An Electrically Operated Smoking Device Including an Optical Projection System for Identifying Smoking Articles Comprising an Indicium

Abstract

The present invention relates to an aerosol-generating consumable article comprising at least one indicium containing coded information about the article arranged on a surface of said article. The coded information is implemented in at least one array of readable code elements that are readable upon illumination by an optical magnification reader system, said readable code elements having a density of at least 10 elements per square mm of said indicium. The invention is also related to an aerosol-generating device configured to receive a consumable article. The aerosol-generating device comprises an optical magnification reader system configured to provide an optically magnified image of at least a portion of said indicium on a detector and to read said coded information, to recognize the authenticity of the consumable article.

Claims

1. An aerosol-generating consumable article comprising at least one indicium containing coded information about the article arranged on a surface of said article, wherein said coded information is implemented in at least one array of readable code elements that are readable upon illumination by an optical magnification reader system, said readable code elements having a density of at least 10 elements per square mm of said indicium.

2. The consumable article according to claim 1, wherein said readable code elements are structural and/or coloured code elements.

3. The consumable article according to claims 1, wherein at least three of the coloured code elements have different colours.

4. The consumable article according to claim 3, wherein at least one portion of said indicium comprises at least eight code elements having a different colour.

5. The consumable article according to claim 1, wherein at least a portion of the code elements are labile code elements.

6. The consumable article according to claim 1, wherein at least a portion of said indicium comprises a waveguide.

7. An aerosol-generating device comprising: an outer body part, a power supply and a cavity defining a cavity axis, said body part having an opening being configured to receive a consumable article according to claim 1 upon insertion of said article, wherein the aerosol-generating device further comprises an optical magnification reader system defining an entry aperture and comprising at least one focusing optical element and at least one detector, said optical magnification reader system being arranged in the outer body part and configured to provide an optically magnified image, magnified by a magnification factor M equal or greater than 1, of at least a portion of said indicium, on said detector and to read said coded information, and wherein the aerosol-generating device further comprises a control unit configured to recognize authenticity of the consumable article based on the content of the information read by the optical magnification reader system in the indicium arranged on the consumable.

8. The aerosol-generating device according to claim 7 wherein the magnification factor of said optical magnification reader system is at least a factor of 2.

9. The aerosol-generating device according to claim 7, wherein said optical magnification reader system comprises at least one concave optical mirror.

10. The aerosol-generating device according to claim 7, wherein said optical magnification reader system comprises at least one adaptable optical element configured to adapt a focal length thereof.

11. The aerosol-generating device according to 7, wherein said optical magnification reader system comprises an optical waveguide arranged between said entry aperture and said detector.

12. The aerosol-generating device according to claim 11 wherein said optical waveguide comprises a diffractive light incoupler and/or a diffractive light outcoupler.

13. The aerosol-generating device according to claim 7, wherein said optical magnification reader system is configured to read at least two indicia arranged on said aerosol-generating consumable article.

14. The aerosol-generating device according to 7, wherein said optical magnification reader system comprises at least one polarizer.

15. The aerosol-generating device according to claim 7, wherein said detector is placed in said device so that, in operation of the device, the temperature of said detector remains lower than 45° C.

16. The aerosol-generating device according to claim 8 wherein the magnification factor of said optical magnification reader system is at least a factor of 10.

17. The aerosol-generating device according to claim 8 wherein the magnification factor of said optical magnification reader system is at least a factor of 20.

18. The aerosol-generating device according to claim 8 wherein the magnification factor of said optical magnification reader system is at least a factor of 50.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 shows a schematic representation of a partial longitudinal cross section of an aerosol-generating device comprising an optical magnification reader system.

[0025] FIG. 2 shows a schematic representation of a partial longitudinal cross section of an optical magnification reader system of the invention comprising a beam splitter and at least two detectors.

[0026] FIG. 3 shows a schematic representation of an embodiment of the optical magnification reader system of the invention.

[0027] FIG. 4 shows a schematic representation of a top view of a transversal cross section of an aerosol-generating device comprising an optical magnification reader system configured to read indicia arranged in an array of indicia.

[0028] FIG. 5 shows a schematic representation of the top view of a transversal cross section of an aerosol-generating device comprising an optical magnification reader system configured to read indicia arranged on at least two surfaces of an aerosol generating article.

[0029] FIG. 6 shows a schematic representation of a longitudinal cross section of an optical magnification reader system comprising a light source arranged to provide to an indicium a grazing incidence light beam that propagates along a surface of an aerosol generating article.

