Abstract: Luminaire provided with a bowl-shaped reflector for an elongated light-emitting part of a light source to be arranged substantially on the principal axis of said reflector. The reflector has a reflecting surface composed of elongated facets whose longitudinal sides extend from adjacent the center to the peripheral edge of the reflector. The facets are concavely curved in a cross-section comprising the principal axis and are straight in a plane at right angles to the peripheral axis and constitute a regular polygon, the axis of symmetry of a facet extending in accordance with a curve approaching the shape of a parabola.

Abstract: A reflector whose reflecting surface is formed as a portion of a solid of revolution, the generatrix of the solid of revolution having a plurality of staggered parabolic segments, the transition portions located between the segments changing smoothly into the segments and being of such a shape that in use in the reflector, of a light source, the reflected light beam has a comparatively large width and that the object to be illuminated is illuminated uniformly.

Abstract: In the electric incandescent lamps having an infrared radiation-reflecting filter which is pervious to visible light, the efficiency can be increased by adapting the geometry of the filter and the geometry of the filament to each other. According to the invention, the filter comprises a major portion of a prolate ellipsoid of revolution and a cylindrical filament extends between the foci thereof, the distance between focal points being from 1-2 times the length of the filament.