Novel system for simultaneously measuring the thickness and refractive index of a transparent plate with two optical paths

This study designs and characterizes a novel optical system for simultaneously measuring the thickness (> 1 mm) and refractive index of a transparent plate with two optical paths. The proposed optical system is based on triangulation methods. In contrast to exiting optical system based on triangulation methods for simultaneous measurements of thickness and refractive index of a transparent plate, the proposed optical system can measure a greater thickness with a simpler structure and lower cost. The two optical paths are combined using a self-written measurement processing algorithm to simultaneously calculate the thickness and refractive index. The principle and measurement methodology of the proposed optical system are analyzed and explained. The performance of the proposed optical system is then verified and evaluated experimentally using a laboratory-built prototype. The experimental results show that the measured thicknesses and refractive indexes for Sample B (the thickness > 1 mm) are in good agreement with those determined by a commercial instrument with the maximum deviation of 0.019% for the thickness d and 0.007% for the refractive index n, respectively.