Improved measurement characteristics in collimation testing using Lau interferometry and Fourier fringe analysis technique

We demonstrate an automated procedure for the detection of collimation position of an incoherent beam in Lau interferometry using Fourier fringe analysis technique. The experimental arrangement consists of a Lau based interferometer in which light from a source grating illuminates a set of two coarse gratings separated by self imaging distance. Direct phase measurement using Fourier Transform Method (FTM) has been used to obtain the slope map of the wavefront and hence the detection of collimation position is undertaken advantageously. The experimental arrangement is simple and interferometric noise is lower. Detailed uncertainty analysis has also been reported. The technique is fully automatic and provides good accuracy and high precision.