Large-Area Surface Measurement of Spherical Parts Based on Interferometry

High-precision spherical parts are widely used in measurement machines, MEMS devices, and other fields, but there are few effective methods for the full annular area measurement of sphere surface. In this article, an interferometry-based method for the full annular surface measurement of spherical parts is proposed. By adding an off-axis parabolic mirror, the parallel beam was converted into an annular beam, enabling the measurement of sphere surface near the equator. The method was validated using a Zygo interferometer and approximately one-sixth of the surface was measured in one single measurement. The eccentricity error was minimized by error compensation algorithm, and the surface error of paraboloid was calibrated using a reference ball. A large range of surface near the equator can be efficiently obtained in one single measurement and verification measurement results indicate its efficiency and reliability.