of the object 10 in the plane of image where the image sensor array 60 is positioned and, on the other hand, a long pass filter (also called "long wavelength pass filter") in order to limit the spectral range used for authentication.

[0026] The system 200 may also optionally comprise various auxiliary elements (not shown in Fig. 1), such as for example any one or any combination of: a) a housing to contain, cover and/or protect the power generation arrangement dispersive image 30 and image sensor arrangement 60; b) support elements integrally formed within the housing, or attached thereto, for maintaining the dispersive imaging arrangement 30 in a fixed or substantially fixed relative position relative to the image sensor arrangement 60; c) a protective covering or protective covering means to be used between the object 10 and the dispersive imaging arrangement 30 to prevent stray illumination from ambient light and/or sunlight (in this case, a controlled lighting source may be contained within this protective covering); d) additional optical filters (longpass, bandpass, etc.), which may be advantageous, for example, if the imaging system 200 operates in luminescence mode, to cut reflection from the irradiation source; e) a controller or control means or units for controlling the operation of the image sensor array 60 and other elements; f) sending and input means for providing information and receiving information from an operator, such as a display screen, a keyboard, buttons, control knobs, LED indicator lights, etc. (in this regard, see also Fig. 38 and the corresponding description); and g) a battery to power various electronic parts of system 200.

[0027] The dispersive imaging arrangement 30 is constituted and positioned so that when electromagnetic radiation 20 from the object 10 illuminates the dispersive imaging arrangement 30 or particularly a part, surface, side, hole or aperture specific to it, at least part of the radiation 20 is scattered. The word "dispersive" here means: separating into its constituent wavelength components. For example, the array 30 may comprise: a diffractive element, a transmission diffraction grating (also known simply as a "transmission grating", or rarely as a "transmissive diffraction grating"), a diffracted transmission diffraction grating, a volume holographic grating, a grism (also called a “grid prism”), a reflective diffraction grating, a dispersive prism, or a combination of any of these. If the array 30 diffracts the radiation 20, the scattered electromagnetic radiation 50 can be referred to as a non-zero diffraction order part, such as, for example, the first negative or positive diffraction order part of the radiation.

[0028] Here are some examples of transmission grids that can be used in some embodiments of the invention: — Example 1: Especially for a transmission grid mounted in front of an objective (also see about it in Figures 4 and 23), a Thorlabs #GT13-06V (by Thorlabs, Inc., based in Newton, New Jersey, USA) with groove density of 600 lines per mm (l/mm), diffraction angle 28.7°, size 12.7 x 12.7 x 3 mm Schott glass B270 can be used. — Example 2: Especially for a transmission grid mounted between an objective and the image sensor(s) (see also in this respect Figs. 5, 6 and 24), a Richardson grid 340056TB07-775R (from Newport Corporation , headquartered in Rochester, New York, USA) with groove density of 360 l/mm, diffraction angle of 21°, and size of 12.7 x 12.7 x 3 mm, can be used. — Example 3: Especially for a rear-mounted grid for an extended field of view, a Thorlabs #GTU13-06 with groove density of 600 l/mm, diffraction angle of 22° and size 12.7 x 12 can be used .7 x 2 mm of fused silica.

[0029] The electromagnetic radiation 20 coming from the object 10 and illuminating the dispersive imaging arrangement 30 may derive, in part or in full, from the reflection of electromagnetic radiation emitted by an electromagnetic radiation source (not shown in Fig. 1) . Radiation 20 from object 0 and illuminating array 30 may alternatively, or additionally, derive, in part or in whole, from some form of photoluminescence (i.e., fluorescence or phosphorescence) of a substance from object 10 during or after illumination of the object 10 by electromagnetic radiation emitted by an electromagnetic radiation source. In either case (i.e. radiation by reflection or by some form of photoluminescence), the source of electromagnetic radiation may, in one embodiment, be integrated with, or connected to, a housing containing the imaging system 200 (or part of this). Said source of electromagnetic radiation can be, for example, a light source, an infrared radiation source and/or a UV radiation source. In one embodiment, the electromagnetic radiation source is a light source controlled by system 200 or in conjunction with system 200.

[0030] Electromagnetic radiation 20 coming from object 10 usually contains radiation of more than one wavelength, especially when object 10 is authentic. That is, radiation 20 is generally polychromatic in the broad sense of the term, i.e. not necessarily limited to visible colors. The radiation 20 can, for example, be in any wavelength range comprised between 180 nm (UV radiation) and 2500 nm (infrared radiation), i.e. in the visible light range and/or outside this range (for example in the near-infrared (NIR) or short-wavelength infrared (SWIR) range. The portion of radiation 20 reaching array 30 that is actually scattered may depend on the characteristics of the optical element(s) that form array 30. For example, the long pass filter can be used to select the spectral range to be analyzed.

[0031] Furthermore, the dispersive imaging array 30 is positioned relative to the image sensor array 60 in a manner to allow the image sensor array 60 to image said scattered electromagnetic radiation 50.

[0032] An example of an image sensor that can be used in some embodiments of the invention is: a 1/3 inch Wide-VGA CMOS Digital Image Sensor MT9V022 from ON Semiconductor, headquartered in Phoenix, Arizona, USA. This sensor has 752 x 480 pixels with a size of 6 μm forming the size of the active imager with dimensions of 4.51 mm x 2.88 mm and a diagonal of 5.35 mm.

[0033] An imaging period is defined herein as being the period during which scattered electromagnetic radiation 50 is acquired (as illustrated by Fig. 39).

[0034] In one embodiment, the imaging period has a duration that has a value selected from a range of 5 to 1200 ms, and preferably selected from the range of 10 to 800 ms, such as, for example, 10 , 20, 30, 50, 75, 100, 150, 200 or 300 ms.

[0035] An illumination period (as illustrated by Fig. 39) is defined herein as being a period during which the illumination conditions are considered sufficiently constant for the purpose of generating an image of the scattered electromagnetic radiation 50, and to generate a authenticity measure based on it.

[0036] The portion of electromagnetic radiation 20 that illuminates and passes through the dispersive imaging arrangement 30 (thus being scattered in at least one set of directions and optionally being unscattered in another set of directions) which is then detected by means of the dispersive imaging arrangement 60 depends on the characteristics of the image sensor(s). The electromagnetic radiation detected by means of the image sensor(s) can, for example, be in any wavelength range falling between 180 nm (UV radiation) and 2500 nm (infrared radiation), i.e. in the range visible light and/or outside this range (e.g. in the near-infrared (NIR) or short-wavelength infrared (SWIR) range. In this example, the lower limit of 180 nm may be imposed by material constraints on both the dispersive imaging arrangement 30 and imaging sensor(s) 60, while the upper limit of 2500 nm may be imposed, for example, by the spectral response of infrared detectors based on indium gallium arsenide (GalnAs). embodiment, the electromagnetic radiation detected by means of the image sensor(s) (60) is in the range of visible light. In one embodiment, the electromagnetic radiation detected by means of the image sensor(s) 60 is in the wavelength range from 180 nm to 2500 nm, more preferably in the range from 400 nm to 1000 nm.

[0037] However, the imaging system 200 is further configured so that, after the arrangement of the image sensor 60 generates an image of the scattered electromagnetic radiation 50 in at least one imaging period, it generates a measure of authenticity of the object 10 depending on at least one relationship between the image generated by the scattered electromagnetic radiation and the reference spectral information. Thus, the system 200 allows verification of whether, and/or to what extent, the relationship between the image generated by the scattered electromagnetic radiation and the reference spectral information, which represents the expected spectral composition of the electromagnetic radiation 20 from the object 10 , is in accordance with the predicted underlying physics of the system, in a situation in which some information is known (or assumed to be known) about the object 10 and/or the marker 11 from which the electromagnetic radiation 20 is incident (by reflection and /or issue). This means that some spatial information about the electromagnetic radiation 20 before scattering is known or assumed, such as, for example, spatial information about the type, shape, shape, dimension or other properties of a mark, sign, code or pattern that this object 10 gate and from which radiation 20 is incident. If the relationship matches the expected underlying physics of the system, Object 10 is likely to be authentic. Otherwise, the object is more likely to be faked. Thus, the system 200 allows for a form of material-based authentication, such as, for example, at least one of: a) authentication based on the material of the ink used to create a mark 11 printed on the object 10, and b) authentication based on the material of the object 10 itself, especially if the object 10 is luminescent with a specific emission spectrum or has a specific reflection or absorption spectrum.

[0038] The nature of the relationship that is analyzed, that is, the relationship between the image generated by the scattered electromagnetic radiation, the reference spectral information and the known or assumed spatial information about the electromagnetic radiation before scattering, that is, information about Mark 11 on object 10 (this spatial information is not necessary for image to be generated by the image sensor arrangement 60, but in some embodiments it can), can be understood in the following sense. If the reference spectral information matches, substantially matches, or plausibly matches the spectral composition of incident electromagnetic radiation 20 from the image generated by the object 10, the image generated by the scattered electromagnetic radiation typically resembles (non-linear effects may also need to be taken into account) to the result of the convolution of electromagnetic radiation before scattering (i.e. information about the mark 11 on object 10) with the reference spectral information, in which case object 10 is probably authentic. In contrast, if the reference spectral information does not or does not plausibly match the spectral composition of incident radiation 20 from the image generated by the object 10, the image generated by the scattered electromagnetic radiation typically differs remarkably from the result of the convolution of the radiation before scattering (i.e., information about the mark 11 on the object 10) with the reference spectral information, in which case the object 10 is likely to be a forgery.

[0039] More generally, the nature of the relationship that is analyzed, i.e., the relationship between the image generated by the scattered electromagnetic radiation, the reference spectral information, and the known or assumed spatial information about the non-scattered electromagnetic radiation (as mentioned above, this spatial information is not necessary for image to be generated by the array of image sensor 60, but in some embodiments it may, it may also differ significantly from a simple convolution, considering the existence of non-linear effects. The nature of the relationship can be determined a) on the basis of underlying physics and geometry, b) empirically, and/or c) by simulation (e.g., using ray tracing methods of commercially available solutions, such as, for example, software Zemax optical design, available from Zemax, LLC, headquartered in Redmond, Washington, USA).

