Stuttgart University scientists have developed a new camera-based system for measuring building deformations in real time.
According to the scientists, the new method which can detect submillimeter movements from 10 meters away.
Although fiber optic sensors can be used for structural health monitoring, they must be installed when the building is built.
The new camera-based system on the other hand can be attached after construction and uses hardware that is less expensive than fiber optic systems.
“Our new approach to detect building deformations could be used to continuously monitor movements,” says Stuttgart researcher Flavio Guerra.
“For bridges, the measured deformations could be used to counteract external loads such as a truck traversing the bridge, thereby increasing the lifetime of the bridge.”
“Because it operates in real time, it could be used to set off an alert the moment any new deformations – which can lead to cracks – are detected.”
The scientists led by Tobias Haist, have described the new technique in The Optical Society (OSA) journal Applied Optics.
According to the scientists, the new method involves fixing a camera on a tripod a small distance away from the front of the building and attaching small light emitters to the building.
The camera then detects whether the light sources move relative to each other.
A computer-generated hologram is used to create multiple copies of each light source image on the image sensor.
Averaging the movement of the multiple copies of the laser spot helps decrease measurement errors, such as noise, yielding measurement uncertainties below a hundredth of a pixel.
According to the scientists, using multiple cameras could improve that accuracy even more and enable the technique to be used on very large structures.
Most camera inspection systems illuminate the object – a building in this case – and then image it with a camera.
The Stuttgart team hence took a different approach by attaching light emitters to the building and directing the light directly toward the camera.
This setup allows faster and more accurate measurements because the camera receives more light.
Image and content: Flavio Guerra/University of Stuttgart