Patent ID: 6538379
Filing Date: 2003-03-25
Classification: H01J

Abstract:
A discharge lamp comprising:an arc tube made of a translucent ceramic and dosed with a metallic halide, said arc tube including: a main tube body having a large diameter portion and small diameter portions each disposed at both sides of the large diameter portion; and a narrow tube having a smaller diameter than that of the small diameter portion and airtightly fixed to the small diameter portion while penetrating the small diameter portion; a pair of electrodes disposed in said arc tube such that discharge is conducted between said electrodes; wherein a relationship (P+268.75)/31.25&lE;L&lE;(P+456.25)/31.25 and 200&lE;P&lE;400 is satisfied where P (W) is the rated power of the discharge lamp and L (mm) is a length of a protrusion of the narrow tube which is protruded form said main tube body.