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The Cluster labs have a Polytec PSV 300 laser scanning vibrometer system. This system can scan a vibrating surface using a laser and use the reflected spot to analyse structural vibrations. Entire surfaces can be rapidly scanned and automatically probed with flexible and interactively created measurement grids, zero mass loading and without time consuming transducer mounting, wiring and signal conditioning. The PSV-400 offers technical excellence, ease of use and features, designed for resolving noise and vibration issues in the automotive, aerospace, data storage, micro systems, commercial manufacturing and R&D markets. The Cluster has also used the system for innovative measurements of ultrasound analysis of osteoporosis in bones and analysis of musical instruments.
| Frequency Range | 1 MHz |
| Velocity Range | ~0.5µm/s to 1m/s |
| Displacement resolution | ~10 picometres |
| Angular Resolution | <0.002º |
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High Speed Imaging is the science of taking pictures of very fast phenomena. The Imaging laboratory houses the Oxford Laser VisiLase V227 system which includes the Phantom V5.0, one of the highest data-rate digital cameras in the world.
It is capable of taking high-speed video at up to 60,000 frames per second. When replayed at normal video rates, this corresponds to 2,400 times slow motion. In addition the camera can operate at a resolution of 1024 x 1024, which is four times the image quality of a TV image. The VisiLase V227 includes a laser illumination source that acts like an ultra-fast strobe light to give effective exposure times of 1/20,000,000 of a second for every image. This is short enough to freeze the motion of a bullet in flight, making the system the most powerful digital imaging tool ever. Post processing of the image sequences with particle velicometry software can then reveal information about flow velocity, particle size distribution or spray parameters.
Application examples include visualisation of spray break up, measurement of droplet sizes, measurement of spray pattern and cone angle, visualisation of liquid and gas flows, measurement of flow velocity and derivatives such as vorticity, shear and strain and measurement of particle sizes (solids or liquids) in gas or liquid flows. The cluster labs have also used the camera to image a glaucoma test on a human eyeball, at a rate of 3,800 frames per second.
| Sensor | 1024 by 1024 pixels, monochrome |
| Pictures per second | Up to 60 000 |
| Memory | 1024 Mb (1024 images) |
| Exposure time | >5 µS |
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Samples of High Speed Imaging and Vibrometry |
Acoustic guitar excited with vibrations of 440 Hz and measured using Polytec Laser Scanning Vibrometer.
Glaucoma test, performed on behalf of Gurj Sammi and Professor Bernard Gilmartin of the School of Life Sciences at Aston University. Measured at 3,800 frames per second by the Photonics Cluster’s Phantom High Speed Camera.
Fluorescent tube, imaged at 1000 frames per second by Dr Gareth John of the Photonics Cluster, using the Phantom High Speed Camera.
Daciana Ilescu of Warwick University demonstrates the use of ultrasound to diagnose osteoporosis. This film is taken from the Laser Scanning Vibrometer, and allows Dr Ilescu to monitor the vibrations caused by the ultrasound.
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