Metal halide lamp and automotive headlamp apparatus

Abstract

To improve the ratio between first and second halides sealed in a mercury-free lamp, thereby providing a metal halide lamp which has a high luminous efficiency and a low lamp voltage reduction and emits light of an appropriate color and an automotive headlamp apparatus incorporating the same. A metal halide lamp includes a hermetic vessel 1 which is fire resistant and translucent; a pair of electrodes 3, 3 sealed in the hermetic vessel with facing each other at a distant of 5 mm or less; and a discharge medium substantially containing no mercury, sealed in the hermetic vessel 1, and containing first halides mainly including scandium halide and sodium halide, a second halide for mainly providing a lamp voltage and a xenon gas at 5 atmospheres or higher at a temperature of 25° C., the amounts of scandium halide and sodium halide sealed in the hermetic vessel satisfying the formula of 0.25<a/(a+b)<0.5, where reference character a denotes the mass of scandium halide and reference character b denotes the mass of sodium halide, in which, in a stable state, the metal halide lamp is turned on with a lamp power of 60 W or lower.

Dependencies are inferred from the claim text.