White-light interferometric spectral analysis for displacement sensing

Channeled spectrum of an optical beam generated by a diode laser below threshold after traversing a two-beam interferometer is spectrally analyzed using a grating and a CCD linear array. The paper focuses attention to the Michelson interferometer for displacement sensing. Some particularities and results are presented for the case when the same technique has been applied for determining the widths of parallel sheets of transparent materials or the index of refraction of some liquids. With the present technique, displacement in the range 20 micrometers to 3.5 mm and index of refraction for some liquids were measured with less than 1% error. An analysis of the experimental error sources is made which shows that the ultimate accuracy may be considerably increased.