The present invention relates to a projector and more particularly to a projector having a cooling mechanism to cool a light source provided in a housing.
A projector is designed for generating an optical image from image data provided by a personal computer or a video camera and projecting it on a screen for display.
Such a projector is disclosed in Japanese Patent Laid-open Publication No. Hei 10-90811 which has an air exhaust opening provided next to projection lens in the front side of a housing for exhausting hot air which was used for cooling by an exhaust fan, hence minimizing the effect of hot exhaust air and noise from the exhaust fan and the effect of unwanted light leaked from a light source which may annoy viewers. This projector is referred to as a first prior art hereinafter.
Another prior art may be featured with a closable lens cover for closing and protecting the front side of the projection lens. For example, some projectors of a type where a lens window for a projection lens is openably closed with a slidable lens cover are disclosed in Japanese Patent Laid-open Publication No.2000-162703, 2001-272648, and 2001-249402. These projectors are referred to as a second prior art hereinafter.
Also, a liquid crystal projector which has a shutter mechanism for protecting the front side of a projection lens is disclosed in Japanese Patent Laid-open Publication No.2001-242542. This liquid crystal projector is referred to as a third prior art hereinafter.
However, the first prior art has the air exhaust opening for exhausting hot air provided next to the projection lens in the front side of its housing, hence permitting the hot air from the air exhaust opening to run across the optical path of projected light from the projection lens and generate undesired shimmers (heat wave) in the optical image projected on the screen.
The generation of shimmers in the optical image will now be explained in detail referring to FIGS. 13 and 14. As shown in FIG. 13 the air for cooling is introduced into the interior of a main body 102 from two air inlets 109 and 122 provided in the right side and the rear side of a housing 103 respectively and directed towards a lamp 120 by the action of an exhaust fan 121. Hot air which was used for cooling the lamp 120 is exhausted from an air outlet 108 provided in the front side of the housing 103. The hot air indicated by arrow A may flow across the optical path of a projected light 123 released from a projection lens 105. As the projected light 123 is interrupted particularly at an area adjacent to the air output 108 by the hot air from the air outlet 108, its image on a screen 131 may fluctuate significantly at the right 132 as shown in FIG. 14.
The second and third prior arts also fail to eliminate the above drawback.
It is hence an object of the present invention to provide a projector which can prevent hot air exhausted from the air outlet from running across the light path of the light projected with the projection lens can eliminate the generation of shimmers in the projected image.
A projector in accordance with an aspect of the present invention comprises a projection lens, an air outlet and a lens cover.
The projection lens projects an optical image using a light emitted by a light source.
The air outlet is for exhausting hot air which was used for cooling the light source to the outside.
The lens cover protects the projection lens.
The lens cover can be held between the air outlet and the projection lens.
The foregoing arrangement allows the lens cover to be turned open and held between the air outlet and the projection lens when the projection of an image is desired. Thus, the lens cover can prevent hot air exhausted from the air outlet from running across the light path of the light projected with the projection lens and can eliminate the generation of shimmers in the projected image.