Phase shifting angle interferometer

Abstract A phase shifting Twymann-Green interferometer for the measurement of plane angle has been developed and characterized using a small-angle generator directly traceable to the definition of the radian. The impact of surface form on the measured angle was explored using a simple deformable mirror. The angle sensitivity of the interferometer did not depend upon the surface form. Comparison of the calibrations of two polygons and two angle gauge blocks by both the angle interferometer and a commercial autocollimator showed excellent agreement with normalized errors of less than 0.4. The standard uncertainty for the angle interferometer when measuring the polygons was less than 0.02.