Abstract: The invention describes a method of driving a gas-discharge lamp (1) according to conditions in a specific region (R) of the lamp (1), which gas-discharge lamp (1) comprises a burner (2) in which a first electrode (4) and a second electrode (5) are arranged on either side of a discharge gap, which lamp (1) is realised such that the position (PCs) of a coldest spot during an AC mode of operation is in the vicinity of the first electrode (4), which method comprises the steps of initially driving the lamp (1) in the AC mode of operation; monitoring an environment variable of the lamp (1), which environment variable is indicative of conditions in a specific region (R) of the lamp (1); switching to a temporary DC mode of operation at a DC power value on the basis of the monitored environment variable, whereby the first electrode (4) is allocated as the anode; and driving the lamp (1) in the DC mode of operation until the monitored environment variable has returned to an intermediate environment variable threshold

Abstract: The invention describes a method of driving an arc-discharge lamp (1), which method comprises the steps of detecting a mechanically induced fluctuation in luminous flux of the lamp (1) occurring as a result of a physical displacement of the discharge arc (2), determining a characteristic (43, 51, 63) of the mechanically induced fluctuation in luminous flux of the lamp (1), and adjusting the lamp power on the basis of the determined characteristic (43, 51, 63) to suppress the mechanically induced fluctuation in luminous flux of the lamp (1).

Abstract: The invention describes a method of driving a gas-discharge lamp (1) according to conditions in a specific region (R) of the lamp (1), which gas-discharge lamp (1) comprises a burner (2) in which a first electrode (4) and a second electrode (5) are arranged on either side of a discharge gap, which lamp (1) is realised such that the position (PCs) of a coldest spot during an AC mode of operation is in the vicinity of the first electrode (4), which method comprises the steps of initially driving the lamp (1) in the AC mode of operation; monitoring an environment variable of the lamp (1), which environment variable is indicative of conditions in a specific region (R) of the lamp (1); switching to a temporary DC mode of operation at a DC power value on the basis of the monitored environment variable, whereby the first electrode (4) is allocated as the anode; and driving the lamp (1) in the DC mode of op eration until the monitored environment variable has returned to an intermediate environment variable threshold

Abstract: The invention describes a method of driving an arc-discharge lamp (1), which method comprises the steps of detecting a mechanically induced fluctuation in luminous flux of the lamp (1) occurring as a result of a physical displacement of the discharge arc (2), determining a characteristic (43, 51, 63) of the mechanically induced fluctuation in luminous flux of the lamp (1), and adjusting the lamp power on the basis of the determined characteristic (43, 51, 63) to suppress the mechanically induced fluctuation in luminous flux of the lamp (1).

Abstract: The invention relates to a method for operating a discharge lamp 11 including two electrodes 12,13. The method comprises applying to the electrodes an alternating current ILamp. In order to improve the performance of the lamp and to increase the life time of the lamp, it is proposed that the alternating current has a direct current component DC for compensating a temperature difference between the two electrodes. The direct current component is selected more specifically such that a first electrode, which is expected to have a lower temperature than the second electrode, functions as anode for the direct current component, while the second electrode functions as cathode for the direct current component. The invention relates equally to an electronic circuit and to a software program for operating a discharge lamp correspondingly, as well as to a lighting system comprising a discharge lamp and means for operating this discharge lamp correspondingly.

Abstract: The invention relates to a method of representing a video image based on a video signal by means of a projector which comprises an image display device and a high-pressure gas discharge lamp, which lamp is supplied with a square-wave alternating current (I0, I10) on which a current pulse (P1, P3, P10, P40) is superimposed before each phase reversal. According to the invention, the alternating current (I0, I10) is superimposed with a second current pulse (P2, P4, P20, P30, P50, P60) of the same polarity. A simple attunement of the alternating current frequency to the image frequency without image artifacts is made possible by the second pulses (P2, P4, P20, P30, P50, P60).

Abstract: A method and a circuit arrangement for the operation of a high-pressure gas discharge lamp (HID [high intensity discharge] lamp or UHP [ultra high performance] lamp) is described, which lamp is particularly suitable for illuminating projection displays with sequential color rendering (for example LCOS or SCR-DMD systems) with a pulsatory lamp current. Artefacts in the color rendering are avoided through the generation of at least one compensation pulse of a given amplitude and a given timing and through superimposition thereof on the lamp current.

Abstract: The invention relates to a method of representing a video image based on a video signal by means of a projector which comprises an image display device and a high-pressure gas discharge lamp, which lamp is supplied with a square-wave alternating current (I0, I10) on which a current pulse (P1, P3, P10, P40) is superimposed before each phase reversal. According to the invention, the alternating current (I0, I10) is superimposed with a second current pulse (P2, P4, P20, P30, P50, P60) of the same polarity. A simple attunement of the alternating current frequency to the image frequency without image artefacts is made possible by the second pulses (P2, P4, P20, P30, P50, P60).

Abstract: The invention relates to a method for operating a discharge lamp 11 including two electrodes 12,13. The method comprises applying to the electrodes an alternating current ILamp. In order to improve the performance of the lamp and to increase the life time of the lamp, it is proposed that the alternating current has a direct current component DC for compensating a temperature difference between the two electrodes. The direct current component is selected more specifically such that a first electrode, which is expected to have a lower temperature than the second electrode, functions as anode for the direct current component, while the second electrode functions as cathode for the direct current component. The invention relates equally to an electronic circuit and to a software program for operating a discharge lamp correspondingly, as well as to a lighting system comprising a discharge lamp and means for operating this discharge lamp correspondingly.

