The research team, led by Gerald Buller, a professor at Heriot-Watt University in Edinburgh, Scotland, describes a ToF imaging system that can gather high-resolution, 3D information about objects that are typically very difficult to image, from up to a kilometer away.
The system can resolve depth on the millimeter scale over long distances using a detector that can “count” individual photons.
The scanner is particularly good at identifying objects hidden behind clutter, such as foliage. However, it cannot render human faces, instead drawing them as dark, featureless areas. This is because at the long wavelength used by the system, human skin does not reflect back a large enough number of photons to obtain a depth measurement. However, the reflectivity of skin can change under different circumstances. "Some reports indicate that humans under duress—for example, with perspiring skin—will have significantly greater return signals,” and thus should produce better images, McCarthy says.
See the full story here: http://www.rdmag.com/news/2013/04/camera-system-creates-high-resolution-3d-images-kilometer-away