Analysis of spectrally resolved white light interferograms: Use of a phase shifting technique

The phase at different pixels along the direction of dispersion, also known as the chromaticity axis, is determined in spectrally resolved white light interferometry (SRWLI). Phase shifting interferometry has been used for this purpose. Previously, the phase shifted intensity values required for phase calculation were obtained from phase shifts due to wavelength variation (spatial phase shifting). This required the intensity values from different pixels be used in the calculations, resulting in errors due to variation in pixel sensitivity. We propose to use multiple intensity values, required for phase calculation obtained from the same pixel, and investigate the use of a polarization phase shifter and the conventional PZT phase shifter for this purpose. The polarization phase shifter aims at introducing nearly the same phase shift (achromatic phase shift) at all the pixels receiving light of different wavelengths. In the PZT phase shifter, the phase shift varies considerably at different pixels, but analysis shows that good measurements can still be made with it.