Patent ID: 8167438

Claim:
A light source device comprising: a discharge lamp that emits light by discharge in an interelectrode space between a first electrode and a second electrode; a main mirror arranged at a side of the first electrode that reflects light flux generated by the discharge in the interelectrode space so as to emit the light flux to an area to be illuminated; a sub-mirror arranged at a side of the second electrode facing opposite the main mirror that reflects the light flux from the interelectrode space toward the interelectrode space; and a driver that supplies alternating current to the first and the second electrodes, and changes duty ratio of the alternating current supplied to the first and the second electrodes in accordance with a predetermined pattern, wherein maximum value of duty ratio of a first anode period in which the first electrode works as anode to one cycle of the alternating current is larger than maximum value of duty ratio of a second anode period in which the second electrode works as anode to the one cycle of the alternating current.