Abstract: A retro-reflective identification tag capable of modulating an optical signal whereby to support bi-directional communication with an associated remote optical interrogation device. The tag comprises a MOEMS modulating layer over a retro-reflective substrate, giving the tag a wide angle of effective operation. The tag modulator may optionally be switched on only responsive to detection of a precursor beam from the interrogation system in order to save power. The interrogation device may make use of multiple optical wavelengths for communicating with the tag.

Abstract: This invention relates to coded aperture imaging apparatus and methods. In one aspect a coded aperture imager has at least one detector array and a reconfigurable coded aperture mask means. A reconfigurable coded aperture mask means can display various coded aperture masks to provide imaging across different fields of view and/or with different resolution without requiring any moving parts or bulky optical components. More than one detector array can be used to provide large area imaging without requiring seamless tiling and this represents another aspect of the invention. The present invention also relates to the use of coded aperture imaging in the visible, ultraviolet or infrared wavebands. The use of coded aperture imaging for imaging through a curved optical element is taught as the image decoding can automatically remove any aberrations introduced by the curved element.

Abstract: This invention relates to coded aperture imaging apparatus and methods. In one aspect a coded aperture imager has at least one detector array and a reconfigurable coded aperture mask means. A reconfigurable coded aperture mask means can display various coded aperture masks to provide imaging across different fields of view and/or with different resolution without requiring any moving parts or bulky optical components. More than one detector array can be used to provide large area imaging without requiring seamless tiling and this represents another aspect of the invention. The present invention also relates to the use of coded aperture imaging in the visible, ultraviolet or infrared wavebands. The use of coded aperture imaging for imaging through a curved optical element is taught as the image decoding can automatically remove any aberrations introduced by the curved element.

Abstract: Optical filters (1) designed in pairs, which are essentially colourless in their individual general appearance designed to take on a strong coloration when viewed together in transmission, said filters being particularly, useful for identification of counterfeit articles. The optical filters (1) utilize resonantly-coupled Fabry-Perot etalons of, an asymmetric design. The filters (1) are configured such that one of the Fabry-Perot cavities within the filter incorporates an additional multiple quarter wave thickness layer (20), said additional layer having a contrasting refractive index to that of the cavity spacer.

Abstract: A tunable filter in particular for use in the visible or near infrared wavelength region, comprising a nano dispersed composite material contained within a resonant cavity structure comprising dielectric mirrors (15, 16), where the material is polarizable by means of an applied electric field. In particular, the polarizable material may be a nano phase polymer dispersed liquid crystal (PDLC) material where the diameter of liquid crystal droplets (2) within the material (3) is less than 0.1 &mgr;m, and for use in the visible wavelength region is typically between 10 nm and 50 nm. The filter also comprises structure for applying a variable electric field across the faces of the material. The transmission-wavelength characteristic of the filter is such that maxima and minima are shifted in wavelength by varying the electric field.

Abstract: Infrared transmitting optical components having a wide variety of substrates (e.g. ZnS, ZnSe, Ge, Si, SiO.sub.2) are disclosed all with an optical coating of boron phosphide (BP). The boron phosphide may be a single layer coating or one layer of a multilayer coating in which case it is preferably the penultimate layer. Coated components are provided which are very low in absorption, which are operable at high temperatures with minimal transmission loss, and which are transmitting in two IR wavebands. The boron phosphide layer is deposited by plasma-assisted chemical vapor deposition at a temperature in the range 300.degree.-500.degree. C. preferably using feedstock gases which are hydrogen-fee. Boron phosphide coatings of up to 40 .mu.m in thickness have been achieved.

Abstract: A coating having low absorbance of laser energy is provided on optical components substrates by molecular beam epitaxial growth techniques.The growth conditions prevent contamination of substrate and coating with water and carbonaceous gases. The method of coating has the following steps:arranging the substrate in a vacuum chamber,cleaning the component while holding the pressure below 10.sup.-4 millibar and the partial pressure of H.sub.2 O and carbonaceous gases below 4.10.sup.-9 mb,applying at least one layer of a coating material to the substrate, while holding the pressure below 10.sup.-8 mb and the partial pressure of H.sub.2 O and carbonaceous gases below 4.10.sup.-9 mb.The optical component may be lenses, windows, or reflectors e.g. of ZnSe, GaAs, glass, etc. The coating may be of selenide e.g. ZnSe, etc.