Liquid refractive index measurement based on inverse ray tracing method

The refractive index of a solution correlates closely with its concentration. Estimating the concentration of a solution from its refractive index is an extremely important technique in a wide variety of fields ranging from medicine to food and industry. In this study, we propose a non-contact measuring method for obtaining the refractive index of a solution using an optical angle sensor. Our approach is based on an inverse ray tracing technique. We formulate two types of inverse ray tracing expressions for simultaneous measurement of the refractive index of a solution and its level. We construct a prototype, and examine the validity of the proposed method.