METAL HALIDE LAMP, METAL HALIDE LAMP LIGHTING DEVICE AND HEAD LIGHT

摘要

There are provided a mercury-free metal halide lamp improved in a luminous flux maintenance factor by limiting an excessive temperature rise at the upper portion of a luminous bulb at starting, and a metal halide lamp lighting device and a head light using this. The metal halide lamp MHL comprises a light-transmitting hermetic vessel 1 having a discharge space 1c therein, the portion thereof facing the center part having a wall thickness of at least 1.7 mm, a pair of electrodes 1b hermetically disposed so as to face each other at a interval in the discharge space, and a discharge medium sealed so as to contain a halide of a light-emitting metal and a rare gas but not to contain mercury (Hg) substantially, the lamp being configured such that a lamp voltage ratio V 16 /V 0 satisfies V 16 /V 0 ‰¥1.5 when performing lighting in such a manner a lamp power supplied from starting up to stable lighting is larger than a lamp power supplied at stable lighting, where V 16 (V) is a lamp voltage 16 seconds after starting and V 0 (V) is the lowest lamp voltage after starting.