An optical module for projecting a light beam comprises a solid body of transparent material into which a light source is sunk and which is delimited by an annular surface and by a central surface, and a substantially annular reflecting surface arranged around the solid body. The central and annular surfaces are suitable for receiving respective distinct portions of the luminous flux produced by the source. The reflecting surface may have a reflecting coating or may form part of a transparent body, in which case it works by total internal reflection. The reflecting surface reflects a portion of luminous flux refracted by the annular surface and shapes the flux into a predetermined distribution of luminous intensity about the principal axis. The annular surface is designed in a manner such as to reduce the overall thickness of the module by moving the refracted ray away from the principal axis. The central surface shapes the other portion of the luminous flux emitted by the source into a predetermined distribution of luminous intensity about the principal axis. The surfaces cooperate so as to shape the luminous flux as a whole emerging from the source into a distribution of luminous intensity having divergences which may be different in two directions that are perpendicular to one another and to the principal axis.