Automated collimation testing in Lau interferometry using phase shifting technique

We demonstrate an automated procedure for detection of collimation position of an incoherent beam in Lau interferometry using phase shifting 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. Phase shifting procedure is incorporated by translating the detector grating, corresponding to different positions of the collimating lens. The phase map is plotted corresponding to each position. The slope of the phase map is indicative of the collimation position of the optical beam. The technique is fully automatic and provides good accuracy and high precision.