[0040] The underlying physics and geometry may include (i) the properties of dispersive imaging array 30, image sensor array 60, the intermediate transmission medium, etc., and (ii) image stretching effects on the direction of dispersion (y-axis), which can be compensated for by mapping the image's y-axis to a new y'-axis using a non-linear function. The image may be stretched due to 1) non-linear grating dispersion, 2) projection distortions, and/or 3) optics-specific field aberrations.

[0041] The non-linear effects can, in one embodiment, be modeled also as a relationship between the scattered image, the non-scattered spatial information, and the reference spectrum in a form close to the linear-invariant translation (LTI) as possible . In such a case, the determination of the non-linear effects can be carried out, for example, by means of a) acquiring several scattered images of objects 10 with a known reference spectrum, and b) adjusting the non-linear parameters to transform the relation for LTI.

[0042] One way of determining the non-linear effects, and therefore the nature of the relationship to be observed, can be a mathematical analysis of the optical system and determination of the correction that needs or should be applied to make the system LTI. This can be done using optical equations, for example found in textbooks such as Yakov G. Sosking, “Field Guide to Diffractive Optics”, SPIE, 2011. This can also be done numerically using optical software such as Zemax OpticStudio™, available from Zemax, LLC.

[0043] In one embodiment, the dispersive imaging arrangement 30 disperses the electromagnetic radiation 20 using, for example, a diffraction grating, and the image generated by the scattered electromagnetic radiation is consequently the output of the image generated by the diffraction grating in the image sensor(s) 60. The structure of the diffraction grating can, in one embodiment, be optimized such that most of the radiation enters first order and the grating has almost no zero order efficiency. An unscattered synthetic image can be reconstructed using the image generated by the scattered electromagnetic radiation and the expected electromagnetic spectrum (the reference spectral information), for example, by deconvolution or by an operation similar to a deconvolution. A deconvolution algorithm based on the Fast Fourier Transform (FFT) can, for example, be used. The algorithm can, for example, use a set of columns from the extracted image along the scattering direction, comprising intensity profiles from the image generated by the scattered electromagnetic radiation.

[0044] The synthetic and reconstructed non-scattered image can then be evaluated by itself and/or in view of known or assumed spatial information about electromagnetic radiation before scattering (i.e. information about mark 11 on object 10), with the authentication purpose of the object 10. In one embodiment, generating the authenticity measure additionally comprises determining at least one of: a) a decodability measure of a machine-readable code image generation in the deconvolution result or deconvolution reconstitution operation (to account for non-linear effects, as explained above); b) a measure of sharpness of the result of the deconvolution or deconvolution reconstitution operation; c) a measure of uncertainty of the outcome of the deconvolution or deconvolution reconstitution operation; d) a measure of the size of the result of the deconvolution or deconvolution reconstitution operation; e) a measure of the area of the result of the deconvolution or deconvolution reconstitution operation; f) a measurement of the total width at the maximum half of a cross section of the deconvolution result or deconvolution reconstitution operation; and g) a measure of the similarity of the deconvolution result, or deconvolution reconstitution operation, to a reference standard.

[0045] In one embodiment, generating a measure of authenticity of the object 10 comprises authenticating it, that is, determining that it is likely to be authentic or not. In one embodiment, generating a measure of authenticity of the object 10 comprises generating a measure (or index) of authenticity, such as, for example, a real value between 0 and 1, where '0' can mean "totally sure that the object is not authentic" and '1' can mean "completely certain that the object is authentic".

[0046] In practice, the authentication index usually does not reach the value '1' for all authentic objects (and '0' for all non-authentic ones). Therefore, in one embodiment, a threshold between '0' and '1' is defined (for example, a value comprised between 0.80 and 0.90, and particularly 0.85) above which the object is considered authentic and below which the object is considered to be inauthentic. This threshold can, for example, be defined through measurements on a set of authentic and non-authentic objects. Typically, these measurements produce a bimodal distribution of indices (ie, a part for the authentic objects concentrated in relation to the value '1' and a part for the non-authentic ones below, both separated by a gap). The robustness of the method is directly related to the extent to which the two parts (modes) of the index distribution are far from each other. The threshold can then be placed between close to the index distribution of authentic objects to minimize false positives or closer to the non-authentic index distribution to minimize false negatives.

[0047] If object 10 is, for example, a container or package containing some products, the authenticity measure generated may simply correspond to a product authenticity measure determined through a mark or sign on the container or package ( assuming the container or packaging has not been tampered with), not necessarily making it possible to directly authenticate the products as such.

[0048] Since the scattered form 50 of electromagnetic radiation can be imaged in one imaging period, and since imaging allows the reconstruction of a synthetic non-scattered form of electromagnetic radiation based on the information spectral reference, system 200 can be thought of as a form of instantaneous imager in the sense that the scene is not digitized during the imaging process.

[0049] Fig. 2 schematically illustrates an object 10 to be imaged and a system 220 in an embodiment of the invention; System 220 comprises both an imaging system 200 (as described above with reference to Fig. 1) and a lighting arrangement 210. In one embodiment, system 220 forms a single device, such as, for example, a device portable, code reading and authentication.

[0050] The lighting arrangement 210 generates electromagnetic radiation 21 to illuminate the object 10. In one embodiment, the radiation 21 has known parameters (e.g., spectrum, power, homogeneity, etc.) to allow excitation, for example, of the luminescence emission spectra to allow generation of scattered image of object 10 and/or mark 11 for authentication. As explained above with reference to Fig. 1, electromagnetic radiation 20 originates from object 10 and/or marker 11 and reaches imaging system 200.

[0051] In one embodiment, the system 220 is connected to the drive electronics and sensor readout electronics, so that, for example, the image data coming out of the image generation system 200 can be transferred to a processing for data processing.

[0052] Fig. 3 schematically illustrates an object 10 to be imaged and a system 220 in an embodiment of the invention, as a possible implementation of the system illustrated in Fig. 2. The system 220 particularly comprises lighting elements 22 arranged around the dispersive imaging array 30. Although two lighting elements 22 are shown in Fig. 3, any number of lighting elements 22 may be provided, such as for example three, four or more. Furthermore, in one embodiment, the lighting elements 22 are arranged symmetrically around the dispersive imaging array 30. The symmetrical arrangement of the lighting elements 22 around the array 30 is advantageous for homogeneously illuminating the target surface of the object 10 .

[0053] Figs. 4 to 6 schematically illustrate three imaging systems 200, respectively in three embodiments of the invention, showing possible components of the dispersive imaging arrangement 30, such as a transmission grid 31, an imaging lens 32, a long pass optical filter 33 and an additional lens arrangement 34.

[0054] The arrangement 30 of Fig. 4 comprises an imaging lens 32, a transmission grid 31 mounted in front of the lens 32, and an optical long pass filter 33 mounted behind the lens 32. This allows producing low optical aberrations using the wide field of view of the lens 32. lens.

[0055] In the arrangement 30 of Fig. 5, both the transmission grid 31 and the optical long pass filter 33 are mounted behind the lens 32. This allows canceling the object's position dependence along the optical axis.

[0056] In the modality of Fig. 6, the optical long pass filter 33 is mounted in front of the lens 32, and the transmission grid 31 is mounted behind the lens 32. Furthermore, an additional array of lenses 34 is also mounted behind the lens 32. This configuration allows efficiently separate the scattered image from the non-scattered image (if any) and avoid object position dependence along the optical axis.

[0057] Figs. 7 and 8 schematically represent, using a fine lens grid approximation, two imaging systems 200 and landmarks 11 in two embodiments of the invention, respectively, to help understand first-order image deflection relative to the optical axis and the definition of the minimum wavelength of a spectral band that is analyzed to authenticate the mark 11.

[0058] In Fig. 7, the dispersive imaging arrangement 30 includes a lens, a transmission grid, and a long-wavelength pass filter to create the dispersed image in the imaging plane 65 where the image sensors are positioned. The scattered beams 50-1 are for the shorter wavelength Ài and create the scattered image 51 corresponding to the wavelength Ài.

[0059] The imaging system 200 receives electromagnetic energy 20 from object i0 to create a scattered part, which is shifted compared to the optical axis (along which unscattered beams can optionally propagate) and is indefinite from electromagnetic energy 20 incident on the array 30. The minimum shift depends on the minimum wavelength present in the spectrum emitted by object i0 or depends on the minimum wavelength transmitted through the array 30. The minimum shift may also depend on some grid parameters and of the system (for example, furrow density, order and angle of incidence), whose parameters define the angular dispersion of the grid.

[0060] The three scattered discrete images of mark ii in Fig. 7 correspond to discrete wavelengths Ài, À2 and À3. These discrete wavelengths can therefore be conveniently resolved since the corresponding images do not overlap.

[0061] Fig. 8 shows the image of an area i2 of object i0, where area i2 contains a printed mark ii, which can be in any position or orientation. If mark i0 is outside area i2, the imaging system 200 must be repositioned to have mark 11 within area 12. The scattered image 51 of area 12 contains the image of mark 11.

[0062] Image 51 corresponds to the minimum wavelength Àmin that can be transmitted by the system and defined by a cutoff wavelength of a long pass filter of the array 30. Reference 62 shows the deflection relative to the optical axis in the plane of image.

[0063] In one embodiment, the lighting arrangement 210 (not illustrated in Fig. 8) illuminates only the portion of the object 10 that corresponds to the area 12. The lighting arrangement 210, together with an optional protective covering (as mentioned above) , can be designed to prevent ambient light from reaching area 12, thus providing better conditions for code reading and authentication.

[0064] Although, in the embodiments discussed above, non-scattered (zero-order) radiation is not used (or is not necessarily used) for authentication, it is in any event advantageous to avoid zero-order and first-order overlap when the array 30 produces both zero and first-order parts. In fact, if the order separation is not enough, the scattered images can be affected by part of an overlapping zero-order image. To avoid such a situation, a mask can be used to reduce the size of the generated image of area 12 of object 10.

[0065] Embodiments that are not using non-scattered radiation (zero order) for authentication are advantageous, notably that the optical aberrations for the first order can be optimized without consideration of any degradation of the aberrations in the zero order. In other words, only acceptable first-order optical aberrations are needed. Furthermore, modalities that are not using non-scattered radiation (zero-order) for authentication are also advantageous in that it is not necessary to acquire both zero-order and first-order images, so that the larger first-order image can be be acquired from an image sensor of a given size.

