Abstract: An elongated luminaire is provided having at least one fluorescent lamp and a louver arranged therebelow. The louver consists of lamp-parallel longitudinal reflectors and reflecting cross-oriented lamellae arranged transversely thereto and subsequently of V-shape in cross section. The lamella legs have a parabolic shape in cross section. A light guiding plate is provided extending from one leg of each cross-oriented lamella, extending diagonally upwardly towards and almost adjacent to the lamp. Each light guiding plate substantially overlaps the interspace between neighboring cross-oriented lamella in the vertical projection. Thus, the entire light flux, emerging downwards, is directed, depending on the position of the cross-oriented lamellae and of the light guiding plates, in the desired direction into the lower hemisphere so that it is possible to obtain different light distribution curves of symmetrical or asymmetrical shape with characteristic preferred directions.

Abstract: A lamp includes a light source having a center and a light diffuser disc having two opposite faces and supported at a distance from the light source. One face of the light diffuser disc is provided with a prism structure which is symmetrical with respect to a normal that passes through the center of the light source and that is perpendicular to the faces of the light diffuser disc. The prism structure is formed of a plurality of prisms extending parallel to one another; each prism has a frontal flank oriented towards the normal and a rear flank oriented away from the normal. The angle of inclination of the frontal flanks gradually decreases from prism to prism in a direction away from the normal, while the angle of inclination of the rear flanks gradually increases at a decreasing rate, from prism to prism towards an upper limit value in a direction away from the normal.