Shari Powell Fisher

Characterization of optically variable film using goniospectroscopy

An optically variable film (OVF) is designed to exhibit a significant color shift with changing observation angle. This color shift was characterized by multi-angle reflectance measurements using a goniospectrophotometer system that also calculated the angle dependent performance of the optically variable film. The reflectance and color of the optically variable film were predicted by optical thin film modelling and compared to the measured values. The optical constants of the materials used in the OVF were then modified based on the goniospectrophotometer measurements to estimate the reflectance more accurately and thus improve the modeled color predictions. Automating this iterative procedure to assess the refractive indices of the OVF components using multi-angle reflectance measurements could create an additional tool for monitoring the fabrication process.