[0066] Fig. 9a schematically illustrates an imaging system 200 in one embodiment of the invention, which differs from the imaging system 200 of Fig. 1, so that the system 200 of Fig. 9a specifically consists of a single imaging device. In addition to the array 30 and image sensor array 60 described with reference to Fig. 1, system 200 comprises a processing unit 70 configured to receive data representing the image generated by scattered electromagnetic radiation (as detected by array 60), generating the authenticity measure as described with reference to FIG. 1, and output information 80 representing the generated authenticity measure for any type of imaging device user interface and/or for an output port for transmission to one or more external devices (not shown in Fig. 9a) .

[0067] In one embodiment, the imaging device that makes up the imaging system 200 of Fig. 9a is a portable device. Such an imaging device can therefore be considered as a portable auditing device capable of generating a measure of the authenticity of an object, and of providing the measure of authenticity, for example, to the operator of the device.

[0068] Fig. 9b schematically illustrates a system 220 in one embodiment of the invention, wherein the system 220 comprises both an imaging system 200 and a lighting arrangement 210, and wherein the system 220 is an imaging device. In other words, the modality of Fig. 9b can be considered a combination of the embodiments described with reference to Figs. 9a and 2. In one embodiment, the imaging device comprising system 200 of Fig. 9b is a portable device.

[0069] Fig. 10a schematically illustrates an imaging system 200 in one embodiment of the invention, which differs from the imaging system 200 of Fig. 1, so that the system 200 of Fig. 10a is shown to specifically comprise more than one device. That is, in the example of Fig. 10a, the system 200 comprises two devices: on the one hand, an imaging device 100 comprising a dispersive imaging arrangement 30 and the image sensor arrangement 60 is described with reference to Fig. 1 and, on the other hand, a processing device 110 comprising a processing unit 70. The processing device 110, instead of the image generation device 100, generates the authenticity measure (as described with reference to Fig. 1) . For this, data 90 representing the image generated by the scattered electromagnetic radiation is transmitted from the imaging device 100 to the processing device 110. The data may be transmitted on any suitable wired or wireless channel using any format. (such as, for example, using Internet Protocol packets, optionally encrypted). Then, within the processing device 110, the authenticity measure is generated by the processing unit 70, and the information 80 representing the generated authenticity measure can then be sent to a user interface of the processing device 110 and/or to a output port for transmission to one or more other external devices (not shown in Fig. 10a).

[0070] Fig. 10b schematically illustrates a system 220 in an embodiment of the invention, wherein the system 220 comprises an imaging device 100 and said imaging device 100 comprises an image sensor array 30, a dispersive imaging array 60 and a lighting arrangement 210, but said imaging device 100 is not configured to actually generate the authenticity measure; In other words, the modality of Fig. 10b can be considered a combination of the embodiments described with reference to Figs. 10a and 2.

[0071] In one embodiment, the imaging device 100 of any one of Figs. 10a and 10b is a portable device.

[0072] In one embodiment, the processing unit 70 of any one of Figs. 9a, 9b, 10a and 10b form part of a computing unit, such as, for example, the one illustrated with reference to Fig. 38 (which is discussed below). In that case, the processing unit 70 of Fig. 9a or 9b and the processing unit 503 of Fig. 38 may actually be the same element. Likewise, in such a case, the processing unit 70 of Fig. 10a or 10b (within processing device 110) and processing unit 503 of Fig. 38 may actually be the same element.

[0073] In some embodiments, the imaging device comprising the imaging system 200 of Fig. 9a or 9b, or imaging device 100 illustrated in Fig. 10a or 10b, comprises a handle formed integrally with or attached to the housing to enable an operator to hold the imaging device toward the object to be imaged and authenticated.

[0074] In one embodiment, the imaging device that makes up the imaging system 200 of Fig. 9a or that constitutes the system 220 of Fig. 9b, or the imaging device 100 illustrated in any one of Figs. 10a and 10b further comprises a storage unit (not shown in any of Figs. 9a, 9, 10a and 10b) for storing, for example, spectral reference information that is known in advance and used to generate the authenticity measure.

[0075] The reference spectral information can be stored in the form of a reference spectral profile.

[0076] Fig. 11 is a flowchart of a method in an embodiment of the invention which makes use of an image sensor arrangement 60 and a dispersive imaging arrangement 30, as described above with reference to Figs. from 1 to 10b. The method comprises the steps of generating an image s300, by means of the array 60, in at least one imaging period of the scattered electromagnetic radiation 50, and generating s400 a measure of authenticity of the object 10 depending on at least one relationship between the image generated by scattered electromagnetic radiation and reference spectral information. Step s400 is performed through convolution or deconvolution operation(s) (as discussed below with reference to Fig. 12) or through operations similar to convolution or deconvolution to account for non-linear effects as explained above.

[0077] If the imaging step s300 consists of imaging the scattered electromagnetic radiation 50 in a single illumination period, the imaging step s300 precedes the imaging step s400, normally without overlapping. However, if the step s300 consists of imaging the scattered electromagnetic radiation 50 in a plurality of lighting periods (typically under different lighting conditions), the imaging step s300 and the generating step s400 may overlap (not shown in Fig. 11). That is, the authenticity measurement generation process s400 can begin based on image data recorded during one or more lighting periods while the imaging step s300 is still ongoing.

[0078] In one embodiment, generating s400 the authenticity measure depends at least on the extent to which the result of the deconvolution of the image generated by scattered electromagnetic radiation through the reference spectral information satisfies or has certain properties or characteristics. In one embodiment, this can be implemented as illustrated by the flowchart of Fig. 12, with a step s410 of deconvolution of the image generated by the scattered electromagnetic radiation by means of the reference spectral information, thus emitting a synthetic and reconstructed non-dispersed image, and a step s420 of evaluation of the result of the deconvolution.

[0079] In one embodiment, as illustrated by the flowchart in Fig. 13, the step s420 of evaluating the deconvolution result is implemented by determining s422 a decodability measure of a machine-readable code produced synthetically in the deconvolution result. If the s422 decode attempt succeeds s424 ("yes"), then object 10 is determined s426 to be likely authentic. On the contrary, if the decoding attempt s422 is unsuccessful s424 ("no"), then object 10 is determined s428 to be probably a fake.

[0080] Fig. 14 schematically illustrates a method in an embodiment of the invention, in which a decodability evaluation is performed to generate s400 a measure of authenticity of an object 10. Two identical codes are shown on the left side, where the first code has been printed with ink A (top left) and the second code was printed with ink B (bottom left). The scattered electromagnetic radiation 50 is then imaged s300 by the image sensor arrangement 60. The respective scattered image is then processed s410 by means of a deconvolution or deconvolution reconstitution operation (to take non-linear effects into account) with based on reference spectral information representing the spectrum of ink A ("Reference A Spectrum") to produce a synthetic and reconstructed non-scattered image (which is illustrated respectively on the right side of Fig. 14 ). It can be seen that the synthetic and reconstructed unscattered image in the upper right corner of Fig. 14, which was generated on the basis of the image generated by the scattered form of the code printed using ink A and the spectral reference information representing the spectrum of ink A, are decodable. It can be seen that, in contrast, the synthetic and reconstructed unscattered image in the lower right corner of Fig. 14, generated based on the image generated by the dispersed form of the code printed using ink B and the reference spectral information representing the spectrum of ink A, are not decodable. The code is not decodable because the spectral information differs from the authentic one and, therefore, the deconvolution produces a distorted synthetic image of the code, whose quality is insufficient for a successful decoding.

[0081] This s420 decodability determination can lead to or quantify a determination that the object that has a non-decodable code (after the processing described above) is false or likely to be false, while the object that has a decodable code is authentic or likely to be authentic.

[0082] Fig. 15 schematically illustrates a method in an embodiment of the invention, in which an evaluation is performed to also generate s400 a measure of authenticity of an object 10. Two identical patterns (e.g. a four-point star-shaped sign) are shown on the left side, where the first pattern was printed with ink A (upper left) and the second code was printed with ink B (lower left). The scattered electromagnetic radiation 50 is then imaged s300 by the image sensor arrangement 60 (see images on the left side of Fig. 15). The respective scattered image is then processed s410 by means of a deconvolution or deconvolution reconstitution operation based on the reference spectral information representing the spectrum of ink A ("Reference A Spectrum") to produce a synthetic non-scattered image and reconstructed (see images on the right side of Fig. 15). It can be seen that the synthetic and reconstructed unscattered image in the upper right corner of Fig. 15, which was generated on the basis of the image generated by the scattered shape of the printed pattern using ink A and the reference spectral information representing the spectrum of ink A, has a pattern that can be recognized and has parameters representing sufficient image quality, for example, when it comes to sharpness and blurring. It is determined, by contrast, the synthetic and reconstructed unscattered image in the lower right corner of Fig. 15, generated based on the image generated by the scattered shape of the pattern printed using ink B and the reference spectral information representing the spectrum of ink A, has a pattern that cannot be recognized or that can be recognized, but has parameters that represent a insufficient image quality, for example, when it comes to sharpness or blurring.

[0083] This recognition and determination of quality based on parameters can lead to or quantify that the object that has the pattern printed with ink B is fake or likely to be fake (determination after processing described above: unrecognizable pattern or pattern recognizable but having insufficient quality parameters), while the object that has the pattern printed with ink A is authentic or probably authentic (determination after processing described above: recognizable pattern with sufficient quality parameters).

[0084] Fig. 16 schematically illustrates an exemplary implementation of a method in one embodiment of the invention, in which, particularly, images of scattered electromagnetic radiation from five objects printed with different inks - with ink in spectra from to E, respectively - are processed for the authentication purpose. The scattered electromagnetic radiation 50 associated with the five objects is then imaged (images on the left side of Fig. 16). The respective scattered image is then processed via a deconvolution or deconvolution reconstitution operation based on the reference spectral information representing the spectrum of ink A ("Reference A Spectrum") to produce a synthetic and reconstructed non-scattered image (images on the right side of Fig. 16). It is then determined that the synthetic and reconstructed unscattered image has a value d (calculated authentication parameter or authentication measure) that is above or below a threshold, as shown in Fig. 17. To this end, the intensity profile of the center column of each of the synthetic and reconstructed unscattered images is used to generate the authenticity measure. This determination can lead to or quantify a determination that an object is fake or likely to be fake, or, instead, authentic or likely to be authentic.

