Qinetiq Limited

Neil Anthony Salmon

Peter Russell Coward

Tej Paul Kaushal

Stephen David Hayward

Sean Price

A passive detection device is disclosed comprising a plurality of antennas, receivers, and a digital beamformer, wherein the antennas and receivers are adapted to receive radiation of millimeter wavelengths from a near field region, to process and digitize it. The beamformer is adapted to process the received information and to generate static image information relating to the region. An indication means is provided to indicate the presence of objects of interest. The beamformer is preferentially adapted to generate information simultaneously in a plurality of planes at different distances from the apparatus. The indication means may comprise an array of pixels along the length of the apparatus to display image information, and may use the multi-planar information to construct images of the region comprising data from a plurality of planes. The invention has utility in security scanning applications such as at airports or other locations where security detection equipment is employed.

Passive detection apparatus

A millimeter wave imaging apparatus and method capable of identifying the presence of relatively thin dielectric materials is disclosed. The method involves taking a plurality of millimeter wave images of a scene at different frequencies and analyzing the images at different frequencies to look for frequency dependent effects in the scene. Relatively thin dielectric materials can lead to interference effects which can be detected. In one embodiment the imaging apparatus comprises a millimeter wave imager () connected to a processor () and at least one variable frequency illumination source (). The or each illumination source sweeps the illumination frequency across a reasonably wide bandwidth and the imager captures radiation returned from the scene at a number of different illuminating frequencies.

Imaging apparatus and method

An improved millimeter wave illumination system includes at least one primary source of millimeter wave radiation, a reflecting surface and a baffle comprising a plurality of exit apertures arranged such that at least some of the radiation from the source is reflected from the reflective surface before proceeding to the baffle, characterized in that means are incorporated for generating a plurality of radiation field states within a pre-determined time interval. The baffle, source and reflector are preferably packaged into a container with the exit apertures providing an illumination output. The generation of the plurality of radiation field states provides an illumination at the illuminator output that is less spatially variable when integrated over the pre-determined time interval. Embodiments of the invention show means for generating the plurality of radiation field states including relative movement of the reflective surface, variable positioning of the source with respect to the reflective surface, and including multiple sources within a single system.

Millimetre and sub-millimetre wave illumination system

Radiometers detect radio wavelength electromagnetic radiation and typically have an antenna (), an amplifier () and a detector (). All three of these components have response characteristics that may be dependent on temperature, and in the case of systems using radiometer arrays dependent upon temperatures throughout the system. Different temperatures across a multi-channel antenna and differential channel temperature response can result in poor image quality from imaging radiometers. Resolution of a linear array of detector horns is limited by the size of the horns. An imaging radiometer () uses a focusing polariser (), a quarter wave plate (), a rotating inclined disk (), and a detector feed array () to perform a conical scan, and compensates for variation in operating temperature of a radiometer using one or more of a variety of techniques including calibrating channels relative to each other, calibrating channels using reference temperatures in-situo, and calibrating channels using temperature response predictions stored in the radiometer signal processor (). Aspects of the invention also optimise image resolution, image quality and allow calibration.

Radiometers

An illumination source of predominantly non-directional and incoherent millimeter-wave radiation for illuminating an area for passive millimeter-wave imaging comprises a container with at least a partly reflective internal surface and a plurality of exit apertures and a primary source of millimeter-wave radiation for emitting millimeter-wave radiation into the container. The primary source and the container are arranged so that a proportion of the millimeter-wave radiation emitted by the source undergoes reflection within the container before being emitted through the apertures, such that the different paths lengths are at least equal to the coherence length of the radiation. This is facilitated if the bandwidth of the radiation is preferably at least 1 GHz. The container may be a box in which a waveguide is used to couple radiation from the primary source into the box. Alternatively, the container may be formed from a mesh and the plurality of holes is provided by the holes in the mesh.

Millimetre-wave illumination source

Radiometers detect radio wavelength electromagnetic radiation and typically have an antenna (), an amplifier () and a detector (). All three of these components have response characteristics that may be dependent on temperature, and in the case of systems using radiometer arrays dependent upon temperatures throughout the system. Different temperatures across a multi-channel antenna and differential channel temperature response can result in poor image quality from imaging radiometers. Resolution of a linear array of detector horns is limited by the size of the horns. An imaging radiometer () uses a focussing polariser (), a quarter wave plate (), a rotating inclined disk (), and a detector feed array () to perform a conical scan, and compensates for variations in operating temperature of a radiometer using one or more of a variety of techniques including calibrating channels relative to each other, calibrating channels using reference temperatures in situo, and calibrating channels using temperature response predictions stored in the radiometer signal processor (). Aspects of the invention also optimise image resolution, image quality and allow calibration.

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Malvern, United Kingdom

Neil Anthony Salmon