[0030] FIG. 7 shows a schematic perspective representation of an optical magnification reader system comprising a hollow concave shaped axial symmetric reflector that faces an axial symmetric array of detectors

[0031] FIG. 8 shows a schematic representation of a longitudinal cross section of an optical magnification reader system configured to detect the superposition of the magnified images of two indicia.

[0032] FIG. 9 shows a schematic representation of a transversal cross section of an optical magnification reader system that comprises an optical beam splitter to illuminate an indicium and at the same time detect light provided by that indicium, by using the same common optical path.

[0033] FIG. 10 shows a schematic representation of a section of an optical magnification reader system that comprises an array of micro lenses.

[0034] FIG. 11 shows a schematic representation of a section of an optical magnification reader system comprising a monolithic optical magnification reader comprising an integrated array of micro lenses and a detector.

[0035] FIG. 12 shows a cross section of an exemplary device according to the invention. The optical reader of the embodiment comprises an optical waveguide to provide an enlarged image at its output.

[0036] FIG. 13 shows an enlarged view of a portion of an indicium of an article of the invention.

[0037] FIG. 14 illustrates a detected height profile of tow structural elements of the portion of an indicium illustrated in FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will be described with respect to particular embodiments and with reference to the appended drawings, but the invention is not limited thereto. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0039] The invention will be described in the following examples in relation to aerosol-generating consumable articles 1 comprising a tobacco-containing charge of aerosol-generating material but the scope of the invention shall not be construed as limited to tobacco-based consumable articles but shall encompass any aerosol-generating consumable articles, such as smoking articles, heat-not-burn articles, e-liquid cartridges and cartomizers, which comprises an aerosol-generating substrate capable to generate an inhalable aerosol upon heating. Aerosol-generating consumable articles 1 according to the current invention may or may not have a symmetry axis and may have any form or shape, such as an elongated, cylindrical shape, or a spherical shape, or the form of a beam. As represented in FIGS. 1 to 8, an aerosol-generating consumable articles 1 according to the invention comprises at least a first portion 1b comprising an indicium 10 arranged on an outer surface and a second portion 1a attached to the first portion, which second portion 1 a may form a mouthpiece for a user to inhale an aerosol generated upon heating of the first portion 1b after insertion of the aerosol-generating consumable articles 1 in a heating cavity of an aerosol-generating device 2. The article 1 comprises a further portion 1c that does not comprise an indicium 10. The indicium 10 may be arranged to one or both of the lateral sides of said further portion 1c (FIG. 7, FIG. 8).

[0040] The invention is realized by an aerosol-generating article 1 and also by an aerosol-generating device 2. The invention is further realized by a system that comprises said aerosol-generating device 2 comprising an aerosol-generating article 1 that is inserted in said aerosol-generating device 2. The aerosol-generating device 2 and the aerosol-generating article 1 of said system are described in detail herein.

[0041] As used herein, the term “aerosol-generating material” refers to a material capable of releasing volatile compounds upon heating, which can form an aerosol. The aerosol generated from aerosol-generating material may be visible or invisible and may include vapours (for example, fine particles of substances, which are in a gaseous state, that are ordinarily liquid or solid at room temperature) as well as gases and liquid droplets of condensed vapours.

[0042] The first portion 1b of the aerosol-generating article 1 may comprise a charge of aerosol-generating material arranged into a wrapper 3 but not necessarily so. The term “wrapper 3” is defined broadly as any structure or layer that protects and contains the charge of aerosol-generating material, and which allows to handle that material. The wrapper 3 has an inner surface that may be in contact with the aerosol-generating material and has an outer surface away from the aerosol-generating material. The wrapper 3 may preferably comprise a cellulose based material such as paper but may also be made of a biodegradable polymer or may be made of glass or a ceramic. The wrapper may be a porous material and may have a smooth or rough outer surface 5 and may be a flexible material or a hard material. A wrapper 3 may constitute an optical opaque or partially transparent optical layer. In the case of paper, a wrapper 3 is partially transparent in the visible and in the infrared and may be partially transparent in the UV. A wrapper 3 may comprise apertures. Said indicium 10 may arranged at least partially in front of at least one aperture provided in the surface of the wrapper 3.

[0043] The term “indicium 10” is defined as an element or a structure containing information about an aerosol-generating article 1 and is typically arranged on a surface of an article 1. The surface may be an outer or an inner surface of an article 1 such as a surface pertaining to a wrapper of the article. An indicium 10 may be imbedded inside the article 1. Also, more than 1 indicium 10 may be arranged to or inside said article 1.

