Abstract: An apparatus and method for detecting an end of life (EOL) condition of a lamp that exhibits a re-ignition behavior. A voltage is applied to the lamp to cause the lamp to start emitting light, and a lamp re-ignition voltage to normal lamp voltage difference after a mask-off period expires is monitored. The lamp is determined to have reached the EOL condition when a predetermined percentage of high difference half cycles occur during a set number of lamp voltage half cycles that are measured during a measurement window. The method continuously monitors the lamp re-ignition voltage to normal lamp voltage difference and records whenever the lamp re-ignition voltage to normal lamp voltage difference is higher than the re-ignition difference threshold level at any lamp voltage half cycle. An EOL lamp is detected when a predetermined number of high difference half cycles occurs in a set total number of lamp voltage half cycles measured in a rolling measurement window.

Abstract: An apparatus and method thereof for igniting and operating a high intensity discharge (HID) lamp during an in service life, and powering down the lamp when an end-of-life (EOL) lamp condition is detected. The apparatus and method defines a series of thresholds of lamp voltage asymmetry, or rectification thresholds, and monitors the lamp rectification from ignition through normal operation. The detection scheme is masked off for a predetermined period of time when the lamp is initially started. Thereafter, the rectification threshold of the lamp voltage asymmetry is gradually reduced over time, until a defined minimum rectification threshold level is reached and maintained. The method continuously monitors the lamp voltage and records whenever the lamp voltage asymmetry is higher than the rectification threshold level at any lamp voltage cycle.

Abstract: An apparatus and method for detecting an end of life (EOL) condition of a lamp that exhibits a re-ignition behavior. A voltage is applied to the lamp to cause the lamp to start emitting light, and a lamp re-ignition voltage to normal lamp voltage difference after a mask-off period expires is monitored. The lamp is determined to have reached the EOL condition when a predetermined percentage of high difference half cycles occur during a set number of lamp voltage half cycles that are measured during a measurement window. The method continuously monitors the lamp re-ignition voltage to normal lamp voltage difference and records whenever the lamp re-ignition voltage to normal lamp voltage difference is higher than the re-ignition difference threshold level at any lamp voltage half cycle. An EOL lamp is detected when a predetermined number of high difference half cycles occurs in a set total number of lamp voltage half cycles measured in a rolling measurement window.

Abstract: An apparatus and method thereof for igniting and operating a high intensity discharge (HID) lamp during an in service life, and powering down the lamp when an end-of-life (EOL) lamp condition is detected. The apparatus and method defines a series of thresholds of lamp voltage asymmetry, or rectification thresholds, and monitors the lamp rectification from ignition through normal operation. The detection scheme is masked off for a predetermined period of time when the lamp is initially started. Thereafter, the rectification threshold of the lamp voltage asymmetry is gradually reduced over time, until a defined minimum rectification threshold level is reached and maintained. The method continuously monitors the lamp voltage and records whenever the lamp voltage asymmetry is higher than the rectification threshold level at any lamp voltage cycle.

Abstract: A lamp ballast for operating a high intensity discharge lamp includes an electronic ballast circuit to supply an operating voltage to the discharge lamp, and an igniter circuit to supply starting pulses to the discharge lamp in a cold state and to supply hot restrike pulses to the discharge lamp when the discharge lamp is in a hot state following turn-off. The hot restrike pulses are sufficient to maintain ionization in the discharge lamp but do not cause the discharge lamp to generate substantial light output.

Abstract: Methods and apparatus are provided for operating very high pressure short arc mercury discharge lamps primarily used for projection applications. The method includes controlling an alternating lamp current supplied to the lamp at a constant RMS value. In some embodiments, the lamp current is adjusted to a new constant RMS value to maintain lamp power between an upper power limit and a lower power limit. In other embodiments, lamp cooling is adjusted to maintain a wall temperature of the arc tube below a softening temperature.

Abstract: An arc discharge metal halide lamp for use in selected lighting fixtures comprising a discharge chamber having light permeable walls of a selected shape including therein a pair of end region wall portions through each of which a corresponding one of a pair of electrodes are supported separated from one another by a separation length. The ratio of the separation length to the effective operation inner diameter of the chamber is greater than two. The lengths of the wall sides between the end wall portions is greater than the effective operation inner diameter. The end wall portions have inner surfaces of constant or smaller varying radii of curvature and they are separated from the interior ends of the electrodes by more than one millimeter. The discharge chamber can be constructed of polycrystalline alumina and contain metal halides.

Abstract: A lamp ballast for operating a high intensity discharge lamp includes an electronic ballast circuit to supply an operating voltage to the discharge lamp, and an igniter circuit to supply starting pulses to the discharge lamp in a cold state and to supply hot restrike pulses to the discharge lamp when the discharge lamp is in a hot state following turn-off. The hot restrike pulses are sufficient to maintain ionization in the discharge lamp but do not cause the discharge lamp to generate substantial light output.

Abstract: A high pressure discharge lamp system and a method for operating a high pressure discharge lamp are provided. The method includes rotating the discharge lamp around its longitudinal axis. The discharge lamp or a lamp assembly including the discharge lamp and a reflector may be rotated through specified angles at specified times or intervals, or upon the occurrence of specified events. The discharge lamp may be rotated when the lamp is deenergized or when the lamp is energized. The discharge lamp may be rotated by a predetermined angle before operation, after operation, or after a predetermined burn time. The lamp system includes a rotation mechanism coupled to the lamp assembly and configured to rotate the discharge lamp about its longitudinal axis.

