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1. WO2020157567 - AUTHENTIFICATION ET SUIVI PAR CODES CACHÉS

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

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Claims

1. A method for authenticating and tracking security documents or goods by smartphone acquisition of at least one spatial code hidden into a base layer multigrating reproduced on a substrate comprising (a) producing the base layer multigrating and (b) acquisition and processing of said base layer multigrating, where producing said base layer multigrating comprises the steps of:

- deriving from each spatial code an elevation profile;

- creating the base layer multigrating with grating lines shifted according to the derived elevation profile;

- reproducing said base layer multigrating by a process on said substrate;

where the acquisition and processing of said base layer multigrating comprises the steps of:

- repeated acquisition of the reproduced base layer multigrating by the camera of the smartphone;

- selection of a sharp instance of the acquired base layer multigrating;

- applying to the selected base layer multigrating a perspective correction;

- applying to the perspectively corrected base layer multigrating a fine grain rectification;

- digitally superposing to the perspectively corrected and fine grain rectified multigrating a digital revealing layer grating having substantially the same repetition period as one of the gratings of the perspectively corrected multigrating;

- applying to the resulting superposition image processing operations and obtaining the hidden spatial code; and

- decoding the obtained spatial code into a message and authenticating it.

2. The method of claim 1, where the smartphone performs the acquisition and the selection of a sharp instance of the acquired base layer multigrating and where each of the other processing steps is performed by a computing device selected from the set comprising said smartphone and a computing server.

3. The method of claim 1, where phase control is applied for synthesizing the digital revealing layer grating in order to ensure in the digital superposition the presence of high-intensity lines in originally white regions of the spatial code and the absence of high-intensity lines in originally black regions of the spatial code or vice-versa.

4. The method of claim 1, where the security document or good is tracked by sending the decoded message to a computing server, together with the smartphone identifier, date, time and location of the multigrating acquisition, where the computing server authenticates the decoded message by comparing it with a list of valid messages, and where tracking comprises storing the decoded message together with the acquisition smartphone identifier, date, time and location information into a tracking data base.

5. The method of claim 1, where said base layer multigrating is a halftone multigrating that is obtained by creating a base layer dither multigrating with a grating band shifted according to said elevation profile and by dithering an original variable intensity image with said base layer dither multigrating.

6. The method of claim 3, where one grating of said base layer multigrating is formed by a family of rectilinear or curvilinear lines defined by the implicit equation Q(x,y)—G(x,y) = k·, Q(x,y) being a function of position (x,y), G(x,y) being the elevation profile, T being the line repetition period and k being the line index and where the revealing layer grating corresponding to that base layer grating is formed by the family of rectilinear or curvilinear lines defined by the implicit equation Q(x,y)=(k+ ƒ )·, where ƒ is an initial phase difference between the base layer grating and the corresponding revealing layer grating that ensures said phase control.

7. The method of claim 1, where the image processing operations applied to the superposition of the fine grain rectified multigrating and the digital revealing layer grating are selected from the set of morphology erosion, morphology dilation, low-pass filtering, histogram modification, and thresholding operations.

8. The method of claim 1, where said elevation profile is obtained by low-pass filtering and inverting the spatial code, where fine grain rectification is carried out by locating the actual positions of grating line intersections and by applying a rectification transformation minimizing a distance metric between actual and desired grating line intersections, where authentication is carried out by comparing the decoded message with a list of valid messages and where the spatial code is selected from the set of data matrix code, Aztec code, QR-code, ID barcode and alphanumeric string.

9. The method of claim 1, where the authentication step is performed locally by the smartphone that carried out the acquisition and processing of said base layer multi grating.

10. The method of claim 1, where the fine grain rectified multi grating is superposed with a second digital revealing layer grating, thereby yielding a second message, different from the first one, that is authenticated by comparing it with a list of valid messages.

1 1. The method of claim 1, where the spatial code is divided into segments separated by space and where the base layer halftone multigrating is an extended multigrating that comprises an additional visible graphical, textual or code element within that space that breaks continuity of part of the multi grating lines.

12. The method of claim 1 1, where after acquisition, perspective correction and fine grain rectification of said extended multigrating the regions incorporating the spatial code segments are extracted from the superposition of the extended multi grating and of an extended digital revealing layer grating and reassembled to form a single spatial code superposition to be further processed by the image processing, decoding, and authentication steps.

13. The method of claim 1, where said base layer multigrating is reproduced by said process for transferring an image onto the substrate, said process being selected from the set of lithographic, photolithographic, photographic, electrophotographic, patterning, engraving, etching, perforating, embossing, vaporizing, material deposition, molding, 2D printing, and 3D printing processes.

14. The method of claim 1, where the process is selected from the set of:

(i) printing with ink on paper, (ii) printing with ink on plastic, (iii) deposition of metal on a substrate selected from metal, plastic, silicon and glass, (iv) deposition of plastic on a substrate selected from metal, plastic, silicon and glass, (v) patterning on plastic, (vi) patterning on metal, (vii) patterning on glass, (viii) injection of plastic, (ix) molding of plastic, (x) molding of metal, (xi) 3D printing of plastic, and (xii) 3D printing of metal.

15. The method of claim 1, where the base layer multigrating incorporates two different gratings within the originally white borders of the hidden spatial code and only one grating inside the hidden spatial code area.

16. A smartphone operable for authentication and tracking of documents or goods comprising a CPU, a memory, a display, a camera and a network interface as well as software modules operable for acquisition, phase controlled superposition, processing, decoding and authentication of a base layer multigrating hiding a spatial code reproduced on a substrate, said software modules comprising .

