Patent ID: 8857998

Claim:
A light source device comprising: an arc tube that has a light emission portion containing a pair of electrodes and electrode extension lines and leads; a cooling channel that has a downstream part branched into a first channel and a second channel, and configured to guide air toward the light emission portion via the first channel or the second channel; a rotational member disposed within the cooling channel in such a condition as to be rotatable around a predetermined rotation shaft by gravity, and configured to switch the cooling channel to the first channel when the light source device is set in a first position, and to switch the cooling channel to the second channel when the light source device is set in a second position different from the first position; a housing that accommodates the arc tube, the housing having a first opening communicating an inside of the housing with an outside of the housing and communicating with the first and second channels and a second opening communicating with a channel of air for cooling an area between the electrode extension lines and the leads; the second opening being disposed on a light emission side of the first opening; and a duct that forms a part of the cooling channel and connects with an outside surface of the housing to guide outside air toward the first and second openings, wherein the rotational member is shaped such that the width of the rotational member in the direction parallel to the rotation shaft decreases in a direction from an end disposed away from rotation shaft toward the rotation shaft, the rotational shaft is disposed on the first opening, and the duct is shaped such that the width of the cooling channel decreases in a direction toward the first opening in accordance with the shape of the rotational member.