A new experimental approach to measure the refractive index of infrared optical ceramic through the transmittance

This paper proposes a new experimental approach to measure the refractive index of infrared optical ceramic through the transmittance in some particular cases such as can not manufacture test lenses or lack of infrared goniometers. The relationships between the refractive index and transmittance as well as the thickness of infrared optical ceramic are established. The refractive index of one type of optical ceramic material can be captured through the transmittance and thickness of two measurement specimens fabricated from that ceramic. The precision of proposed method is evaluated by manufacturing three measurement specimens from the same optical ceramic material and determining their transmittances and thicknesses as the basis of this exploration. The accuracy of present approach is verified by comparing refractive indexes obtained from proposed method with those of confirmed autocollimation method and the dispersion formula. The comparative results show that the present method has good precision and accuracy. In which, the relative errors between the proposed approach and the autocollimation method are less than 1%. © 2020