Abstract: An interferometric confocal method and assembly for terabyte volume optical data memories couples two-beam spectral interferometry to chromatic confocal technology and permits a longitudinal splitting of foci in the memory volume, with the foci having limited diffraction. A spectrometer is located downstream of the interferometer with confocal discrimination in the beam path. A diffractive optical zone lens (DOZE) with a usage of the first diffraction order is introduced into the interferometric beam path to achieve longitudinal chromatic splitting. The interferometer can be a fibre-coupled interferometer with a retroreflector in the fibre-coupled reference arm and with wavelength-dependent optical path difference modification by dispersion or diffraction. The optical path difference in the interferometer is set so that easily detectable wavelets are formed from detectable interferograms by spectral analysis.

Abstract: A measuring head (4) according to the invention comprises the combination of a zone lens (26), which is preferably a diffractive lens, with a hemispherical lens (23) or a GRIN lens (33). This represents a concept capable of miniaturization, resulting in very slender measuring heads (4) having a high numeric aperture and, accordingly, leads to the best resolution capacity. Such measuring heads are insensitive to angular errors as concerns the orientation of the measuring head to the surface to be measured or to an oblique positioning of the surface relative to the optical axis of the measuring head.