Patent ID: 8217582

Claim:
A light source device comprising: a discharge lamp provided with two electrodes; a discharge lamp lighting section adapted to light the discharge lamp by supplying the discharge lamp with electrical power while alternately switching a polarity of one of the electrodes of the discharge lamp with respect to the other of the electrodes; and a time-division color separation section adapted to receive light emitted from the discharge lamp in a lighted state and sequentially emit light beams with colors different from each other, wherein the discharge lamp lighting section switches the polarity in sync with a change in the color of the light beam emitted from the time-division color separation section, retains a duty ratio, which is a ratio of a positive polarity period with the polarity kept positive to a period of the polarity switching, at a constant value during a first retentive period, and retains the duty ratio at a different constant value from the duty ratio in the first retentive period during a second retentive period, thereby modulating the duty ratio.