| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-pressure mercury vapor discharge lamp free from deterioration of optical characteristic by blacking of an arc tube during the rated life period of the discharge lamp, ever causing an unexpected accident such as crack or breakage of the arc tube, and excellent, particularly, as image equipment or a light source or light source device for image equipment. SOLUTION: This discharge lamp comprises a quartz arc tube having a pair of electrodes sealed on both ends, and a rare gas sealed therein together with mercury of the quantity giving a vapor pressure of 100-200 atm in lighting and 1.1×10<-5> -1.2×10<-7> mol/cc of bromine. The arc length between the electrodes is regulated to 0.5-1.5 mm. When the lamp current in stable time is I (A), the electrode core bar diameter from the electrode buried part to the electrode coil part is D (mm), and the arc length is L (mm), the relation of 0.2<=L.D/I<=0.4 is satisfied.
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