1. Technical Field
The present invention relates to a projector having a housing encasing a projection lens.
2. Description of the Background Art
Projectors use a projection lens to project enlarged images on a screen. When a projector is used for image projection, an object such as notebooks and notepads may be deliberately placed in front of the projection lens to block the light. However, the heat caused by light received by the object may damage the object, and may cause the projection lens and projector to malfunction as well.
Conventional projectors are generally horizontal projectors having the projection lens on one lateral side of the projector, and such projector may use an upward projection system in view of the positional relationship with the screen. Therefore, even if the object is placed in front of the projection lens, a gap or space can be set between the projection lens and the object. Therefore, the object, the projection lens, and the projector are protected from damage.
Further, JP-2001-092014-A discloses a configuration of a projector shown in FIG. 1 having a housing 30 and a projection lens 31, in which air that has cooled the inside of the housing 30 is exhausted from the side of the projection lens 31 as exhaust 33. The pressure of the exhaust 33 may fluctuate due to the presence of an object 34 placed in front of the projection lens 31, and such fluctuation can be detected by a sensor 32. Based on readings from the sensor 32, the lamp output power of the projector is reduced to prevent malfunction of the projector due to the presence of the object.
However, some projectors have the projection unit on the top face of the housing, which may be a horizontal or slanted surface, wherein the projection unit outputs light via the projection lens. When an object such as paper or the like is placed on top of such a housing, the light projection unit and paper may contact each other very closely, and thus a gap or space is unlikely to be maintained between the projection unit and the object. Therefore, heat accumulates between the projection unit and paper, possibly damaging the projector. Moreover, because there is not enough space between the light projection unit and the object, the configuration disclosed in JP-2001-092014-A cannot be used.
Further, even if the light projection unit is disposed at the lateral side of the horizontal projector, if the object such as paper, cloth, or the like is placed on top of the housing, some part of the object may drape over the light projection unit, blocking the light output from the projection unit and causing the problems described above.