Optics: image projectors – Temperature control – Blower
Reexamination Certificate
1999-11-09
2002-02-26
Adams, Russell (Department: 2851)
Optics: image projectors
Temperature control
Blower
C353S060000, C353S119000, C353S056000
Reexamination Certificate
active
06350033
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a projector including a light source, an optical modulation device for modulating a luminous flux emitted from the light source according to image information, and a projection lens for enlarging and projecting an image formed by the optical modulation device.
2. Description of Related Art
Hitherto, projectors have been used which include a light source, an optical system for forming an image by a luminous flux emitted from the light source according to image information, and a projection lens for enlarging and projecting the image formed by the optical system onto a projection plane. The optical system consists of an illuminating optical system for producing a uniform in-plane illumination distribution of a luminous flux emitted from the light source, a color separation optical system for separating the luminous flux from the illuminating optical system into three primary colors of red, blue, and green, an optical modulation system including an electro-optical apparatus for modulating color luminous fluxes according to image information, and a color-synthesizing optical system for synthesizing modulated color luminous fluxes. The electro-optical apparatus includes three optical modulation devices for modulating each of a red luminous flux, a blue luminous flux and a green luminous flux separated by the color separation optical system according to image information. For example, a liquid crystal panel using a polysilicon TFT as a switching element is used.
Since the optical modulation devices are important portions for forming an optical image according to image information, if dust or oil mist adheres to the surface of the liquid crystal panel, the image quality of the projector will deteriorate. For this reason, a projector including an enclosing structure for enclosing an optical path from the optical modulation devices to the projection lens may be adopted. Since such a projector can prevent the entry of dust or oil mist from the outside by the enclosing structure, dust or oil mist does not adhere to the surface of the liquid crystal panel of the optical modulation device, and the image quality of the projector can be stably secured over a long period of time. Such a projector is suitably used as a stationary projector, such as a hanging-type projector.
However, since the optical modulation device, such as the liquid crystal panel, is easily affected by heat, if the optical path from the optical modulation device to the projection lens is enclosed by the enclosing structure, it is difficult to efficiently cool the optical modulation device by introducing cooling air from the outside. In particular, in a recent trend toward an increase in brightness and a reduction in size of the projector, efficiently cooling the optical modulation device is an important problem.
On the other hand, the electro-optical apparatus is usually mounted on a structure to which the projection lens is attached. Thus, in order to enclose an optical path from the electro-optical apparatus to the projection lens, a large enclosing structure for enclosing the electro-optical apparatus and the structure is required, and it is therefore difficult to reduce the size of the projector.
SUMMARY OF THE INVENTION
It is an aspect of the present invention to provide a projector capable of efficiently cooling an electro-optical apparatus, and of stably securing the image quality for a long period of time.
It is another aspect of the present invention to provide a projector capable of preventing dust from adhering to an electro-optical apparatus by enclosing an optical path from the electro-optical apparatus to a projection lens, and of reducing the size of the device.
According to the first aspect of the present invention, there is provided a projector having a light source, an electro-optical apparatus for modulating a luminous flux emitted from the light source according to image information, and a projection lens for enlarging and projecting an image formed by the electro-optical apparatus, the projector may include an enclosing structure for enclosing an optical path from the electro-optical apparatus to the projection lens, and an air circulation path for circulating air of the enclosing structure, wherein the air circulation path is disposed in a flow path for cooling air formed inside the projector.
The enclosing structure can be formed by a box-like member for sealing and accommodating therein the electro-optical apparatus. The box-like member made of metal, such as magnesium alloy, may be adopted. In addition, the air circulation path can be formed by, for example, a pipe-like member connected to the upper portion of the enclosing structure at one end thereof, and connected to the lower portion of the enclosing structure. In short, the air circulation path may have a structure such that it can circulate air inside the enclosing structure from above to the below, or from below to above while holding sealing performance of the enclosing structure. Furthermore, in order to circulate internal air, a forcible circulation device, such as a fan, may preferably be provided inside the enclosing structure. As the forcible circulation device, a common axial flow fan can be adopted. However, a centrifugal fan for exhausting air drawn by the rotation of the fan in the direction tangential to the rotation may preferably be adopted.
According to the present invention, since the air circulation path is disposed in a flow path for cooling air formed inside the projector, the air circulation path is cooled and the air flowing in the air circulation path is cooled. The cooled air inside the air circulation path circulates inside the enclosing structure, whereby the electro-optical apparatus can be efficiently cooled. In addition, since the air for cooling the electro-optical apparatus circulates only in the enclosing structure and the air circulation path, dust or oil mist does not enter from the outside, and image quality of the projector can be stably secured for a long period of time.
In the foregoing, the air circulation path may preferably be formed by a metal pipe-like member. Since the pipe-like member made of metal, such as copper, aluminum or the like, has high heat-radiating performance, air inside the air circulation path can be further efficiently cooled if it is disposed in the flow path for cooling air inside the projector. In addition, when the above-described centrifugal fan is adopted as the forcible circulation device, the air inside the enclosing structure can be sufficiently circulated by the centrifugal fan, considering the length of the flow path of the air circulation path in which discharge pressure of the centrifugal fan is substantially equal to the area of the air outlet of the centrifugal fan. In this case, the inside diameter of the pipe-like member may preferably be set at 10 mm to 30 mm.
In addition, the air circulation path may preferably be detachable to the enclosing structure and the air circulation path and the enclosing structure may preferably be connected via a seal material. In this way, since the enclosing structure and the air circulation path are detachable, maintenance of the electro-optical apparatus inside the enclosing structure can be easily carried out. In addition, since the air circulation path and the enclosing structure is connected via the seal material, it is possible to securely prevent air leakage inside the enclosing structure. Furthermore, even if the enclosing structure and the air circulation path are made of different metals such that the material of the enclosing structure is a magnesium alloy and the material of the air circulation path is aluminum, since they are connected by the seal material, such as rubber, electrolytic corrosion does not occur at a joint portion between two different metals, and sealing performance of the enclosed structure can be permanently secured.
Furthermore, the air circulation path may include a radiating structure for releasing heat inside the air
Adams Russell
Cruz Magda
Oliff & Berridg,e PLC
Seiko Epson Corporation
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