| 摘要 |
PURPOSE: To prevent a color shade of the light projected on a screen and nonuniformity of illuminance by downward dislocating an integral electrode arranged in the horizontal direction, and inclining a curved surface reflector arranged around the vertical central axis in a metal halide lamp. CONSTITUTION: In a metal halide lamp where a discharge medium is sealed in an airtight vessel 14 and lamp input per unit surface area is not less than 40w/cm<2> , a pair of electrodes 16a and 16b are enclosed at prescribed intervals in the horizontal direction in the vessel 14 with its center 0 as the center. A curved surface reflector 13 having a spherical surface, an ellipse or a paraboloid is arranged around its vertical central axis Ov. When an inside diameter of the vessel 14 is set inΦmm, the electrode axis between the electrodes 16a and 16b is dislocated downward by L mm expressed by an expression I, and therefore, upward displacement by bending of an arc is almost offset. The horizontal central axis of the reflector 13 is arranged so as to have an angleθexpressed by an expression II to the horizontal central axis of the vessel 14, and, therefore, chromaticity of the light projected on a screen and nonuniformity of illuminance can be prevented.
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