Optical device with holographic layer

1 . An optical device comprising:

a textured layer comprising a first surface having first macro-textures; and

a carrier comprising on its surface a holographic layer intermediate between the textured layer and the carrier, the holographic layer comprising a diffraction grating forming, via a holographic effect, an arrangement of pixels in a basis of at least two distinct colours,

the first surface of the textured layer being assembled by lamination with the carrier so that the holographic layer, placed between the textured layer and the carrier, is deformed by the first macro-textures so as to comprise second macro-textures conformal with said first macro-textures, a visual appearance of the arrangement of pixels being personalized via the second macro-textures, the visual appearance being created by forming different patterned portions of the second macro-textures in the holographic layer,

wherein the second macro-textures of the holographic layer are of semi-cylindrical or elliptical shape and extend along a first orientation in a plane of the holographic layer,

each pixel being formed by a corresponding segment of the diffraction grating, said corresponding segment being structured into diffractive lines extending along a second orientation perpendicular to the first orientation in the plane of the holographic layer.

2 . The device according to claim 1 , wherein the first and second macro-textures have a height comprised between 1 μm and 100 μm.

3 . The device according to claim 1 , wherein the pixels of the diffraction grating are at least partially arranged so as to form rows of pixels each in a single colour among the basis of at least two distinct colours, the rows of pixels extending along the second orientation.

4 . The device according to claim 3 , wherein the rows of pixels are arranged periodically in the holographic layer.

5 . The device according to claim 3 , wherein the rows of pixels are arranged in groups of rows of pixels in each colour among the basis of at least two distinct colours, each group comprising a plurality of rows of pixels in a given colour among said basis of at least two distinct colours,

the rows of pixels being arranged periodically in each group.

6 . The device according to claim 5 , wherein the rows of pixels are arranged spatially in each said group according to a pitch separating each pair of adjacent rows of pixels, such that P≤100 μm.

7 . The device according to claim 1 , wherein the textured layer has a glass transition temperature higher than or equal to that of the carrier.

8 . The device according to claim 1 , wherein the textured layer and the carrier are formed from a same material or from a same set of materials.

9 . The device according to claim 1 , wherein the holographic layer is comprised by diffractive optical properties that are dependent on the second macro-textures formed by lamination in a pattern in relief imposed by the first macro-textures of the textured layer.

10 . The device according to claim 1 , wherein the pixels in said arrangement of pixels each comprise a plurality of sub-pixels of distinct colours in the basis of at least two distinct colours,

the device comprising a personalization layer positioned facing the holographic layer,

wherein the holographic layer comprises perforations formed by a laser radiation, said perforations revealing locally through the holographic layer zones of colorimetric nuance in the sub-pixels that are caused by subjacent regions, of the personalization layer, that are located facing the perforations, so as to form a personalized holographic image based on the arrangement of pixels combined with the zones of colorimetric nuance.

11 . The device according to claim 10 , wherein the personalization layer is one among:

the textured layer; and

a layer positioned facing the holographic layer so that the textured layer is intermediate between the holographic layer and the personalization layer.

12 . The device according to claim 10 , wherein said personalization layer is opaque with respect to at least a spectrum of wavelengths of visible light, the zones of colorimetric nuance caused by the subjacent regions of the personalization layer being dark zones in the sub-pixels.

13 . A secure document comprising:

a document body; and

the optical device according to claim 1 incorporated by way of a security device in or on the document body.

14 . A process for manufacturing an optical device, said process comprising:

forming a textured layer comprising a first surface having first macro-textures; and

positioning the first surface of the textured layer facing a carrier comprising on its surface a holographic layer intermediate between the textured layer and the carrier,

the holographic layer comprising a diffraction grating forming, via a holographic effect, an arrangement of pixels in a basis of at least two distinct colours; and

laminating the first surface of the textured layer on the carrier, causing a deformation by the first macro-textures of the holographic layer placed between the textured layer and the carrier, so as to form in the holographic layer second macro-textures conformal with said first macro-textures, a visual appearance of the arrangement of pixels being personalized via the second macro-textures, the visual appearance being created by forming different patterned portions of the second macro-textures in the holographic layer,

wherein the second macro-textures of the holographic layer are of semi-cylindrical or elliptical shape and extend along a first orientation in a plane of the holographic layer,

each pixel being formed by a corresponding segment of the diffraction grating, said corresponding segment being structured into diffractive lines extending along a second orientation perpendicular to the first orientation in the plane of the holographic layer.