Patent ID: 8884543

Claim:
A light source device comprising: a discharge lamp having a light emitting case including a hollow section in which a discharge medium is encapsulated, and a pair of electrodes having respective end portions disposed so as to be opposed to each other in the hollow section; a drive device adapted to supply the pair of electrodes with a drive current; a voltage detector adapted to detect an inter-electrode voltage of the pair of electrodes; and a time measurement device adapted to measure time, wherein the drive device is configured to alternately repeat a first alternating current supply interval in which the pair of electrodes are supplied with a first alternating current with a frequency higher than 1 kHz and a second alternating current supply interval in which the pair of electrodes are supplied with a second alternating current with a frequency one of equal to and lower than 1 kHz, a period of the first alternating current supply interval is measured with the time measurement device, the drive device performs a change from the first alternating current supply interval to the second alternating current supply interval when the period of the first alternating current supply interval measured reaches a predetermined period A, a period of the second alternating current supply interval is measured with the time measurement device, and the drive device performs a change from the second alternating current supply interval to the first alternating current supply interval one of when the period of the second alternating current supply interval measured reaches a predetermined period B, and when an absolute value of the inter-electrode voltage of the pair of electrodes reaches a threshold value.