Abstract: An arc discharge metal halide lamp having a discharge chamber with visible light permeable walls bounding a discharge region through which walls a pair of electrode assemblies are supported with interior ends thereof positioned in the discharge region spaced apart from one another. These electrode assemblies each also extend through a corresponding capillary tube affixed to the walls to have exterior ends thereof positioned outside the arc discharge chamber. At least one of these electrode assemblies comprises an electrode discharge structure with a discharge region shaft extending into the capillary tube corresponding thereto. A discharge region shaft extends outwardly in that corresponding capillary tube to be in direct contact with an interconnection shaft extending outside of that corresponding capillary tube to provide an exterior end of this electrode assembly, and which is in direct contact with a sealing cap over the end of the tube.

Abstract: An arc discharge metal halide lamp having a discharge chamber having visible light permeable walls bounding a discharge region supported electrodes in a discharge region spaced apart by a distance Le with an average interior diameter equal to D so they have a selected ratio. Ionizable materials are provided in this chamber involving a noble gas, one or more halides, and mercury in an amount sufficiently small so as to result in a relatively low maximum voltage drop between the electrodes during lamp operation.

Abstract: Methods and apparatus are provided for operating very high pressure short arc mercury discharge lamps primarily used for projection applications. The method includes controlling an alternating lamp current supplied to the lamp at a constant RMS value. In some embodiments, the lamp current is adjusted to a new constant RMS value to maintain lamp power between an upper power limit and a lower power limit. In other embodiments, lamp cooling is adjusted to maintain a wall temperature of the arc tube below a softening temperature.

Abstract: An arc discharge metal halide lamp having a discharge chamber with visible light permeable walls bounding a discharge region through which walls a pair of electrode assemblies are supported with interior ends thereof positioned in the discharge region spaced apart from one another. These electrode assemblies each also extend through a corresponding capillary tube affixed to the walls to have exterior ends thereof positioned outside the arc discharge chamber. At least one of these electrode assemblies comprises an electrode discharge structure with a discharge region shaft extending into the capillary tube corresponding thereto. A discharge region shaft extends outwardly in that corresponding capillary tube to be in direct contact with an interconnection shaft extending outside of that corresponding capillary tube to provide an exterior end of this electrode assembly, and which is in direct contact with a sealing cap over the end of the tube.

Abstract: An arc discharge metal halide lamp having a discharge chamber having visible light permeable walls bounding a discharge region supported electrodes in a discharge region spaced apart by a distance Le with an average interior diameter equal to D so they have a selected ratio. Ionizable materials are provided in this chamber involving a noble gas, one or more halides, and mercury in an amount sufficiently small so as to result in a relatively low maximum voltage drop between the electrodes during lamp operation.

Abstract: An arc discharge metal halide lamp for use in selected lighting fixtures comprising a discharge chamber having light permeable walls of a selected shape including therein a pair of end region wall portions through each of which a corresponding one of a pair of electrodes are supported separated from one another by a separation length. The ratio of the separation length to the effective operation inner diameter of the chamber is greater than two. The lengths of the wall sides between the end wall portions is greater than the effective operation inner diameter. The end wall portions have inner surfaces of constant or smaller varying radii of curvature and they are separated from the interior ends of the electrodes by more than one millimeter. The discharge chamber can be constructed of polycrystalline alumina and contain metal halides.

Abstract: A mercury-free metal halide arc lamp having an arc vessel of fused silica, an aspect ratio greater than 5, and containing a noble gas such as xenon, argon or krypton and a metal halide. In a preferred embodiment, the arc vessel has a diameter of 8 mm and a length of 80 mm, a fill of sodium/scandium iodides and a buffer gas of xenon.

Abstract: Rare-earth halides are shown to be a replacement for scandium halides in mercury-free discharge arc lamps if modifications are made to the prior art lamp design and operating temperatures. The inventive chemical compositions of the discharge medium provide enhanced color rendition index values. In addition, it has been unexpectedly determined that during the operation of the discharge lamps, the rare earth iodides do not react significantly with the fused silica arc tube. Equally as significant, any free iodine, which is so formed, has minimal impact on the efficacy of the lamp compared to the conventional scandium iodide lamps. Therefore, the rare earth iodide-containing lamps provide longer lifetime with superior illumination characteristics than conventional discharge lamps.

Abstract: A starting aid for a metal halide discharge lamp. An arc discharge tube is positioned in a hermetically sealed jacket. The jacket contains a partial pressure (e.g., 400 torr nitrogen) of a gas that will aid in starting the discharge and one of the arc tube lead-ins has an electrical conductor affixed thereto and exposed to the partial pressure of the gas. An outer conductor extends on the outside of the jacket and is electrically connected to the other lead-in. When voltage is applied to the electrodes a capacitive coupling takes place between the inner conductor and the outer conductor which generates a discharge that causes a breakdown in the arc generating and sustaining medium within the arc tube and causes the lamp to start.

Abstract: A ballast for a mercury-free, metal halide arc lamp having a quartz or fused silica envelope. The ballast provides a square-wave voltage, which substantially reduces or eliminates the re-ignition voltage in the mercury-free, metal halide arc lamp. The ballast reverses the voltage polarity, and reestablishes the arc current in the opposite direction, before the free halogen in the envelope can quench the arc.

Abstract: A system and method for the operation of a mercury free high intensity discharge lamp is disclosed which provides lamp longevity and improved photometric results regardless of the orientation of the lamp. To this end, an acoustically modulated ballast without off-time and low power time is supplied to the lamp.