Measurement of the refractive index using a goniometric system in an automated mode

Subject of study. A method for the measurement of the refractive index using an automated autocollimating goniometric system is proposed. Aim of study. The study facilitates the precise measurement of the refractive indices of transparent solid and liquid optical materials. Method. Goniometric methods based on the measurement of angles of light refraction caused by a substance are often used to measure the refractive indices of trihedral prisms. A method to determine the refractive index via measuring the light deviation angle caused by a prism after reflection from the internal facet in the automated mode is proposed. Main results. The refractive indices of two trihedral prisms composed of different glass types, namely, N-BK7 and SF-1, measured using the proposed method and autocollimating goniometric system are presented. The measurement error did not exceed 1.5×10−4 when compared with the nominal value for these prisms at the wavelength of the radiation source of the autocollimator, thus confirming the prospect of application of this method in high-precision refractive index measurements. Practical significance. The method proposed in this study can be used to measure the refractive indices of trihedral prisms made of optically transparent materials with different apex angles using the goniometric system in an automated mode. The method can also be applied to optically transparent liquid materials located in a hollow trihedral prism.