Millimeter-wave video rate imagers

The author will describe millimeter wave focal plane array (FPA) imagers developed primarily for concealed weapons detection (CWD) and through wall surveillance (TWS) applications. Both passive (radiometric) and active (radar) imagers will be described. The technology employed in these cameras is ideally suited to a wide range of other applications as well. Traditionally, passive millimeter wave images have been generated using scanned sensors of various types ranging from single elements to line arrays. A line scanner using FPA technology is being developed at Millimetrix for CWD and other applications. Scanning imagers, however, cannot meet the frame rate and sensitivity requirements for some applications. Certain CWD applications, in particular, require a passive, video rate (30 fps) imager which we are also developing using a patented focal plane array technology we call Millivision((R)*). Similarly, TWS applications demand an active, video rate imager which shares much of the same Millivision((R)) FPA technology. Customers always need more resolution, more sensitivity, and a wider field-of-view all in the smallest possible package and at the lowest cost. To meet these difficult requirements, the Millivision((R)) video rate imagers operate near 94 GHz and employ active optics and filled focal plane arrays, both of which will be briefly described. The optimally (EM) filled FPA is small angle scanned (dithered) electronically relative to the scene in a 4 x 4 matrix to achieve a 2 x 2 oversampling of the image. A multiplicative ''super resolution'' algorithm is then used to digitally enhance the spatial frequency resolution of the resulting image by a factor of approximately 2.