Light source device and projector

A light source device comprising:

• an arc tube;
• a first reflection mirror which surrounds a part of the entire circumference of the arc tube around an optical axis of the arc tube to reflect light emitted from the arc tube toward an illumination target;
• and
• a second reflection mirror disposed oppositely to the first reflection mirror with the optical axis of the arc tube interposed between the first and second reflection mirrors to reflect light emitted from the arc tube toward the first reflection mirror,
• wherein
• the second reflection mirror is located in one of two spaces divided by a first plane passing through a light emission area within the arc tube and extending in parallel with the optical axis,
• a part of the first reflection mirror positioned on the side opposite to the illumination target with respect to a second plane extending perpendicular to the optical axis and containing the light emission area has a cross-sectional shape on a third plane which passes through the light emission area, extends in parallel with the optical axis, and crosses the first plane as a cross-sectional shape containing a part of an ellipse or a parabola, and
• the curvature at the cross point of a fourth plane extending in parallel with the second plane and the cross-sectional shape on the third plane in a part of the first reflection mirror is larger than the curvature at the cross point of the fourth plane and the cross-sectional shape on the first plane in the part of the first reflection mirror.