Millimeter-wave imaging system

Abstract

An improved millimeter imaging system is disclosed which generates high quality images from the field of view. Such system can be employed in a variety of application ranging from providing an aircraft pilot with an image of the landing field in fog, rain, snow, blowing sand, etc. to detection of concealed non-metallic contraband. The system elements, in which different elements detect signals from different portions of the field of view, so that images of the entire field of view are generated in real time, without using electrical or mechanical scanning. The outputs of the array elements are mapped to display pixels. The resolution of such images has previously been limited by the response characteristics of array elements to energy from only a portion of the corresponding field of view. One aspect of the invention is a significant improvement in image resolution. In the preferred embodiment, a radiation redirecting element redirects incident radiation toward the centerline of each element, so that the elements are uniformly exposed to different portions of the corresponding field of view. As a result, a plurality of display pixels corresponding to different portion of the field of view of each array element are generated, thus significantly increasing display resolution. Another aspect of the invention relates to a novel way of periodically illuminating the imaging array with background noise signal, which is then subtracted from the field of view signal, in order to reduce signal-to-noise ratio. In the preferred embodiment, an optical arrangement of a reflector/load element and a rotating polarization rotation element supplies background signal synchronously with generation of the field of view images, without utilizing electronic switching devices or special 'noise' power illuminators.