Thickness measurement of low reflectance optical thin film with transparent substrate

Because of the substrate back reflectance phenomena, the reflectance of optical thin film stack on a transparent substrate is totally different from that of on an opaque substrate. In this paper, a method for the measurement of low reflectance optical film thickness that has substrate back reflectance is proposed for the first time. Through the analysis of the actual substrate back reflectance, a compensation model is introduced to reduce the influence of substrate back reflectance. The experimental results show good fitting precision and proves that this model can be used directly for the measurement of the optical film thickness with substrate back reflectance, and no extra process is needed.