Publication

A measurement method for the axisymmetric refractive index distribution inside a polymeric optical component manufactured by injection molding is proposed. Improvement of optical quality, such as the uniformity of the refractive index inside components, is essential for achieving optical performance that meets industrial needs. When optimizing settings for injection molding to improve product quality, a simple measurement method for the refractive index distribution is important in order to analyze the relationship between product quality and the settings. Therefore, in this study, the background-oriented schlieren method was used to measure refractive indices by measuring the deflection angles of light rays passed through experimental objects. By measuring molded samples with an axisymmetric refractive index distribution, reasonable changes in refractive indices were shown to be caused by annealing under different temperature conditions, with a deviation level of 1×10-4. Moreover, it was possible to quantitatively understand changes in the refractive index due to molding conditions, such as the mold temperature, holding pressure, and cooling retention time. The results of regression and correlation analysis on molding conditions agreed well with qualitative expectations based on the rate of temperature change.