A new method to measure optical surface radius

Radius is a fundamental performance specification of an optical surface. A new method to directly measure radius interferometrically is presented. This new method measures radius simultaneously with surface form at the confocal position. Only one measurement position is required which improves the error budget while removing the requirement for precision mechanics and additional operator training. Measurements are presented here that compare the new Direct RoC method to the industry standard using a Displacement Measuring Interferometer combined with additional mechanics. Comparable measurement uncertainty is demonstrated along with greatly simplified operation.