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Scientists Have Found A Way To Photograph People In 3D Through Walls Using Wi-Fi

3D holograms using WIFI544

Philip Holls and Friedemann Reinhard/Physical Review Letters (CC BY 3.0)

This might be every spy service’s ultimate fantasy! It turns out that even Wi-Fi can be used to photograph people and everything around them!

WiFi signals can pass through solid objects and walls, and they scatter everywhere in our rooms since a very small amount is absorbed by our phones, tablets, and laptops. Using this fact, German scientists have come up with a way to use WiFi signals and create holograms, or 3D photographs of the objects within WiFi router range.

“It can basically scan a room with someone’s Wi-Fi transmission,” Philipp Holl, a 23-year-old undergraduate physics student at the Technical University of Munich, told Business Insider.

The device was initially Holl’s bachelor thesis done with the help of project supervisor Friedemann Reinhard. The findings were submitted to the journal Physical Review Letters and were published in early May. The technology is still in its prototype stages and has limited results, but the prospects are very exciting.

Philip Holls and Friedemann Reinhard/Physical Review Letters (CC BY 3.0)

“If there’s a cup of coffee on a table, you may see something is there, but you couldn’t see the shape,” Holl says. “But you could make out the shape of a person, or a dog on a couch. Really any object that’s more than 4 centimeters in size.”

The technique of using WiFi to look through walls have been around for quite some time, but Holl’s method is different since it allows a 3D hologram creation of everything inside a room.

“Our method gives you much better images, since we record much more signal. We scan the whole plane of a room,” he says.

The technique employs two antennas, one fixed and the other mobile which record the WiFi field’s background.


“These antennas don’t need to be big. They can be very small, like the ones in a smartphone,” Holl says.

Another difference is how the antennas record not only the intensity but also the phase of the electromagnetic wave. Similar to lasers, which have a single phase helpful in creating holograms, Wi-Fi routers emit microwaves in discrete frequencies and phases.

These signals from both the antennas are then simultaneously fed into the computer, and the software is used to mark out the differences of intensity and phase “more or less in real-time,” Holl says. The stack of 2D images is used by the moving antenna to create a 3D hologram.

Below are the first holograms of a shiny metal cross made by Holl and Reinhard’s technology.

Philip Holls and Friedemann Reinhard/Physical Review Letters (CC BY 3.0)

Watch the technology in action below!

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