Abstract: The invention relates to an image projector with a High-Intensity-Discharge HID lamp (112) and a method of operating it. Such lamps have the disadvantage that their voltaic arc jumps back and forth between different positions at unforeseeable times during operation. This so-called arc jumping has the effect of changing the brightness, i.e. the overall brightness and/or the brightness distribution of the light emitted by the HID lamp (112). For the viewer of an image projected with such a projector, this effect appears as a jolt of this projected image. To avoid such effects for the viewer, it is first proposed according to the invention that changes in the brightness of the light in the image projector's beam path are detected. As soon as a change in brightness caused by an arc jump has been detected, this brightness is reset to a brightness detected at a moment t-2 before the arc jump, in order subsequently to convert it during a predetermined time interval T to the brightness resulting from the arc jump.

Abstract: A method and a circuit arrangement for the operation of a high-pressure gas discharge lamp (HID [high intensity discharge] lamp or UHP [ultra high performance] lamp) is described, which lamp is particularly suitable for illuminating projection displays with sequential color rendering (for example LCOS or SCR-DMD systems) with a pulsatory lamp current. Artefacts in the color rendering are avoided through the generation of at least one compensation pulse of a given amplitude and a given timing and through superimposition thereof on the lamp current.

Abstract: The invention relates to an image projector with a High-Intensity-Discharge HID lamp (112) and a method of operating it. Such lamps have the disadvantage that their voltaic arc jumps back and forth between different positions at unforeseeable times during operation. This so-called arc jumping has the effect of changing the brightness, i.e. the overall brightness and/or the brightness distribution of the light emitted by the HID lamp (112). For the viewer of an image projected with such a projector, this effect appears as a jolt of this projected image. To avoid such effects for the viewer, it is first proposed according to the invention that changes in the brightness of the light in the image projector's beam path are detected. As soon as a change in brightness caused by an arc jump has been detected, this brightness is reset to a brightness detected at a moment t-2 before the arc jump, in order subsequently to convert it during a predetermined time interval T to the brightness resulting from the arc jump.

Abstract: A high pressure lamp is driven with a pulse width modulated, alternating current pulses having an absolute value that is substantially constant and a short term average that varies approximately sinusoidally.

Abstract: A method of operating a projection system with at least one high intensity discharge lamp (HID lamp), a rotatable color disc with at least three segments of different colors, and an array (DMD) comprising a plurality of individually movable mirrors, wherein the current strength of the electrical operating current supplied to the HID lamp is varied in time such that the light arc of the lamp is stabilized, is to be constructed such that the power and operational life of the HID lamp used are optimized. The current strength of the operating current for the HID lamp is for this purpose varied such that the current strength reaches a maximum when a given segment of the color disc, and preferably exclusively this segment, is present in the radiation path of the light rays used for the projection.

Abstract: A method of and a device for operating a gas discharge lamp which is fed with an alternating voltage or an alternating current and wherein the instantaneous power of the lamp is increased at given time intervals are used to form the electrodes. The value of an operational datum of the lamp which varies in time is continuously or discontinuously measured and the frequency of the alternating voltage or the alternating current (operating frequency) is selected in dependence on the measured values.

Abstract: The high-pressure discharge lamp comprises a lamp vessel (1) in which an anode (4) and a cathode (5) are disposed spaced apart by an electrode distance D of 1-2 mm, the anode (4) having a tip (9) with a blunt end surface S. The area of the end surface S in mm2 and the lamp current I in amperes satisfy a relationship according to which 0.09≦S/I≦0.16, with 3.5≦I≦8.0 amperes. The ionizable filling containing metal halide comprises an amount of mercury between 65-125 mg/cm3. The power range of the lamp is between 200 and 400 watts. The calculated power gap ratio, PGR=P/D, is over 120 W/mm. The lamp is suitable for comparatively high brightness applications and at the same time is comparatively stable and has a comparatively long life.

Abstract: The invention relates to a method for operating a high pressure lamp, where an alternating lamp current (2) is supplied to the lamp. To improve the light-arc stability and to decrease dissipation power in the circuit arrangement, the absolute value of said lamp current (2) is substantially constant, and said alternating lamp current (2) is pulse-width modulated, whereby the pulse-width ratio between a pulse-width of a positive pulse and a pulse-width of a negative pulse is modulated. Also a circuit arrangement, a lamp current signal (2), and the use of these is disclosed.

Abstract: A method of and a device for operating a gas discharge lamp which is fed with an alternating voltage or an alternating current and wherein the instantaneous power of the lamp is increased at given time intervals are used to form the electrodes. The value of an operational datum of the lamp which varies in time is continuously or discontinuously measured and the frequency of the alternating voltage or the alternating current (operating frequency) is selected in dependence on the measured values.

Abstract: A method of operating a projection system with at least one high intensity discharge lamp (HID lamp), a rotatable color disc with at least three segments of different colors, and an array (DMD) comprising a plurality of individually movable mirrors, wherein the current strength of the electrical operating current supplied to the HID lamp is varied in time such that the light arc of the lamp is stabilized, is to be constructed such that the power and operational life of the HID lamp used are optimized. The current strength of the operating current for the HID lamp is for this purpose varied such that the current strength reaches a maximum when a given segment of the color disc, and preferably exclusively this segment, is present in the radiation path of the light rays used for the projection.

Abstract: A circuit arrangement for operating a high pressure discharge lamp includes input terminals for connection to a supply voltage source, lamp connection terminals for connection of the lamp, and a power supply coupled to the input terminals. The power supply provides a current to the lamp in the form of successive periods of current and includes a pulse generating element for generating a current pulse superpositioned on the periods of the current to the lamp. The pulse generation element is synchronized with an image writing signal.