1. Technical Field
The present invention relates to a projector.
2. Related Art
There has been known a projector including: a light source device; an optical modulator for modulating a light beam irradiated by the light source device; and a projection optical device for projecting the light beam modulated by the optical modulator in an enlarged manner.
For the projector, there has been proposed an arrangement in which an optical diaphragm for adjusting light quantity of the light beam incident on the optical modulator is employed to enhance image quality of a projection image by appropriately changing a brightness of the projection image. The light quantity is adjusted by moving a light shield into and out of an optical path to shield at least a part of the light beam irradiated by a light source. However, it has been difficult to enhance the image quality of the projection image because change over time or manufacturing errors in mechanism components for driving the light shield hinder the light shield from being located at a desired position, in other words, because the projection image cannot be changed to a desired brightness.
To solve the problem, there has been proposed a projector employing a light beam detector for detecting the light quantity adjusted by the optical diaphragm, the projector driving the optical diaphragm based on the detected light quantity (see, for example, JP-A-2005-55760). In a case of such projector, even with change over time or manufacturing errors in mechanism components for driving the light shield, the image quality of the projection image can be enhanced, because the light quantity adjusted by the optical diaphragm is detected to reliably detect changes in the light quantity adjusted by the optical diaphragm.
Noted that, as the light source device for the projectors, light source lamps for generating a light beam by an electric discharge are often used. Such light source lamp for generating a light beam by an electric discharge irradiates a light beam not only in a visible light region but also in a nonvisible light region (such as an infrared region).
The projector disclosed in the above-cited document has a problem in using the light source lamp for generating a light beam by an electric discharge, in which, when the light beam including a light beam in the nonvisible light region is irradiated by the light source device on an optical component such as the optical modulator, the temperature of the optical component rises to deteriorate features of the optical component, making it difficult to appropriately maintain the image quality of the projection image.