Patent ID: 7242144

Claim:
A high-pressure discharge lamp, characterized in that the high-pressure discharge lamp comprises: a discharge vessel having a hermetic vessel which is fire resistant and translucent and has a discharge space therein, and a pair of electrodes hermetically provided at opposite ends of the discharge space in the hermetic vessel facing each other at a distance of 5 mm or less; and a discharge medium substantially containing no mercury, sealed in the hermetic vessel, and containing xenon gas at 3 atmospheres or higher, and at least two of halides of light-emitting metals including iodides of sodium (Na), scandium (Sc), and rare earth metals, the high-pressure discharge lamp is kept on with a lamp power of 50 W or lower in a stable state, and the temperature T (° C.) of the electrode at a point at a distance of 0.3 mm from the tip end to the base end in the stable state and the amount A (mol/cc) of free iodine produced when the lamp is tumed off after 100 hours of on-time satisfy the formula (1): T 2 /A> 10 11 (1).