The freeform millimeter-wave imaging invention is a general imaging method that allows rapid 3-D microwave and mm-wave images to be formed from data collected from antenna arrays scanned by hand or in a loosely controlled manner as an alternative to the use of mechanical scanners and strict motion control. This freeform radar imaging method requires precise tracking of the position and orientation of the radar imaging array as it is swept across an aperture. Alternatively, the target can be tracked moving past fixed arrays. This tracking is accomplished using inexpensive optical camera-based motion capture sensors mounted in the stationary scene, or on the imaging array. Calculated position and orientation data are then be used with new advanced imaging algorithms to form high-resolution 3-D microwave or mm-wave images of the scene. Additionally, multiple images can be integrated into larger composite images of the scene using the measured position information. A wide variety of scenarios are applicable to the freeform imaging method, including moving array scenarios such as arrays scanned by hand and arrays mounted on vehicles, as well as moving-target scenarios in which the imaging target moves past fixed arrays. Applications for this technology include in-wall imaging for technical security countermeasures (TSCM), concealed weapon detection on personnel (secondary hand-wand screening or walk-through portals at aviation security checkpoints), IED detection, and others.