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

• Interferometric technique for detection of collimation of an incoherent beam.
• Technique is based on Lau effect coupled with Fourier fringe analysis.
• Simple experimental arrangement with minimum interferometric noise.
• The technique can be well extended in phase imaging X-ray grating interferometer.
• Fully automatic technique with good accuracy and high precision.

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.