| 摘要 |
PROBLEM TO BE SOLVED: To increase a rise speed of luminous energy when switching to a constant lighting mode, and to prevent blackening of an inner wall of an arc tube by preventing coagulation of mercury in a low power lighting mode.SOLUTION: An ultra high pressure mercury lamp includes the arc tube including a light emitter 2, in which mercury in an amount of enclosure of 0.15 mg/mmor more is enclosed, and a sealer 3 provided to connect to the light emitter 2, a pair of electrodes 4 having a head 41 and a shank part 43, wherein the heads 41 are arranged so as to oppose each other in the light emitter 2, and metal foil 6 buried in the sealer 3 and at the same time, connected to an end part of the shank part 43. The ultra high pressure mercury lamp is driven so as to switch between the constant lighting mode and the low power lighting mode in which a lamp is driven at a power value within a range of 20 to 50% of the rated power consumption and the ultra high pressure mercury lamp 1 is characterized in that radiant intensity in an ultraviolet wavelength range of 300 to 350 nm in the low power lighting mode is higher compared to the radiant intensity in the ultraviolet wavelength range in the constant lighting mode and an ultraviolet reflective film is formed in the sealer 3. |
