Abstract: The invention relates to a lighting unit comprising at least a high-pressure gas discharge lamp, which comprises at least a lamp bulb (1) with a discharge space (21) in which two electrodes (41, 42) are arranged and in which a gas mixture with ingredients capable of condensation is present, wherein a risk of condensation deposit between and/or on the two electrodes (41, 42) exists, and which comprises an ignition device and a unit for local heating (5) of the lamp bulb (1), characterized in that the lighting unit comprises at least one unit for local cooling (6) of the lamp bulb (1).

Abstract: A high-pressure mercury vapor discharge lamp (1) comprising an envelope (2) of high temperature resistant material having a discharge vessel (3) and two electrodes (5, 6) extending from two seal portions (4) into the discharge vessel (3), the two electrodes having an electrode gap (de) smaller than or equal to 2.5 mm, preferably smaller than or equal to 1.5 mm, is described. The discharge vessel (3) contains a filling which essentially comprises the following substances: rare gas, oxygen, halogen consisting of chlorine, bromine, iodine, or a mixture thereof, as well as mercury in a quantity greater than or equal to 0.15 mg/mm3? The seal portions (4) have a cross-sectional area of between 6 mm2 and 20 mm2, preferably approximately 10 mm2. A method of manufacturing such a high-pressure mercury vapor discharge lamp (1) and a projector system for such a high-pressure mercury vapor discharge lamp (1) are also described.

Abstract: A method and a circuit arrangement are described for operating a discharge lamp is described, especially a high-intensity discharge lamp or lamps (HID) or UHP [ultra high performance]-lamp, which is/are distinguished by a first and a second operating phase with a higher first or a lower second frequency of the lamp AC, wherein the operating phases are activated alternatingly at defined intervals and for defined periods of time, in order to achieve a stable arc discharge and only a low burnout or rise in burning voltage of the lamp during its life by configuring certain forms of electrode tips. Furthermore, are described an illumination unit with a discharge lamp and such a circuit arrangement as well as a projection system with a projection display and such an illumination unit.

Abstract: A method and a circuit arrangement for the operation of a discharge lamp, in particular of a high-pressure gas mercury discharge lamp (HID[high intensity discharge]) lamp or a UHP [ultra high performance] lamp, are described, which are used to improve the color rendering index of the light. This is essentially achieved by feeding the lamp current on which current pulses with a suitably adjusted amplitude Ip and/or duration ?p and/or repetition rate f are superimposed.

Abstract: The invention relates to an electrode for a high intensity discharge lamp, at least consisting of an electrode head (2), which has a spherical shape, and an electrode base (1), wherein, in the direction perpendicular to the longitudinal axis of the electrode, the electrode head (2) has a greater dimension than the electrode base (1) at the transition between electrode head (2) and electrode base (1), and a spherical electrode tip (3) is arranged on the electrode head (2), which electrode tip, in the direction perpendicular to the longitudinal axis of the electrode, has a smaller maximum dimension than the electrode head (2). A cylindrical protrusion (4) is arranged on the electrode tip (3), which cylindrical protrusion, in the direction perpendicular to the longitudinal axis of the electrode, has a smaller maximum dimension than the adjoining electrode tip (3). The electrode can be produced from a one-piece blank.

Abstract: The invention relates to a method and an arrangement (10) for monitoring a gas discharge lamp (22), comprising a control circuit (18) for detecting an electrical measured value assigned to the lamp voltage. The control circuit (18) is provided for detecting one voltage value prior to a change in current and a second voltage value after a change in current, or a setting time, and for producing a control signal which depends on the difference in the voltage values or on the setting time. In this way, a pressure within the lamp is monitored and a control signal can be produced which can be used to cool the lamp or to switch the lamp off. This methods detects inflation and therefore prevents an explosion of the lamp.

Abstract: The invention relates to an electrode for a high-intensity discharge lamp, at least consisting of an electrode head (7) and an electrode base (5), wherein at least one region of the electrode base (5) has a lower thermal conductivity than the electrode head (5) and/or at least one element designed for limiting the heat flow in the electrode base is arranged between the electrode head and the electrode base.

Abstract: The invention describes a method of monitoring the mercury condensation in a gas filled arc tube (2) of a mercury vapour discharge lamp (1), wherein a lamp voltage and a lamp current are determined and analysed to give an indication of the state of mercury saturation of the gas in the arc tube. Moreover the invention describes an appropriate monitoring arrangement for performing this method.

Abstract: A method and a circuit arrangement for operating a discharge lamp, in particular during the first hours of operation after lamp manufacture, are described. The method and the circuit arrangement are provided in particular for high-pressure gas discharge lamps (HID or high intensity discharge lamps or UHP or ultra high performance lamps). Furthermore, a lighting unit with a discharge lamp and such a circuit arrangement and a projection system with a projection display and such a lighting unit are described. Switching-over between various modes of operation with different operating frequencies serves to avoid that the burning voltage of the lamp drops into a region of a minimum voltage of a lamp driver unit below which the latter can no longer drive the lamp with its rated power or a desired power.