An optical waveguide for the propagation of a light beam adapted to travel by successive total reflections off the faces of the waveguide to an output face where the light beam is refracted. One of the faces of the waveguide forms, facing towards the output face, a support face for a pattern extending across the main direction of the beam to divert same towards the output face. According to a characterizing feature of the invention, the pattern is a bifunctional reflective pattern that is integral with the support face, having three portions including end portions formed by cone portions between which there is interposed an intermediate portion that comprises two facets that meet at a top edge, which is not parallel to the support face for the patterns.