Discharge lamp has electrode comprising tip end face whose surface roughness is lesser than surface roughness of side surface

摘要

The discharge lamp has an arc tube in which a pair of electrodes (12) is arranged. A sealed space (18) is formed in inner wall (2) of electrode. A heat conductor (m) is provided in a tip end face (2a) of inner wall of electrode. A side surface (2b) is located adjacent to the tip end face of the electrode. The surface roughness of the tip end face is lesser than the surface roughness of the side surface. The surface roughness of tip end face is 0.58mu m.