A security device, including at least first and second embossed, reflective metal diffraction gratings in respective regions: wherein the first diffraction grating exhibits, in incident white light, a zero-order output over a first area of substantially uniform grating period, wherein the zero-order output of the first diffraction grating comprises different coloured first and second sub-outputs for respective first and second polarisations parallel and perpendicular to the first diffraction grating; wherein the second diffraction grating exhibits, in incident white light, a zero-order output over a second area of substantially uniform grating period; wherein the zero-order output of the second diffraction grating comprises third and fourth sub-outputs for respective first and second polarisations parallel and perpendicular to the second diffraction grating; and wherein the first and second diffraction gratings exhibit, for incident white light, substantially the same first order diffraction efficiency over the first and second areas.

A security device, including at least first and second embossed, reflective metal diffraction gratings in respective regions: wherein the first diffraction grating exhibits, in incident white light, a zero-order output over a first area of substantially uniform grating period, wherein the zero-order output of the first diffraction grating comprises different coloured first and second sub-outputs for respective first and second polarisations parallel and perpendicular to the first diffraction grating; wherein the second diffraction grating exhibits, in incident white light, a zero-order output over a second area of substantially uniform grating period; wherein the zero-order output of the second diffraction grating comprises third and fourth sub-outputs for respective first and second polarisations parallel and perpendicular to the second diffraction grating; and wherein the first and second diffraction gratings exhibit, for incident white light, substantially the same first order diffraction efficiency over the first and second areas.

An identification medium includes a first layer, and a second layer disposed thereon in a manner of overlapping with the first layer. The first layer is capable of reflecting one of clockwise circular polarized light and counterclockwise circular polarized light and allowing to pass therethrough the remaining circular polarized light. The second layer is capable of reflecting at least a portion of circular polarized light having the same rotation direction as that of the circular polarized light that the first layer reflects, and allowing to pass therethrough circular polarized light having an opposite rotation direction to that of the circular polarized light reflected by the first layer. A ratio (Ssf.sub.2/S.sub.2) of Ssf.sub.2 defined by the following formula (2) relative to S.sub.2 defined by the following formula (1) is more than 0.7: $\begin{array}{cc}{S}_2={?}_{400}^{780}{\left\{\left({\mathrm{Rf}}_2\left(?\right)\right)?\left({\mathrm{Rf}}_2\left(?\right)\right)\right\}}^{.Math.}\left(1/2\right)?d?& \left(1\right)\end{array}$ $\begin{array}{c}{\mathrm{Ssf}}_2={?}_{400}^{780}{\{(}^{}\end{array}$

An identification medium includes a first layer, and a second layer disposed thereon in a manner of overlapping with the first layer. The first layer is capable of reflecting one of clockwise circular polarized light and counterclockwise circular polarized light and allowing to pass therethrough the remaining circular polarized light. The second layer is capable of reflecting at least a portion of circular polarized light having the same rotation direction as that of the circular polarized light that the first layer reflects, and allowing to pass therethrough circular polarized light having an opposite rotation direction to that of the circular polarized light reflected by the first layer. A ratio (Ssf.sub.2/S.sub.2) of Ssf.sub.2 defined by the following formula (2) relative to S.sub.2 defined by the following formula (1) is more than 0.7: $\begin{array}{cc}{S}_2={?}_{400}^{780}{\left\{\left({\mathrm{Rf}}_2\left(?\right)\right)?\left({\mathrm{Rf}}_2\left(?\right)\right)\right\}}^{.Math.}\left(1/2\right)?d?& \left(1\right)\end{array}$ $\begin{array}{c}{\mathrm{Ssf}}_2={?}_{400}^{780}{\{(}^{}\end{array}$

A method and apparatus for establishing product items unique identity for purpose of anti-counterfeiting or anti-theft is disclosed. It employs a fluorescent taggant embedded in product item, template, digitally based Encoder and Decoder. The taggant comprising plurality of fluorescent entities which in turn may comprise such distinct geometric and spectral optical characteristics-attributes as relative locations, emission/absorption spectra, polarization degrees and post luminanc delay and duration times. Such uniqueness is determined by the presence of a combination of a wide variety of fluorescent materials used during the application. The set of fluorescent entities are result of a random process and form a product item's fingerprint. The said template is a particular digitized representation of a taggant. The Encoder may comprise a camera, LED array based activator, configured to follow a particular illumination sequence and computation unit. The said camera further comprises at least two polarizing filters and template generator and the respective controllers. The Decoder may comprise at least one camera identical to the of the Encoder, at least one template/taggant readers and a computation unit, which may be shared with the said Encoder. Product item identity is based on the fluorescent taggant uniqueness, with the later embedded into the product in a non separable way. After the extracted attribute values assiciated with the taggant, are digitized. Digitazing comprises mixing with chaff (spurious) patterns of the same format, error correction, transformation in a non invertible and compression and encryption. This forms a template, embedded in the product in a readable form. The decoding comprises feature extraction of taggant, reading template and decrypting, its content, error correction, decompression. Then the extracted and the decoding results are cross-matched in order to identify the product item. Irreproducibility of a plurality of fluorescent entities and high degree of security of its digital representation due to encryption, high variability of LED patterns and non-invertible transformation is a basis of a chaosmetric anti-counterfeiting solution disclosed in the present invention.

