These days, Wi-Fi has become a common fixture in most American households, but as it turns out, all those signals could provide yet another way for others to spy on us. A pair of German researchers discovered a way to use Wi-Fi signals to take a sort of 3D snapshot without even being in the room.

wi-fi 3d
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A new use for spare Wi-Fi signals

Technical University of Munich student Philipp Holl built a device that is able to exploit a certain property of Wi-Fi signals. They’re able to pass through walls, which is why people can use Internet from a Wi-Fi router that’s not in the same room as them.

Holl worked on it with his academic supervisor, Friedemann Reinhard, and together, they wrote a study about the technique they worked out, which was published earlier this month in the Physical Review Letters journal. Holl spoke to Business Insider about how their device works. Essentially, their device captures the spare Wi-Fi signals that bounce off objects and people in a room (rather than being used by laptops, tablets, smartphones, and other devices).

A new method for X-ray vision?

According to Holl his device is able to “scan a room with someone’s Wi-Fi transmission.” However, he added that it’s still only in the prototype phase. The 3D holograms it can create have very limited resolution, so it’s possible to have a vague sense of things within a space without a lot of details.

For example, he explained that it may be possible to see that there’s something sitting on a table, but the resolution isn’t good enough to tell that the item is a cup of coffee. Also it doesn’t pick up objects that aren’t at least 4 centimeters in size. However, he feels that the idea behind the technology has promise.

According to Business Insider, it’s been possible to use Wi-Fi signals for X-ray vision for years, and some applications are in use, like in home security systems that are able to detect that there’s an intruder. However, Holl says his method is the first to create a 3D hologram out of a whole room using Wi-Fi. Additionally, his setup uses one fixed antenna and a second that moves. The antennas also record the Wi-Fi signals’ brightness and phase to create the 3D hologram.

He sees a variety of different applications for his 3D technology, such as helping rescue workers locate people in rubble left after an earthquake. It could also be used in intelligence work to detect the presence of people in a room or by drones to map a building in seconds.

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