Assessment of the complex refractive index of an optically very dense solid layer: Case study offset magenta ink

A recently built multifunction spectrophotometer is used to measure reflectance from a dried liquid layer of optically very dense medium applied as a liquid onto the probe window in the form of a face of a prism. The measurement consists of scanning across of the wavelength range 400–800 nm and recording the s- and p-polarized light reflection. Complex refractive data is extracted using Azzam’s theory for light reflection. As an example, data for the case of dry magenta offset ink are shown, an application where the complex refractive index of the solidified ink layer is important in the evaluation of the print quality. The present method is not restricted to the case of inks but is proposed to be applicable across a broad range of applications, such as assessment of the optical properties of paints and biomedical samples.