Just like peering through a window, holograms project a seemingly three-dimensional image. While optical holograms require elaborate laser technology, generating holograms with the microwave radiation of a Wi-Fi transmitter requires merely one fixed and one movable antenna, as Dr. Friedenmann Reinhard and Philipp Holl report in the current issue of the renowned scientific journal Physical Review Letters.
"Using this technology, we can generate a three-dimensional image of the space around the Wi-Fi transmitter, as if our eyes could see microwave radiation," says Friedemann Reinhard, director of the Emmy Noether Research Group for Quantum Sensors at the Walter Schottky Institute of the TU Munich. The researchers envision fields of deployment especially in the domain of industry 4.0 - automated industrial facilities, in which localizing parts and devices is often difficult.
Processes that allow the localization of microwave radiation, even through walls, or in which changes in a signal pattern signify the presence of a person already exist. The novelty is that an entire space can be imaged via holographic processing of Wi-Fi or cell phone signals.
"Of course, this raises privacy questions. After all, to a certain degree even encrypted signals transmit an image of their surroundings to the outside world," says the project leader, Friedemann Reinhard. "However, it is rather unlikely that this process will be used for the view into foreign bedrooms in the near future. For that, you would need to go around the building with a large antenna, which would hardly go unnoticed. There are simpler ways available."