| 摘要 |
PURPOSE:To reduce the irregularity in efficiency, color and temperature, by almost elliptically shaping the cross section of the lowest portion of a light emission tube which is housed in an outer tube, to diminish the irregularity in the location of clinging of an unevaporated iodide. CONSTITUTION:A luminous tube 1, which has electrodes 2' and in which rare gas, mercury and a metal halide are sealed, is housed in an outer tube so that a high-pressure discharge lamp is constructed. The cross section of the luminous tube 1, which extends on the middle point between the bottom T of the lower sealed portion of the tube and the tip P of the electrode 2' and is perpendicular to the straight line extending on both the electrodes 2', is almost elliptically shaped so as to establish a relation of 0.5<b/a<0.86 where a denotes the length of a half of the major axis of the ellipse defined by the intersection of the cross section and the inside surface of the tube 1, and b denotes the length of a half of the minor axis of the ellipse. The portions of the sealed surface of the tube 1, the forms of which become less irregular at the time of the sealing of the tube 1, are thus placed at a larger distance from the arc therein to reduce the irregularity in luminous property which is caused by the irregularity in the location of clinging of an unevaporated iodide 10.
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