Simultaneous measurement of thickness and refractive index using wedge plate lateral shearing interferometry and fourier transform method

We propose a technique for simultaneous measurement of thickness and refractive index (RI) using wedge plate lateral shearing interferometry combined with Fourier fringe analysis. Collimated light beam transmitted through transparent glass plate (GP) is analyzed by a wedge plate and spatial filtering arrangement. Wedge plate displaces incident wavefront by a small amount. Fringe pattern is obtained by interference of original and displaced wavefronts. To extract the information of thickness and RI simultaneously, the specimen is rotated and the phase variation of interferograms before and after rotation are determined using Fourier fringe analysis technique.