An interfermetric systm capable of precisely and automatically measuring an aspheric surface is described. Major techniques are lateral-shearing interferometry using the fringe scanning detection method and automated alignment. Key elements of this system are a 1ateral shearing interferometer with a beam-splitter and a piezoelectrically-driven corner-cubes-prism, a precise alignment mechanism driven by an output signal of a sensor which detects an object location, and a computer for analyzing fringe information and controlling the system. Rms accuracy of λ/32 is achieved from the evaluation on a convex parabolic mirror with asphericity of 200λ and a curvature radius of 35 mm.
"Automated Interferometric System For Aspheric Surface Testing", Proc. SPIE 0680, Surface Characterization and Testing, (23 March 1987); doi: 10.1117/12.939595; https://doi.org/10.1117/12.939595