Fabrication of moiré on curved surfaces

A method for producing a curved surface level-line moiré device formed by a curved revealing layer made of a curved grating of cylindrical lenses superposed with a curved base layer formed by a grating of shifted bands, said method comprising the steps of:

• (i) defining a curved surface on which the level-line moiré is to appear;
• (ii) creating a planar level-line moiré design by selecting an elevation profile, by defining the common repetition period of planar instances of the grating of cylindrical lenses and of the grating of bands and by shifting said grating of bands according to said elevation profile;
• (iii) projecting the grating of cylindrical lenses onto said curved surface thereby obtaining a curved pitch surface;
• (iv) calculating the curvature radii of the cylindrical lenses that are placed onto the curved pitch surface, thereby obtaining the curved grating of cylindrical lenses;
• (v) laying out the grating of shifted bands as a smooth surface at distances below the pitch surface, said distances being equal or larger than the curvature radii of the cylindrical lenses located above them, thereby obtaining the curved base layer;
• (vi) creating the meshes of the curved base layer and of the curved revealing layer including the curved grating of cylindrical lenses;
• (vii) with the created meshes fabricating the curved surface level-line moiré device;
• where the elevation profile represents a recognizable shape that is reproduced as a level-line moiré on the fabricated curved surface level-line moiré device.