1.  Field of the Invention
The present invention relates to a light source device comprising a light source lamp for use in, for example, an optical device, to a light source lamp unit comprising the light source device, and to a projection display device comprising the light source lamp unit. 
2.  Description of Related Art
These days, research and development of projection display devices for use in, for example, personal computers, for enlarging and projecting images is popular. 
In such projection display devices, light emitted from a light source lamp is reflected by a reflector, the emitted light is modulated by a light valve, such as a liquid crystal panel, based on image signals, and a modulated-light image is enlarged and projected by a projection lens or the like onto a projection surface. 
In a conventional projection display device, a light source device is composed of a light source lamp and a substantially conical reflector having the light source lamp attached to the axis thereof, and a light source lamp unit is composed of the light source device and a lamp housing for detachably mounting the light source device.  The light source lamp unit is arranged inside a casing of the projection display device together with the light valve, the projection lens, etc. 
In the projection display device having the configuration as described above, in order to efficiently use the luminous flux, the light source lamp is accurately positioned on a focal point of the reflector when the light source lamp is mounted in the casing, and the reflector having the light source lamp attached thereto is positioned so as to correspond to the lamp housing on the optical axis. 
However, when assembling the light source lamp unit, the light source lamp has been conventionally positioned and fixed to the reflector at the brightest position with the light source lamp lit, in other words, at a position where parallel light is emitted, and then the light source device is mounted to the lamp housing by springs, etc. 
In this case, as described above, while the light source lamp is positioned relative to the inner surface (substantially conical reflection surface) of the reflector, it is not positioned relative to the outer periphery of the reflector.  In addition, the light source device is incorporated in the lamp housing by pressing the outer periphery of the reflector by a fixing member, such as a spring, to the lamp housing. 
In other words, the light source lamp is positioned relative only to the inner surface of the reflector, and is not positioned relative to the outer periphery of the reflector and the lamp housing.  Thus, when the lamp housing is mounted in the casing, the position of the light source lamp varies to the designed optical axis, resulting in the problem of a reduction in illuminance at the projection screen, or of illumination non-uniformity. 
It is an object of the present invention to provide a light source device which can positively arrange a light source lamp at a predetermined position on an optical axis, and to a light source lamp unit and a projection display device. 
To this end, the present invention is intended to achieve the above object by the provision of an alignment reference surface on a reflector to which the light source lamp is attached. 
More specifically, a light source device of the present invention comprises a light source lamp, and a reflector for reflecting light emitted from the light source lamp, the light source lamp being attached to the reflector, wherein an alignment reference surface for aligning and mounting the light source lamp is formed on the reflector.  According to the present invention, the light source device can be assembled by mounting the light source lamp apart from the alignment reference surface by a predetermined distance with respect to, for example, the X-axis, Y-axis, and Z-axis, respectively. 
That is, in mounting the light source lamp to the reflector, it is possible to assemble the light source device without fine adjustment of the mounting position of the light source lamp while the light source lamp is lit. 
In the present invention, the reflector can be mounted to a lamp housing, and the alignment reference surface may also serve as a mounting reference surface for mounting the reflector to the lamp housing. 
With this arrangement, since the alignment reference surface also serves as a mounting reference surface, in assembling a light source lamp unit by mounting the light source device to the lamp housing, an optical lamp is accurately positioned relative to the lamp housing only by pressing the reference surface of the reflector against the lamp housing. 
Furthermore, the reflector may be cut out at side surfaces thereof to form an opening surface into a substantially rectangular shape. 
With this arrangement, not only a reduction in size of the light source device can be achieved, but also the light source lamp can be attached to the reflector more accurately by using the two sides of the substantially rectangular opening surface that are perpendicular to each other as the alignment reference surface. 
Moreover, the reflector may comprise a surface section for covering cutouts formed in the side surfaces thereof, and an edge of the surface section may constitute the alignment reference surface. 
With this arrangement, by covering the cutouts with the surface section, even if the light source lamp is broke due to an accident or the like, broken pieces of the light source lamp are blocked by the surface section, whereby the broken pieces are prevented from flying to the outside of the light source lamp unit. 
In addition, according to the present invention, the light source lamp unit comprises the above-described light source device, and the lamp housing for mounting thereto the light source device. 
Furthermore, according to the present invention, a projection display device is composed of the above-described light source lamp unit, a light valve for modulating light emitted from the light source lamp unit, and a projection lens for enlarging and projecting the light modulated by the light valve onto a projection surface. 
Therefore, according to these inventions, it is possible to provide a light source device which can positively arrange a light source lamp at a predetermined position on an optical axis, and to a light source lamp unit and a projection display device.