[0044] As used herein the term “magnification M”, defined also as magnification factor, means that the produced image B is at least as large as the object A (indicium or portion of an indicium) to be imaged The magnification M=is determined by b/a=B/A and so is greater or equal to 1. A and B are respectively the size of the indicium or portion of indicium to be imaged and B is the size of the image in the image plane.

[0045] The imaging is realized by an optical system that has an object distance a of an indicium to a focusing system that is smaller than the image distance b between the focusing system and the image plane, i.e. b a wherein a and b are related by 1/f=1/a+1/b, f being the focal length of the focusing system of the optical reader of the device. It is generally understood that the image size B must not necessarily be equal to the size of the detector that is used to detect the image. The detector may have, in at least one cross section, a size that is smaller or greater than the produced image.

[0046] To the contrary of articles of prior art that comprise indicia, the code elements or structures of the indicium 10 indicia of the present invention are individually difficult or impossible to detect or identify by the unaided human eye. The high-density indicia of the present invention require an optical reader system that provides an image size at least as great than the size of the portion of the indicium to be detected. Simple bar codes for example rely on an optical reduction system, meaning that the magnification factor is smaller than 1. The reason is that a wide field of view has to be provided by the optical imaging system. In the present invention, the field of view is small as it is intended to detect an indicium or a portion of an indicium that has a very high code density. Therefor a magnification M of at least one (M>1) is required, but is typically more than a factor 2 up to 100 or more as described further. Therefor the device of the invention is well suited for detecting indicia that are arranged on a circumference of an article. The devices of the invention may also be configured to detected and measure indicia that are arranged along a longitudinal direction of the article, which requires devices in which the article is inserted according to a predetermined angular orientation, or by using at least a rotatable part of the optical reader configured to rotate around a cavity 112.

[0047] The indicium 10 may be of different types, some of which are described in further details below. Typical classes of 2D or 3D shaped indicia 10 applicable to the aerosol-generating articles 1 according to the invention comprise, but are not limited to: [0048] reflecting or diffracting indicia 10; [0049] reflecting and diffracting indicia 10; [0050] indicia 10 comprising meta-surfaces; [0051] holographic indicia 10; [0052] polarization-sensitive indicia 10; [0053] indicia 10 comprising at least one indicium waveguide such as a resonating waveguide grating (RWG) that is arranged onto or in the indicia 10;

[0054] As appropriate for design and/or security purpose an indicium 10 may be a partially transparent indicium 10. It may further be configured such that the optical effect it provides to be, upon illumination, is independent of the axial position of the aerosol-generating article 1 relative to a fixed illumination source.

[0055] Further, any indicium 10 may be arranged on a substrate that is arranged on a surface of said wrapper and/or be realized by any physical or chemical means onto said wrapper or into said article 1;

[0056] In preferred embodiments, indicia 10 may be labile indicia, i.e. they may be altered in time or in function of physical and chemical conditions in the aerosol generating article 1 or device.

[0057] Particularly advantageous forms of indicia 10 are those where at least one indicium is configured as a resonant waveguide grating (RWG). RWG's are described in for example: [0058] A. Sharon et al.: “Resonating grating-waveguide structures for visible and near-infrared radiation”: J.Opt.Soc.Am” vol.14, nr.11, pp.2985-2993, 1997.

[0059] The use of RWG in indicia 10 allows to provide unique optical effects that are extremely difficult to recognize and to duplicate. Because of their small periodicity, they do not allow various diffractive orders, which distinguishes them from much simpler diffractive optical elements (DOE).

[0060] Of course, a combination of different types of said typical classes of indicia 10 as previously recited is foreseeable in the context of the present invention.

[0061] Indicia 10 may be arranged on a portion of a circumference of an article 1 or may be arranged on a complete circumference (e.g. in FIGS. 1-4). It can comprise a high density of coded elements, which may be imbedded in structures such as diffractive structures or a thin waveguide or a hologram arranged in or on said indicium 10, or an array of such structures. Code elements may also be absorption structures or layers arranged on or inside the indicium 10. Code elements may also be structures that are polarization sensitive.

[0062] The indicium 10 provided to the aerosol-generating article of the invention may be arranged to provide predetermined direct reflection effects such as providing, upon illumination by a light beam provided by a light source, a plurality of light beams that may have different spectra and/or different reflection angles. The reflected light beams may be diffracted light beams projected in any diffraction order. An indicium 10 may comprise structures on at least one of its surfaces or sides and may comprise structures imbedded inside a layer of the indicium 10. For example, diffractive structures may be provided on an outer surface of the indicium 10. Light beams may be collimated light beams or may be large aperture light beams and may be divergent or convergent light beams.

