To provide a light source device capable of improving the utilization ratio of light of a light source by preventing fouling of a member reflecting a light flux emitted from the light source.
In this light source device, since a photocalytic reaction is induced by the light flux containing ultraviolet emitted from a light source lamp because a titanium oxide film 63 is formed near a reflecting surface 131 of a sub reflecting mirror as a part of a dielectric multilayered film 60, dust such as an organic substance adhering to the reflecting surface 131 of the sub reflecting mirror is decomposed and removed. Even if there is dew condensation on the reflecting surface 131 of the sub reflecting mirror, it is hydrophilized by the photocalytic reaction, thus, contact traces with waterdroplets hardly remains and antifouling of the reflecting surface 131 is prevented at this point as well. Therefore, the light flux emitted from the light source lamp is surely reflected by the sub reflecting mirror, decline in the reflection factor by haze of the reflecting surface 131 is prevented and the utilization ratio of the light of the light source can be substantially improved.
Kanji Nakayama
Tsuyoshi Ishizaki