Watchdog windows: motion sensitive glass could boost home security

Besides letting in light and providing pleasant views, (hopefully), windows unfortunately also provide a convenient entrance for burglars. Security systems have long employed contacts that, when broken, activate an alarm, but what if the simple act of moving around outside a window were enough to raise the alert. That’s the concept behind a system developed by the Fraunhofer Institutes for Applied Polymer Research IAP in Potsdam-Golm and Computer Architecture and Software Technology FIRST in Berlin that sensitizes windows and doors to detect suspicious movements.

The motion sensor enables window panes and glass doors to detect movements thanks to a special coating. If anything changes in front of the pane, or someone sneaks up to it, an alarm signal is triggered. “The glass is coated with a fluorescent material,” explains IAP group manager Dr. Burkhard Elling. “The coating contains nanoparticles that convert light into fluorescent radiation,” so when the invisible light of a UV lamp “illuminates” the window panes it generates fluorescent radiation in the coating which is channeled to the edges of the window, where it is detected by sensors. Therefore if someone blocks the light of the lamp, less light reaches the coating and less fluorescent radiation is produced, which the sensors detect.

Simple applications would require only one sensor, but if several sensors are installed on all four sides of the window frame, conclusions can be drawn from the data as to how fast and in what direction an object is moving. Its size, too, can be estimated by the sensors so that moving objects the size of birds for instance do not trigger an alarm. Likewise, the sensors do not react to light from passing cars, as the system can interpret different light signals. The system can also be implemented on existing windows with the coating able to be sprayed on by airbrush or glued on as a film.

A demonstrator system already exists, and the researchers now plan to optimize the dyes and their concentration in the coating. Looks like my days as a peeping tom may be numbered. Oh well, it was good while it lasted.

Darren Quick