RF-Capture works by sending out radio waves; when they strike an individual behind a wall, reflections come back to the device for analysis. RF-Capture measures the intensity of the return waves, among other variables, and then uses an algorithm to put together a rudimentary silhouette model of the person’s body type.
We present RF-Capture, a system that captures the human figure – i.e., a coarse skeleton – through a wall. RF-Capture tracks the 3D positions of a person’s limbs and body parts even when the person is fully occluded from its sensor, and does so without placing any markers on the subject’s body.
In designing RF-Capture, we built on recent advances in wireless research, which have shown that certain radio frequency (RF) signals can traverse walls and re-flect off the human body, allowing for the detection of human motion through walls. In contrast to these past systems which abstract the entire human body as a single point and find the overall location of that point through walls, we show how we can reconstruct various human body parts and stitch them together to capture the human figure.
We built a prototype of RF-Capture and tested it on 15 subjects. Our results show that the system can capture a representative human figure through walls and use it to distinguish between various users.
SF movie fans may recall the device from the 1997 film The Fifth Element; police used a hand-held device to see through doorways in to apartments.
Fans of sf literature have of course enjoyed various versions of this technology for many years. Consider the Subphoton Search Ray from The Shining One (1937, Nat Schachner), the
Probability Time Wave Tube from Elimination (1936, John W. Campbell) and the
X-Beam Projector from Diamond Planetoid (1937, Gordon A. Giles).