Elimination of dispersion effect in a white-light scanning interferometer by using a spectral analyzer

A general equation of the interference signal of white-light scanning interferometer (WSI) and its Fourier transform are derived. Based on these equations, a new method for elimination of a dispersion effect in WSI is proposed to measure exactly a reflecting surface position. A dispersion phase caused by the two sides of unequal length in a beam splitter is detected with a spectrally resolved interferometer (SRI). A spectral distribution is obtained by using Fourier transform from an interference signal detected with a WSI. The spectral phase of the SRI is subtracted from the spectral phase of the WSI to get a dispersion-free spectral phase, which provides an improved complex-valued interference signal where a position of zero phase is almost equal to a position of maximum amplitude. An accurate measurement is achieved by using the position of zero phase.