Dispersive white-light spectral interferometry to measure distances and displacements

Processing of the spectral interferograms recorded at the output of a dispersive Michelson interferometer by a low-resolution spectrometer is performed with a knowledge of both dispersion and thickness of the interferometer optical element (beam splitter or optical sample). The recorded spectral interferograms, including the equalization wavelengths, are fitted by using a least-squares method to the theoretical interferograms to obtain the optical path differences (OPDs) between interfering beams. From the OPDs, which vary with both the wavelength-dependent refractive index and the thickness of fused-silica optical element, distances or displacements are determined. Within two different configurations of a dispersive Michelson interferometer we show that the range of measurable distances depends on the thickness of the optical element. We also confirm by this measurement technique that errors of manually adjusted 10 mum displacements of the interferometer mirror are below 1 mum. (C) 2002 Elsevier Science B.V. All rights reserved.