Scientists have found a way to take photos across walls through Wi-Fi

German scientists have found a way to exploit the special feature of Wi-Fi waves to capture three-dimensional images, or 3D images of objects through walls.

Wi-Fi waves can penetrate walls. But not all wave radiation comes to our mobile device. Routers disperse and cover signals on objects, illuminating the house like invisible lights.

Philipp Holl , a physics student at Munich Engineering, said: "Basically, it is possible to scan a room with a Wi-Fi transmitter of any person."

Holl is developing such a device with the graduate thesis assistant Friedemann Reinhard. The two men showed their research on this technology in Physical Review Letters in early May.

Philipp Holl said that this technology is currently in the first prototype stage and has limited resolution, but he is excited about its potential.

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He said: "If there's a cup of coffee on the table, you can see something in the cup, but you can't see its shape. However, you can create the shape of a person, a child. a dog or a chair Anything bigger than 4cm ".

Wi-Fi through-wall visibility has been in use for several years. Some devices may observe intruders or track moving objects with one or two Wi-Fi antennas.

Others use an antenna array to create 3D images. But, Holl said no one used Wi-Fi to create three-dimensional images of the entire room with objects in it.

Holl's methods differ significantly from previous methods.

Firstly , it uses two antennas: one fixed and one moving. The fixed antenna will record the Wi-Fi field at the installed location, for reference. The remaining antenna is moved to record the Wi-Fi field at different points.

Holl added: "The antennas don't need to be too big. They can be very small, just like smartphones antennas."

Second , both antennas not only record the intensity (or brightness) of the Wi-Fi signal, but also the wave phase. The Wi-Fi router emits wave radiation with discrete frequencies and phases, making it easy for the antenna to record the difference.

Finally , the signal that both antennae will record is simultaneously taken into the computer. Dedicated software will show the difference in intensity and wave phase at actual locations.

The mechanism works as follows : When an antenna receives waves, the software creates many 2D images, and then stacks them up to create 3D images. Because Wi-Fi penetrates almost every wall, 3D images are of objects inside the room.

Wi-Fi through-wall visibility has been in use for several years.

The final image may not be too similar to reality, but it proves that moving antennas can identify parts without Wi-Fi and create three-dimensional images of objects across a wall.

The application of technology for taking photos across the wall with Wi-Fi is quite diverse.

According to Philipp Holl, the application of cross-wall imaging technology with Wi-Fi is quite diverse. For example, help rescue workers identify victims within the rubble of an earthquake, or help investigators track crime.

He added: "You can use an unmanned aircraft to create an image of an entire building in just 20 to 30 seconds."