Smart fiber fence foils intruders

15 Aug 2003

An optical alarm system with built-in intelligence stops intruders in their tracks.

An "intelligent" optical fiber security fence that uses machine vision to distinguish between a real intruder and a false alarm will make its public debut next month.

Intruder alert

The system, dubbed Fenceguard, requires optical fiber to be laid around the perimeter of a secure facility such as a prison, bank or military base, for example. Each system is custom-designed and the fiber may be installed into a conventional fence or alternatively buried underground.

Light from a semiconductor laser is launched into one end of the fiber and detected at the other end by a CCD sensor. Image analysis software than monitors the speckle pattern on the CCD sensor and triggers an alarm if the pattern changes due to any movement or microbending of the fiber.

Sensitive detector

The system is trained so that it can differentiate between disturbances caused by a potential intruder touching it or treading on it, rather than random vibrations or the wind. According to the inventors, the system is so sensitive that the fiber can be installed under concrete flooring, beneath roads or from inside walls.

Fenceguard was developed under the European Commission's EUTIST-IMV initiative that promotes the adoption of machine vision technology. Partners in the project include two Finnish firms, CCD Photonics and Multitec, and Electro-Technics of Hungary.

Following the successful completion of the project and trials at a European major explosives factory, Multitec is now marketing Fenceguard as a commercial product. It will be shown to the public for the first time at next month's Automaatio exhibition in Finland.

"There are a total of 23 projects within EUTIST-IMV all based on using machine vision and optical sensing to solve problems in industry," said Mark Sawyer, the UK coordinator for the scheme. "As for Fenceguard, I know that they have had a huge amount of interest in this project. My experience from a demonstration is that it's a very smart system and impossible to fool."

Author
Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.