Speed and length measurement

Non-contact measurement with laser

Optical measurement technology is an indispensable tool in all these processes, since it is a non-contact measurement.  Unlike mechanical, touching systems, it does not affect the surface of the material.

An important process parameter for rolling is the speed difference before and after forming in the rolling mill.  Since no material is lost during rolling, a change in thickness must necessarily result in a change in speed.  Laser measuring devices are used which work according to the Doppler principle.

The high-precision Velemeters® measure these speed differences.  It is used for mass flow control or for measuring the degree of dressing in cold and hot rolling mills


Laser Doppler Velocimetry is the most commonly used method for non-contact velocity measurements on solid surfaces.  A laser beam is divided into two partial beams of equal intensity by means of a beam splitter.  These two laser beams are processed by optical components and cut using adjustable mirrors at the measuring distance.  When two laser beams intersect at an angle, an interference strip pattern of light and dark stripes is created in the measuring volume.  The photo receiver looks at this stripe pattern and detects the Doppler frequency in the back scattered light, i.e. the frequency caused by the material movement.


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