Even the smallest of deformations in structures such as buildings or bridges can lead to cracks or other failures, so the sooner that they're noticed, the better. A new laser-based system is designed to do just that, quicker and cheaper than ever before.
Being developed by a team at Germany's University of Stuttgart, the setup incorporates multiple lasers that are permanently mounted on the front of a structure, shining outward from it. Each of these light sources is detected as a spot on the image sensor of a tripod-mounted video camera, located 10 meters (32.8 ft) from the structure.
A linked computer continuously compares the pattern of light spots received by the camera to a hologram of what the pattern should look like for the structure in question. If any of the lasers has moved even a slight amount relative to the others, the two patterns won't match, and a warning will be issued.
While there are already systems that utilize fiber optic sensors to measure the deformation of structures, the hardware involved is considerably more expensive than that required for the Stuttgart system. Additionally, while the former typically has to be built into structures as they're being constructed, the latter can be added afterwards.
There are also existing systems that shine light onto structures, then use a camera to visually analyze the resulting images. The new system is claimed to work quicker and be more accurate, though, as it delivers more light to the camera by shining the lasers directly onto its image sensor.
So far, the technology has been tested on a building frame measuring 9 meters tall (29.5 ft). Readings obtained using the lasers and camera were found to be similar to those detected utilizing vibrometers and strain gauge sensors. It is hoped that once developed further, the system could not only be used to provide warnings, but even to trigger the structures themselves to react.
"One day we could have lightweight buildings that change forms in response to complex wind forces and can stay still during an earthquake," says team member Flavio Guerra. "This type of adaptation requires extremely precise building deformation measurement so that the building’s current state is estimated and the direction in which it will likely move can be predicted."
A paper on the research, led by Dr. Tobias Haist, was recently published in the journal Applied Optics.
Source: The Optical Society
