Validation of a novel technique for the measurement of the refractive index of a prism by means of interlaboratory comparison

A new method to measure the refractive index of glass prism with very low uncertainty was developed at INRiM. The method is based on a modification of the classical minimum deviation method. In order to validate the technique, an interlaboratory comparison between INRiM and two other laboratories started in February 2008. Three prismatic glass samples with nominal refractive index at 633 nm of 1.515 were sent to each participant one by one, the homogeneity of the base glass material used to fabricate the prisms being better than 10^(-6). Each participant was asked to measure the refractive index of the prism with its own technique at 633 nm at 20 and 23 °C. A brief description of the method developed at INRiM and the evaluated uncertainty is reported together with the first preliminary results of the comparison.