Uncertainty contribution of surface form errors in refractive index measurement of solid prisms

The Physikalisch-Techniche Bundesanstalt (PTB) in Braunschweig offers a calibration service for the refractive index of solid prisms. Such calibrated prisms are used as reference standards for refractometers. At PTB a combination of the prism’s apex angle and its minimum deviation angle is employed to determine the refractive index of the material. The measurement uncertainty of the refractive index measurement is directly linked to the uncertainty of the apex angle and the angle of minimum deviation. Therefore, surface form errors on the prism’s transmitting surfaces impact the measurement uncertainty in refractive index measurement with this method. This contribution presents a new modelling concept to estimate the refractive index uncertainty contribution of surface form errors, which are determined by a Fizeau interferometer. 12 che Messtechnik I T Andreas W. Stark