Millimetre-wave radiometric imaging for concealed contraband detection on personnel

摘要

Millimetre-wave (MMW) radiometric imaging has established itself in a wide range of military and civil applications, but the fact that the radiometric temperature contrast between different objects indoors is low restricts the commercial application of MMW radiometric imaging to some extent. Based on the particular analysis of MMW radiometric imaging model suitable for concealed contraband detection on personnel, the method of adopting MMW noise source to illuminate the scene of being imaged to improve the radiometric temperature contrast, just like the flash lamp of camera, is proposed in this study. In addition, the choice of both the ways of illumination and the excess noise ratio (ENR) of the noise source is analysed. Then the image degradation model is discussed and the projection onto the convex sets (POCS) algorithm for MMW radiometric image super-resolution restoration is depicted in detail. In addition, a series of experiments are carried out both indoors and outdoors, with the dual-channel radiometric imaging system that has been implemented at W-band with the mode of two-dimensional planar scanning. The experimental results are presented and analysed to validate the significance of the imaging model and it is indicated that the radiometric imaging system is capable of detecting metal objects hidden underneath clothing, and the method of adopting noise illumination can improve the quality of radiometric images.