| 摘要 |
PROBLEM TO BE SOLVED: To provide a free lighting direction type high-efficiency/long-life metal halide lamp capable of restraining luminescent color variation by a specific lighting direction, and of improving a lamp life characteristic. SOLUTION: This low-wattage type metal halide lamp is provided with an arc tube 1 formed of a ceramic material and having a luminescent part 3 having a pair of electrodes on its inside, and thin tube parts 4 and 5 at both end parts of the luminescent part 3, respectively, and composed by filling the inside of the arc tube 1 with, as filling substances, metal halides including at least one kind out of dysprosium halide, thulium halide, holmium halide, and cerium halide, and sodium halide. When it is assumed that an inter-electrode distance in the arc tube 3 and the tube inside diameter at the center part of the arc tube 3 are Le (mm) andϕi (mm), respectively, the value of an arc tube shape parameter Le/ϕi satisfies a range of 0.45-0.65. COPYRIGHT: (C)2003,JPO
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