Abstract: 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 (2) connected to a processor (16) and at least one variable frequency illumination source (22a . . . d, 24a . . . d). 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.

Abstract: 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.

Abstract: A radiation detection apparatus comprises a radiation detector and a lens arrangement. The lens arrangement comprises a polarising element and an optical corrector. The optical corrector is preferably located between the polarising element and the radiation detector and has at least one surface designed to correct optical aberrations present in the lens arrangement. The optical corrector may be arranged to provide a mechanical support to the polarising element. The optical corrector is arranged to increase a diffraction limited acceptance angle of the apparatus.

Abstract: A scanning imaging apparatus comprises an optical system including a curved polariser/reflector, a rotatable reflector, a polarisation twisting plate, and a receiver array, wherein a convex reflective element is incorporated in the optical path that acts as a sub-reflector that increases the optical system focal length. It has been found that an increase to the optical focal length in this manner gives a greater 3 dB spot size at the image plane, thus easing design constraints on the receiver array packing density, whilst maintaining a given spatial sampling interval. An additional benefit is that radiation from differing scan locations diverges as it approaches the image plane, which provides more volume in which to position receiver electronics. Focussing of the optical system may be achieved by movement of the sub-reflector.

Abstract: A system for imaging the contents of containers includes an imager arranged to receive millimetre wave radiation from a reception volume through a receive antenna wherein, in use, the container is moving relative to the receive antenna, the reception volume is positioned such that the relative movement causes the reception volume to move through the container; data from the antenna is recorded as the reception volume moves through the container, and an image of the contents of the container is built up from the recorded data. The system is particularly suitable for imaging containers mounted on vehicles. The imager may advantageously be mounted in a portal, allowing convenient and controllable relative positioning of the container, and allowing the relative speed to be controlled or measured easily. The invention allows 3D or pseudo 3D images to be produced to aid identification of container contents. The invention also includes a method for imaging.

Abstract: A system for imaging the contents of containers includes an imager arranged to receive millimetre wave radiation from a reception volume through a receive antenna wherein, in use, the container is moving relative to the receive antenna, the reception volume is positioned such that the relative movement causes the reception volume to move through the container; data from the antenna is recorded as the reception volume moves through the container, and an image of the contents of the container is built up from the recorded data. The system is particularly suitable for imaging containers mounted on vehicles. The imager may advantageously be mounted in a portal, allowing convenient and controllable relative positioning of the container, and allowing the relative speed to be controlled or measured easily. The invention allows 3D or pseudo 3D images to be produced to aid identification of container contents. The invention also includes a method for imaging.