MilliCam: Hand-held Millimeter-Wave Imaging

We present MilliCam, a system that captures the shape of small metallic objects, such as a gun, through obstructions, like clothing. MilliCam builds on the millimeter-wave (mmWave) imaging systems, which are widely used today in airport security checkpoints. Existing systems achieve high-resolution using a Synthetic Aperture Radar (SAR) principle, but require bulky motion controllers to position the mmWave device precisely. In contrast, MilliCam emulates the SAR principle by pure hand-swiping. However, alias-free, high-resolution imaging requires a linear, error-free hand-swiping motion. Furthermore, image focusing on an object of interest requires steering perfectly-shaped beam over the target-scene; but it is unavailable in off-the-shelf devices. We design a set of algorithms to enable high-quality handheld imaging: compensating for the errors in hand-swipe motion; and focusing the target-scene digitally without beam-steer. We have prototyped MilliCam on a 60 GHz testbed. Our experiments demonstrate that MilliCam can effectively combat motion errors and focus on the object in target-scene.