Three-dimensional millimeter-wave imaging for concealed weapon detection

Millimeter-wave imaging techniques and systems have been developed at the P acific Northwest National Laboratory (PNNL), Richland, WA, for the detectio n of concealed weapons and contraband at airports and other secure location s. These techniques were derived from microwave holography techniques that utilize phase and amplitude information recorded over a two-dimensional ape rture to reconstruct a focused image of the target. Millimeter-wave imaging is well suited for the detection of concealed weapons or other contraband carried on personnel since millimeter-waves are nonionizing, readily penetr ate common clothing material, and are reflected from the human body and any concealed items. In this paper, a wide-bandwidth three-dimensional hologra phic microwave imaging technique is described. Practical weapon detection s ystems for airport or other high-throughput applications require high-speed scanning on the order of 3 to 10 s. To achieve this goal, a prototype imag ing system utilizing a 27-33 GHz linear sequentially switched array and a h igh-speed linear scanner has been developed and tested. This system is desc ribed in detail along with numerous imaging results.