A laser-based surveillance system that can automatically detect millimetre-scale changes to a scene has been developed by US researchers.

Created by a team at Oak Ridge National Laboratory (ORNL) in Tennessee, US, the system rapidly scans an area with a laser to pinpoint any changes.

Rather than detecting intruders or monitoring people, it keeps track of static objects in a scene. This is done by attaching tags to important items, which reflect laser light, allowing a connected sensor to monitor their location precisely. If one of the tags is moved, or disturbed even slightly, this will be revealed by the laser reflection.

The researchers suggest that the system could be suitable for use in high security situations where even CCTV is a security risk, since video footage can be intercepted, and might potentially reveal sensitive information. Also, unlike CCTV, it does not require constant human supervision.

Light speed

The laser surveillance system can scan a room many times per second to keep track dozens of tags. The number of tags can be increased to hundreds, or more, although this will reduce the scanning speed.

If a tag disappears, or is disturbed, the system can automatically sound the alarm. Should someone attempt to place a dummy tag in front of the beam, they will inevitably be detected, since the task is impossible to complete quickly and accurately enough.

Peter Chiaro, who developed the system with Tim McIntyre and Curt Maxey at ORNL, believes the technology could be ideal for monitoring access to sensitive areas. "Tracking tags could be placed on doors to track when a door is accessed," he explains, "or the tag could be placed on a valve or other similar device to detect movement."

No motion

Tests at the International Atomic Energy Agency in Vienna, Austria, and at the EU Joint Research Center in Ispra, Italy, have proven the surveillance system to be highly effective, he says.

Chiaro and colleagues add that it has fewer problems than alternative non-camera surveillance technologies. Light detection and ranging (LIDAR), which uses scattered light to build 3D images, provides less resolution, while Radio Frequency Identificatoin (RFID) tags require an antenna to be placed close to an object and are also vulnerable to jamming.

Currently, the system cannot track moving objects. However, with the correct programming it should be possible to do so, Chiaro says. It could then detect when a tag leaves a particular area or its movement deviates.