Optical security marking component, method of manufacturing such a component, system comprising such a component, and reader for checking such a component
The present invention relates to an optical security marking component producing a first visible configuration when observed through a polarizer oriented in a first orientation, and a second configuration, separate from the first, visible when observed through the polarizer oriented in a second orientation, the optical component comprising a stamped film for forming at least two diffraction gratings having different orientations, characterized in that each of said gratings has a period of less than 550 nm and a modulation between 0.25 and 0.5 relative to a reference plane.
1. An optical security marking component producing a first configuration visible when observed through a polarizer oriented in a first orientation, and a second configuration separate from the first, visible when observed through a polarizer oriented in a second orientation, the optical component comprising:
a stamped transparent film for forming at least two diffraction gratings having different orientations; and
a reflecting coating coated on the stamped transparent film, the reflecting coating being at least one of metallic and transparent,
wherein each of said gratings has a period of less than 550 nm, and a uniform modulation μ=h/d between 0.25 and 0.5 relative to a reference plane, wherein h is the groove height and d is the groove spacing, the stamped transparent film having a surface, said surface having a random and chaotic nature.
2. An optical marking component according to claim 1 , further comprising a diffusing treatment.
3. An optical marking component according to claim 2 , wherein the diffusing treatment is constituted by a diffusing layer.
4. An optical marking component according to claim 3 , wherein said stamped film, said structure, and said diffusing layer are integrated in a sub wavelength grating.
5. An optical marking component according to claim 4 , wherein a diffusing structure comprises said stamped film, said structure, and said diffusing layer, and wherein the diffusing structure is encapsulated between a first layer having a low index of refraction, and a second layer having a high index of refraction, and wherein the encapsulated diffusing structure enables an immediate visual check without an additional reading tool.
6. An optical marking component according to claim 1 , wherein each of the gratings is formed in a predefined graphic configuration having visible dimensions, the gratings having adjacent limits.
7. An optical marking component according to claim 1 , wherein the two diffraction gratings have perpendicular main vectors.
8. An optical marking component according to claim 1 , wherein said stamped film comprises a transparent film coated with a metallic reflecting layer.
9. An optical marking component according to claim 8 , wherein the reflecting layer is formed by a transparent material having a high refraction index.
10. An optical marking component according to claim 8 , wherein the reflecting layer is coated with an adhesive for the positioning on a support to be authentified.
11. An optical marking component according to claim 8 , wherein the reflecting layer is partially de-metallized.
12. An optical marking component according to claim 1 , wherein the stamped film comprises a transparent birefringent material.
13. An authentication system that enables a user to visually observe an optical security marking component, the authentication system comprising:
an optical security marking component including: a stamped transparent film for forming at least two diffraction gratings having different orientations, a metallic reflecting layer coated on the stamped transparent film, each of said gratings having a period of less than 550 nm and a uniform modulation μ=h/d between 0.25 and 0.5 relative to a reference plane, wherein h is the groove height and d is the groove spacing, wherein the stamped transparent film has a surface, said surface having a random and chaotic nature; and
an adapted reader including a polarizer, the reader configured to enable a user to observe the optical component along two different polarization directions.
14. The authentication system according to claim 13 , wherein the polarizer is movable in relative rotation with respect to an optical component to be checked and positioned in the reader.
15. The authentication system according to claim 14 , further comprising a diffusing element positioned between the polarizers and the component to be checked.
16. The authentication system according to claim 13 , wherein the polarizer includes two pieces of adjacent polarizers, the main axes of which are oriented perpendicularly, with the orientation of the axes of such polarizers being adapted to the orientations of the grating vectors, said polarizers being movable in translation to make the various configurations of the optical component to be checked appear successively in an observation window.
17. The authentication system according to claim 16 , further comprising a diffusing element positioned between the polarizers and the component to be checked.
18. The authentication system according to claim 13 , further comprising a diffusing element positioned between the polarizers and the component to be checked.
19. The authentication system according to claim 13 , further comprising a Wollaston prism performing the separation of the two modes of the optical component in an observation plane.