We discuss methods of improving the quality and resolution of passive milli
meter-wave images, particularly those obtained using the Defense Evaluation
and Research Agency (DERA) MITRE imager and the more recent MERIT imager.
This later real time imager consists of some novel optics followed by a con
ical scanner in the form of a disk rotating about an axis through its cente
r and tilted with respect to its normal. A horizontal array of receivers is
scanned such that each receiver performs a conical scan pattern in the sce
ne. The resulting image, which has a 40x20 deg field of view, consists of a
series of circles whose centers are uniformly displaced horizontally. Each
receiver is calibrated initially using a two point correction but then dri
fts in time and a scene based correction is applied. Following preprocessin
g the images are superresolved using nonlinear restoration techniques. Two
such techniques are described. The first is an error energy reduction algor
ithm that uses background subtraction and the second assumes a Lorentzian d
istribution of gradients within an image. Both are able to superresolve wit
hout significantly enhancing the noise. These various processes are describ
ed and images presented. (C) 2001 Society of Photo-Optical Instrumentation
Engineers.