Applied Physics

Sensing the Vibes Remotely

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Science  20 Feb 2009:
Vol. 323, Issue 5917, pp. 985
DOI: 10.1126/science.323.5917.985c

Vibrations in machinery can lead to excessive wear, and, in the worst case, to catastrophic failure. Monitoring unwanted vibration is therefore an important safety issue. Probing the response of materials to vibrations at ultrasonic frequencies can provide a diagnostic test for defects and cracks in materials that may appear before the device breaks down. It is not always possible, or feasible, to use mechanically attached sensors, and so optical sensors may allow for nonintrusive monitoring. Bouncing laser light off a textured surface (such as a wall, a can, or paper) produces a speckle pattern. Bessette et al. introduce a photoconductive sensor that probes the movement of the speckle pattern as the sample, in this case a metal surface cut from a can, is vibrated at high frequency. Using a simple silicon-based photoconductive element, which can be shrunk to micrometer size, they can look at the movement of a single speckle, thereby giving them the ability to monitor vibrations at ultrasonic frequencies remotely. — ISO

Appl. Phys. Lett. 94, 41121 (2009).

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