It’s not hard to forget the fact that WiFi can pass through walls, despite the fact that this is something that’s been giving us wireless internet access for years now. It doesn’t matter in which room in your house the router is, as long as you’re within the range of its signal, you’ll have internet access.
However, not all of the signal that the routers emit go to our devices, but instead, the signal bounces off objects within our homes. They’re able to illuminate our homes and turn them into invisible light bulbs. Now, German scientists have discovered a way to exploit this. They’ve revealed that, by using this new tech, they can take 3D photographs, or holograms, of objects that are within the rooms, while they themselves are outside.
Technical University of Munich’s physics student Philipp Holl has stated that they can actually use WiFi signal to scan a room or a house. This entire project started as a segment of his thesis, and with the help of Friedemann Reinhard, his academic supervisor, he submitted their study. The study was published in early May of this year by journal Physical Review Letters.
Holl claims that this tech is still in the prototype stage. For now, he says, if there was a coffee cup on the table, you wouldn’t be able to tell what it is. However, you could still see that something’s there, and the table is very recognizable, just like people or furniture. Basically, the bigger the object, the clearer the scan.
The tech that allows us to see through walls via WiFi isn’t exactly new, but instead, it’s around for several years, now. There are setups that can be used for detecting home intruders or tracking the moving objects. Some can even create 2D images through the use of an array of antennas. However, 3D holograms of rooms with things in them was never done before, claims Holl. He even says that their method provides with much better images that show the entire room.
His method is different, and this is because several things are done in another way. First of all, he uses two antennas. One of them is fixed in place, while the other one moves. The first one records the background of the WiFi’s field, while the other one scans the same space from different points and angles. They can even be small, like the size of a smartphone’s antennas.
The second thing that’s different is the fact that both antennas can record not only the brightness of the signal but the phase as well. That’s the property of light that’s there because the light is a wave. A laser represents the light that’ in one phase, and that makes it great for producing holograms. On the other hand, an incandescent bulb releases an entire mix of phases. WiFi routers are emitting microwave radiation that’s similar to lasers.
When the signals from these antennas are fed into a computer, the software is able to produce an image of the scanned room. The image is, as Holl says, more or less in real-time.
Basically, the software builds a lot of 2D images from the antenna that’s scanning around and combines them into a 3D hologram. The fact that WiFi can go through walls allows things from within the room to be scanned from the outside.
The raw results might not look like much, but they are the proof that this concept is working. This tech can be used in many different ways. They might be used for finding and rescuing people from the rubble that remains after an earthquake. Also, spy agencies might use this tech to scan houses and reveal the position of their suspects. Combined with a drone, this tech could scan entire buildings in less than half a minute.