High pressure discharge lamp

摘要

A high-pressure discharge lamp (21) includes: an arc tube (1) that is made from a translucent ceramic material and composed of a main-tube part (3) in which a discharge space (25) is formed and thin-tube parts (4,5) extending from both ends of the main-tube part (3); and a pair of electrodes (10,11) having rods (12,13) respectively extending from the two thin-tube parts (4,5) into the discharge space (25) so that the tops face each other with a distance (Le) in-between The rod (12,13) of at least one of the electrodes (10,11) is held by a tubular electrode holder made of a halide-resistant metal embedded in and bonded to the thin-tube part (4,5) via an adhesive agent (8,9) including a sintered halide-resistant metal impregnated with mixture glass. The electrode holder is at such a position that satisfies "L‰§0.012P+2.5[mm]", where "L" is distance [mm] between the electrode top and one end of the electrode holders closer to the discharge space (25), and "P" is the lamp wattage (W).