We studied the director configuration in thin liquid crystalline layers of 5 CB using a null ellipsometry technique. Liquid crystal (LC) material was spin- coated on polyimide (PI) substrates. The influence of different treatment of PI substrates on the director configuration was investigated. The PI substrates without additional treatment provide homeotropic LC alignment. The UV irradiated substrates provide the formation of biaxial (fan-like) LC structure that is symmetric with respect to the film normal. The rubbed PI substrates provide the splayed optic axis distribution with the average tilt angle of 25 degrees with respect to the film normal.