[0085] In one embodiment, referred to hereinafter as "E1 embodiment" (not illustrated in the figures), a DataMatrix code, or any type of machine-readable code, is printed on the object 10 using an ink having a reference spectrum ( reflectance or luminescence). After imaging s300 the scattered electromagnetic radiation (hereinafter referred to as the “first order image”), an authenticity measure is generated s400 by deconvoluting s410 the first order image by the expected genuine ink response (reference spectrum ) and therefore computation (reconstruction) of a synthetic zero-order image. An attempt is then made s422 to decode the resulting zero order picture. If it can be decoded, object 10 is considered genuine. If it cannot be decoded, object 10 is considered non-genuine.

[0086] In one embodiment, decode quality metrics returned by the decoder are used to generate the s420 authentication measure. Quality metrics (from the Print Quality Test of 2D Barcode Specification Symbols in accordance with ISO/IEC 15415, see page 31/section 4.6.1.2 entitled “Parameters Measured and their Significance” of “ GS1 DataMatrix Guideline, Overview and technical introduction to the use of GS1 DataMatrix”, Release 2.2.1, Approved, July 2015, taken from http://www.gs1.org/docs/barcodes/GS1_DataMatrix_Guideline.pdf) can be, for example, at least one of: 1. Symbol Contrast, which is “the difference between the highest and lowest reflectance values in the profile - in simple terms, the difference between the dark and light areas (including the Zones Silent) as seen by the scanner”. (from page 32 of the GS1 DataMatrix Guideline referred to above) 2. Impression Growth (size of cells in the reconstructed machine readable code), which “is not a ranked parameter but is a very informative measure for process control purposes . It is a measure of how the symbols may have grown or shrunk from the target size. If the growth or shrinkage is too large, scanning performance will be affected.” (from page 34 of the GS1 DataMatrix Guideline referred to above) 3. Axial non-uniformity, which “measures and grades (on a 4 to 0 scale) the spacing of centers and tests mapping for uneven symbol scaling along the X or Y axis” (from page 32 GS1 DataMatrix Guideline referred to above); and 4. Modulation, which “is related to Symbol Contrast in the sense that it measures the reflectance consistency of dark to light areas across the symbol” (from page 32 of the GS1 DataMatrix Guideline referred to).

[0087] In one embodiment, a voting approach, taking into account several of these metrics with different weights, is used to generate the authenticity measure. This increases robustness.

[0088] In one embodiment, referred to below as “modality E2” (as illustrated in Fig. 15), a sticker, logo and/or marking, the exact shape of which is known in advance, is printed on the object 10. After generating image s300 the scattered electromagnetic radiation (hereinafter referred to as the “first order image”), an authenticity measure is generated s400 by means of the s410 deconvulsion of the first order image by the expected genuine ink response (reference spectrum) and thus , computation (reconstruction) of a synthetic zero-order image. The reconstructed zero-order image is then evaluated s420 by applying standard image processing quality metrics, such as at least one of: sharpness, first derivative intensity, contrast, and dynamic range.

[0089] In a sub-modality, these quality metrics can be applied separately in the direction collinear with the direction of diffraction, or scattering, and the direction perpendicular to the direction of diffraction, or scattering. Metrics such as sharpness are normally not altered by diffraction, or scattering, when measured perpendicular to the direction of diffraction or scattering. But the metrics can be shifted in the collinear direction for diffraction, or dispersion, for a non-genuine mark. The two metrics in the two respective directions are similar when the reference spectrum matches the print and otherwise does not match. A threshold on similarity can classify the result as genuine/non-genuine.

[0090] In a sub-modality, these quality metrics can be applied in the direction only collinear with the diffraction, or dispersion, direction. A simple threshold on the metrics might be enough to classify the result as genuine or non-genuine.

[0091] The confidence level of the result of a pattern matching algorithm using the reconstructed non-dispersed synthetic pattern can be used also as a measure of authenticity.

[0092] In one embodiment, referred to hereinafter as "E3 embodiment" (not illustrated in the figures), a small dot is printed on the object 10 using an ink that has several distinct spectral peaks. After imaging s300 the scattered electromagnetic radiation (hereinafter referred to as the “first order image”), an authenticity measure is generated s400 by deconvoluting s410 the first order image by the expected genuine ink response (reference spectrum ) and thus computation (reconstruction) of a synthetic zero-order image. If the reconstituted synthetic zero-order image results in a single dot, the printed ink spectrum matches the reference spectrum and the marking is considered authentic. Analysis of the reconstructed spot intensity profile can also provide metrics to determine whether the marking is genuine or not.

[0093] In one embodiment, referred to hereinafter as "modality E4" (not illustrated in the figures), the marking on the object 10 is a solid impression, that is, a uniform ink deposition without any pattern or thickness modulation. A transition between an area containing the printed ink and an unprinted area is advantageous to generate some variation in the first-order image to allow processing of the intensity profile by deconvolution. The nose end of the imaging system can be in contact with the marking and can be equipped with a physical mask with holes, such as, for example: a large square hole, a rectangular hole, a star-shaped hole, a grid of several holes of any shape. The mask can also be the end of the nose itself. The purpose of the mask is to create the missing modulation/transition in the printed mark. For the optical system, it makes no difference whether a lack of signal is due to an unpainted area or an inked but masked area. After imaging s300 the scattered electromagnetic radiation (hereinafter referred to as the “first order image”), an authenticity measure is generated s400 by deconvoluting s410 the first order image by the expected genuine ink response (reference spectrum ) and thus computation (reconstruction) of a synthetic zero-order image. The reconstructed zero-order image is then evaluated s420 by applying image processing quality metrics such as those mentioned above in relation to the E2 modality.

[0094] The deconvolution step s420 is invariant in translation with respect to the spectrum and the position of the first order image on the sensor. This means that only the shape of the reference spectrum is important. The same shape, but shifted by longer or shorter wavelengths, would produce the same computed zero-order image, but shifted. Therefore, there is usually no way to isolate the shift due to wavelength from a physical shift of the marking position under the imaging system. The E1, E2 and E3 modalities typically suffer from this limitation. The E4 modality does not, however, since the modulation is not due to a modulated impression, but due to the mask, whose position is fixed in relation to the optical system. In fact, in E4 mode, there is no way to shift the mask, therefore, there is no way to induce a physical shift of the modulation position under the image generation system. Therefore, the absolute position of the synthetic and reconstructed zero order within the reconstructed image is only related to the absolute wavelength of the reference spectrum. This absolute position is an additional element of authentication.

[0095] In one embodiment, the deconvolution operation of step 410 is performed per image line along the diffraction and scattering direction. Furthermore, when the deconvolution step s410 is carried out in a line-by-line manner, the result of the deconvolution can then be calculated to reduce noise and cancel possible modulation through background non-uniformities, before comparing the result with the reference spectral information as part of step s420.

[0096] In one embodiment, the marking comprises at least one machine-readable code, which may, for example, comprise at least one of a linear barcode and a matrix barcode (e.g., a Data Matrix code printout or QR code).

[0097] In one embodiment, the tag comprises unique spectral features over at least one region of the tag. The tag can also comprise unique spectral features throughout the entire tag.

[0098] In one embodiment, a mask is intentionally provided as part of the imaging system 200 and furthermore on or in the vicinity of the object 10 to reveal only a portion of the object 10. This is advantageous in the case where that the entire object carries a substance having spectral reference information or a large marker that covers the entire image. The mask artificially creates a transition from the unmarked area to the marked area, even if there is no such transition without the mask.

[0099] Figs. 18 to 21 provide additional explanations in relation to some embodiments of the invention, particularly in relation to the advantages of using a mask;

[00100] On the left side of Fig. 18, two markers are shown, namely markers A and B. They have the same shape but are not located at the same position within the field of view of the system. The same ink was used to print markings A and B. On the right side of Fig. 18, the respective images are shown on the image sensor array 60 after scattering. Both images detected by the image sensor array 60 give the same shape but in different position. Therefore, position within the image cannot be used as an authentication factor.

[00101] On the left side of Fig. 19, two marks are shown, namely marks A and B. They have the same shape, and are not located at the same position within the field of view of the system. Different inks were used to print the A and B markings, and they have a spectrum of a different shape. On the right side of Fig. 19, the respective images are shown on the image sensor array 60 after scattering. The images detected by the array of image sensor 60 differ in their shape. Thus, it is possible to discriminate between the two inks, and this can be used as an authentication factor.

[00102] On the left side of Fig. 20, two marks are shown, namely marks A and B. They have the same shape, and are not located at the same position within the field of view of the system. Different inks were used to print the A and B markings, and they have a spectrum with the same shape, but not the same wavelength. On the right side of Fig. 20, the respective images are shown on the image sensor array 60 after scattering. Both images detected by the image sensor array 60 give the same shape at the same position. Therefore, this cannot be used as an authentication factor.

[00103] On the left side of Fig. 21, two markers are shown, namely markers A and B. They have the same shape which is defined by the mask and the position within the field of view is defined by the mask. Different inks were used to print the A and B markings, and they have a spectrum with the same shape, but not the same wavelength. On the right side of Fig. 21, the respective images are shown on the image sensor array 60 after scattering. The images detected by the image sensor array 60 have the same shape, but in a different position. Thus, it is possible to discriminate between the two inks based on their position within the image (as the only way to move the position is to use a different spectrum), and this can be used as an authentication factor.

[00104] In one embodiment, the imaging system 200 does not use any slit between the dispersive imaging array 30 and the object 10. Not using a slit is advantageous insofar as it allows acquisition of the dispersed image, without having to scan (by moving the imaging device or spectrometer) the surface of the object.

[00105] Now, before describing other embodiments of the invention, it may be useful to discuss some of the advantages brought by some of its embodiments, especially compared to prior art systems.

[00106] The systems and methods described above according to some embodiments of the invention are advantageous because they allow the construction of simple, compact, instantaneous (non-scanning) based, versatile low-cost devices, which can, for example, be incorporated on portable audit devices. Acquiring an image of the scattered electromagnetic radiation is sufficient, together with spectral reference information that is known in advance and some information about the radiation before scattering (i.e., information about the mark 11 on object 10), to generate the authenticity measure. .

[00107] In contrast, imaging spectrometers used for scientific observations, as mentioned above, are typically complex, expensive or bulky. This is due to the fact that these prior art systems generally aim to obtain high resolution spatial and spectral information about all regions of the object or scene.

[00108] The mechanical sweep of different band-pass filters in front of an imager allows the reconstruction of a spectral irradiance map of the object l(x, y, Á). However, the time to check all the filters and the complexity and fragility of the scanner makes the optical system cumbersome, not robust and expensive to implement.

