Compared to Millimeter waves THz frequencies can provide an almost magnitude higher resolution, which enables
detection of small threats at larger distances. Here we present an active THz standoff imaging system based on
commercially available BWO sources and a thermal detector. At a excitation frequency of 720GHz an almost
diffraction limited resolution was achieved of about 1.6mm at 1.2m distance to the target. With signal to noise ratio of
35dB detection of metal and ceramic weapons covered by different clothing is demonstrated. A detailed system analysis
is done, which led to limiting factors of the proposed system.