White Light Interferometry: Correlogram Correlation for Surface Height Gauging: Noise stability

摘要

Established methods to gauge the surface height by the white light interferometry do not use the full information contained in a correlogram. As the result, the envelope evaluation methods suffer from susceptibility to noise, whereas the phase methods are prone to the "2-pi ambiguity". In the approach of the present paper, the surface position is determined via the correlation of the local correlogram with a reference correlogram, thus benefiting from its complete information. Accuracy and tolerance to noise of this method is by more than one order of magnitude higher, than that of the envelope methods; the 2-pi ambiguity has not revealed itself so far. Another advantage of the suggested method is the immediate availability of a suitability criterion for a local correlogram - the correlation coefficient with the reference correlogram.