| 摘要 |
PROBLEM TO BE SOLVED: To provide a metal halide lamp capable of preventing thermal breakdown of a lighting circuit, and capable of exhibiting excellent light distribution characteristics. SOLUTION: The metal halide lamp 1 includes a double-tube structure body 20 having an arc tube 10 having a pair of electrodes 15a and 15b, and an inner tube 28 airtightly sealing the arc tube 10; a holder 30 for holding a longitudinal one end of the inner tube 28; and a case 40 attached to one opening side end part so that the opening is closed by the holder 30 and storing the lighting circuit for lighting the arc tube 10 in an inside thereof. When the maximum outside diameter (mm) of a bottom side end surface of a lamp casing 80 constituted by the holder 30 and the case 40 is D and the shortest distance (mm) from a distal end of the electrode 15a arranged in a side nearer to the lamp casing 80 of the pair of the electrodes 15a and 15b to a virtual plane A including the bottom side end surface of the lamp casing 80 is L, the following relationship is satisfied; 0.29≤D/2L≤3.6, 40≤D≤122, and 10≤L≤75. COPYRIGHT: (C)2011,JPO&INPIT
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