VIS - Telesensor
The VIS - speckle-tracking infrasonic vibrometer - is an innovative laser measuring system that characterizes the behavior of structures under dynamic loads.
It is extremely sensitive and can intercept vibrations induced by micro seismicity, wind as well as traffic and other human activities. It is particularly suitable for rapidly deployed measurement and monitoring of infrastructure (bridges, buildings, machinery) and small landslides. It can be used for dangerous or not directly accessible places. Unlike other sensors, it can be placed at up to 150 meters from the surface being monitored and it does not need to be positioned perpendicularly. Measurement can be taken also in darkness or in the presence of moisture.
SpacEarth Technology holds the rights to intellectual property and commercial exploitation (PAT. n° 102020000006703)
Operating Principle
Differently from other optical vibration sensors, which work with the detection of reflected light, the TIS is based on the acquisition and analysis of digital images of scattered light. When a laser illuminates a rough surface, the scattering of light brings about a random diffraction image - the speckle pattern - which is extremely sensitive to the microscopic detail of the reflecting surface. Each vibration induced by dynamic loads moves the structure, changes its inclination and, consequently, the pattern. By analyzing the correlation between the various images acquired over time, the TIS measures the changes in the pattern in terms of the amplitude, frequency and spectral content of the vibration.
Technical Specifications
The VIS is a compact and lightweight instrument. Internally, the VIS comprises an optical transceiver device, an inertial accelerometer that removes the effect of ground vibrations, and hardware and software components that acquire and process the data for vibration analysis Data transfer to and from the VIS can be done wirelessly or via Ethernet.
| Weight | 7 kg |
| Size L x W x H | 300 mm x 100 mm x 100 mm |
| Bandwidth1 | 0 - 100 Hz |
| 2D Angular Velocity2 | from 0.1μrad/s to 10mrad/s |
| 2D Angular Displacement | from 0.015μm to 1.5mrad |
| 2D Deduced Linear Velocity3 | from 0.1μm/s to 10mm/s |
| 2D Deduced Linear Displacement3 | from 0.01μm to 1.5mm |
| Resolution | Velocity < 0.05 μrad/s/√Hz
Relative Displacement < 0.08μnm |
| Accepted angles of incidence towards normal surface area | ±15 degrees at 50m |
| Laser Spatial resolution | up to 150 m |
| Operability | On all rough surfaces, either corroded or dirty, such as masonry, cement, wood, metals |
1 Up to 300 Hz “relaxing” the sensitivity values (ongoing development)
2 Around the horizontal-vertical axis for angle quantities and in the two orthogonal directions for linear quantities
3 At 1 Hz
Demonstration Video
See the extraordinary sensitivity of the VIS in action
VIS - Infrasonic Speckle-tracking Telesensor