Novel optical sensor measures the shape of rotational bodies

The Laser Zentrum Hannover e.V. (LZH) has developed a novel optical sensor for the direct measurement of the shape and radius of a rotational body. For the first time, this sensor enables the simultaneous measurement of both the position, speed and angular speed. Precise distance and speed measurements for process monitoring and manufacturing metrology can be done using this sensor.

The sensor developed at LZH is based upon the Laser-Doppler-Velocimetry. Here, two laser beams with a different wavelength are split up into two coherent beams each. Then, all the beams are focused on one cross-over point and two interference stripes are formed. A scatter object crossing these two stripe systems generates scattering light signals at two different Doppler-frequencies. By means of calibration both the speed and position of the measurement object can thus be determined.

Besides the usual speed measurement the position of e.g. a technical surface can be determined simultaneously. Characteristics of the position measurement:

  • online
  • contactless (the surface is not destructed by tactile scanners)
  • axial (only very little shadowing effects)
  • absolute (no reference position
  • micrometer and millisecond resolutions

In addition, the angular speed can be recorded.

This sensor is innovative because the radius of rotational bodies can be determined without any reference positions. This opens up various applications in industry, such as in-situ removal measurements for grinding and polishing machines at a precision of 1 µm. Also, for turbo-machines, the size of the gap between the blades and the housing can be measured at a speed of 300m/s.

This research project is sponsored by the German Research Foundation (DFG).

Laser Zentrum Hannover e.V. (LZH)
Michael Botts
Tel.: +49 511 2788-151
Fax: +49 511 2788-100
Hollerithallee 8
D-30419 Hannover