A method and an apparatus for determining the distance between a collimator lens and an object

摘要

It is disclosed a method and an apparatus of determining the distance (D) between a collimator lens (13) and an object. Low-coherence light is emitted from a light source (1) and directed through a collimator lens (13) to the object. The reflected light from the collimator lens (13) and the object is directed to a beam splitter (4) and split into two beams. Within the reference arm the frequency of the beam is shifted by an acousto-optical modulator (5) to a certain frequency and within the delay arm the time delay of the beam is scanned by a variable delay line (7). After combining both beams in a beam combiner (8), the presence of a frequency component equal to the frequency shift of the acousto-optical modulator (5) is detected and the distance (D) between the collimator lens (13) and the object is calculated. <IMAGE>