[0063] The coded information is implemented in at least one array of readable code elements that are readable upon illumination by an optical magnification reader system 200 as described hereinafter in various examples. The array of readable code elements has a density of at least 10 elements per square mm of said indicium 10. Preferably the array of readable code elements has a density of more than 20, more preferably more than 50 elements per square mm of said indicium 10.

[0064] The indicium 10 may be arranged according to a 2D or 3D arrangement of structures and may have any shape such as a square, or a rectangular shaped band. Preferably said band comprises an array of redundant code elements that are arranged on a complete circumference of said article 1. The term “redundant herein means that the indicium 10 comprises an array of repetitive code elements, or blocks of code elements, and may be read by a fixed optical magnification reader 200, independent of the position of the article 1, such as the angular position, relative to the optical magnification reader system 200. This may be realized for example, without limitation, by an indicium 10 that is constituted by an array of reflective or diffractive structure, an array of absorptive structures, or an array of resonating waveguides or a combination of them.

[0065] Apart from anti-counterfeit properties it is desired that the indicium 10 may also contain information of specific parameters that should be used by the inhaler devices such as the ideal temperature range, or the heating profile in function of time, or parameters which allow to provide to the smoker different smoking tastes or intensities.

[0066] A particular interesting application of the device and system of the invention consists in detecting and measuring the 3D shape of structural elements of an indicium 10. To detect information from such indicia 10, the device 2 if the invention is mandatory as it requires a high magnification factor M, at least greater than 1, typically greater than 10. In an embodiment the indicia 10 are inkjet-printed elements, such as printed domes having a well-defined and predetermined shape or 3D dimension. This is feasible by existing inkjet machines and may be applied on typical paper wrapper 3. Inkjet deposition may be realized such that the printed plots or domes have a well-defined predetermined shape. The indicia 10 may incorporate photonic crystals to provide unique optical properties such as reflection effects. The reader system may comprise means to detect the shape of the printed inkjet elements. Such means may be realized by an optical configuration based on a static detection by two detectors that have different viewing axis, or may be also realized by a reader system that comprises a movable projection lens or any optical microsystem that allows to retrieve information on the 3D shape of the printed elements. Optical detection systems such as mm sized cameras that provide a magnification lower than 1do not allow such detection.

[0067] According to a first embodiment, represented in FIG. 1, an optical magnification reader system 200 comprises a concave mirror 20 which is fit to provide a magnified image 10′ of an indicium 10 onto a detector 30 that is positioned in the image plane of the magnification system 200. In variants of FIG. 1 the detector 30 may be configured to detect a spectral reflectance of the indicium 10 or may be configured to provide an image of at least a portion of the indicium 10. In an advantageous embodiment the indicium 10 contains redundant optical structures and is configured onto a complete circumference so that the optical effect of the indicium is independent of the orientation of the aerosol generating article relative to a fixed light source 40 arranged in the optical magnification reader system 200. In variants, the detector 30 may be arranged in the cavity 112 of the device 2.

[0068] The use of an optical magnification reader system 200 allows providing aerosol generating devices 2 that may be arranged according to different types of high-density indicia 10 as described and allow to provide a great design flexibility of such aerosol generating devices 2, coping with issues such as extremely limited available space and heating issues of the components, such as the detector, of the needed optical reader system.

[0069] The optical magnification reader system 200 as described herein is configured to transmit electromagnetic radiation, typically radiation having wavelengths including the UV, Visible and the whole infrared (IR) range.

[0070] The optical magnification reader system 200 may comprise, but not exclusively: [0071] refractive elements, for example single or compound lenses, prisms, beam splitters, Fresnel lenses; [0072] reflective elements, for example flat or concave mirrors; [0073] diffractive elements, for example diffractive lenses realized on a transparent substrate, [0074] optical elements which optical function is provided by metasurfaces; [0075] electrically addressable elements such as MEMS devices, or a combination of such elements.

[0076] The optical magnification reader system 200 will be chosen according to the type of indicium 10 and the geometrical and temperature requirements and are typical, but not exclusively the following choices:

[0077] In embodiments, not illustrated in figures, optical fibers may be arranged in the optical reader system 200. For example, an entry face of a waveguide may be positioned in the image plane of the projection system, and a portion of the light of that magnified image 10′ of the indicium 10 may be transmitted to a distant detector 30 that is configured to detect the intensity and/or the spectrum of the guided light. In variants means may be provided to scan or switch the entry face of a waveguide in the image plane. In variants, not illustrated in the figures, a waveguide may be arranged between a light source 40 and said indicium. Such a configuration allows to illuminate the indicium by a light beam provided by an outcoupling surface of the waveguide.

