Laser vibrometry is a non-contacting technique for evaluating the characteristics of vibrating or oscillating objects.

The technique is used in a diverse range of applications; from art conservation to land mine detection; bridge oscillations to car vibrations; assessing the biomechanics of the human middle ear to understanding honeybee communication in the honeycomb.

At Birmingham School of Dentistry, we apply the technique to a range of vibrating dental instruments in an attempt to understand better the manner in which they work and ways in which their design can be modified to increase clinical efficacy.

Our research has focussed primarily upon the vibration characteristics of ultrasonic scalers - studying the effects of generator power, load, wear, water flow rate, tip design and ultrasound generation type (piezoelectric / magnetostrictive) on the vibrations of the instrument.

The scanning laser vibrometer (PSV-300-F/S High Frequency Scanning Vibrometer System, Polytec GmbH, Germany) consists of a scanner head and a controller / workstation, where measured data is decoded and manipulated.

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The optical system of the scanner head (Polytec OFV 056, Polytec GmbH, Germany) combines a laser, optics and video camera. The laser is a low power (<1mW), Helium-Neon (He-Ne) beam with a wavelength of 632.8nm.

The laser beam of the vibrometer is guided over the surface of the target object using a measurement grid. From each point in the grid, vibration data is acquired for further analysis.

Scans reveal data such as vibration frequency, displacement amplitude and velocity. Vibration data is superimposed over a captured image of the target object in the form of a coloured grid. Colours give an indication of the direction of the vibration as well as the magnitude.

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