Ultra-high pressure discharge lamp lighting method, ultra-high pressure discharge lamp to which the method is applicable and ballast for use therein, and lighting system incorporating the lamp and the ballast

A method of lighting an ultra-high pressure discharge lamp having a discharge bulb made of quartz glass in which a pair of electrodes are disposed facing each other, the method comprising:

• lighting the lamp with alternating current;
• and
• providing a time period of at least one second for which the alternating current assumes a value equal to or higher than a rated current value during a period for which the lamp lights steadily, wherein
• the electrodes each have a current withstanding capability against a current at least 1.5 times greater than a current value at which the lamp light is stabilized, and
• wherein during the time period a surface of at least one of the electrodes reaches a temperature sufficient to cause projections on the surface to fuse and extend over the surface.

A method of lighting an ultra-high pressure discharge lamp having a discharge bulb made of quartz glass in which a pair of electrodes are disposed facing each other, the method comprising:

• lighting the lamp with direct current;
• and
• performing a control such that a time period of at least one second for which the direct current is applied in a direction opposite to a direction of the current applied in usual lighting is intermittently provided during a period for which the lamp lights, wherein
• a negative electrode of the pair of electrodes has a current withstanding capability against a current at least 1.2 times greater than a current value at which the lamp light is stabilized.

A method of lighting an ultra-high pressure discharge lamp having a discharge bulb made of quartz glass in which a pair of electrodes are disposed facing each other, the method comprising:

• lighting the lamp with direct current;
• and
• performing a control such that a time period of at least one second for which the direct current is applied in a direction opposite to a direction of the current applied in usual lighting is intermittently provided during a period for which the lamp lights, while a time period of at least one second for which the the alternating current assumes a value equal to or higher than a rated current value during a period for which the lamp lights steadily, wherein
• a negative electrode of the pair of electrodes has a current withstanding capability against a current at least 1.2 times greater than a current value at which the lamp light is stabilized.

An ultra-high pressure discharge lamp configured to be lit with an alternating current, comprising:

• a discharge bulb made of quartz glass and imposed with a bulb load of 0.7 w/cm2 or more;
• and
• a pair of electrodes disposed facing each other in the discharge bulb, wherein
• the discharge bulb encapsulates at least one halogen selected from the group consisting of I, Br, and Cl in an amount ranging between 1×10−4 μmol/mm3 and 1×10−2 μmol/mm3, mercury in an amount of 0.15 mg/mm3 or more, and a rare gas as an initiator gas, and
• the electrodes each have a current withstanding capability against a current at least 1.5 times greater than a current value at which the lamp light is stabilized.

A ballast for use in an ultra-high pressure discharge lamp configured to be lit with alternating current, said ultra-high pressure discharge lamp including,

• a discharge bulb made of quartz glass and imposed with a bulb load of 0.7 w/cm2 or more, and
• a pair of electrodes disposed facing each other in the discharge bulb, wherein
• the discharge bulb encapsulates at least one halogen selected from the group consisting of I, Br, and Cl in an amount ranging between 1×10−4 μmol/mm3 and 1×10−2 μmol/mm3, mercury in an amount of 0.15 mg/mm3 or more, and a rare gas as an initiator gas,
• the electrodes each have a current withstanding capability against a current at least 1.5 times greater than a current value at which the lamp light is stabilized, and
• the ballast provides a time period of at least one second for which the alternating current assumes a lighting frequency of 5 Hz or lower during a period for which the lamp light is stabilized.

An ultra-high pressure discharge lamp configured to be lit with direct current, comprising:

• a discharge bulb made of quartz glass and imposed with a bulb load of 0.7 w/cm2 or more;
• and
• a pair of electrodes disposed facing each other in the discharge bulb, wherein
• the discharge bulb encapsulates at least one halogen selected from the group consisting of I, Br, and Cl in an amount ranging between 1×10−4 μmol/mm3 and 1×10−2 μmol/mm3, mercury in an amount of 0.15 mg/mm3 or more, and a rare gas as an initiator gas, and
• a negative electrode of the electrodes has a current withstanding capability against a current at least 1.2 times greater than a current value at which the lamp is lit.

A ballast for use in an ultra-high pressure discharge lamp configured to be lit with direct current, said ultra-high pressure discharge lamp including,

• a discharge bulb made of quartz glass and imposed with a bulb load of 0.7 w/cm2 or more, and
• a pair of electrodes disposed facing each other in the discharge bulb, wherein
• the discharge bulb encapsulates at least one halogen selected from the group consisting of I, Br, and Cl in an amount ranging between 1×10−4 μmol/mm3 and 1×10−2 μmol/mm3, mercury in an amount of 0.15 mg/mm3 or more, and a rare gas as an initiator gas,
• a negative electrode of the electrodes has a current withstanding capability against a current at least 1.2 times greater than a current value at which the lamp is lit, and
• the ballast performs a control such that a time period of at least one second for which the direct current is applied in a direction opposite to a direction of the current applied in usual lighting is intermittently provided during a period for which the lamp is lit.

A lighting system comprising:

• an ultra-high pressure discharge lamp configured to be lit with alternating current, said ultra-high pressure discharge lamp including a discharge bulb made of quartz glass and imposed with a bulb load of 0.7 w/cm2 or more, and a pair of electrodes disposed facing each other in the discharge bulb;
• and
• a ballast that provides a time period of at least one second for which the alternating current assumes a lighting frequency of 5 Hz or lower during a period for which the lamp light is stabilized, wherein
• the discharge bulb encapsulates at least one halogen selected from the group consisting of I, Br, and Cl in an amount ranging between 1×10−4 μmol/mm3 and 1×10−2 μmol/mm3, mercury in an amount of 0.15 mg/mm3 or more, and a rare gas as an initiator gas, and
• the electrodes each have a current withstanding capability against a current at least 1.5 times greater than a current value at which the lamp light is stabilized.

A lighting system comprising:

• an ultra-high pressure discharge lamp configured to be lit with direct current, said ultra-high pressure discharge lamp including a discharge bulb made of quartz glass and imposed with a bulb load of 0.7 w/cm2 or more, and a pair of electrodes disposed facing each other in the discharge bulb;
• and
• a ballast that performs a control such that a time period of at least one section for which the direct current is applied in a direction opposite to a direction of the current applied in usual lighting is intermittently provided during a period for which the lamp is lit, wherein
• the discharge bulb encapsulates at least one halogen selected from the group consisting of I, Br, and Cl in an amount ranging between 1×10−4 μmol/mm3 and 1×10−2 μmol/mm3, mercury in an amount of 0.15 mg/mm3 or more, and a rare gas as an initiator gas, and
• a negative electrode of the electrodes has a current withstanding capability against a current at least 1.2 times greater than a current value at which the lamp is lit.