[0078] Waveguides that may be arranged into the optical magnification reader system 200 may be, without limitation: [0079] single fibers 10: for transmitting intensity, polarisation and spectral information; [0080] fiber bundles 10: for transmitting images and illuminating light beams; [0081] flat waveguides 10: for transmitting intensity, polarisation and spectral information, as well as the transmission of images and illumination light beams.

[0082] All the embodiments described herein may be adapted to transmit also an illumination beam that is provided by a light source 40, 42 arranged in the optical magnification reader system 200, to the side away from an indicium 10. This may be realized by using for example a beam splitter or a semi-transparent mirror. Arranging an illumination beam in optical systems, such as a microscope, is well known and is not further described herein.

[0083] The “optical magnification reader 200” comprises an optical projection system having a magnification factor greater than 1 and at least one detector. The detector 30 may be a single detector, a detector array, a detector system comprising optical elements and electronics, or may be or comprise an imager and/or or a miniaturized spectrometer.

[0084] The “light source 40, 42” can be any source 40, 42 that may provide a light beam, preferably in the range of UV (ultraviolet), visible or infrared (IR) light. A light source may be for example a LED or a semiconductor laser. The light source must not be necessarily a power-driven light source, and thus may for example be a part or an area of a heater or a hot part of the aerosol generating device and/or or the consumable article that provides a beam of infrared light.

[0085] Upon illumination by the light source 40, the indicium 10 of an aerosol-generating article 1 will generate a projected light beam 410, which can be a reflected, transmitted or diffracted light beam. The projected light beam 410 provides, after reflection or refraction or diffraction by a first focusing element 20, at least one secondary light beam 420 that is transmitted directly onto a detector 30, or by using for example single or compound reflective, refractive or diffractive elements, beam splitters or a combination of such elements.

[0086] Said projected light beam 410 is then received on a detection system, also defined as “a detector 30”, which includes means to convert optical information provided by at least one indicium 10 of an aerosol generating article into an electrical signal or data that may be used to recognize the article and/or identify information related to the parameters of the aerosol generating device 2, for example parameters that should be used, in operation of the device 2, for said article 1. A detection system 30 may comprise a single detector or a detector array or may comprise a vision system. The detection system 30 may also comprise color filters or a miniaturised spectrometer.

[0087] Optical information on the aerosol generating article 1 may be provided by an indicium 10 arranged on an article 1 or by an indicium 10 arranged inside said aerosol generating article 1. The optical magnification system 200 transmits, in operation of the aerosol generating device 2, the optical effect provided by the indicium 10 to said detection system.

[0088] Further embodiments illustrating typical variants are now described in detail.

[0089] FIG. 2 illustrates a schematic cross section of an optical magnification system 200 comprising a beam splitter 50 (BS) and two detectors 30, 32. In variants, as illustrated, the system 200 may comprise two polarisers P1, P2, allowing to provided polarisation information of the indicium 10 according to, for example, two orthogonal polarisation planes. Using polarisation effects allows to provide more complex indicia 10 and makes the identification of the coded information of an indicium 10 much more difficult to recognize and to replicate.

[0090] In some variants it may be necessary to provide a projection system 200 having an important magnification factor, for example a factor of 10, or more than 20 or more than 50. This may be realized by embodiments, such as the one illustrated in FIG. 3, that are based on a long optical projection path. Due to the lack of space in a typical aerosol generating device, the optical path is deviated by using at least one secondary deflection mirror 22, which may be a flat or a curved mirror. In variants, not illustrated herein, the optical magnification system may be based on a catadioptric configuration. This allows to provide a compact optical system while at the same time providing a long projection length and thus a high magnification factor.

[0091] FIG. 4 illustrates an embodiment wherein the indicium is an array of identical indicia 10-15. In variants said array of indicia 10-15 may be different indicia that are configured to project the same information to the detector system 30. This may be realized by using a first focusing element 20 that has a wide angular aperture. In variants, illustrated in FIG. 4 more than 1 deflection mirror 22, 24 may be used to provide a high projection length. The embodiment in FIG. 4 illustrates an example wherein the primary projected light beam 410 is directed to the detector 30 by 3 successive convergent light beams 412, 414, 416.

