Operational issues for passive millimetre wave imaging systems

Passive millimetre wave (mm-wave) imaging systems have attracted an increasing interest over the past years due to their superior poor weather performance compared with visible and infrared (IR) systems. In the UK the Defence Evaluation and Research Agency Malvern developed its first mm-wave radiometers in the late 1950s. These systems were bulky and had poor spatial resolution and low thermal sensitivity, but the considerable advances in semiconductor solid state devices have allowed the size and weight of imagers to be reduced. Advantage can also be taken of sophisticated on-line signal processing and of complex theoretical modelling and analysis. This paper examines the merits of the different operating frequencies in terms of atmospheric transmission vs. resolution and also discusses issues such as image processing. High quality images are presented to demonstrate the potential of this emerging technology.