An apparatus comprises a substrate, a striped pattern and a lenticular sheet. The substrate has a flat surface to which the striped pattern is applied. The lenticular sheet is arranged to be parallelly movable with respect to the striped pattern which is on the flat surface of the substrate. The lenticular sheet has a front surface including a plurality of lenticules oriented along an axial direction and a back surface facing and spaced apart from the striped pattern.