Vibration measurements of rotating objects by a novel interferometric technique

The precise vibration and displacement measurement of fast moving solid objects is an important task both in process control and production engineering. A lot of measurement techniques are available, but their distance uncertainty at fast rotating objects is often not sufficient. The interferometric evaluation of the phase difference of two scattered light signals in principle allows precise velocity and distance measurements of high-speed objects. However, the speckle effect at rough surfaces usually results in systematic deviations. Recently, a new concept has been developed, which successfully suppresses these deviations resulting in a measurement uncertainty of only 110 nm. This novel interferometric phase sensor has been applied successfully to vibration measurements at vacuum pumps (48000 rpm, surface velocity of 23 m/s) and to diameter measurements of rotating workpieces in a lathe.