Optical interferometric measuring device and method

An optical interferometric measuring device, the measuring device comprising:

• a light source that is configured to generate measuring light having a continuous wavelength range;
• a measuring head that is optically connected to the light source, directs the measuring light onto a measurement object and receives measuring light reflected from the measurement object;
• an evaluation device;
• and
• an optical spectrometer, wherein the optical spectrmeter
• i) is configured to output a first spectrum to the evaluation device, wherein the first spectrum results from an interference between a first portion of the measuring light, which was reflected by a first boundary surface of the measurement object, and a second portion of the measuring light, which was reflected by at least one second boundary surface of the measurement object or by a reference boundary surface,
• ii) includes at least one grating configured to fan out the measured light guided into the spectrometer according to wavelengths, and
• iii) includes a first detector line, to which fanned measuring light is directed and which comprises a plurality of detector pixels, and
• wherein
• the first spectrum includes a series of intensity values measured by the detector pixels of the first detector line,
• the evaluation device is configured to calculate, based on the first spectrum, an optical path difference between the first boundary surface on the one hand and the second boundary surface or the reference surface on the other hand,
• the optical spectrometer includes at least one second detector line, to which fanned measuring light is directed and which comprises a plurality of detector pixels,
• a second spectrum includes a series of intensity values measured by the detector pixels of the second detector line,
• the first spectrum covers at least substantially the entire continuous wavelength range with a first resolution, and
• the second spectrum covers a section of the continuous wavelength range in a second resolution that is higher than the first resolution.

A method for optical interferometric measurement, the method comprising:

• directing measuring light having a continuous wavelength range onto a measurement object by a measuring head;
• feeding measuring light, which was reflected from the measured object via the measuring head, into a spectrometer;
• outputting a first spectrum, which results from an interference between a first portion of the measuring light, which was reflected by a first boundary surface of the measurement object, and a second portion of the measuring light, which was reflected by at least one second boundary surface of the measurement object or by a reference boundary surface, wherein the first spectrum includes a discrete data series of intensity values over wavelengths;
• outputting a second spectrum, which results from the interference between the first and second portions of the measuring light, wherein the second spectrum includes a second discrete data series of intensity values over wavelengths, and wherein a number of data points per wavelength unit is greater for the second spectrum than for the first spectrum;
• and
• calculating an optical path length differences from the first spectrum and from the second spectrum using an evaluation unit based on a modulation of the first spectrum and on a modulation of the second spectrum.