a panoramic light emitter of an omnidirectional horizontal light beam with very sharp cut - off in the vertical plane is disclosed . the sharp cut - off prevents interference near airports . high average powers are attainable because the light source can be distributed rather than be a point source . the omnidirectional - in - the - horizontal - plane light emitter with a high degree of vertical beam control is achieved by combining a generally cylindrical refractor with an internally emitting open - ended generally conical light source . the internal emitting surface of the conical light source is in the focal plane of the cylindrical refractor . the refractor sharply images the source with its edges , and that image is projected panoramically as the light beam having sharp cut - off at the edges of the image . the external surface of the conical light source does not emit , thus preventing undesired angles of light from passing out through the refractor . the light source disclosed is made up of a circular lamp illuminating the interior surface of a conical section in a reflector , although other light sources yielding the above characteristics are also suitable .