Detection of illegal passengers in lorries using a passive millimetre wave scanner

Transport operators to the UK have responsibility for ensuring that they do not transfer unauthorised people into Great Britain. A common way for people to try and enter the UK is by passage in the freight compartments of lorries. In Europe 90% of lorries have non-metallic sides which are transparent to millimetre wave (MMW) radiation. A 35 GHz linescan imaging system has been used to detect stowaways hidden in the rear of lorries. A video based sensor is used to provide vehicle speed information to the passive MMW linescan system, allowing a MMW image to be built up as the vehicle passes. Contrast is increased by the use of a large reflector panel on the opposite side of the vehicle to the sensor. This panel reflects the sky, which is cold millimetrically, through the lorry in the direction of the sensor. The linescan operation of the system does not require passing vehicles to stop, allowing all non-metallic sided vehicles to be scanned with minimal interference to flow patterns. The system has achieved considerable success since it entered operation, detecting several hundred stowaways per month.