“…Since the x-, y-and z-axes of the laboratory frame can be chosen coinciding with A-, B-and C-axes respectively, n A , n B and n C can be easily translated as n x , n y and n z respectively. One can find the detailed classification elsewhere [4]. Moreover, to characterize biaxiality of retarders, here we define NZ value as (n s -n z )/(n s -n f ), where n s and n f are higher and lower in-plane refractive indices respectively.…”