[0092] FIG. 5 illustrates an embodiment of an aerosol generating device 2 in which an aerosol generating article 1 is inserted that comprises two different indicia 10, 11. Each indicium 10, 11 is associated with an optical projection system 200′, 200″ arranged in the optical magnification reader system 200. A first optical projection system 200′ is arranged in the plane of a lateral cross section of the part 1b of the article comprising the indicium 11, and a second projection system 200″ is arranged to an angle relative to said first projection system 200′. Said angle is preferably orthogonal as illustrated in FIG. 5.

[0093] FIG. 6 shows a schematic representation of a cross section of an optical magnification reader system 200 comprising a light source 40 arranged to provide to an indicium 10 a grazing incidence light beam 400 that propagates along a surface of an aerosol generating article 1. In operation, the grazing incident light beam 400 interacts optically with the indicium 10 and provides a projected light beam 410 that is directed typically at 90° relative to said grazing incidence light beam 400. Using a grazing incidence light beam 400 allows to provide to a detector 30 an image 10′ of the indicium 10 that has a great contrast. Illumination techniques by using grazing incidence, such as used in microscopy or image processing instruments, is known and is not further described herein. In an advantageous embodiment, illustrated in FIG. 6, optical filters F1-F3 may be inserted in the projected or secondary light beam 410, 420. In the example of FIG. 6 an indicium 10 comprises dots that have each a specific color upon illumination by a white light beam. The colors or spectral characteristics are represented, for illustration only, in the FIG. 6 by the wavelength symbols λ1-λ3. The code elements may be black or grey elements and may have any color as defined in the 1976 CIE Chromaticity Diagram. Combining arrays of dense structures such as dots, thin lines, or symbols, in which the structures have different shaped and/or spectral characteristics are difficult to recognize or reproduce if a magnification system is required, which is the object of the invention as described herein.

[0094] FIG. 7 shows a schematic 3D representation of an optical magnification reader system comprising a hollow concave shaped axial symmetric reflector 20 that faces an axial symmetric, disc shaped, array of detectors 31-39. FIG. 7 illustrates, for the purpose of clarity, two exemplary convergent reflected light beams 410′, 410″ reflected off said reflector 20. Such a configuration allows to provide a magnification system that is not dependant on the axial orientation of an article 1, in as far that the indicium 10 comprises redundant optical structures or arrays as describe before. The detectors 31-39 may be single detectors or may each be an array of detectors.

[0095] FIG. 8 shows a schematic representation of a cross section of an embodiment of an optical magnification reader system configured to detect the superposition of the magnified images of an indicium 10 comprising two indicia 11, 13. Embodiments like the one shown in FIG. 8 are particularly interesting as the superposition of the optical effects of at least two indicia requires a magnification system 200 and is difficult to recognize and reproduce. In variants, color or polarization effects may be combined in the system 200 of FIG. 8, making the reading and recognition of the indicium further complicated and so difficult to replicate.

[0096] FIG. 9 shows a schematic representation of a lateral cross section of an optical magnification reader system 200 that comprises an optical beam splitter BS to illuminate an indicium 10 by an incident light beam 400′, and at the same time detect a light beam 420 provided by that indicium 10, by using the same common optical path. Some wrappers, such as paper wrappers are partially transparent in the visible range and especially in the infrared part of the spectrum. This property is used in the embodiment of FIG. 9 wherein an indicium 10 is arranged at or near to the inner surface of the wrapper of an article 1. The indicium may be made of a substance 104 having a predetermined shape, such as the bell-shaped indicium 100 as illustrated in the insert of FIG. 9. In the embodiment of FIG. 9 light is focused on said indicium by the optical magnification system 200. The interaction of the incident light 400′ provides a reflected or diffused light beam 410 that is recollected by the optical magnification reader system 200 and projected onto a detector 30. In a variant the indicium 10 may comprises a portion 102 that has a different optical property as the rest of the indicium. For example, the portion 102 may be a reflecting portion 102 which provides, in the image plane 10′, a light peak or light peaks characteristic of the reflecting portion 102. In the case of a totally transparent wrapper 3 or an article 1 that has no wrapper, the profile of the indicium is straightforward to detect. Even in the case of a partially diffusing wrapper, such as a thin layer of paper, geometric and spectral or intensity information may be detected of the embedded indicium. For example, the particular backscattered properties of the light scattered by the embedded structure 100, 102, 104 may be detected by using the light beam 410 that is retroreflected or diffused by that element 100, 102, 104 and that is transmitted through said wrapper as illustrated in FIG. 9. Without using an optical magnification system 200 this would not be possible or at least extremely difficult and would provide not reliable information. Providing embedded indicia 100 allows to make counterfeit more difficult as the indicia are not visible from the outside of an aerosol-generating article 1.

