A high pressure discharge lamp includes a quartz glass bulb, a conductive element
which is sealed at a sealing portion of the bulb, and a pair of electrodes. Each
electrode is disposed in the quartz glass bulb so as to be opposite the other and
connected to the conductive element. A part of each electrode is sealed with the
quartz glass bulb at the sealing portion so as to generate a contacting portion
formed by the part of each electrode and the bulb. The maximum length, Lmax,
of the contacting portion is defined as: Lmax (mm)200/(PD);
and the minimum length, Lmin, of the contacting portion is defined as:
Lmin (mm)0.8/(D2) or Lmin (mm)0.7
whichever is longer, where D is the diameter (mm) of the electrode and P is the
power (W) supplied to the electrode.