A method and apparatus for establishing product items unique identity for purpose of anti-counterfeiting or anti-theft is disclosed. It employs a fluorescent taggant embedded in product item, template, digitally based Encoder and Decoder. The taggant comprising plurality of fluorescent entities which in turn may comprise such distinct geometric and spectral optical characteristics-attributes as relative locations, emission/absorption spectra, polarization degrees and post luminanc delay and duration times. Such uniqueness is determined by the presence of a combination of a wide variety of fluorescent materials used during the application. The set of fluorescent entities are result of a random process and form a product item's fingerprint. The said template is a particular digitized representation of a taggant. The Encoder may comprise a camera, LED array based activator, configured to follow a particular illumination sequence and computation unit. The said camera further comprises at least two polarizing filters and template generator and the respective controllers. The Decoder may comprise at least one camera identical to the of the Encoder, at least one template/taggant readers and a computation unit, which may be shared with the said Encoder. Product item identity is based on the fluorescent taggant uniqueness, with the later embedded into the product in a non separable way. After the extracted attribute values assiciated with the taggant, are digitized. Digitazing comprises mixing with chaff (spurious) patterns of the same format, error correction, transformation in a non invertible and compression and encryption. This forms a template, embedded in the product in a readable form. The decoding comprises feature extraction of taggant, reading template and decrypting, its content, error correction, decompression. Then the extracted and the decoding results are cross-matched in order to identify the product item. Irreproducibility of a plurality of fluorescent entities and high degree of security of its digital representation due to encryption, high variability of LED patterns and non-invertible transformation is a basis of a chaosmetric anti-counterfeiting solution disclosed in the present invention.

A system and method of using the same, wherein the system comprises: an optical surface having a diffractive image generating structure disposed thereon, the diffractive image generating structure itself comprising a layer of reflective material incorporating a plurality of grooved diffractive elements each having a periodic wave surface profile, the periodic wave surface profiles each having a groove alignment direction; a source of incident electromagnetic radiation arranged to illuminate the diffractive elements at an angle of incidence substantially normal to the plane of the surface of the diffractive elements; means for polarizing the radiation from the source, and means for polarizing radiation reflected from the diffractive elements; wherein the diffractive elements are configured such that, in use, polarization conversion of the incident radiation takes place, and wherein the diffractive elements are disposed in a two dimensional array of pixels to represent an image; and further wherein the means for polarizing is arranged to pass incident radiation having a polarization state of approximately 45 azimuth to the groove alignment direction, and is arranged to select a polarization, using the means for polarizing the radiation reflected from the diffractive elements, and to pass radiation of the selected polarization to a detection point.

A system and method of using the same, wherein the system comprises: an optical surface having a diffractive image generating structure disposed thereon, the diffractive image generating structure itself comprising a layer of reflective material incorporating a plurality of grooved diffractive elements each having a periodic wave surface profile, the periodic wave surface profiles each having a groove alignment direction; a source of incident electromagnetic radiation arranged to illuminate the diffractive elements at an angle of incidence substantially normal to the plane of the surface of the diffractive elements; means for polarizing the radiation from the source, and means for polarizing radiation reflected from the diffractive elements; wherein the diffractive elements are configured such that, in use, polarization conversion of the incident radiation takes place, and wherein the diffractive elements are disposed in a two dimensional array of pixels to represent an image; and further wherein the means for polarizing is arranged to pass incident radiation having a polarization state of approximately 45 azimuth to the groove alignment direction, and is arranged to select a polarization, using the means for polarizing the radiation reflected from the diffractive elements, and to pass radiation of the selected polarization to a detection point.

An anti-counterfeit medium, a method for manufacturing the same and a method for preventing counterfeiting are provided. The anti-counterfeit medium includes a retardation layer having birefringence and a reflection layer, and identification data is recorded in the anti-counterfeit medium. The identification data is divided into a plurality of partial images, and a plurality of transparent areas which correspond to the plurality of partial images are disposed adjacent to each other in the same plane so as to form the retardation layer, the plurality of transparent areas having optical axes which are oriented in different directions from each other in a rotation direction. The identification data includes biometric information.

An anti-counterfeit medium, a method for manufacturing the same and a method for preventing counterfeiting are provided. The anti-counterfeit medium includes a retardation layer having birefringence and a reflection layer, and identification data is recorded in the anti-counterfeit medium. The identification data is divided into a plurality of partial images, and a plurality of transparent areas which correspond to the plurality of partial images are disposed adjacent to each other in the same plane so as to form the retardation layer, the plurality of transparent areas having optical axes which are oriented in different directions from each other in a rotation direction. The identification data includes biometric information.