Device and method for the optical measurement of relative distances

A method for the optical measurement of relative distances of structures of an object using optical time domain coherence tomography, comprising

• directing a measuring beam onto the object,
• detecting sample radiation reflected or backscattered from the object with a detection unit,
• splitting either the measuring radiation or the sample radiation into a first beam part and a second beam part,
• passing the beam parts through different optical path lengths,
• superimposing the beam parts to generate a dual beam, which has components axially offset to one another because of the different optical path lengths,
• the different optical path lengths influencing the relative distance of the structures sensed on the object, sample radiation from the structures being capable of interfering at a detector unit,
• scanning a relative distance of the sensed structures by adjusting the different optical path lengths relative to one another, and
• adjusting both the path length of the first beam part and the path length of the second beam part in coordinated manner, so that the coordinated adjustments define a covered range of the relative distances of the structures sensed on the object.

A device for the optical measurement of relative distances of structures of an object, which is implemented as an optical time domain coherence tomograph, comprising:

• an object beam path, through which measuring radiation is incident on the object,
• a detection beam path, which comprises a detector unit and through which sample radiation reflected or backscattered by the object reaches the detector unit,
• an interferometer unit, which has a first and a second beam path part having different optical path lengths, the interferometer unit splitting sample radiation and feeding the sample radiation into the two beam path parts and superimposing the sample radiation again after the sample radiation's passage through the beam path parts and thus generating a dual beam, which has components which are axially offset to one another because of the different optical path length of the two beam path parts,
• the interferometer unit either being situated in the object beam path, so that the measuring radiation is incident on the object as the dual beam, or being situated in the detection beam path, so that the sample radiation reaches the detector unit as the dual beam, and the different optical path lengths of the beam path parts influencing the sensing of relative distance of the structures the object, the sample radiation returning from the structures being capable of interference at the detector unit,
• a scanning unit for scanning the relative distance of the structures, the scanning unit being implemented to adjust the optical relative path lengths of the beam path parts, and
• a control unit, which drives the scanning unit,
• wherein
• the scanning unit includes a first adjuster that adjusts the optical path length of the first beam path part and a second adjuster that adjusts the optical path length of the second beam path part and
• the first adjuster and the second adjuster adjust the path lengths for scanning the object in coordination to one another under control by the control unit, so that the coordinated adjustments jointly define a covered range of the relative distances.