Patent ID: 8777417

Claim:
A high-pressure discharge lamp comprising an arc tube, the arc tube including: a light-emitting part which is substantially ellipsoidal, which encloses a predetermined amount of mercury, and in which a pair of electrodes are disposed so that heads of the electrodes face each other; and sealing parts which extend from either end of the light-emitting part and in which bases of the electrodes are sealed, the high-pressure discharge lamp having a power rating greater than 355 W and not greater than 600 W, the predetermined amount falling within a range of 0.3 mg/mm 3 to 0.4 mg/mm 3 , wherein 5.4≦D≦5.8 and 3.1≦X≦D−2.3 when 355<P≦380, 5.8≦D≦6.2 and 3.1≦X≦D−2.7 when 380<P≦450, and 6.2≦D≦6.6 and 3.1≦X≦D−3.3 when 450<P≦600, where P denotes the power rating in watts of the high-pressure discharge lamp, D denotes an inside diameter in millimeters of the light-emitting part with reference to a midpoint between the electrodes, and X denotes a wall thickness in millimeters of the light-emitting part with reference to the midpoint between the electrodes.