Qinetiq Limited

British Technology Group Limited

John Roy Sambles

Christopher Robert Lawrence

Peter Vukusic

Ian Richard Hooper

Alastair Paul Hibbins

Ewan David Finlayson

Andrew Shaun Treen

William Leslie Barnes

Peter Allen Hobson

Matthew J Lockyear

Stephen Wedge

Alistair P Hibbins

Paul A Gass

Guy P Bryan-Brown

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&#xb0; 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.

Optical identification system

A radiation absorber comprising multiple layers has a conducting base layer, and at least first and second further layers, each separated by a dielectric material, the first and second layers having patches thereon of highly conducting material, and defining resonant cavities in cooperation with the dielectric material, wherein the resonant cavities formed on adjacent layers differ in frequency. Characteristics of the patch, such as size or shape may vary on each layer to provide different resonant frequencies, and/or dielectric or magnetic properties of the dielectric material, and/or separation distance of the patches may be varied. In some embodiments, complex dielectrics may have their loss factors adapted to tune a resonant frequency, or to adapt its resonant bandwidth.

Electromagnetic radiation absorber

This invention relates to optoelectronic devices of improved efficiency. In particular it relates to light emitting diodes, photodiodes and photovoltaics. By careful design of periodic microstructures, e.g. gratings, associated with such devices more efficient light generation or detection is achieved.

Optoelectronic device with periodic grating microstructure

An iridescent material comprises a diffraction grating incorporating a plurality of sheets () of a first substantially transparent material in parallel alignment and spaced away apart by quantities of a second substantially transparent material (), the second material having a refractive index significantly lower than the refractive index of the first material, the plates being tilted at an angle &#x3b8; to an axis X and the grating having a period d(X) in the direction of axis X, the angle &#x3b8; and period d being such that a second diffraction grating is provided along an axis Z, perpendicular to axis X, the second diffraction grating having a period d(Z) and consisting of ten periods or less and whereby, the diffraction conditions of the grating can be simultaneously fulfilled by electromagentic radiation of a range of wavelength thereby causing iridescence. Materials according to the invention have applications in inter alia document security, anti-counterfeiting measures, artwork, gift wrapping paper and cards and clothing design.

Iridescent materials and devices

An electromagnetic radiation absorber for absorbing radiation in the wavelength range &#x3bb;to &#x3bb;. The absorber has a conductor layer in contact with a dielectric layer. The conductor layer carries a plurality of apertures of sub-wavelength dimension and the thickness of the absorber is less than &#x3bb;/4n, where n is the refractive index of the dielectric. The dielectric layer may be sandwiched between two conductor layers, one of which has the structure described above. The invention is also directed to various articles comprising such an absorber.

A multilayer surface comprising at least two layers, said layers having different refractive indexes such that selective wavelengths/colours are transmitted and or reflected. The layers are preferably laid onto a transparent substrate. The surface can be used as an anti-counterfeit device. A method of determining whether an article is counterfeit comprising: providing such a surface; determining its transmission/absorption characteristics of particular colour(s); matching these up with the expected characteristics to determine whether the surface is counterfeit. This may comprise observing the reflected or transmitted colour at two different angles of incidence or detecting changes in the polarisation state of transmitted light.

Specialised surface

A grating comprising a plurality of substantially parallel members having a conducting surface of depth L, separated by a dielectric layer gap, and having of pitch &lgr; and where L>16&lgr; . The members are preferably metallic or comprise metallic foil covered plastic. The gap may be filled wholly or partially with dielectric material including liquid crystal whose refractive index can be controlled by suitable application of voltage across the gap.

Grating

A radiation absorber comprising a substrate having free charges capable of being driven to form resonance charge density oscillators and a dielectric layer coated onto said surface wherein the dielectric layer has a textured/patterned surface. The substrate is preferably metallic and the dielectric layer is waveform.

Low frequency electromagnetic absorption surface

A surface capable of supporting surface charge oscillations and exhibiting a profiled grating, said profile comprising at least two superposed periodic profiles. The surface has applications as radar absorber and authentication devices. Also disclosed is a method of detecting the authenticity of an object comprising providing a surface as described above claim adjacent to or on the object, illuminating said surface with radiation from at least one angle and determining the reflectivity characteristics and comparing this with reflectivity characteristics of a reference surface.

Textured surface

A signature recognition system for identifying an article with a distinctive diffraction element (or elements) and verifying the presence of that element or elements comprising: an article with one or more diffraction gratings impressed thereon, the grating(s) exhibiting periodic wave surface profiles having a depth-to-pitch ratio &dgr; of between 0.1 and 0.5, a source of polarized electromagnetic radiation of wavelength &lgr; such that the pitch G of the periodic wave surface profile of the grating(s) is comparable to an integer multiple n of that wavelength, a device for directing the source of polarized electromagnetic radiation to the surface of the grating(s) at a plane of incidence substantially normal to the plane of the surface of the diffraction grating and at an angle of approximately 45&deg; azimuth to the alignment of the grooves on the surface, and a device for detecting radiation reflected from the grating(s) surface which is oppositely polarized to the incident radiation.

Signature mark recognition systems

An optical sensing device that incorporates either a surface plasmon-polariton or guided mode apparatus for converting radiation between s and p modes together with a sensor for detecting a maximum in conversion between the s and p modes.

Optical sensor for orthogonal radiation modes

Optical measuring apparatus including an acousto-optical device (3) which molulates either the angle or the wavelength of a light beam (1) at a frequency determined by a signal generator (15). A detector (13) detects the modulated beam after interrogation of a sample under test; and a lock-in amplifier (14) is connected to the signal generator (15) and to the detector (13) to determine the differential of an optical property of the sample under test.

Growing community of inventors

Crediton, United Kingdom

John Roy Sambles