Detection of hidden metallic targets by radiometric system and low aberration lens design

The millimeter-wave radiometric detection and imaging system currently find wide application in diverse security setups intended for disclosure of dangerous objects concealed under persons' clothing. Electromagnetic waves of this range are quite safe at modest intensities, penetrate many common barrier materials and short enough to give adequate spatial resolution for imaging of concealed objects. Among the incontestable advantages of passive radiometric systems are absolute harmlessness and ability of operation without revealing themselves. However a passive imaging system in principle suffers from lack of sensitivity for detection of weapons covered with several layers of textiles.