INTERFEROMETRIC MEASURING DEVICE FOR FORM MEASUREMENT ON ROUGH SURFACES

摘要

The invention relates to an interferometric measuring device for form measurement on rough surfaces of a measurement object (7). Measurement is carried out by means of short-coherent radiation, whereby the light path or duration of a reference beam (4) are periodically modulated and brought to interference with a measuring beam (18) reflected by the surface of the measurement object (7) and the interfered radiation is analysed for the maximum of the interference contrast. Although simple to construct the measuring device achieves high measuring accuracy because it comprises a modulation interferometer system (MI) in which the light path is altered by means of acousto-optic deflectors (8, 9) and a compensation device (C1, C2) for correcting spatial decoherence and dispersion. In a demodulation interferometer system (DI) positioned downstream the measuring beam (18) is interfered with the reference beam (4) and transmitted to a photodetector (11).