| 摘要 |
PURPOSE: To obtain a light source having the excellent characteristics as a light source for a liquid crystal projecting-type display, and having the long life, by restraining instability of light emission output to be generated in a short arc metal halide lamp for d.c. lamp, wherein opaque white is restrained. CONSTITUTION: In a quartz-made lamp 3 provided with a positive electrode 1 and a negative electrode 2, the tip of the positive electrode is formed into a shape wherein a flat surface 4 having the constant area is made to remain on the tip, and the corner is ground, in order to obtain the stable discharge in lighting wherein an arc shaft is approximately horizontally placed. When the lamp current is taken as I ampere, the positive electrode is so designed that the relationship of 0.45(mm<2> /A)<S/I<0.08(mm<2> /A) (corresponding to input current from 100W to 250W) may be satisfied between the area of Smm<2> of the flat surface on the tip of the positive electrode and the current I ampere in relation to a lamp having the lamp current having the degree of the range from 1.6 ampere to 4.5 ampere. Moreover, it is desirable that the grinding tilt angleθon the tip of the electrode is 45 deg. or more.
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