Precision test technology of liquid refractive index using the method of minimum deviation angle

A self-developed container made up of a metal frame and a glass window of equal thickness is proposed to improve the test accuracy of liquid refractive index. It improves test accuracy as the manufacturing process is relatively simple, which reduces the systematic error that arises due to the transflective surface and the equal optical path of the glass window. The test method in this paper uses the minimum deviation angle method, which is mainly used for testing solid refractive index but is less frequently applied to test liquid refractive index. Because a special container is needed, the manufacturing process is more complex, and the equal optical path length of transmission glass windows are difficult to control, which will greatly affect the test results. Using the container designed in this paper, theoretical test accuracy of liquid refractive index can reach the order of magnitudes 10^-6. In the experimental case of 0.2″ high-precision turntable, the systematic error brought by the coupled container and the theoretical measurement accuracy of the test system can satisfy the demands in the order of magnitudes 10^-6. The standard deviation of the actual measurement of an ionic liquid under the characteristic spectral line of 546.08 nm is 1.42×10^-6. The self-developing container meets the precise testing needs of the liquid refractive index.