Laser Doppler profile sensor with sub-micrometre position resolution for velocity and absolute radius measurements of rotating objects

We have investigated the application of a laser Doppler profile sensor for simultaneous measurement of position and velocity on moving rough surfaces. It is shown that, with this technique, the shape of rotating workpieces and components, e.g., turbine blades or turning parts, can be measured absolutely and in-process with only one single sensor. Measurements on different surfaces with defined shape and roughness are presented. The obtained minimum uncertainty in the position is about 250 nm in the centre of the measurement volume. For the velocity, a relative statistical error of 0.02% was obtained. Furthermore, shading effects as occurring for example at triangulation are reduced since illumination and signal detection can be coaxial. Because the measurement occurs contactless and a high temporal resolution is achievable, this sensor can open up new perspectives in the field of real-time production metrology, for example controlling the turning and the grinding process or at tip-clearance measurements in gas turbines.