Abstract: This paper describes the application of Multiple Beam Shearing Interferometry (MBSI) to beam collimation. To realize MBSI, a plate with two optically flat surfaces, wedged slightly in thickness at an angle of 2.7 arc seconds and coated with silver is used. A high reflecting coating, in our case with 90% reflectance, is necessary to ensure that multiple beams occur resulting in sharp fringes for the transmitted light. Without the high reflecting coating the transmittance level is unsuitable for beam collimation. The small wedge angle is necessary for high accuracy. When a collimated beam is incident on the plate a sharp horizontal fringe line is observed because of the wedge in the plate. When the beam is not collimated the effect of the wedge and shear of the wavefront results in oblique fringe lines. In this paper, theoretical calculations, sensitivity of collimation and experimental results are discussed.!6
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