Metal halide lamp with reduced change in color temperature

摘要

A metal halide lamp includes: an arc tube having a light-emitting unit forming a discharge space therein, and two thin-tube units fitted into openings in both ends of the light-emitting unit; two electrode holding members provided through the thin-tube units so that one ends hold the electrodes and the other ends extend from one ends of the thin-tube units not facing the discharge space, and sealed to the thin-tube units via sealing members; and a metal tubular member through which the electrode and/or electrode holding member is inserted within the thin-tube units. Expressions "X>=0.0056P+0.194" and "0<=L<=0.44X" are satisfied, where "P" is lamp wattage [W], "X" distance [mm] from one end of the thin-tube unit facing the discharge space to one end of the coil facing the thin-tube unit, and "L" length [mm] of a part of the tubular member protruding into the discharge space.