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Precise measurements of distance, eccentricity and 3D-shape of fast moving objects such as turning parts of lathes, gear
shafts, magnetic bearings, camshafts, crankshafts and rotors of vacuum pumps are on the one hand important tasks. On
the other hand they are big challenges, since contactless precise measurement techniques are required. Optical techniques
are well suitable for distance measurements of non-moving surfaces. However, measurements of laterally fast moving
surfaces are still challenging. For such tasks the laser Doppler distance sensor technique was invented by the TU
Dresden some years ago. This technique has been realized by two mutually tilted interference fringe systems, where the
distance is coded in the phase difference between the generated interference signals. However, due to the speckle effect
different random envelopes and phase jumps of the interference signals occur. They disturb the phase difference
estimation between the interference signals. In this paper, we will report on a scientific breakthrough on the
measurement uncertainty budget which has been achieved recently. Via matching of the illumination and receiving
optics the measurement uncertainty of the displacement and distance can be reduced by about one magnitude. For
displacement measurements of a recurring rough surface a standard deviation of 110 nm were attained at lateral
velocities of 5 m ∕ s. Due to the additionally measured lateral velocity and the rotational speed, the two-dimensional
shape of rotating objects is calculated. The three-dimensional shape can be conducted by employment of a line camera.
Since the measurement uncertainty of the displacement, vibration, distance, eccentricity, and shape is nearly independent
of the lateral surface velocity, this technique is predestined for fast-rotating objects. Especially it can be advantageously
used for the quality control of workpieces inside of a lathe towards the reduction of process tolerances, installation times
and costs.
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