(i) a module operable for the repeated acquisition of the reproduced base layer multigrating by the smartphone's camera;

(ii) a module operable for the sharpness evaluation and selection of a sharp instance of said acquired multigrating;

(iii) a module operable for applying to the selected acquired base layer multigrating a perspective correction;

(iv) a module operable for applying to the perspectively corrected base layer multigrating a fine grain rectification;

(v) a module operable for performing digital phase controlled superposition of the base layer fine grain rectified multigrating and a digital revealing layer grating having the same repetition period as one of the gratings of said fine grain rectified multigrating;

(vi) a module operable for applying image processing operations to the resulting phase-controlled superposition and for obtaining the hidden spatial code;

(vii) a module operable for decoding the obtained spatial code into a message and for authenticating it.

17. The smartphone of claim 16, where the phase controlled superposition is carried out by synthesizing the revealing layer grating at a phase ensuring in the digital superposition the presence of high-intensity lines in originally white regions of the spatial code and the absence of high-intensity lines in originally black regions of the spatial code or vice-versa.

18. The smartphone of claim 16, where the documents or goods are tracked by sending the decoded message to an authentication and tracking server, together with the smartphone

identifier, date, time and location of the multigrating acquisition, where the server authenticates the decoded message by comparing it with a list of valid messages, and where tracking comprises storing the decoded message together with the smartphone identifier, date, time and location of the acquisition into a tracking data base.

19. The smartphone of claim 16, where the image processing operations applied to the phase-controlled superposition of the fine grain rectified multigrating and the corresponding digital revealing layer grating are selected from the set of morphology erosion and dilation, low-pass filtering, histogram modification, and thresholding operations.

20. The smartphone of claim 16, where the fine grain rectified multigrating is superposed with a second digital revealing layer grating, thereby yielding a second spatial code, different from the first one, that is decoded and then authenticated by comparing it with a list of valid messages.

21. The smartphone of claim 16, where the authentication step is performed locally by said smartphone by comparing the obtained message with a list of valid messages.

22. The smartphone of claim 16, where successively displaced or phase shifted instances of the revealing layer grating superposed with the fine grain rectified multigrating are shown as animation to the holder of the smartphone, said animation allowing him verifying the presence of the spatial code.

23. The smartphone of claim 22, where upon interaction with the user the fine grain rectified multigrating is superposed with a second digital revealing layer grating, thereby making visible to the holder of the smartphone also a second spatial code, different from the first one.

24. The smartphone of claim 23, where each grating of the perspectively corrected and fine grain rectified base layer multigrating is formed by a family of rectilinear or curvilinear lines.

25. The smartphone of claim 22, where the spatial codes are selected from the set of data matrix code, Aztec code, QR-code, ID barcode and alphanumeric string.

26. The smartphone of claim 16, where the fine grain rectified multigrating incorporates two gratings within the originally white borders of the spatial code and only one grating within the black and white inside regions of the spatial code.

27. A computing infrastructure for localizing persons relying on the smartphone acquisition by the person holding the smartphone of a halftone picture comprising a base layer multigrating hiding a spatial code, said computing infrastructure including software modules running on said smartphone operable for

(i) the repeated acquisition of the reproduced base layer multigrating by the smartphone's camera;

(ii) evaluating the sharpness and selecting a sharp instance of said acquired multigrating;

(iii) applying to the selected acquired base layer multigrating a perspective correction;

(iv) applying to the perspectively corrected base layer multigrating a fine grain rectification;

(v) performing digital phase controlled superposition of the base layer fine grain rectified multigrating and of a digital revealing layer grating having the same repetition period as one of the gratings of said fine grain rectified multigrating;

(vi) applying image processing operations to the resulting phase-controlled superposition and obtaining the hidden spatial code;

(vii) decoding the obtained spatial code into a message; and

(viii) localizing said person.

28. The computing infrastructure for localizing persons of claim 27, where the phase controlled superposition is carried out by synthesizing the revealing layer grating at a phase ensuring in the digital superposition the presence of high-intensity lines in originally white regions of the spatial code and the absence of high-intensity lines in originally black regions of the spatial code or vice-versa.

29. The computing infrastructure for localizing persons of claim 27, where the localization of the person holding the smartphone is carried out by sending the obtained message to a server, by having the server finding the associated spatial location and by having the server sending a reply message to the smartphone giving information related to the spatial location of said person.

30. The computing infrastructure for localizing persons of claim 27, where the image processing operations applied to the phase-controlled superposition of the fine grain rectified multigrating and the corresponding digital revealing layer grating are selected from the set of morphology erosion and dilation, low-pass filtering, histogram modification, and thresholding operations.

31. The computing infrastructure for localizing persons of claim 27, where the fine grain rectified multigrating is superposed with a second digital revealing layer grating, thereby yielding a second message, different from the first one.

32. The computing infrastructure for localizing persons of claim 27, where at least one grating of the perspectively corrected and fine grain rectified base layer multigrating is formed by a family of rectilinear or curvilinear lines and where the spatial codes are selected from the set of data matrix code, Aztec code, QR-code, ID code and alphanumeric string.

33. The computing infrastructure for localizing persons of claim 27, where the localization step is performed locally by the smartphone that carried out the acquisition and processing of said base layer multigrating by comparing the obtained message with messages from a table associating input messages and spatial locations.