[00109] Fitting systems based on the Fabry-Perot interferometer or multistage liquid crystals avoid mechanical complexity, but require high quality and expensive optical components (eg interferometric mirrors). Scanning the filter parameters needed to acquire the full set of images can be slow and can become another limitation for use in portable authentication systems.

[00110] Snapshot solutions that rely on simultaneously imaging an object through the array of bandpass filters can achieve fast data acquisition and are tailored especially for portable auditing devices. In addition, such systems are compact and easily fit into a small volume of a portable device. The limited number of different bandpass filters is, however, a disadvantage, and it is also difficult to obtain suitable lens arrays. Furthermore, the spectral bands of the filter array have to be optimized for the ink's spectral response, which avoids the use of off-the-shelf filter arrays, whereas custom filter sets are typically expensive to design and manufacture.

[00111] The example of a grid-based imager using computed tomography (i.e. CTIS) requires either a complex holographically recorded Kinoform-type grid or multiple cross grids capable of scattering light in a set of orders around zero order . The need for multiple gratings complicates setup and, in addition, exposure time must be extended to compensate for poor efficiency at higher diffraction orders. Data acquisition is therefore slowed down, making the setup unsuitable for a handheld device. Such arrangements also require large, expensive, multi-megapixel sensors and extensive calculations for tomographic inversion.

[00112] Coded aperture imagers are as slow as CTIS devices. Furthermore, there is an intrinsic problem to reconstruct the full spectrum for the specific design of the coded aperture. Meanwhile, integral field spectrometers require cumbersome image slicing optics and require relatively large surface image sensors.

[00113] Fourier transform imaging spectrometers are complex instruments that rely on expensive interferometers or birefringent prisms. In both cases, spectrometers require scanning an air gap or an angular orientation of the elements to obtain spectra that make them slow and brittle.

[00114] The prior art configurations described above require complex optics and data handling algorithms to compute a complete spectral data cube l(x, y, Á), which is actually not necessary for authentication purposes. The inventors have not found any of these prior art configurations suitable for an economical, compact, robust and fast audit device based on a spectral imager.

[00115] Now, we will describe other embodiments of the invention, which may help to understand some aspects and advantages of the invention.

[00116] In one embodiment, the imaging system 200 has an optical configuration with a transmission diffraction grating 31 mounted in front of a lens objective 32 in a dispersive imaging arrangement 30 which is then disposed in front of the image sensor arrangement 60, as schematically illustrated on the left side of the two Figs. 22a and 22b. The 200 system uses a 32-lens objective or model EO57907 from Edmund Optics Ltd (based in York, UK) with f/2.5 and f = 3.6 mm focal length. The dispersive element in array 30 is a transmission diffraction grating 31 of type GT13-06V from Thorlabs, Inc., as mentioned above, with 600 lines per mm and flame angle of 28.7°. Area 12 of object 10 is within the field of view of imaging system 200.

[00117] Fig. 22a also shows, on the right side of the Figure, the simulated dispersion of a single point (of, for example, a two-dimensional matrix bar code) at three discrete wavelengths obtained by means of the transmission diffraction grating 31 installed in front of the imaging objective 32. Shown is the scattering of the diffraction grating 31 obtained from a Zemax OpticStudio™ simulation. One can see the direct ("Order 0") (not necessarily used in embodiments of the invention) and scattered images in first positive orders ("Order 1") and first negative ("Order -1") of the single point (with diameter 0.5 mm) in image space for three discrete wavelengths.

[00118] More complex marks, such as bar codes with a full two-dimensional array, normally produce blurred images in the first order of the grid 31 due to the broader specific emission spectra of the inks, and an associated overlap of the successive scattered dots is observed in the direction of the diffraction, as illustrated on the right side of Fig. 22b. Particularly, Fig. 22b shows the simulated scattering of a data matrix with the unscattered image ("Order 0") (not necessarily used in embodiments of the invention) and two images associated with both orders spread, i.e., the first positive order ("Order 1 ”) and the first negative order (“Order - 1”). The direct image at grid zero order is not influenced by the grid (except for intensity attenuation) and can be used to decode a printed two-dimensional matrix barcode. The scale shown in Fig. 22b is in intensity in arbitrary units (“I, au”).

[00119] Figs. 23 to 24 schematically illustrate three imaging systems 200, respectively in three embodiments of the invention, showing possible components of the dispersive imaging arrangement 30, such as a transmission grid 31, an imaging lens 32 and a long pass optical filter 33. Area 12 of item 10 can be visualized by array 30, considering its field of view (FOV) 15. The scattered image 51 of area 12 is indicated corresponding to the shortest wavelength. Reference 61 is window 61 of image sensor(s) 63.

[00120] The arrangement 30 of Fig. 23 comprises an imaging lens 32, a transmission grid 31 (600 l/mm) mounted in front of the lens 32 (Edmund Optics lens objective 57907), and a long pass optical filter 33 mounted behind the lens 32. already explained in relation to Fig. 4, this allows producing low optical aberrations using the wide field of view of the lens objective.

[00121] The grid 31, which is mounted in front of the imaging lens 32, deflects the beams to the first order and the imaging lens 32 receives the incoming beams. In such a configuration, a wide field of view imaging lens 32 is used, which allows incident beams at specific angles to the first order.

[00122] In the arrangement 30 of Fig. 24, both the transmission grid 31 (360 l/mm) and the optical long pass filter 33 are mounted behind the lens 32 (Edmund Optics lens objective 57907). As already explained with reference to Fig. 5, this allows canceling the dependence of the object's position along the optical axis.

[00123] Now, let us describe further embodiments of the invention involving imaging over a plurality of illumination periods, first with reference to Figs. 25 and 27 and then with reference to Figs. 26 and 28. These additional embodiments can, of course, be combined with any of the embodiments described above.

[00124] Fig. 25 schematically illustrates the generation of an authenticity measure of the object 10 in one embodiment of the imaging system 200. In this embodiment, as a first step, the array of the image sensor 60 image the scattered electromagnetic radiation 50 described above in a plurality of lighting periods t1, t2, ..., tn. In one embodiment, n equals 2. In another embodiment, n equals 3. Object 10 is illuminated differently during each lighting period. Each illumination period encompasses an imaging period, as illustrated schematically with reference to Fig. 39.

[00125] Then the authenticity measure is generated. Generating the authenticity measure comprises the following steps.

[00126] First, for each illumination period ti (1 < i < n), an intermediate measure of authenticity ki is generated depending, at least, on a relationship between the image generated by the scattered electromagnetic radiation 50 (Ai) in the period of illumination ti and a part of the reference spectral information, said part of the reference spectral information being associated with the way in which the object 10 was illuminated during the period of illumination ti. In one embodiment, the intermediate authenticity measure ki comprises, for each illumination period ti, decoding the image generated by the scattered electromagnetic radiation in the illumination period ti by means of said part of the reference spectral information associated with the way the object 10 was illuminated during the ti enlightenment period.

[00127] Second, the authenticity measure (m) is generated based on the plurality of intermediate authenticity measures generated (k1, k2, ..., kn). This is illustrated in Fig. 25 by means of the exemplary equation: m = f(k1, k2, ..., kn), where f is a function such as, for example, the arithmetic mean of the intermediate measures of authenticity.

[00128] Figs. 27 is a flowchart of an imaging method corresponding to the process illustrated by Fig. 25, wherein the generation s400 of the authenticity measure of object 10 follows the array of image sensor 60 generating image s300 of scattered electromagnetic radiation 50 at a plurality of illumination periods t1, t2, ..., tn. Generating the authenticity measure s400 comprises generating s470, for each illumination period ti, an intermediate authenticity measure ki, as described above, and then generating s475 the authenticity measure m based on the plurality of generated intermediate measures k1, k2, ..., kn.

[00129] In one embodiment, generate s470, for each lighting period ti, the intermediate measure of authenticity ki comprises: deconveying, for each lighting period ti, the image generated by electromagnetic radiation scattered in the lighting period ti by means of said part of the reference spectral information associated with the way in which the object 10 was illuminated during the illumination period ti.

[00130] In one embodiment (not illustrated in Fig. 27), the intermediate measure ki of authenticity of each illumination period is generated s470 without waiting for the completion of the imaging step s300 for all illumination periods. That is, step s470 can be performed while step s300 is still in progress. For example, once the image sensor array 60 has the image generated by scattered electromagnetic radiation 50 for illumination period t1, an intermediate measure of authenticity k1 can be generated s470 for illumination period t1 and then stored, so that the generation step s475 can be performed later based on all stored intermediate authenticity measures k1, ..., kn.

[00131] Fig. 26 illustrates, schematically, the generation of an authenticity measure of the object 10, in another embodiment of the invention. In this embodiment, as in the embodiment described with reference to Figs. 25 and 27, the image sensor arrangement 60 first image scattered electromagnetic radiation 50 at a plurality of illumination periods t1, t2, ..., tn. The value n can, for example, be equal to 2 or 3, and object 10 is illuminated differently during each lighting period. Again, each illumination period encompasses an imaging period, as illustrated schematically with reference to Fig. 40. The authenticity measure is then generated through the following steps:

[00132] The image generated by scattered electromagnetic radiation {A1, A2, ..., An} is processed at least on the basis of the image generated by scattered electromagnetic radiation A1 in a first illumination period t1 among the plurality of illumination periods t1 , t2, ..., tn and on the image generated by scattered electromagnetic radiation A2 in a second illumination period t2, to produce the scattered part of the generated image processed Ax. All images A1, A2, ..., An can also be taken into account to produce the so-called composite image from the image generated by the scattered electromagnetic radiation Ax. That is, the image composed of the image generated by the scattered electromagnetic radiation Ax can be generated based on the images generated by the scattered electromagnetic radiation in a first to nth periods of illumination t1, t2, ..., tn.

[00133] Then, the authenticity measure m is generated depending on at least one ratio between the composite image processed by the image generated by scattered electromagnetic radiation (Ax), and the reference spectral information. In one embodiment, generating the authenticity measure m comprises decoding the composite image processed by the image generated by the scattered electromagnetic radiation Ax by means of the reference spectral information.

[00134] Figs. 28 is a flowchart of an imaging method in an embodiment corresponding to the process illustrated by Fig. 26, wherein the generation s400 of the authenticity measure follows the array of image sensor 60 generating image s300 of scattered electromagnetic radiation 50 at a plurality of illumination periods t1, t2, ..., tn.

