Abstract: The present invention provides a back-lighting device, comprising a housing (10) with a plurality of fluorescent lamps (12), which are operated either individually or in groups (11A, 11B, 11C), wherein operation is controlled by a control device (1) which is fed with response signal; from one or more sensor devices (13A, 13B, 13C). The response signals relate to the intensity of the (groups) of fluorescent lamps. This allows a correction of inhomogeneities in the intensity distribution, based on group or individual variations, and thus a more homogeneous illumination. The invention also provides a display device comprising a back-lighting device according to the invention and a liquid crystal display.

Abstract: A hot cathode fluorescent lamp (2) comprises a vessel (4) containing two electrodes (8, 9) at a distance from each other with each electrode having two connection leads (10, 11, 12, 13) extending to the outside of the vessel. Across each electrode a heating voltage is applied to have a heating current (IH1, IH2) flowing through the electrode. Across 5 the electrodes a discharge voltage is applied to have a discharge or lamp current (IL) flowing through the lamp. At least for one electrode the lamp current is divided into partial lamp currents (IL1, IL2, IL3, IL4). A control circuit (32) is arranged to control the partial lamp currents, such that one of the partial lamp currents is greater, possibly maximum when taking a reference value for the heating current in account, than the other partial lamp current.

Abstract: Low-pressure mercury vapor discharge lamp has a discharge vessel (1) enclosing a discharge space (3) provided with an inert gas mixture and mercury. A first portion (11) of the discharge vessel is provided with a first electrode (12) and a luminescent layer (16), radiating light in a first range of the electromagnetic spectrum. A second portion (21) of the discharge vessel is provided with a second electrode (22), radiating light in a second range of the electromagnetic spectrum, said second range being different from the first range. According to the invention, the low-pressure mercury vapor discharge lamp comprises current supply conductors (12A, 12B; 22A, 22B) for receiving a DC current, and the discharge space contains only two electrodes (12, 22). The discharge lamp has a variable color temperature. Preferably, the discharge lamp influences the melatonin cycle in a human subject. Preferably, the lumen output level is independent of temperature.