[0097] FIG. 10 shows a schematic representation of a section of an embodiment of an optical magnification reader system 200 that comprises an array 20 of micro lenses. Using an array 20 of micro lenses 20a-20d allows to provide a very compact optical projection system 200. In the arrangement of FIG. 10 and FIG. 11 each micro lens 20a-20d of the micro lens array 20 provides a projected light beam and an enlarged image of a portion 10a-10d of an indicium 10 onto the detector 30. Each portion 10a-10d may be imaged on a corresponding portion 30a-30d of the detector 30, as illustrated in FIG. 10. Said detector portions 30a-30d may be single detector elements or may be an array of detectors. The detector 30 may be configured to detect a complete image of the indicium 10 or may be configured to detect optical properties of each portion 10a-d of the indicium 10. For example, detector element 30a may detect spectral properties of a first indicium portion 10a. In another example detector portion 10a is configured to detect an image 10′ of said first indicium portion 10a. In variants, a part of the detector 30 may be configured to detect intensities and/or spectral information and another part may be configured to provide an image. For example, the central detector parts 30b-c may provide an image of two indicia elements 10b, 10c and the remaining detector parts 30a, 30d may be configured to detect color or intensity effects provided by the corresponding indicia portions 10a, 10d.

[0098] FIG. 11 shows a schematic representation of a section of an optical magnification reader system 200 comprising a monolithic optical magnification system comprising a monolithically integrated array of micro lenses. The embodiment of FIG. 11 is particularly interesting as it allows to provide a very compact magnification system 200. Typical height t1 and lateral t2, t3 dimensions may be smaller than 5 mm, preferably smaller than 3 mm so that the total volume of the magnification system 200, including the light source 40 and the detector 30 may be smaller than 100 mm.sup.3, smaller than 30 mm.sup.3. In variants the monolithic projection system 200 may be based on a prism-like substrate wherein projected light 420 provided by the indicium is directed to an integrated detector 30 by total internal reflection on the reflecting surface RS of a prismatic element. A light source 40 may be adapted on the reflecting surface RS and the illumination beam 400 may be refracted through the reflecting surface RS as illustrated.

[0099] In variants of the embodiment of FIG. 11, optical filters or other elements may be integrated in a layer 30′ situated in front of or in contact with the detector array 30″ of the detector 30. In all embodiments of the invention the focal length f of the focusing elements is chosen in function of the desired magnification and the desired aperture of the focusing elements. FIG. 11 illustrates the needed formula 1/f=1/a+1/(b1+b2) wherein f is the focal length of the focusing elements, a is the distance between the indicium 10 and the entry face of the focusing elements 20 and b=b1+b2 is the distance between a focusing element 20 and the image plane 10′. Making the right comprise between focal length f, the required apertures, the overall dimensions, the choice of materials and the cost of an imaging optical system is well known in the field of optics and is not further described herein.

[0100] In embodiments that aim to reduce further the overall dimensions and the production costs, optical structures such as metasurfaces may be used to realize some of the needed optical elements, such as the first focusing element 20. The use of metasurfaces to make for example metalenses allow to reduce considerably the size of the projection system, as well of their cost as they can be bath-processed using typical microtechnology processes. Using metasurfaces allows integrating lens arrays on a flat substrate and may be implemented as the first focusing element 20, and/or, if needed, in front of the detector 30. The advantage of using metasurfaces consist in providing planar microlens arrays on which other microstructures may be provided such as an array of pinholes to the backside of the first focusing planar meta surface lens array 20. This allows to provide baffle structures, reducing considerably cross talk between the different optical projection beams and so improve the contrast of the projected images in the image plane 10′. It is possible to realize metalens projector systems 200 that use for example metalenses. In an example a metalens is designed to be used with monochromatic light having a wavelength of 532 nm. The metalens may have a diameter of 2 mm and a focal length of 0.7 mm and is able to image and resolve indicia 10 linewidths of 2 μm large and centre-to-centre distance of the lines of 4 μm.

[0101] Realizing flat optics using metasurfaces are described in for example the review article: N. Yu and F. Capasso, “Flat optics with designer metasurfaces”; Nature Materials 13, p.139 (2014).

[0102] Also, in variants, if the detector 30 has to be positioned far from a hot surface, a relay-lens or curved relay-mirror providing preferably a 1:1 image may be arranged between the indicium 10 and the first focusing element 20. This allows positioning the first focusing element and the detector 30 further away from the hot surface at a distance of preferably two times the focal length of said relay lens.

