Alstom Technology Limited

Thomas Roesgen

Ken-Yves Haffner

Andreas Kempe

Stefan Schlamp

It is disclosed a method and an apparatus of determining the distance (D) between a collimator lens () and an object. Low-coherence light is emitted from a light source () and directed the low-coherence light through a collimator lens () to the object. The reflected light from the collimator lens () and the object is directed to a beam splitter () and split into two beams. Within the reference arm the frequency of the beam is shifted by an acousto-optical modulator () to a certain frequency and within the delay arm the time delay of the beam is scanned by a variable delay line (). After combining both beams in a beam combiner (), the presence of a frequency component equal to the frequency shift of the acousto-optical modulator () is detected and the distance (D) between the collimator lens () and the object is calculated.

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Kilchberg, Switzerland

Thomas Roesgen