The present invention provides photoluminescent iron-doped barium stannate materials absorbing ultraviolet (UV) light and exhibiting strong near-infrared (NIR) luminescence. Such materials exhibit increased integrated photoluminescence intensity in comparison to known BaSnO.sub.3 and iron-doped barium stannate materials, and therefore they are particularly useful for the production of photoluminescent security ink compositions and transparent covert security features with improved anti-counterfeiting resistance that can be used for protection of documents and articles against counterfeit and illegal reproduction.

The present invention provides photoluminescent iron-doped barium stannate materials absorbing ultraviolet (UV) light and exhibiting strong near-infrared (NIR) luminescence. Such materials exhibit increased integrated photoluminescence intensity in comparison to known BaSnO.sub.3 and iron-doped barium stannate materials, and therefore they are particularly useful for the production of photoluminescent security ink compositions and transparent covert security features with improved anti-counterfeiting resistance that can be used for protection of documents and articles against counterfeit and illegal reproduction.

The present invention disclosed a shaped object comprising nano cellulose alone or a composition of nano cellulose for inclusion in a paper product and process for preparation thereof. The present invention further disclosed a paper product having the shaped objects incorporated therein. The shaped objects are used as a security feature for identifying and authenticating security documents.

The present invention disclosed a shaped object comprising nano cellulose alone or a composition of nano cellulose for inclusion in a paper product and process for preparation thereof. The present invention further disclosed a paper product having the shaped objects incorporated therein. The shaped objects are used as a security feature for identifying and authenticating security documents.

A security marking has a physically unclonable function (PUF) wherein the PUF includes a disordered multilayer photonic crystal structure having an electromagnetic transmission and/or reflection spectrum and/or spectra upon receipt of electromagnetic radiation within a photonic bandgap region of the structure that is unique to the structure.

An optically variable security arrangement for securing valuable articles, comprises a first sub-element having a two-dimensional relief grid composed of a plurality of grid elements and that has, in at least one spatial direction R.sub.1, a first line screen p below 500 μm, and in which the grid elements are each formed from at least two relief elements that are directionally reflective in different directions, and a second sub-element having at least one dot and/or line grid that, in a spatial direction R.sub.2, has a second line screen q. A movement effect is created by the interplay of the relief grid and the dot and/or line grid when the security arrangement is tilted.

A security device is disclosed including a substrate and one or more focusing elements or lens structures located on one side of the substrate. The security device includes a plurality of image elements associated with each focusing element wherein the image elements include at least first and second groups of image elements. Each image element may be composed of pixels located in an object plane to be viewable through the associated focusing element. Each image element comprises a diffractive grating element or sub-wavelength grating element which when illuminated by a light source generates a diffraction image observable at a range of viewing angles around the device. Image elements of the first group are visible in a first range of viewing angles and image elements of the second group are visible in a second range of viewing angles. The security device is particularly suitable for use on security documents, such as banknotes. A method of forming a security device is also disclosed.

A device comprising: an optical emitter for emitting light having an emitted optical spectrum; an optical sensor for receiving light reflected from a tag attached to an object; and a processor configured to: determine a reflected optical colour spectrum of the light reflected from the tag based on an output of the optical sensor; retrieve an optical signature associated with said object from memory; and determine the authenticity of said object based on comparing the optical signature and the reflected optical colour spectrum.

An optical device includes an array of lenses and a plurality of segments disposed under the array of lenses. The plurality of segments corresponds to a plurality of images. Upon tilting the device at different viewing angle, the array of lenses presents images sequentially. In some examples, individual ones of the segments can comprise specular reflecting, transparent, diffusely reflecting, and/or diffusely transmissive features. In some examples, individual ones of the segments can comprise transparent and non-transparent regions. The images can produce one or more optical effects.

An optical device includes an array of lenses and a plurality of segments disposed under the array of lenses. The plurality of segments corresponds to a plurality of images. Upon tilting the device at different viewing angle, the array of lenses presents images sequentially. In some examples, individual ones of the segments can comprise specular reflecting, transparent, diffusely reflecting, and/or diffusely transmissive features. In some examples, individual ones of the segments can comprise transparent and non-transparent regions. The images can produce one or more optical effects.