Analysis of spectrally resolved white light interferograms: use of a phaseshifting 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 th is purpose. Previously, the phase shifted intensity values required for pha se 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 i n 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 th e same phase shift (achromatic phase shift) at all the pixels receiving lig ht of different wavelengths. In the PZT phase shifter, the phase shift vari es considerably at different pixels, but analysis shows that good measureme nts can still be made with it. (C) 2001 Society of Photo-Optical Instrument ation Engineers.