A grating coupler may be fabricated by exposing a photopolymer layer to grating forming light for forming periodic refractive index variations in the photopolymer layer. The photopolymer layer may be exposed to apodization light for reducing an amplitude of the periodic refractive index variations in a spatially-selective manner. The apodization may also be achieved or facilitated by subjecting outer surface(s) of the photopolymer layer to a chemically reactive agent that causes the refractive index contrast to be reduced near the surface(s) of application. The apodized refractive index profile of the gratings facilitates the reduction of optical crosstalk between different gratings of the grating coupler.

The invention relates to a scaled holographic medium comprising a layer construction B′-C1′-C2′, to a process for producing the sealed holographic medium, to a kit of parts, to a layer construction comprising a protective layer and a substrate layer and to the use thereof.

A method includes projecting, with a holographic optical element, a first view of an eye toward an imaging device, and projecting, with the holographic optical element, a second view of the eye, distinct from the first view of the eye, toward the imaging device so that the first view and the second view of the eye are concurrently received by the imaging device. An eye tracking device for performing the method, a holographic optical element used for the method, and a method of making the holographic optical element are also disclosed.

A method includes providing a radiation with a predetermined intensity profile. The method also includes providing a photo-sensitive medium layer including a mixture of a photo-sensitive material and an absorbing additive. The absorbing additive has a predetermined non-uniform distribution in at least one of a direction within a film plane or a thickness direction of the photo-sensitive medium layer. The predetermined non-uniform distribution of the absorbing additive is configured to result in a predetermined non-uniform absorption of the radiation. The method also includes exposing the photo-sensitive medium layer to the radiation to form a polymer film. The optical film includes at least one predetermined birefringence variation in at least one of a direction within a film plane or a thickness direction of the polymer film.

The invention relates to a process for producing an optical casting comprising at least one volume-holographic optical element by means of at least one casting operation, the process comprising the following steps: providing a casting mould comprising a first mould section having a flat, spherical, aspherical or free-form first surface and a second mould section having a flat, spherical, aspherical or free-form second surface, the first mould section being connectable to the second mould section to form the casting mould, providing at least one holographic optical element, positioning and aligning the at least one holographic optical element with respect to the first mould section or/and with respect to the second mould section, combining the first and second mould sections to form the casting mould, introducing casting material in one or more casting steps, the casting material having a maximum viscosity at 25° C. of 100 000 mPas, curing the casting material, removing the cured casting material comprising the at least one holographic optical element from the casting mould, the at least one holographic optical element being at least partly surrounded by the casting material.

A polarization volume grating (PVG) includes a bulk, birefringent medium characterized by a plurality of helical structures with helix axes and a periodicity Λ.sub.y and an anisotropic alignment material having a rotatable optical axis, disposed on a top or bottom surface of the medium. The PVG is characterized in that the optical axis of the alignment material has a continuously rotated optical axis orientation in a plane of the material surface and a periodicity Λ.sub.x, wherein the helix axes are normal to the optical axes in the alignment material surface, further wherein the birefringent medium is characterized by a plurality of controllably slanted refractive index planes having a slant angle φ=±arctan (Λ.sub.y/Λ.sub.x) and a Bragg period Λ.sub.B. Fabrication methods are disclosed.

The invention relates to novel compounds which are especially suitable for use as writing monomers in holographic media. The invention further provides a photopolymer and a holographic medium comprising the inventive compounds, and an optical display, a security document and a holographic optical element comprising an inventive holographic medium.

The Disclosure concerns a laser projection arrangement and a process for the generation of virtual images, the purpose of which is to present a solution which allows a representation of multiple virtual images in different distances or planes and different points of view and that can be manufactured economically. On the arrangement side, this purpose is solved when one of at least two picture generating units that generate virtual images that differ in their wavelength and/or their polarization is arranged and when a holographic optical element is arranged on or in the projection surface. On the process side, the purpose is solved when two virtual images with different wavelengths and/or different polarizations are generated, when a holographic optical element is provided which exhibits different optical properties for different wavelengths and/or different polarizations, and when, in the case of projection of the virtual images while making use of the holographic optical element, the virtual images are represented, due to the different optical properties, at different distances from the driver and/or in different points of view from the driver.

An eye-tracking system includes a substrate transparent to visible light and configured to be placed in a field of view of an eye of a user, a plurality of waveguides on the substrate, a light source optically coupled to the plurality of waveguides, and a plurality of polarization volume holograms (PVHs) in the field of view of the eye of the user. Each PVH of the plurality of PVHs is optically coupled to a respective waveguide of the plurality of waveguides and is configured to couple a respective light beam out of the respective waveguide towards the eye of the user.

A method for producing a hologram (1), (1) for security elements (1a) and/or security documents (1b). One or more virtual hologram planes (10) are arranged in front of and/or behind one or more virtual models (20) and/or one or more virtual hologram planes (10) are arranged such that they intersect one or more virtual models (20). One or more virtual light sources (30) are arranged on one or more partial regions of the surface (21) of one or more of the virtual models (20). One or more virtual electromagnetic fields (40) are calculated starting from at least one of the virtual light sources (30) in one or more zones (11) of the one or more virtual hologram planes (10). In the one or more zones (11), in each case, a virtual total electromagnetic field (41) is calculated on the basis of the sum of two or more, of the virtual electromagnetic fields (40) in the respective zone (11). One or more phase images (50) are calculated from the virtual total electromagnetic fields (41) in the one or more zones (11). A height profile (60) of the hologram (1) is calculated from the one or more phase images (50) and the height profile (60) of the hologram (1) is incorporated into a substrate (2) to provide the hologram (1).