Polarization phase shifting in white light interferometry

In applications of surface profilometry with white light interferometry (WLI), the detection of the peak of the fringe contrast function is of prime importance. Several procedures have been proposed for the determination of the fringe contrast function. Fourier transform technique and phase shifting technique are two important methods. In the Fourier transform technique, the interference pattern is scanned to obtain the interference signal which is then subjected to filtering in the frequency domain. This involves two discrete Fourier transform operations. The phase shifting technique makes use of the algorithms introduced in the monochromatic interferometry for the calculation of the fringe contrast function. Both PZT and polarization phase shifters are proposed to be used for WLI. In this paper, it will be shown that polarization phase shifter offers some advantages over PZT phase shifter.