Patent ID: 6744206
Filing Date: 2004-06-01
Classification: H01J

Abstract:
A metal halide lamp, comprising:a bulb that is made up of a light-emitting unit in which a discharge space is formed, and a pair of thin-tube units each being fitted into an opening in a different one of both ends of the light-emitting unit; a pair of electrodes that extend into the discharge space so that tops thereof are opposed to each other, each electrode having an electrode coil at a top part thereof; a pair of electrode holding members each being provided through a different one of the thin-tube units so that one end thereof holds the electrode and the other end thereof extends from one end of the thin-tube unit not facing the discharge space, each electrode holding member being sealed to the thin-tube unit via a sealing member; a tubular member that is provided in at least one of the thin-tube units, so that the electrode and/or the electrode holding member therein is inserted through the tubular member, the tubular member being made of a heat-proof and heat-conductive material, wherein the expressions X&gE;0.0056P+0.194 and 0&lE;L&lE;0.44X are satisfied, where â€œPâ€  is a lamp wattage [W], â€œXâ€  is a distance [mm] from one end of the thin-tube unit facing the discharge space to one end of the electrode coil facing the thin-tube unit, and â€œLâ€  is a length [mm] of a part of the tubular member protruding from the end of the thin-tube unit facing the discharge space into the discharge space.