Abstract: A substantially U-shaped gas discharge lamp (1′), containing mercury for the gas discharge, is connected to a high-frequency driver circuit (6′). To ensure that the gas discharge lamp operates with minimum loss and maximum light yield, the respective output terminals (4′, 5′) of the high-frequency driver circuit are not electrically grounded and the central section (11′) of the gas discharge lamp is capacitively coupled to an electric ground. A substantial reduction of lamp current in the central section is ensured, thus lowering thermal production in the central section of the gas discharge lamp. Accordingly, the central section becomes the coldest place in the gas discharge chamber and the place where condensation of the mercury occurs. The mercury vapor pressure can thus be regulated and the light yield optimized.

Abstract: A substantially U-shaped gas discharge lamp (1′), containing mercury for the gas discharge, is connected to a high-frequency driver circuit (6′). To ensure that the gas discharge lamp operates with minimum loss and maximum light yield, the respective output terminals (4′, 5′) of the high-frequency driver circuit are not electrically grounded and the central section (11′) of the gas discharge lamp is capacitively coupled to an electric ground. A substantial reduction of lamp current in the central section is ensured, thus lowering thermal production in the central section of the gas discharge lamp. Accordingly, the central section becomes the coldest place in the gas discharge chamber and the place where condensation of the mercury occurs. The mercury vapor pressure can thus be regulated and the light yield optimized.

Abstract: A flat lighting unit that is particularly easy to produce having high luminous efficiency and compact dimensions. The lighting unit is provided with a light-guiding plate (1), which includes volume elements (2) with different refractive indices for scattering the light. The plate (1) forms a light-emitting surface (3) on one side and has recesses (4) on the other side, facing away from the light-emitting surface. The recesses are distributed over the surface of the light-guiding plate and each recess has an individual light source (5) embedded therein.