[00135] Namely, after imaging S300, by the arrangement of the image sensor 60, the scattered electromagnetic radiation 50 in a plurality of illumination periods t1, t2, ..., tn, the authenticity measurement is generated s400 . Step s400 comprises, first, generating S482 of the so-called composite image processed by the image generated by the scattered electromagnetic radiation Ax, based at least on the image generated by the scattered electromagnetic radiation A1, A2 in a first and second illumination period t1, t2, and preferably on the basis of all images generated by the images of scattered electromagnetic radiation A1, A2, ..., An in illumination periods t1, t2, ..., tn. Then, the authenticity measure m is generated s486 depending on at least one ratio between the composite image processed by the image generated by scattered electromagnetic radiation (Ax), and the reference spectral information.

[00136] In one embodiment, step s482 can be implemented as follows: First, a weighting factor is calculated based on a statistical processing of the pixel values of the data of the first image A1 (that is, the image generated by the radiation electromagnetic radiation scattered at illumination period t1) and the pixel values of the data from the second A2 image (that is, the image generated by electromagnetic radiation scattered at illumination period t2). Then, the data of the third image Ax (that is, the so-called composite image generated by the scattered electromagnetic radiation) is generated by calculating a weighted combination using the pixel values of said data of the first image A1, the pixel values of the said data from the second A2 image and said weighting factor. Such an implementation can be carried out to maximize the image contrast between a scattered image of the marking (e.g. a bar code) and the remaining background scattered image, as described in PCT application WO 2014/187474 A1 by the same applicant. WO 2014/187474 A1 discloses techniques for improving the image of a mark or code printed on a fluorescent background or other backgrounds. Multiple images of a mark or code are acquired under different lighting conditions, and an image subtraction algorithm suppresses the background to make it easier to extract the printed codes from the images.

[00137] This embodiment, which will be described in greater detail with reference to Figs. 29a to 31 can be considered as a method of improving the spectral recognition and authentication of a mark (such as, for example, a printed mark) on backgrounds (such as, for example, complex fluorescent backgrounds), using a generator of imaging with a dispersive imaging arrangement 30 (such as, for example, a transmission diffraction grating) and background subtraction using differential imaging (as described in WO 2014/187474 A1). Background subtraction using differential imaging as described in WO 2014/187474 A1 will be referred to hereinafter as Differential Illumination Background Subtraction (DIBS) feature, technique or algorithm.

[00138] This embodiment particularly addresses the following potential problems: The image generated by electromagnetic radiation scattered through the dispersive imaging arrangement 30, as discussed above, may overlap with the zero image and, for example, the background fluorescent light from a tin lid (or similar) could pose problems for the authentication process. One embodiment of the invention to reduce the overlapping effect is to optionally use an appropriate mask that hides part of the image of the object 10 to avoid overlapping between the zero-order and first-order images of the code created by means of the arrangement 30 (in embodiments in the which zero order and first code order are displayed). Such a mask, however, is physical and may complicate the opto-mechanical design of the imaging system 200.

[00139] The modality based on DIBS aims to solve these problems. It uses images obtained through array 30, which has an overlap between the orders, and background subtraction is applied using the DIBS technique. The DIBS technique reduces the fluorescent (or similar) background effect in zero-order images (in modalities in which zero-order and first-order code are visualized) and corrects first-order images (scattered electromagnetic radiation 50), improving thus the spectrum-based generation of the authenticity measure. This is particularly advantageous when the fluorescent background has an excitation spectrum that differs from the ink to be authenticated (eg matrix code).

[00140] An example of images of a sample object 10 with a fluorescent background obtained with an imaging system 200 of Fig. 1 is shown in Fig. 29a (an image of a soda can lid without wearing a mask). A region with overlapping zero-order or first-order images of the sample object 10 can be seen in figure 29a. This region may be unusable for spectrum-based authentication purposes.

[00141] Therefore, the image in Fig. 29a has two problems: 1) the visible zero-order background overwhelms the first-order image, and 2) the background emits light that is diffracted in 1st-order and can “spectrally” interfere with the spectral information to be authenticated. The first problem can be treated using a physical mask. The DIBS technique specifically addresses the second problem by significantly reducing the background signal in the image.

[00142] Fig. 29b shows an image of the same object as sample 10 extracted with a physical mask in an embodiment of the invention. No overlap between orders is present, which makes efficient spectrum-based authentication possible, but the usable field of view may be limited. Such a limitation may, under certain circumstances, restrict the user to operating the device only with specific guidelines, possibly leading to an increase in authentication time for a sample object 10.

[00143] According to the aforementioned DIBS-based modality, no mask is used, but images are acquired in a plurality of illumination periods t1, t2, ..., tn with several different illuminations and then an image subtraction is performed according to the DIBS technique. This reduces the influence of a fluorescent (or similar) background on decoding (if used) and spectrum extraction.

[00144] For example, the DIBS algorithm can use two first-order images acquired by the illuminated object 10 with blue and green light, respectively. As an output of the algorithm, an image is obtained which is the linear difference or combination of images captured with blue and green lighting. This image usually has better contrast when it comes to the printed code compared to the initial images, thus improving the performance of the decoding engine (if used). The resulting image enhances the authentication process using the first order image (i.e. scattered electromagnetic radiation 50) created through dispersive imaging arrangement 30. This effect can be explained by the different excitation spectra for both the ink and used to print the code for the fluorescent background of object 10 (for example, a soda can lid). Paint is excited better in blue than in green, while the bottom of the soda can can be excited equally for both colors. Subtracting images leads to increased code contrast and improved authentication capability.

[00145] Fig. 30 shows example images of a soda can lid acquired without a physical mask, but excited in two different lighting periods by blue light (left image) and green light (right image), in an embodiment of the invention.

[00146] Fig. 31 shows examples of subtracted background images using the DIBS algorithm, using respectively the linear combinations B - 0.94*G (right image) and 8.22*(B - 0.94*G) (left image), in one embodiment of the invention. In the linear combination B - 0.94*G, B is a first image excited in a first period of blue light illumination, G is a second image excited in a second period of green light illumination, and 0.94 the weighting factor . In the linear combination 8.22*(B - 0.94*G), the significance of B, G and 0.94 is the same as in the first linear combination, and 8.22 is a scale factor. Regarding these linear combinations, the weighting factor and the scale factor, see equation (1) in document WO 2014/187474 A1, page 8, and the corresponding description.

[00147] Thanks to the DIBS algorithm, the treated image is more suitable for decoding (in modalities in which zero-order and first-order code images are generated) and improves generation based on the spectrum of the authenticity measure.

[00148] Now, let us describe other embodiments of the invention applicable both to imaging over a single period of illumination and to imaging over a plurality of periods of illumination. These additional embodiments can be combined with any of the embodiments described above.

[00149] In one embodiment, the object 10 has a visible or invisible mark 11 (or sign) printed with a printing ink. Such ink contains coloring and/or luminescent agents, such as dye(s) and/or pigment(s) which are typically difficult to produce and reverse engineer. These optical agents can be classified into two main classes: 1) optical agents that produce specific reflective properties under controlled lighting, and 2) optical agents that produce luminescence under controlled lighting.

[00150] The expected spectral response of said optical agents, when subjected to particular lighting conditions, is known a priori and constitutes the reference spectral information.

[00151] In the case of reflective properties, the spectral response is called spectral reflectivity, which is the fraction of electromagnetic power reflected per unit wavelength. For example, Fig. 32 shows the spectral reflectivity of two different color pigments (Microlith® from BASF AG, based in Ludwigshafen, Germany) as measured with a spectrophotometer in reflectance mode (e.g. model DU-640 spectrophotometer from Beckman Coulter Inc., based in Brea, California, USA).

[00152] For the reflectivity to be determined, a known broadband illumination source can be used, since the reflected electromagnetic radiation 20 (spectral radiation, which is measured), dependent on the wavelength, depends on the incident spectral composition of illumination (spectral irradiance). Spectral reflectivity can be determined using a calibrated light source (in wavelength) or by comparison to a surface of known spectral reflectivity (such as a white reference surface such as Spectralon® by LabSphere, based in North Sutton, New Hampshire , USA) using an uncalibrated broadband light source. The term “broadband” means that the light source emits at least all wavelengths in the range of interest. Examples of the spectral distribution of the broadband light source are shown for a white LED (e.g. an OSRAM OSLON SSL white LED) in Fig. 33 and tungsten filament lamp (incandescent lamp) in Fig. 34 (Source: Schroeder, D.V., 2003. "Radiant Energy," online chapter for the course, 'Energy, Entropy, and Everything,' Physics Department, Weber State University [accessed May 2016] http://physics.weber .edu/schroeder/eee/chapter6.pdf .).

[00153] This can be seen in Figs. 33 and 34 that the reflected spectrum of a given brand strongly depends on the spectrum of the irradiation source. Therefore, the so-called “reference spectral information” should be the spectral reflectivity (reflectance) of the object or mark. In modalities where the reference spectral information is the recorded spectral irradiance, said reference spectral information is, then, intrinsically related to the spectral distribution of the irradiation source, which should preferably be controlled when the reference spectral information is recorded in the first time (allowed) and also when it is measured to determine the authenticity of the object 10.

[00154] A second class of optical agents covers dyes or luminescent pigments and has different requirements when it comes to illumination and measurement.

[00155] Fluorescent dyes and pigments can be selected, for example, from perylenes (eg Lumogen F Yellow 083, Lumogen F Orange 240, Lumogen F Red 300, all available from BASF AG). Fig. 35 (source: WO 2016/042025 A1) shows an example of excitation and emission spectrum of such a fluorescent dye. In particular, it shows the excitation spectrum 601 and emission spectrum 602 of a fluorescent dye (Lumogen® F Orange 240 from BASF AG) added to an ink used for printing as an example of a digital code. Double headed arrow 603 indicates the range of wavelengths where the emission spectrum can be used as reference spectral information. It can be observed from Fig. 35 that the excitation spectrum extends between about 400 and 550 nm and the emission spectrum from about 550 to 700 nm. This requires that the light source emit at least in the excitation region for the fluorescent dye to be excited, but preferably not in the spectral emission region to avoid interfering with the fluorescence emission to be detected, which is typically several orders of magnitude weaker. than direct reflection.

