Rapid passive MMW security screening portal

Trex Enterprises Corporation has developed a full body passive millimeter-wave security screening imager. The system images naturally occurring W-band blackbody radiation, which penetrates most types of clothing. When operated indoors, the primary mechanism for image formation is the contrast between body heat radiation and the room temperature radiation emitted or reflected by concealed objects that are opaque at millimeter-wave wavelengths. Trex Enterprises has previously demonstrated that an imager noise level of 0.25 to 0.5 K is necessary to detect and image small concealed threats indoors. Achieving this noise level in a head-to-toe image required image collection times of 24 seconds using the previous imager design. This paper first discusses the measurement of the noise temperature of the MMW detectors employed. The paper then explores reducing the image collection times through a new front-end amplifier design and the addition of more imaging units. By changing the orientation and direction of travel of the imaging units, the new design is able to employ more detectors and collect imagery from a subject's front and sides. The combination of lower noise amplifiers and a new scanning architecture results in an imager appropriate for high throughput security screening scenarios. Imagery from the new configuration is also presented.