[0103] In all embodiments described herein, not illustrated, a light source 40, 42 may be arranged so as to provide a light beam 400 that is transmitted through a complete diameter of an article 1. Such variants are especially useful in aerosol-generating articles 1 wherein the infrared transparency of a cross section of the article 1 is at least partial in an infrared wavelength range, for example more than 1%, more preferably more than 5%.

[0104] It is generally understood that the optical reader system 200 may comprise addressable optical elements, such as a flipping mirror or MEMS components that may be located in one of the incident or projected light paths. Other variants comprising for example optical filters or miniaturized spectrometers may be integrated in said aerosol-generating device 2. In a variant the aerosol-generating device 2 comprises a display that is configured to display information provided by the indicium 10 of the article of the invention.

[0105] It is understood that in all embodiments of the invention, the optical magnification reader system may comprise beam shaping elements or means to modify actively the path and/or the shape and/or the aperture of a light beam. For example, addressable MEMS mirrors may be implemented. MEMS devices may be very small, i.e. smaller than 10-20 mm.sup.3, and may be implemented to scan portions of an indicium 10, or collect light provided by light beams that have different orientations, such as may be provided by indicia that comprise diffraction gratings or RWG's.

[0106] Example of a Practical Realization

[0107] FIG. 12 illustrates an example of realization of a device comprising a heater 2′ and an optical reader comprising an image magnification system based on the use of a waveguide 1000 comprising a diffractive focusing incoupler 2002 and a diffractive outcoupler 2004. In variants the incoupler 2002 may be the same structure as the outcoupler 2004. For reasons of clarity of the FIG. 12 the illumination source of the indicium 10 is not shown, and may be a LED, or light provided by the waveguide, for example by using incoupled light from a LED situated to the end of the waveguide that comprises the outcoupling area. Light may be incoupled in the waveguide 1000 by either a wedge of the waveguide or by a third diffractive incoupler arranged to any area of the waveguide 1000 The indicium 10 in the embodiment of FIG. 12 has an arrangement of repetitive redundant structures 10a that have a well-defined shape, providing not only information on the 2D arrangement on the surface of a wrapper, but also information on the height profile of the structures. The optical system is arranged so that its angular aperture always captures the image of a portion P of the indicium 10 so that the code imbedded in the indicium 10 may be detected independent of the angular orientation of the article 1 when inserted in the cavity 112 of the device 2.

[0108] By using a static projection system, the 2D arrangement or the 2D shape of the structures of the indicium may be detected. In the advantageous arrangement of FIG. 12 a flat waveguide 1000 is used to provide an enlarged image 10′ of a portion P of an indicium 10. The portion P may have a maximal width of 500 μm or less than 250 μm. It would not be possible to detect detailed information from such small areas P with optical systems of prior art. Aerosol-generating devices of prior art that comprise vision systems are based on widefield imagers, i.e. they are image reduction optical systems, so have a magnification factor M that is less than 1.

[0109] By moving the waveguide 1000, either orthogonal to the axis of the cavity 112 or by applying a slight rotation θ1, θ2 of at least one side of the end portion of the waveguide 1000, the optical reader may retrieve information on the 3D shape of the structures of the indicium 10. These structures may be realized by for example ink-jet printing allowing to provide well controlled deposited dots on, for example, a paper wrapper. FIG. 14 illustrates a height measurement of two elements of the portion P along a section P1 as illustrated in FIG. 13.

[0110] In the practical realization of FIG. 12, the projection distance b is composed of the length b1 of the waveguide and the projection distance b2, i.e the distance between the outcoupling area of the waveguide to the detector. The distance a of the indicium 10 to the incoupling window, that comprises a focusing element such as a diffractive grating, is much smaller than the total projection distance b (=b1+b2). The total projection distance b is typically 45 mm and a is typically 3 mm, proving a magnification M of a factor of 15, i.e. M=b/a=45/3=15.

[0111] In variants, the arrangement of FIG. 12 may be realized by other projection systems that do not rely on an optical waveguide, as described before. The advantage of using at least one waveguide 1000 is that it is easy to bend the waveguide and to apply a rotation θ1, θ2 of its ends. The rotations θ1, θ2 and possibly the lateral movement Δ are small, typically smaller than 5 degrees (θ1, θ2), respectively 100 82 m (Δ). This may be realized by for example a piezo-or electrostatic driven mechanism.