1. An apparatus for detecting concealed weapons disposed on a subject's body, the apparatus comprising: a millimeter wave camera having a field of view and operative to detect millimeter wave radiation within said field of view and further operative to provide a sequence of images about the periphery of the body; a image processing system coupled to the millimeter wave camera and operative to: transform said sequence of images of the periphery of the body into a plurality of spatio temporal images formed by assembling together, for each specific row number, all those image rows with the specific row number in successive millimeter wave images in the original sequence, said plurality of spatio temporal images corresponding to a plurality of row evolution images; classify each of said plurality of row evolution image according to its location within the body's image; identify valley edges in each of said plurality of row evolution images; calculate the strength of said identified valley edges; identify ridges in each of said plurality of row evolution images calculate the strength of the identified ridges; and identify an object of a class of preselected objects as a function of the identified and calculated strength of valley edges and the identified and calculated strength of ridges in each of said plurality of row evolution image; and said image processing operative to provide an output indicative of an identified object.