Radius of Curvature Measurement of Large Optics Using Interferometry and Laser Tracker

The determination of radius of curvature (ROC) of optics typically uses either a phase measuring interferometer on an adjustable stage to determine the position of the ROC and the optics surface under test. Alternatively, a spherometer or a profilometer are used for this measurement. The difficulty of this approach is that for large optics, translation of the interferometer or optic under test is problematic because of the distance of translation required and the mass of the optic. Profilometry and spherometry are alternative techniques that can work, but require a profilometer or a measurement of subapertures of the optic. The proposed approach allows a measurement of the optic figure simultaneous with the full aperture radius of curvature.