Optics: image projectors – Temperature control – Blower
Reexamination Certificate
2001-12-28
2003-07-22
Adams, Russell (Department: 2851)
Optics: image projectors
Temperature control
Blower
C353S101000, C353S119000
Reexamination Certificate
active
06595645
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a display-apparatus technology used for projecting a picture on a screen by using a light valve device such as a liquid-crystal display panel and adopted in equipment such as a liquid-crystal projector apparatus, a liquid-crystal television and a projective display apparatus.
There have been provided conventional display apparatuses such as a liquid-crystal projector for projecting a picture on a screen or the like in an enlarged size by conversion of a light emitted by a light source such as a lamp into concentrations of pixels and adjustment of the concentrations using a light valve device such as a liquid-crystal display panel.
The light valve device generally comprises a semiconductor driving device and an optically functioning material. In order to have the semiconductor driving device and the optically functioning material operate normally, it is necessary to keep them at a predetermined temperature, for example the temperature is about 60 degrees Celsius or lower. On the other hand, all the light emitted by the light source except that eventually used for projection is absorbed by elements such as the light valve device and its peripheral optical devices, being converted thereby into heat energy. For this reason, it is necessary to cool the light valve device employed in the projective display apparatus so as to prevent the temperature of the light valve device from exceeding a range of the normal operation due to overheating. The need for such cooling is rising more and more as the intensity of the light source is increased in recent years to raise the luminance of the projected picture. This is because the amount of heat dissipated by the light valve device increases as the intensity of the light source is raised.
The performances and functions of some optically functioning components other than the light valve device and some of those made of a polymer material change at a high temperature. It is thus necessary to keep them at a predetermined temperature, for example the temperature is about 150 degrees Celsius or lower. That is, it is necessary to cool the optically functioning components other than the light valve device as the luminance of the projected picture is increased.
In addition, since the focus of an optical system employed in such a display apparatus is positioned on the picture surface of the light valve device, a foreign particle such as dust stuck to the light valve device or areas in close proximity thereto is projected on the screen as it is in an enlarged size as a shadow appearing on the screen. In consequence, there are raised serious problems of prevention of dust from being stuck to the light valve device or areas in close proximity thereto and maintainability including removal of stuck dust as a matter of course.
There is a typical conventional technology of cooling a light valve device which is disclosed in Japanese Patent Laid-open No. Hei 9-120046. According to this technology which is relevant to the present invention, a wind is blown to a side surface of a liquid-crystal light valve to cool the heated liquid-crystal light valve. In this way, an increase in temperature caused by heat dissipated by the liquid-crystal light valve device (liquid-crystal display panel) can be suppressed by the cooling. According to this relevant technology, since a wind is blown from one side only, however, the temperature on the entrance side of the cooling wind decreases while the temperature on the exit side increases, resulting in a difference in temperature which makes it impossible to obtain a sufficient performance particularly at a high luminance. In this respect, this conventional technology does not adequately address the problem. In addition, this conventional technology also does not address a lack of cooling power as evidenced by the fact that the total amount of heat dissipated by the light valve device is raised with an increase in luminance. Furthermore, this conventional technology also does not address the necessity to cool optically functioning components other than the light valve device as the luminance is increased.
There is another relevant technology of cooling a light valve device which is disclosed in Japanese Patent Laid-open No. Hei 5-53200. According to this relevant technology, a sirocco fan of a pressure centrifugal type is used for cooling a light valve means. By doing so, a sufficient wind blowing capacity can be assured by using even a duct with a relatively small diameter, allowing the cooling to be carried out with a high degree of efficiency. Nevertheless, this conventional technology also does not address the necessity to cool optically functioning components other than the light valve device as the luminance is increased.
There is also a relevant technology of preventing dust from being stuck in a picture display apparatus as is disclosed in Japanese Patent Laid-open No. Hei 7-152009. According to this relevant technology, a transmission light valve device serving as a liquid-crystal display panel is placed in a hermetically sealed space. An air is circulated in the hermetically sealed space to let the liquid-crystal display panel radiate heat dissipated thereby to the outside of the space. In this way, it is possible to prevent dust from being stuck to the liquid-crystal display panel. In some cases, however, the cooling power becomes insufficient as heat is dissipated as a result of increasing the luminance. In addition, dust introduced during a fabrication process may be inadvertently included in the hermetically sealed space. Thus, this relevant technology also does not address a problem of maintainability caused by, among other things, the difficulty to remove such dust.
With respect to the maintainability of a picture display apparatus, there is a relevant technology disclosed in Japanese Patent Laid-open No. Hei 7-311372. According to this relevant technology, the interior of the picture display apparatus comprises a combination of units which can be attached and detached individually. With such a configuration, each of the units can be maintained and replaced with ease. According to this relevant technology, however, a unit including a liquid-crystal light valve device and a projection lens requiring frequent maintenance checks has a configuration which allows this specific unit to be attached and detached only in the projection direction of the projection lens. It is thus necessary to disassemble units of the whole optical system in order to attach or detach the specific unit.
In the case of the technologies disclosed in Japanese Patent Laid-open Nos. Hei 9-120046 and Hei 5-53200, the cooling of the light valve device and the disposition of dust stuck to the light valve device and areas in close proximity thereto are required as the luminance is increased. Otherwise, problems such as an abnormal operation caused by overheating and a shadow appearing on the screen due to the stuck dust as described above will likely arise. However, the relevant technologies do not address these problems and, of course, do not take solutions to the problems into consideration. In addition, these relevant technologies do not address the necessity to cool optically functioning devices at the same time either.
In the case of the technology disclosed in Japanese Patent Laid-open No. Hei 7-152009, cooling is done by an air circulated in a hermetically sealed space. Thus, efficient cooling can not be much expected. As a result, it is quite within the bounds of possibility that the light valve device can not be cooled sufficiently in the event of an increased amount of dissipated heat due to an increased intensity of the light emitted by the light source. In this case, in spite of the fact that the picture display apparatus will no longer operate normally, the relevant technology does not address the problem and, of course, does not take a solution to the problem into consideration. The relevant technology also does not address a problem related to the maintenance of the pictur
Abe Fukuyasu
Fuse Kenji
Kaku Nobuyuki
Masuoka Nobuo
Morita Tatsuo
Adams Russell
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Smith Arthur A
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