Method for authenticating a security element, and optically variable security element

Patent metadata

Field	Value
Publication number	US-10019626-B2
Application number	US-201415100769-A
Country	US
Kind code	B2
Filing date	Nov 28, 2014
Priority date	Dec 2, 2013
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

The invention relates to a method for authenticating an optically variable security element ( 1 ), in particular a diffractive security element, with the steps:
a) capturing an image sequence with at least one individual image of the security element ( 1 ) by means of a sensor ( 31 ), in particular a hand-held device ( 3 ), preferably a smartphone, tablet or a PDA; b) checking whether at least one predetermined item of optical information is present in at least one individual image of the image sequence.

First claim

The invention claimed is:

1. A method for authenticating an optically variable security element comprising:
a) capturing an image sequence with at least one individual image of the security element by means of a hand-held sensor device;
b) checking whether at least one predetermined item of optical information is present in at least one individual image of the image sequence,
wherein the image sequence comprises more than two individual images of the security element, and wherein at least two individual images of the image sequence are used to check whether the security element comprises an optically variable structure, and
wherein the optically variable security element comprises at least one predetermined item of optical information automatically detected by the hand-held sensor device, the at least one predetermined item of optical information being formed by a variation of at least one relief parameter of a relief structure of the security element between at least one first zone and at least one second zone of the security element, wherein the relief structure provided in the first and/or second zone is a grating with grating lines which are curved circularly, parabolically or in the form of wavy lines, with a periodic azimuthal variation, wherein in at least one of the partial regions the period of the azimuthal variation and/or the grid width of the one- or two-dimensional grid is less than 300 μm.

2. A method according to claim 1 , wherein each individual image has more than 1920×1280 pixels.

3. A method according to claim 1 , wherein in step b) it is first checked whether a predetermined object is present in at least one individual image of the image sequence.

4. A method according to claim 3 , wherein an image recognition algorithm, is used to check whether the predetermined object is present.

5. A method according to claim 3 , wherein, to check whether the predetermined object is present, a comparison of the at least one individual image with a previously acquired training data set is carried out by means of the image recognition algorithm.

6. A method according to claim 5 , wherein, to acquire the training data set, a plurality of images is created, wherein a first subset of the images in each case has the predetermined object and a second subset of the images in each case does not have the predetermined object, and wherein each image of the first subset is allocated respective image coordinates of features to be recognized of the predetermined object.

7. A method according to claim 6 , wherein using the first and second subsets as well as the allocated respective image coordinates, a training of the image recognition algorithm is carried out.

8. A method according to claim 3 , wherein during the check of whether the at least one predetermined item of optical information of the optically variable security element is present, a contour of the predetermined object is ascertained from at least one individual image of the image sequence.

9. A method according to claim 8 , wherein, an edge detection algorithm, is executed to ascertain the contour.

10. A method according to claim 9 , wherein, during the execution of the edge detection algorithm, a noise filtering is carried out, by means of a Gaussian filter with a kernel size of from 3 to 7.

11. A method according to claim 9 , wherein, during the execution of the edge detection algorithm, an edge detection is carried out by applying a Sobel operator in at least one preferred direction of the at least one individual image, in two orthogonal directions of the at least one individual image.

12. A method according to claim 9 , wherein, during the execution of the edge detection algorithm, an edge filtering is carried out.

13. A method according to claim 9 , wherein, during the execution of the edge detection algorithm, a threshold-based ascertaining of the image coordinates of the contour of the object is carried out.

14. A method according to claim 13 , wherein based on the ascertained image coordinates of the contour, at least one individual image of the image sequence is divided into at least two partial regions and for each partial region the ascertained image coordinates of the contour are compared with corresponding target coordinates and, from this, a presence and/or a size and/or a relative position of predetermined contours is ascertained.

15. A method according to claim 8 , wherein at least one partial region of the individual image, which is positioned in a predetermined location relative to the contour of a predetermined object, and which comprises at least one pixel and/or at least one pixel group of the individual image, is selected and at least one property of the at least one pixel and/or of the at least one pixel group of the at least one selected partial region is compared with a corresponding target value.

16. A method according to claim 15 , wherein a location of the at least one partial region of the individual image is determined using the ascertained image coordinates of the contour.

17. A method according to claim 15 , wherein the at least one partial region comprises less than 50% of a surface area of the individual image.

18. A method according to claim 1 , wherein, during the capture of the image sequence in step a), an angle between the sensor and the security element and/or an angle between a light source and the security element is changed.

19. A method according to claim 1 , wherein, during the capture of the image sequence in step a), by means of a position sensor of the hand-held sensor device, for each individual image of the image sequence, a relative position of the hand-held sensor device with respect to a predetermined position is recorded and allocated to the respective individual image.

20. A method according to claim 18 , wherein, to check whether the security element comprises an optically variable structure, in step b) two individual images of the image sequence which have been captured at different observation and/or illumination angles are compared.

21. A method according to claim 18 , wherein, to check whether the security element comprises an optically variable structure, in each case corresponding pixels and/or pixel groups, of partial regions, of the individual images are compared.

22. A method according to claim 21 , wherein it is checked whether respective pixels and/or pixel groups, of the partial regions, of the individual images differ in terms of a color value and/or lightness value.

23. A method according to claim 21 , wherein the predetermined item of optical information comprises one or more items of information selected from: object, contour of the object, part of the contour of the object, properties of pixels and/or pixel group of the at least one selected partial region.

24. A method according to claim 21 , wherein one or more items of information selected from: object, contour of the object, part of the contour of the object, properties of pixels and/or pixel group of the at least one selected partial region, are compared with target values, in order to ascertain whether the predetermined item of optical information is present.

25. A method according to claim 1 , wherein the at least one predetermined item of optical information is or comprises a visually recognizable item of information.

26. A method according to claim 1 , wherein the at least one predetermined item of optical information is or c

Assignees

• Leonhard Kurz Stiftung & Co Kg
• Ovd Kinegram Ag
• Adorsys Gmbh & Co Kg

Inventors

• Schilling Andreas
• Frieser Uwe
• Schmitzer Benno
• Tompkin Wayne Robert
• Metzger Jurgen
• Wondratschek Ralf
• Gugel Alexander

Classifications

• G07D7/2083 Primary

  Learning · CPC title

• G06V30/418

  Document matching, e.g. of document images · CPC title

• G06F18/214

  Generating training patterns; Bootstrap methods, e.g. bagging or boosting · CPC title

• G06T2207/20021

  Dividing image into blocks, subimages or windows · CPC title

• B42D25/351

  Translucent or partly translucent parts, e.g. windows · CPC title