Abstract: A CCTV surveillance system is provided with an optical device (60) for providing different images through different areas of the CCTV camera lens (14) controllably at different times. The different images can be used to improve the resolution of the images obtained, or to increase the field of view, by sacrificing the image refresh rate.

Abstract: Apparatus for the identification of articles (5) endowed with device for changing the polarization properties of the radiation, comprising a source (1) of non-randomly polarized microwave radiation, and a detector (3) for detecting the change in polarization properties of the radiation. The microwave radiation may have a first plane of polarization and, in use, the device for changing the plane of polarization properties of radiation may change the first plane of polarization to a second plane of polarization. The detector (3) for detecting the change in polarization properties of radiation may comprise a receiving antenna (4c) connected to suitable microwave detector (3), where the receiving antenna (4c) is arranged to favour reception of radiation having the second plane of polarization. For example, the transmitting (4b) and receiving (4c) antennas may be waveguide antennas.

Abstract: An optical filtering device incorporates first and second prisms, the latter prism counteracting the angular dispersion of the former prism. A spatial light modulator provides a positionally variable optical stop located to block radiation within a wavelength interval and received from a location within a scene. Unobscured radiation from that and other scene locations passes to a camera, which produces an image on a display. Opaque pixels in the stop are positioned to block unwanted light sources. The invention attenuates potentially dazzling monochromatic radiation while retaining radiation at other wavelengths for imaging purposes.

Abstract: A method of authenticating watermarked paper comprises the steps of transtly heating a first surface (50) of a watermarked sheet of paper (40) using a hot air source (22); forming a thermal image of the watermark (42) using a thermal imager (30); and analyzing the thermal image to determine whether or not the watermarked paper is authentic. The evolution of the thermal image with time is characteristic of the watermark and is dependent on the local thermal mass of the paper in the region of the watermark.