Light projector intended to produce a directional flat light beam for signalling tall obstacles, the projector comprising: an elongate cylindrical lens the cylindrical shape of which is defined by a horizontal generatrix direction and by a director curve, the cylindrical lens having a horizontal plane (100, 1000) of symmetry, a linear light source (14, 15) parallel to the generatrix direction, extending over all or part of the length of the cylindrical lens to emit light in the direction of the cylindrical lens, the cylindrical lens being adapted to generate a principal flat light beam (26, 27) by concentrating the light in a predefined elevation angular sector around the horizontal generatrix direction in the direction of the space situated on the opposite side of the cylindrical lens to the light source, and being adapted to project the light in a predefined azimuth angular sector around the vertical direction, characterized in that it further comprises a deflector comprising a metal blade, positioned in the space situated on the side opposite the light source of the cylindrical lens, the deflector having a rectangular plate shape, the longitudinal sides of the deflector being parallel to the generatrix direction, the transverse sides of the deflector being oriented around the generatrix direction in accordance with an elevation angle (s) contained in the predefined elevation angular sector (s) of the principal flat light beam (26, 27), the deflector further being positioned above the horizontal plane of symmetry of the cylindrical lens and below the upper surface of the cylindrical lens so as to interrupt light rays from the light source oriented outside the elevation angular sector (s) of the principal flat light beam (26, 27). an elongate cylindrical lens the cylindrical shape of which is defined by a horizontal generatrix direction and by a director curve, the cylindrical lens having a horizontal plane (100, 1000) of symmetry, a linear light source (14, 15) parallel to the generatrix direction, extending over all or part of the length of the cylindrical lens to emit light in the direction of the cylindrical lens, the cylindrical lens being adapted to generate a principal flat light beam (26, 27) by concentrating the light in a predefined elevation angular sector around the horizontal generatrix direction in the direction of the space situated on the opposite side of the cylindrical lens to the light source, and being adapted to project the light in a predefined azimuth angular sector around the vertical direction, characterized in that it further comprises a deflector comprising a metal blade, positioned in the space situated on the side opposite the light source of the cylindrical lens, the deflector having a rectangular plate shape, the longitudinal sides of the deflector being parallel to the generatrix direction, the transverse sides of the deflector being oriented around the generatrix direction in accordance with an elevation angle (s) contained in the predefined elevation angular sector (s) of the principal flat light beam (26, 27), the deflector further being positioned above the horizontal plane of symmetry of the cylindrical lens and below the upper surface of the cylindrical lens so as to interrupt light rays from the light source oriented outside the elevation angular sector (s) of the principal flat light beam (26, 27).