A double-prism lateral shear interferometer for wavefront analysis and collimation testing

Abstract

A novel method of using two prisms to perform lateral-shear interferometry for wavefront analysis and collimation testing over a wide dynamic beam size range is presented. Two right-angled prisms are utilized to establish an adjustable air gap with a small wedge angle. A test beam directed into the air wedge will result in reflected beams that are laterally sheared and produce an interference pattern which can be analyzed in the conventional manner. The thickness of air gap can be adjusted to allow a wide range of beam sizes to be tested down to a few millimeters in diameter. By using rightangled prisms instead of shear plates, several advantages such as the elimination of unwanted beam reflections, increase in the amount of shear per unit separation, and the enhancement of intensity and contrast of the output beams. The gap separation and wedge angle can be varied to maintain high sensitivity over the wide beam size range. Theoretical and experimental investigation into the sensitivity achievable in collimation testing with the method will be reported.