Non-Contact Real-Time Measurement of Refractive Index of Flowing Liquid Based on Optical Coherence Tomography

The refractive index (RI) is one of the liquid's most important physical parameters of liquid. The change of RI usually indicates the change of liquid properties, and this relation leads to broad application. This paper proposes a method based on optical coherence tomography (OCT) to measure the RI of liquid in real time. A series of targeted image-processing techniques play a vital role in this method. Benefiting from the advantages of OCT, this method does not require the operators to come into direct contact with liquids. Moreover, the principles and techniques adopted in this method imply that the measuring range of RI of unknown liquids is unlimited. The effectiveness of this method is validated by the experiment measuring the RI of sucrose liquids with gradient concentration. Another experiment thoroughly verifies this method's feasibility in predicting sucrose concentration based on real-time measured RI. This simple and easy proposed method indicates an immense potential application prospect in the industry and scientific research.