Long life metal halide lamp and an illumination optical apparatus and image display system using same

A metal halide lamp comprising:

• a light transparent container possessing a pair of electrodes, wherein
• at least gadolinium halide (GdX.sub.3), lutetium halide (LuX.sub.3), and cesium halide (CsX), using iodine or bromine or their mixture as halogen, are sealed in said light transparent container, together with mercury and starting rare gas;
• and wherein
• the total weight of the gadolinium halide, lutetium halide, and cesium halide per unit volume of the light transparent container is 1 mg/cc or more,
• the weight of cesium halide in the total weight of halides is 15-50 percent, and
• the weight ratio of gadolinium halide and lutetium halide is in a range of 0.1.ltoreq.GdX.sub.3 /LuX.sub.3 .ltoreq.10.

A metal halide lamp comprising:

• a light transparent container possessing a pair of electrodes, wherein
• gadolinium halide (GdX.sub.3), lutetium halide (LuX.sub.3), and cesium halide (CsX), using iodine or bromine or their mixture as halogen, are sealed in said light transparent container, together with mercury and starting rare gas, and at least one of dysprosium halide and thallium halide, using iodine or bromine or their mixture as haligen, is sealed in said light transparent container in addition to the above halides;
• and wherein
• the total weight of the halides per unit volume of the light transparent container is 1 mg/cc or more,
• the weight of cesium halide in the total weight of halides is 15-50 percent.

A metal halide lamp comprising;

• a light transparent container possessing a pair of electrodes, wherein
• at least dysprosium halide (DyX.sub.3), lutetium halide (LuX.sub.3), neodymium halide (NdX.sub.3), and cesium halide (CsX), using iodine or bromine or their mixture as halogen, are sealed in said light transparent container, together with mercury and starting rare gas;
• and wherein
• a lamp electric power per distance between the electrodes is 20 W/mm or more,
• the total weight of the dysprosium halide, lutetium halide, neodymium halide, and cesium halide per unit volume of the light transparent container is 1 mg/cc or more,
• the weight of cesium halide in the total weight of halides is 15-50 percent.