Patent ID: 7357531

Claim:
A light source device comprising: a light source lamp including an emitting tube having a discharge space and a pair of electrodes disposed in the discharge space of the emitting tube; and a reflector that reflects a light beam irradiated from the light source lamp, the emitting tube includes an emitting portion having the discharge space thereinside, sealing portions provided on both sides of the emitting portion and a curved surface connecting the outer circumferential surface of the emitting portion and the outer circumferential surface of the sealing portion, the reflector includes a cylindrical neck extending along a first sealing portion of the sealing portions of the emitting tube and a reflecting portion that extends from a base end in an extending direction of the neck to have a substantially concave cross section, the reflecting portion reflecting the light beam irradiated from the light source lamp to align in a predetermined direction, the light source lamp is so disposed that an emitting center of the emitting portion is positioned on a focus position of the reflecting portion of the reflector, the emitting tube has an inflection point on the curved surface at which refraction direction of the light beam irradiated from the emitting center changes when being irradiated from the outer circumferential surface of the emitting portion, and relations of θ1≦Tan −1 ( Hd /(2 F )) and T1<H≦Hd are established, where a diameter of a circle defining an edge on the neck side of a usable-light reflection area of the reflecting portion of the reflector is Hd, a distance between the edge on the neck side of the usable-light reflection area of the reflecting portion of the reflector and the emitting center of the emitting portion in a central axis direction of the light beam irradiated from the light source device is F, an opening diameter of the neck on the base end in the extending direction is H, a diameter of the sealing portion is T 1 , and an angle formed by a line connecting the inflection point between the emitting portion and the first sealing portion with the emitting center of the emitting portion and the central axis of the light beam irradiated from the light source device is θ 1 .