Patent ID: 6137228
Filing Date: 2000-10-24
Classification: H01J

Abstract:
A metal halide lamp comprising:a quartz glass bulb forming a discharge chamber;a pair of electrodes, discharge ends of said electrodes being provided so as to face each other within said discharge chamber;tungsten coils respectively fixed around said electrodes;molybdenum foils respectively connected to ends of said electrodes which are opposite to said discharge ends; andlead-in wires for supplying current from outside to the electrodes, said lead-in wires being respectively connected to said molybdenum foils; whereinsaid tungsten coils, having been fixed around said electrodes, are sealed by means of said quartz glass bulb; portions of said tungsten coils that extend from respective molybdenum foils to a position that is roughly halfway along the lengths of respective electrodes are tightly fixed around said electrodes, the coil pitch of said tungsten coils being sufficiently wide that molten quartz glass reaches said electrodes; andinner diameters of portions of said tungsten coils that extend from a position that is halfway along the lengths of the respective electrodes to said discharge ends of said respective electrodes are set to provide an appropriate gap between the coils and said electrodes, and the coil pitch of said portions of said tungsten coils that extend from said position that is halfway along the lengths of said respective electrodes to the discharge ends of said respective electrodes is sufficiently narrow such that molten quartz does not reach the electrodes.