[00156] This illumination and detection scheme is known in the field of fluorescence measurement and normally comprises a narrowband illumination source, such as, for example, a single color LED (a blue one at 450 nm or a green one at 530 nm can be adapted to excite the Lumogen of Fig. 35) and an optical long pass filter in the detection optical path to cut off any reflection towards the tail of the illumination source in the emission region. Optionally, an optical short-pass filter can also be arranged between the LED and the object 10 to be authenticated.

[00157] Figs. 35 and 36 show the emission and excitation spectra for two exemplary phosphorescent phosphor pigments: Lumilux® blue SN and Lumilux® green SN-F2Y from Honeywell International, Inc., headquartered in Morris Plains, New Jersey, USA. The spectroscopic properties shown in Figs. 35 and 36 were measured on samples printed with screen printing inks using a spectrofluorimeter (Horiba Jobin Yvon Fluorolog model FLIII-22, from Horiba, headquartered in Kyoto, Japan). The approach is the same as for fluorescent dyes or pigments described above. The excitation spectra 501 and 511 and the emission spectra 502 and 522 of two phosphorescent pigments are used to print marks to be authenticated in the form of a sticker, logo or designs. Black arrow 505 in each of Figs. 35 and 36 indicate the peak wavelength of a deep blue LED at 410 nm that can be used to efficiently excite phosphorescent pigments.

[00158] In one embodiment, spectral reference information is generated before operating the system and authentication method. This can be done by recording and recording the extracted spectral information, under the same or very similar lighting and detection conditions (for example, using the same device or instrument) as those to be used in the field.

[00159] In one embodiment, an uncontrolled lighting source can be used, provided that its spectral characteristics can be determined, through a spectral measurement and a subsequent correction can be made before extracting the measured spectral information from the object 10 or tag 11 to be authenticated.

[00160] Fig. 38 is a schematic diagram of an exemplary implementation of a computation unit 700 that may be used in embodiments of the invention, such as, but not limited to, to generate the authenticity measure discussed above.

[00161] As illustrated by Fig. 38, a computing unit 700 may include a bus 705, a processing unit 703, a main memory 707, a ROM 708, a storage device 709, an input device 702, an output device 704 and a communication interface 706. Bus 705 may include a path that allows communication between components of computing unit 700.

[00162] The processing unit 703 may include a processor, a microprocessor or processing logic that can interpret and execute the instructions. Main memory 707 can include a RAM or other type of dynamic storage device that can store information and instructions for execution by processing unit 703. ROM 708 can include a ROM device or other type of static storage device that can storing static information and instructions for use by processing unit 703. Storage device 709 may include a magnetic and/or optical recording medium and driver therefor.

[00163] The input device 702 may include a mechanism that allows an operator to enter information into the processing unit 703, such as a numeric keypad, a keyboard, a mouse, a pen, voice recognition and/or biometric mechanisms, etc. . Output device 704 may include a mechanism that outputs information to the operator, including a display, printer, speaker, etc. Communication interface 706 may include any transceiver-type mechanism that enables computing unit 700 to communicate with other devices and/or systems (such as a base station, WLAN access point, etc.). For example, communication interface 706 may include mechanisms for communicating with another device or system over a network.

[00164] The computing unit 700 can perform certain operations or processes described in this document. These operations may be performed in response to processing unit 703 executing software instructions contained on a computer-readable medium, such as main memory 707, ROM 708, and/or storage device 709. A computer-readable medium may be defined as a physical or logical memory device. For example, a logical memory device can include memory space within a single physical memory device or distributed across multiple physical memory devices. Each of main memory 707, ROM 708, and storage device 709 may include computer-readable media. The magnetic and/or optical recording media (e.g., readable CDs or DVDs) of storage device 709 may also include computer-readable media. Software instructions may be read into main memory 707 from another computer-readable medium, such as storage device 709, or from another device via communication interface 706.

[00165] The software instructions contained in the main memory 709 can cause the processing unit 703 to perform operations or processes described in this document, such as, for example, generating an authenticity measure. Alternatively, wired circuitry can be used in place of or in combination with software instructions to implement processes and/or operations described in this document. Thus, the implementations described in this document are not limited to any specific combination of hardware and software.

[00166] Fig. 39 schematically illustrates an example of an imaging period and illumination period, in an embodiment of the invention. This design has already been referred to and elaborated on throughout the above description.

[00167] In one embodiment, the imaging system 200 comprises, on the one hand, an imaging device comprising an image sensor arrangement 60 and, on the other hand, a piece of equipment, referred to hereinafter as " imaging accessory", comprising a dispersive imaging arrangement 30.

[00168] In this modality, the image generation device has an integrated camera (including associated lenses) and can be a portable device, such as, for example, at least one of: a cell phone, a smartphone, a conventional telephone, a tablet computer, a phablet, a portable media player, a netbook, a gaming device, a personal digital assistant and a portable computer device. The image sensors incorporated in the imaging device's integrated camera act as an array of image sensor 60 in system 200.

[00169] As mentioned above, the imaging accessory comprises a dispersive imaging arrangement 30, such as, for example, a transmission diffraction grating or any other dispersive element, as already discussed above with reference to Fig. . 1.

[00170] The imaging accessory is connectable, directly or indirectly (for example through a connecting piece of equipment), to the imaging device so that the dispersive imaging arrangement 30 of the imaging accessory is positioned relative to the imaging device 60 array of the imaging device in such a way that the imaging device and the imaging accessory form an imaging system 200 as described above, operable for imaging of an object and generating a measure of object authenticity. In other words, the imaging accessory can be used, for example, to transform a smartphone into a portable imaging and authentication system, as described above. The imaging accessory can, for example, be fixedly positioned over the smartphone's rear camera. The smartphone's processing and communication capabilities can then be used to implement a processing unit 70 of the imaging system 200.

[00171] Furthermore, if the imaging device has a light source (such as, for example, flash LEDs used in a smartphone), said light source can function as a lighting arrangement 210 to illuminate the object 10 to have the image generated and authenticated. A smartphone's light source is typically well suited for reflectivity measurements. Alternatively, lighting arrangement 210 may be provided as part of the imaging accessory.

[00172] This modality is advantageous in that the image generation accessory can be a passive accessory, not requiring additional energy and thus providing an accessible authentication solution.

[00173] Fig. 40 schematically illustrates an imaging system 200 according to the embodiment described above comprising, on the one hand, an imaging device comprising an image sensor arrangement 60, wherein the imaging device is a mobile phone with a camera, and, on the other hand, an imaging fixture 36 comprising a dispersive imaging array 30. In this exemplary optical configuration, the imaging fixture 36 comprises a diffraction grating 31 and a pass filter 33 arranged in front of the cell phone camera 64. The cell phone camera 64 comprises an imaging sensor 60 and an integrated lens 66. Optionally, an additional collimator lens 35 can be positioned in front of the imaging accessory 36.

[00174] The invention additionally concerns the following embodiments:Modality (X2). The imaging system (200) according to claim 1, wherein the imaging system (200) is an imaging device. Modality (X3). The imaging system (200) according to claim 1, comprising an imaging device (100) comprising the image sensor array (60) and the dispersive imaging array (30), wherein the imaging device (100) is not configured to actually generate the authenticity measure. Mode (X4). Imaging system (200) of embodiment (X2) or (X3), wherein the imaging device is a portable device. Mode (X7). Imaging system (200) according to any one of claims 1 to 3 and embodiments (X2) to (X4), wherein the imaging system (200) is configured to generate the authenticity measure after that the image sensor arrangement (60) has, in a plurality of illumination periods (t1, t2, tn), the image generated by the scattered electromagnetic radiation (50); and generating the authenticity measure comprises: generating, for each illumination period (ti), an intermediate authenticity measure (ki) depending, at least, on a relation between the image generated by the scattered electromagnetic radiation (50) in the illumination period (ti) and a part of the reference spectral information, said part of the reference spectral information being associated with the way in which the object (10) was illuminated during the period of illumination (ti); and generating the authenticity measure (m) based on the plurality of intermediate authenticity measures generated (k1, k2, ..., kn). Mode (X8). Image generation system (200) of the modality (X7), in which generating, for each period of illumination (ti), the intermediate measure of authenticity (ki) comprises: developing the image generated by the scattered electromagnetic radiation (50) in the period of illumination (ti) by means of said part of the reference spectral information associated with the manner in which the object (10) was illuminated during the period of illumination (ti). Mode (X9). Imaging system (200) according to any one of claims 1 to 3 and embodiments (X2) to (X4), wherein the imaging system (200) is configured to generate the authenticity measure after that the image sensor arrangement (60) has, in a plurality of illumination periods (t1, t2, tn), the image generated by the scattered electromagnetic radiation (50); and generating the authenticity measure comprises: processing the image generated by the scattered electromagnetic radiation based on at least the image generated by the scattered electromagnetic radiation in a first illumination period (t1) among the plurality of illumination periods (t1, t2, .. ., tn) and the image generated by scattered electromagnetic radiation in a second illumination period (t2) among the plurality of illumination periods (t1, t2, ..., tn), wherein the illumination conditions during the first period of lighting (t1) differ, at least partially, from the lighting conditions during the second lighting period (t2); and generating the authenticity measure (m) depending on at least one ratio between the generated image processed by scattered electromagnetic radiation (Ax), and the reference spectral information. Modality (X10). Image generation system (200) of the modality (X9), in which generating the authenticity measure (m) comprises: decoding the processed image generated by scattered electromagnetic radiation (Ax) by means of spectral reference information. Modality (X15). The imaging system (200) of claim 6, wherein the at least one machine-readable code comprises at least one of a linear barcode and a two-dimensional barcode. Modality (X16). Imaging system (200) according to any one of claims 5 and 6 and embodiment (X15), wherein the marking (11) comprises unique spectral characteristics in at least one region of the marking (11). Modality (X17). Imaging system (200) of modality (X16), wherein the marking (11) comprises unique spectral characteristics throughout the marking (11). Modality (X18). Imaging system (200) according to any one of claims 5 and 6 and embodiments (X15) to (X17), wherein the marking (11) comprises at least one of: optical agents that produce specific reflective properties under controlled lighting and optical agents that produce luminescence under controlled lighting. Modality (X19). System (220), comprising an imaging system (200) according to any one of claims 1 to 6, and modalities (X2) to (X4), (X7) to (X10) and (X15) to (X18), and a lighting arrangement (210) for controlled lighting of the object (10). Modality (X21). The imaging method of claim 7, wherein the imaging method is performed by an imaging device. Modality (X22). The imaging method of claim 7, wherein the imaging method is performed by an imaging system (200) comprising an imaging device (100) comprising the image sensor array (60) and the dispersive imaging arrangement (30), wherein the imaging device (100) does not generate (s400) the authenticity measure. Modality (X23). Imaging method of embodiment (X21) or (X22), wherein the imaging device is a portable device. Modality (X30). Imaging method (200) according to any one of claims 7 to 13 and embodiments (X21) to (X23), wherein the dispersive imaging array (30) comprises at least one of: a diffractive element, a transmission diffraction grating, a diffracted transmission diffraction grating, a holographic grating volume, a grism; a reflective diffraction grating, and a dispersive prism. Modality (X31). Imaging method according to any one of claims 7 to 13 and embodiments (X21) to (X23) and (X30), wherein a slit is not used between the dispersive imaging arrangement (30) and the object (10) to be imaged. Modality (X33). The imaging method of claim 14, wherein the marking (11) comprises at least one machine readable code. Modality (X34). Modality imaging method (X33), wherein the at least one machine-readable code comprises at least one of a linear barcode and a two-dimensional barcode. Modality (X35). Imaging method according to any one of claim 14 and embodiments (X33) and (X34), wherein the marker (11) comprises unique spectral characteristics over at least one region of the marker (11). Modality (X36). Modality imaging method (X35), wherein the tag (11) comprises unique spectral characteristics across the tag (11). Modality (X37). Imaging method according to any one of claim 14 and embodiments (X33) to (X36), wherein the marking (11) comprises at least one of: optical agents that produce specific reflective properties under controlled lighting and agents optics that produce luminescence under controlled lighting. Modality (X39). Computer program or set of computer programs comprising computer executable instructions configured, when executed by a computer or set of computers, to perform an imaging method according to any one of claims 7 to 15, and embodiments (X21) to (X23) and (X30) to (X37). Mode (X40). Computer program product or set of computer program products comprising a computer program or set of computer programs according to embodiment (X39). Mode (X41). Storage medium storing a computer program or set of computer programs according to the modality (X39).

