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

Abstract

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.

Spectrally resolved white–light phase–shifting interference microscopy for thickness–profile measurements of transparent thin film layers on patterned substrates

“…The phase difference between the beams, at each point on the object along the line defined by the slit can then be obtained from the intensity distribution in the resulting channeled spectrum. Much higher accuracy can be obtained by phase shifting, using an achromatic phase-shifter operating on the Pancharatnam phase, [10] however, this technique requires specialized hardware.…”

Thickness-profile measurement of transparent thin-film layers by spectrally resolved phase-shifting interferometry

“…Much higher accuracy can be obtained by phase shifting, using an achromatic phase-shifter operating on the Pancharatnam phase. 10 However, this technique requires specialized hardware.…”

Use of monochromatic phase data for improved profile measurement in spectrally resolved white light interferometry

“…We have suggested use of phase shifting technique with a PZT phase shifter and an appropriate error compensating algorithm to determine the phase at several wavelengths simultaneously. [18][19] In SWLI a large number of frames need to be processed to get the profile. But in SRWLI, only few frames are required.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] Another white light technique is the Spectrally Resolved White Light Interferometry (SRWLI). [15][16][17][18][19] Here the white light interferogram is spectrally decomposed by passing it through a spectrometer. The interferogram displayed at the exit plane of the spectrometer has a continuous variation of wavelength along the chromaticity axis (dispersion axis).…”