Reliable method to characterise parameters and surface effects in wedge and thin liquid crystal cells

<p>Augmented and virtual reality displays require the use of thin liquid crystal cells, with thickness of the order of 1-2 µm. Here, we demonstrate a method, based on cross-polarised intensity measurements coupled to a Frank-Oseen model of the liquid crystal alignment, to characterise such thin cells and the interactions between the liquid crystal and the cell substrates. We first u se w edge s haped c ells t o c alibrate t he m easurement process and show that the cross-polarised intensity data can be used to reliably characterise cells with a non-uniform thickness profile. P reviously, w e h ave s hown t hat w e c an c haracterise o ptically t hin c ells (cells w ith a phase lag of less than 2π). In this report we apply the method to characterise the optical properties of cells with a non-uniform thickness profile a nd g eometrically t hin c ells. W e s how t hat r educing t he t hickness o f t he cell increases the pretilt.</p>