[00175] Where the terms "processing unit", "storage unit", etc., are used in this document, no restrictions are made as to how these elements may be distributed and as to how elements may be assembled. That is, the constituent elements of a unit can be distributed in different software or hardware components or devices to promote the intended function. A plurality of distinct elements can also be assembled to provide the intended functionalities.

[00176] Any of the units mentioned above, such as, for example, processing unit 70, or devices, such as, for example, image generation device 110, can be implemented in hardware, software, programmable gate array in the field (FPGA), application specific integrated circuit (ASICs), firmware or similar.

[00177] In other embodiments of the invention, any of the processing units, storage unit, etc. mentioned above, is replaced by processing means, storage means, etc. or processing module, storage module, etc. respectively, to realize the functions of processing unit, storage unit, etc.

[00178] In further embodiments of the invention, any of the procedures, steps or processes described above can be implemented using computer-executable instructions, for example in the form of computer-executable procedures, methods or the like, in any type of computer language and/or in the form of software incorporated in firmware, integrated circuits or the like.

[00179] Although the present invention has been described based on the detailed examples, the detailed examples only serve to provide the person skilled in the art with a better understanding, and are not intended to limit the scope of the invention. The scope of the invention is much better defined by the appended claims. Abbreviations: ASICs application-specific integrated circuit a.u. CASSI arbitrary units CCD Aperture Coded Instantaneous Spectral Imager Charge Coupled Device CMOS Supplementary Metal Oxide Semiconductor CTIS CT Imaging Spectrometer DIBS Differential Illumination Background Subtraction FOV Field of View FPGA Field Programmable Gate Array l/ mm lines per mm LED light-emitting diode LTI linear translation invariant MAFC multi-aperture filtered camera MIFTS multi-image fourier transform spectrometer NIR near-infrared RAM random access memory RMS root mean square ROM read-only memory SHIFT transform spectrometer Fourier imaging instantaneous hyperspectral imaging SWIR short-wavelength infrared UV ultraviolet WLAN wireless local area network

Claims (15)

1. Imaging system (200) for generating a measure of authenticity of an object (10), the imaging system (200) comprising: one or more image sensors, the one or more image sensors being referred to hereinafter as "image sensor arrangement" (60); and one or more optical elements, the one or more optical elements being referred to hereinafter as "dispersive imaging arrangement" (30), wherein the dispersive imaging arrangement (30) is such that when the electromagnetic radiation (20) from the object (10) illuminates the dispersive imaging arrangement (30), at least part of the electromagnetic radiation (20) is scattered; and positioned with respect to the image sensor array (60) in a manner to allow the image sensor array (60) to image said scattered electromagnetic radiation (50); the image generation system (200) being configured so that, after the arrangement of the image sensor (60), in at least one image generation period, it has generated an image of the scattered electromagnetic radiation, generating a measure of authenticity of the object ( 10) depending on at least one ratio between the image generated from the scattered electromagnetic radiation (50) and the reference spectral information, characterized in that a synthetic non-scattered image calculated using the image generated from the scattered electromagnetic radiation (50) and the reference spectral information is used in generating the object authenticity measure. 2. Image generation system (200), according to claim 1, characterized in that generating the authenticity measure comprises: decoding the generated image of scattered electromagnetic radiation (50) by means of spectral reference information. 3. Image generation system (200), according to claim 2, characterized in that generating the authenticity measure further comprises determining at least one of: a decodability measure of an image generated from the code machine-readable in the deconvolution result; a measure of sharpness of the deconvolution result; a measure of uncertainty of the deconvolution result; a measure of the size of the deconvolution result; a measure of the area of the deconvolution result; a measure of the total width at the maximum half of a cross section of the deconvolution result; and a measure of the similarity of the deconvolution result to a reference standard. 4. Image generation system (200), according to any one of the preceding claims, characterized in that the dispersive image generation arrangement (30) comprises at least one of: a diffractive element, a diffraction grating of transmission, a diffracted transmission grating, a volume holographic grating, a grism; a reflective diffraction grating, and a dispersive prism. 5. Image generation system (200), according to any one of the preceding claims, characterized in that it generates an image of an object (10) bearing a marking (11). 6. Image generation system (200), according to claim 5, characterized in that the marking (11) comprises at least one machine-readable code. 7. Imaging method (200) for generating a measure of authenticity of an object (10), the imaging method characterized in that it makes use of: one or more image sensors, the one or more sensors image being referred to below as "image sensor arrangement" (60); and one or more optical elements, the one or more optical elements being referred to hereinafter as "dispersive imaging arrangement" (30), wherein the dispersive imaging arrangement (30) is such that when the electromagnetic radiation (20) from the object (10) illuminates the dispersive imaging arrangement (30), at least part of the electromagnetic radiation (20) is scattered; and positioned with respect to the image sensor array (60) in a manner to allow the image sensor array (60) to image said scattered electromagnetic radiation (50); and the imaging method comprising: imaging (s300), by means of the imaging sensor arrangement (60), in at least one imaging period, the scattered electromagnetic radiation (50), and generating a measurement of authenticity of the object (10) depending on at least one relation between the image generated from the scattered electromagnetic radiation (50) and the reference spectral information, characterized in that a synthetic non-scattered image calculated using the image generated from the scattered electromagnetic radiation (50) and the reference spectral information is used in the generation of the authenticity measure of the object. 8. Image generation method, according to claim 7, characterized in that generating (s400) the authenticity measure comprises decoding (s410) the generated image of scattered electromagnetic radiation (50) through spectral reference information . 9. Image generation method, according to claim 8, characterized in that generating (s400) the authenticity measure further comprises determining at least one of: a decodability measure of an image generated from the code machine-readable in the deconvolution result; a measure of sharpness of the deconvolution result; a measure of uncertainty of the deconvolution result; a measure of the size of the deconvolution result; a measure of the area of the deconvolution result; a measure of the total width at the maximum half of a cross section of the deconvolution result; and a measure of the similarity of the deconvolution result to a reference standard. 10. Image generation method, according to any one of claims 7 to 9, characterized in that it comprises image generation (s300), by arranging the image sensor (60), in a plurality of periods of illumination (ti, t2, ..., tn), of the scattered electromagnetic radiation (50), in which generating (s400) the authenticity measure comprises: generating (s470), for each period of illumination (ti), a intermediate measure of authenticity (ki) depending on at least one relation between the image generated from the scattered electromagnetic radiation (50) in the period of illumination (ti) and a part of the reference spectral information, said part of the reference spectral information being associated with the way the object (i0) was illuminated during the lighting period (ti); and generating (s475) the authenticity measure (m) based on the plurality of generated intermediate authenticity measures (ki, k2, ..., kn). 11. Image generation method, according to claim i0, characterized in that generating (s470), for each period of illumination (ti), the intermediate measure of authenticity (ki) comprises: decoding the image generated from the radiation scattered electromagnetic radiation (50) in the period of illumination (ti) by means of said part of the spectral reference information associated with the manner in which the object (i0) was illuminated during the period of illumination (ti). 12. Image generation method, according to any one of claims 7 to 9, characterized in that it comprises generating image (s300), through the arrangement of the image sensor (60), in a plurality of periods of illumination (t1, t2, ..., tn), of the scattered electromagnetic radiation (50), wherein generating (s400) the authenticity measure comprises: processing (s482) the generated image of the scattered electromagnetic radiation based on at least the image generated from electromagnetic radiation scattered in a first period of illumination (t1) between the plurality of periods of illumination (t1, t2, ..., tn) and the image generated from electromagnetic radiation scattered in a second period of illumination (t2) between the plurality of lighting periods (t1, t2, ..., tn), wherein the lighting conditions during the first lighting period (t1) differ at least partially from the lighting conditions during the second lighting period ( t2); and generating (s486) the authenticity measure (m) depending on at least one ratio between the generated image processed from the scattered electromagnetic radiation (Ax), and the reference spectral information. 13. Image generation method, according to claim 12, characterized in that the generation (s486) of the authenticity measure (m) comprises: developing the processed image generated from scattered electromagnetic radiation (Ax) through the information reference spectrum. 14. Image generation system, according to any one of claims 7 to 13, characterized in that it is to generate an image of an object (10) carrying a marking (11). 15. Image generation method, according to any one of claims 7 to 14, characterized in that it additionally comprises a step of controlled lighting of the object (10).