Illumination – Light source and modifier – With ventilating – cooling or heat insulating means
Reexamination Certificate
2000-01-14
2001-09-04
Cariaso, Alan (Department: 2875)
Illumination
Light source and modifier
With ventilating, cooling or heat insulating means
C362S345000, C362S318000, C362S373000, C362S264000, C362S227000
Reexamination Certificate
active
06283614
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a liquid crystal projection apparatus for magnifying and projecting images of liquid crystal panel and the like, and more particularly to cooling of the lamp used as the light source of the liquid crystal projection apparatus.
BACKGROUND OF THE INVENTION
An apparatus for magnifying and projecting images of a liquid crystal panel by using a light source such as metal halide lamp has been hitherto known. In such liquid crystal projection apparatuses, the light generated from the lamp light source is focused on the liquid crystal panel through an optical system of mirrors and others, and displayed on the screen through a projection lens. Recently, a liquid crystal projection apparatus of a high luminance type is available so that images projected on a wide screen can be seen even in a bright room. The liquid crystal projection apparatus of high luminance type comprises an optical system having a high output lamp, small-sized light emitting device, and an improved light utilization rate.
FIG. 5
shows an example of an optical system of such liquid crystal projection apparatus. In order to further enhance the brightness of the image, a liquid crystal projection apparatus having two or more lamps as the light source is also developed. The liquid crystal projection apparatus of the invention has two or more lamps as the light source. FIGS.
6
(
a
) and (
b
) show the two-lamp optical system of the liquid crystal projection apparatus disclosed in Japanese Laid-open Patent No. 5-29320.
FIG. 7
shows the two-lamp optical system of the liquid crystal projection apparatus disclosed in Japanese Laid-open Patent No. 5-49569. As shown in
FIG. 7
, a light emitting tube
20
is fixed near the focus of a reflecting mirror
21
of an elliptical or parabolic surface, and the light from the light emitting tube passes through the focusing system parts consisting of first lens array
24
, second lens array
25
, and field lens
23
, and illuminates a liquid crystal panel
26
. The first lens array
24
and second lens array
25
have an integrator function for illuminating the screen uniformly. The image from the liquid crystal panel
26
is synthesized into a color image by a cross prism, and is magnified and projected on the screen by a projection lens
27
. The two-lamp optical system is capable of obtaining a bright image, but it has its own problem in cooling of two lamps.
FIG. 7
shows an example of cooling of two lamps. An axial flow fan
30
cools the lamps from behind in order to keep the temperature below about 950° C. in the upper part of the light emitting tube
20
, and below 350° C. in the seal part. However, the case of two-lamp system, for example, in the case of lamps in a structure enclosed by the reflecting mirrors and front glass as in the super-high pressure mercury lamps, if there is an air vent near the front glass of the lamp, it is difficult to limit temperature rise of lamps by cooling from behind by the axial flow fan
30
. It is also difficult to cool the two lamps in the same state. Cooling of two lamps and cooling of the entire apparatus are more difficult as the size of the apparatus is more compact. To solve these problems, it is hence an object of the invention to present a liquid crystal projection apparatus having two or more lamps capable of keeping the temperature in the apparatus within a specified temperature and cooling two or more lamps in a same state. It is also an object of the invention to present a lamp capable of keeping the temperature of the light emitting tube and other parts in the lamp within a specified temperature, by forming an air passage in the lamp.
SUMMARY OF THE INVENTION
To achieve the objects, the liquid crystal projection apparatus of the invention has a plurality of lamps, and each lamp of the plurality of lamps is furnished with cooling means for cooling the lamp. In other words, the liquid crystal projection apparatus of the invention has the same number of cooling means as the plurality of lamps in order to cool the plurality of lamps individually. As a result, the plurality of lamps are cooled in a same state. The cooling means includes an air suction port and an air discharge port. A centrifugal fan having air suction port and air discharge port can be used as cooling means. The furnished cooling means is disposed in the upper part or lower part of the lamp. That is, all furnished cooling means are disposed parallel in the upper part of the plurality of lamps, or all furnished cooling means are disposed parallel in the lower part of the plurality of lamps. The lamp has an air suction hole and an air discharge hole. The cooling means sucks in hot air from the air discharge hole of the lamp, and exhausts this hot air outside of the apparatus through a louver of the case of the liquid crystal projection apparatus. Since the louver is disposed near the air discharge port of the cooling means, the hot air from the lamp is exhausted outside of the apparatus without heating the inside of the apparatus. Thus, an air stream flowing in the lamp from the air suction hole of the lamp into the air discharge hole is formed, and this air stream effectively cools the light emitting tube and other parts in the lamp.
The louver is opened obliquely to the front direction, in which the image projecting direction is defined to be the front direction. Therefore, the user of the liquid crystal projection apparatus is usually situated beside or behind the apparatus, and is hence free from effects of hot air, noise or leak light from the apparatus.
REFERENCES:
patent: 5676442 (1997-10-01), Fujimori
patent: 5743610 (1998-04-01), Yajima et al.
patent: 5-276523 (1993-10-01), None
patent: 6-194621 (1994-07-01), None
patent: 10-27518 (1998-01-01), None
Hoshino Makoto
Okada Takehiro
Alavi Ali
Cariaso Alan
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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