Patent ID: 6476555
Filing Date: 2002-11-05
Classification: H01J

Abstract:
A metal halide lamp comprising:an arc tube made up of a light emitting part and a sealing part at each end of the light emitting part, the light emitting part including a discharge chamber that contains a metal halogen substance; a pair of electrodes that each extend from the sealing part and have inner and outer ends, the inner ends facing each other at a predetermined distance in the discharge chamber so that discharge takes place between the facing inner ends, and the outer ends being sealed in the sealing parts and connected to conductors sealed in the sealing parts; and a pair of metal members that are attached to the pair of electrodes in a one-to-one relationship, each metal member partially covering an electrode within a length measured along the electrode from a boundary between the light emitting part and the sealing part to an inner end of the conductor, wherein an inequality of 0.2&lE;A/B&lE;1.6 is satisfied, where A is a weight of the metal member and B is a weight of a part of the electrode between the boundary and the inner end of the conductor, and wherein an inequality 0.5&lE;d/OD&lE;3.5 is satisfied, where OD is an outer diameter of the metal member and d is a length of the electrode measured from the boundary to an inner end of the metal member.