Illumination – Light modifier – Reflector
Reexamination Certificate
2000-10-19
2004-09-07
O'Shea, Sandra (Department: 2875)
Illumination
Light modifier
Reflector
C362S294000, C362S264000, C313S113000
Reexamination Certificate
active
06786620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light source device and a projector that utilizes the light source device to project and display images.
2. Description of the Related Art
A projector usually comprises an illuminating optical system and liquid crystal panels for modulating light from the illuminating optical system responsive to image information (an image signal). The modulated light is then projected onto a screen by a projection lens.
The illuminating optical system generally includes a light source device that has a light source lamp and a reflector having a concave surface to reflect light emitted from the light source lamp. Available examples of the light source lamp include high-pressure mercury lamps, xenon lamps, and metal halide lamps. The reflector may have a reflecting film formed on a concave surface of a hard glass.
The conventional light source device has a problem that the heat emitted from the light source lamp is not sufficiently released to the outside but remains inside the reflector (the concave portion). This is because the hard glass of the reflector functions as a heat insulator. The reflector thus undesirably increases ambient temperature of the light source lamp. The surface temperature of the reflector may be as high as about 200° C. in some cases. Such a high temperature disadvantageously shortens the life of the light source lamp or even breaks a glass tube of the light source lamp. The problem of raising the ambient temperature of the light source lamp is prominent in a light source device having a front glass at an opening of the reflector. The problem is especially significant for higher-powered light source lamps and smaller-sized light source devices.
SUMMARY OF THE INVENTION
The object of the present invention is thus to provide a technique that lowers the ambient temperature of a light source lamp in a light source device.
At least part of the above and the other related objects is attained by a light source device that includes a light source lamp and a reflector that reflects light emitted from the light source lamp. The reflector is formed of a ceramic having a thermal conductivity of at least about 0.005 (cal/cm·.sec·.deg) at a temperature of 200° C.
In the light source device of the present invention, the reflector is formed of a ceramic having a relatively large thermal conductivity. This arrangement effectively lowers the ambient temperature of the light source lamp.
In the light source device of the present invention, it is preferable that the ceramic has a thermal conductivity of at least about 0.004 (cal/cm·sec·deg) in a temperature range of about 0 to about 200° C.
The use of such a reflector remarkably lowers the ambient temperature of the light source lamp.
In the light source device of the present invention, it is further preferable that the ceramic is composed of any material selected among the group consisting of Al
2
O
3
, 2MgO·SiO
2
, MgO·SiO
2
, ZrO
2
·SiO
2
, TiO
2
compounds, SiC
1
Si
3
N
4
, ZrO
2
, and cermet.
Application of any of these ceramic materials for the reflector readily lowers the ambient temperature of the light source lamp.
In accordance with one preferable application of the present invention, the light source device further includes a transmissive front panel fitted in an opening of the reflector.
In accordance with another preferable application of the present invention, the light source device further includes a cooling device that forcibly cools down the reflector.
The use of the cooling device to cool down the reflector further lowers the ambient temperature of the light source lamp.
In accordance with still another preferable application of the present invention, the light source device further includes a power source that activates the light source lamp.
The present invention is also directed to a projector that includes: an illuminating optical system including a light source device that has any of the above configurations; an electrooptic device that modulates light emitted from the illuminating optical system in response to image information; and a projection optical system that projects a modulated light obtained by the electrooptic device.
The projector of the present invention includes the light source device having the arrangement described above. In the projector, this arrangement effectively lowers the ambient temperature of the light source lamp.
In accordance with one preferable application of the present invention, the projector further includes a driving section that supplies the image information to drive the electrooptic device.
REFERENCES:
patent: 4755711 (1988-07-01), Fields et al.
patent: 4993405 (1991-02-01), Takamura
patent: 5621267 (1997-04-01), Shaffner et al.
patent: 5679453 (1997-10-01), Konagaya et al.
patent: 5789850 (1998-08-01), Iwafuji et al.
patent: 0 605 248 (1993-12-01), None
patent: 0 605 248 (1993-12-01), None
Eugene A. Avallone & Theodore Baumeister iii, Mark's Standard Hand Book, Mc Graw Hill, 10thEdition, Table 1.2.32 (theria conductivity).*
Handbook of Industrial Refractoies Technology, Table XI.3 Thermal Conductivity of dense solid substances (Ref. 32), pp., 376, and 378.
Alavi Ali
O'Shea Sandra
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Seiko Epson Corporation
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