Metal halide discharge lamp, lighting device for metal halide discharge lamp, and illuminating apparatus using metal halide discharge lamp

A metal halide discharge lamp which essentially permits disusing mercury, comprising:

• a refractory and transparent hermetic vessel;
• a pair of electrodes fixed to said hermetic vessel;
• and
• a discharge medium sealed in the hermetic vessel and containing a first halide, a second halide and a rare gas, said first halide being a halide of at least one metal selected from the group consisting of sodium, scandium, and a rare earth metal, and said second halide having a relatively high vapor pressure and being a halide of at least one metal which is unlikely to emit a visible Light compared with the metal of the first halide.

A metal halide discharge lamp which essentially permits disusing mercury and which is lit by a DC current, comprising:

• a refractory and transparent hermetic vessel;
• an anode and a cathode fixed to said hermetic vessel;
• and
• a discharge medium sealed in the hermetic vessel and containing a first halide, a second halide and a rare gas, said first halide being a halide of at least one metal selected from the group consisting of sodium, scandium, and a rare earth metal, and said second halide having a relatively high vapor pressure and being a halide of at least one metal which is unlikely to emit a visible light compared with the metal of the first halide.

A metal halide discharge lamp which essentially permits disusing mercury and which is used in a headlamp having a rated power of at most 100W, comprising:

• a refractory and transparent hermetic vessel;
• a pair of electrodes fixed to said hermetic vessel;
• and
• a discharge medium sealed in the hermetic vessel and containing a first halide, a second halide and a rare gas, said first halide being a halide of at least one metal selected from the group consisting of sodium and scandium, and said second halide having a relatively high vapor pressure and being a halide of at least one metal which is unlikely to emit a visible light compared with the metal of the first halide.