Betriebsforschungsinstitut Vdeh Institut Fur Angewandte Forschung Gmbh

Bertold Kruger

Roland Keck

Guido Wurbs

A method and apparatus for determining the profile of a surface using contactless distance measurement, wherein a light pencil which has been scattered and reflected from the surface is split into two light pencils having substantially the same distribution of intensities in a plane transverse to the direction of propagation. In doing so, the ratio of the intensities of the two partial pencils is dependent on the principal beam direction of the light pencil which was scattered and reflected from the surface. At least one of the partial pencils is then detected by a photodetector and a resulting signal from the photodetector is evaluated as an accurate measure of surface profile or roughness. By providing this method and apparatus, noise from interference phenomena such as 'speckles' is significantly reduced, and thus, the evaluated signal(s) from the photodetector(s) become more reliable.

Method and apparatus for highly accurate distance measurement with

The invention relates to a process and a device for the interferometric detection of surface displacements of solids, particularly in test material which is excited with ultrasonic waves, in which an illumination laser 10 radiates the test material surface 2, and a portion of the reflected light, after passing through a differing optical path length, is brought into a state of interference, while the interference is identified by an installed detector 9. In arrangements of this type known to the prior art, a very expensive apparatus and control system is needed to assure that demodulation of the reflected laser light is performed with maximum sensitivity. This is improved by the invention in that a joint illumination laser 10 is employed to operate several interferometer equipped with waveguides 5, 7, which in bundled fashion terminate in a common transmitter and receiver lens 4 positioned at a distance from the test material, from which lens detector-waveguides also emerge; here allocations which are dependent on the phase relation arise and whose signals are at the least added quantitatively and are employed to identify the ultrasonic events.

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Krefeld-Fischeln, Germany

Bertold Kruger