IET SCIENCE MEASUREMENT & TECHNOLOGY, cilt.5, ss.81-87, 2011 (SCI İndekslerine Giren Dergi)
This study presents the analysis of thermal lens fringes obtained by heating the Nile-blue/ethanol solution with a He-Cd laser in aMichelson interferometer by utilising the Hilbert transform method (HTM) and the Fourier transform method (FTM) with a Gaussian filter. HTM and FTM are used for obtaining local phase and refractive index change maps of the interferograms. The results reveal that HTM creates harmonics in the frequency spectrum; hence, the signal cannot be filtered very accurately, whereas FTM with a Gaussian filter can create a smooth filtering effect.