Optics: image projectors – Temperature control – Heat resistant or insulating material
Reexamination Certificate
2000-07-10
2003-02-04
Adams, Russell (Department: 2851)
Optics: image projectors
Temperature control
Heat resistant or insulating material
C353S055000, C353S058000, C353S060000, C353S061000, C353S119000
Reexamination Certificate
active
06513936
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a projector having heat-generating elements such as polarizing plates and liquid crystal panels, and particularly relates to a projector provided with cooling mechanisms for cooling the heat-generating elements.
A projector, such as a liquid crystal projector, is provided with an optical system including elements such as a folding mirror, color separating dichroic mirrors, liquid crystal panels, color composition mirrors (prism). Since the liquid crystal panels and polarizing plates provided adjacent to the liquid crystal panels absorb light and generate heat, it is necessary to cool the liquid crystal panels and the polarizing plates. Therefore, there is a need for efficiently cooling the liquid crystal panels and the polarizing plates.
Also, the projector is commonly used for meetings and presentations in an office or may be used as a home image output device (a screen for television and games). Therefore, there is a need for reducing the noise generated by the projector.
Further, since the projector is provided with a fine optical system as described above, in order to improve the quality of the projected image and to improve the reliability of the projector itself, it is necessary to prevent dust from entering the projector.
2. Description of the Related Art
Referring to
FIGS. 1 and 2
, a projector
10
of the related art will be described to facilitate the understanding of the projector of the present invention.
FIG. 1
is a transverse cross section of the projector
10
and
FIG. 2
is an enlarged diagram showing a portion of the projector of the related art provided with air intake fans
29
to
31
.
As shown in
FIG. 1
, the projector
10
includes an inner housing
11
, an outer housing
12
, a light source
13
, liquid crystal panel units
24
to
26
, a projecting lens
27
, the air intake fans
29
to
31
and an air discharge fan
32
.
The inner housing
11
is provided inside the outer housing
12
, and a space
28
is formed between the inner housing
11
and the outer housing
12
. The inner housing
11
surrounds an optical system including elements such as total reflection mirrors
14
to
16
, color separation dichroic mirrors
17
and
18
, color composition dichroic mirrors
19
and
20
, condenser lens
21
to
23
, and the liquid crystal panel units
24
to
26
.
The projector
10
having the above-described optical system generates images in the following manner. When passing through the optical system, light emitted from the light source
13
is separated into beams of, for example, three fundamental colors by means of the color separation dichroic mirrors
17
and
18
. Then, the separated beams are directed through the liquid crystal panel units
24
to
26
so as to be subjected to an image signal superimposing process for each color. This image signal superimposing process may also be referred to as an image modulation process.
Then, the beams are color composited through the color composition dichroic mirrors
19
and
20
. The beams are then projected through the projecting lens
27
towards a screen (not shown).
The above-described liquid crystal panel units
24
to
26
each includes a liquid crystal panel and a pair of polarizing plates provided on either sides of the liquid crystal panel. The liquid crystal panel and the polarizing plates absorb light and generate heat. Since polarizing film made of organic material is normally used as the polarizing plates, the liquid crystal panel units
24
to
26
will be degraded when heated to a temperature exceeding 70° C.
In order to prevent the liquid crystal panel units
24
to
26
from being overheated, the air intake fans
29
to
31
are provided on a lower surface of the inner housing
11
at a position opposing the liquid crystal panel units
24
to
26
. The air intake fans
29
to
31
generate cooling airflows which are directed to polarizing plates of the liquid crystal panel units
24
to
26
. Thus, each of the polarizing plates is air-cooled.
The temperature of the cooling airflows is raised when passing by the polarizing plates of the liquid crystal panel units
24
to
26
. Thus-heated airflows are discharged into the outer housing
12
through vents
33
,
34
,
35
provided in a top plate of the inner housing
11
. Further, the heated airflows are discharged outside the apparatus through external vent
36
by means of the discharge fan
32
.
The space
28
also includes various devices
39
a
other than the inner housing
11
. There are some devices
39
a
which may generate heat. The light source
13
also generates heat. In order to cool the heat-generating devices
39
a
and the light source
13
, the projector
10
is provided with internal cooling fans
39
for each of the devices
39
a
and the light source
13
.
In the
FIG. 2
, three air intake fans
29
to
31
are provided to correspond to the number of liquid crystal panel units
24
to
26
provided in the projector
10
. However, as illustrated in
FIG. 3
, the liquid crystal panel units
24
to
26
may be cooled by a single air intake fan
37
via an air-conducting duct
38
.
Thus, the degradation of the polarizing plates and the liquid crystal panels due to heat can be prevented by means of the air intake fans
29
to
31
provided at positions opposing the liquid crystal panel units
24
to
26
. Thus, the reliability of the projector
10
is improved.
However, since each of the air intake fans
29
to
31
generates cooling airflows by rotating its blades, there is a drawback that whistling sounds are generated when the blades of the fans cut through the air. These whistling sounds give rise to a noise during operation of the projector
10
. With the structure illustrated in
FIG. 2
, since each fan
29
to
31
generates whistling sounds, the noise is increased. With the structure illustrate in
FIG. 3
, although there is only one air intake fan
37
, the noise is increased since the air-conducting plates cut through the air flowing within the air-conducting duct
38
.
Thus generated noise passes through the inner housing
11
and is transferred to the space
28
between the inner housing
11
and the outer housing
12
via the vents
33
to
35
formed in the inner housing
11
. Then, the noise is reflected of f the walls of the outer housing
12
and is transferred to the external vent
36
. Finally, the noise propagates outside the projector
10
through the external vent
36
.
FIG. 4
is a diagram showing a chart of noise values generated in the projector
10
of the related art. The chart includes columns indicating name, number, type, applied voltage, and noise value of each fan provided in the projector
10
. The noise value represents a value measured using a measuring device provided at the external vent
36
.
As can be seen from
FIG. 4
, when only three air intake fans
29
to
31
were driven, the noise value was 40.0 dB. When only the air discharge fan
32
was driven, the noise value was 41.8 dB. When only three internal cooling fans
39
were driven, the noise value was 39.5 dB.
Also, when all the fans, that is to say, the air intake fans
29
to
31
, the air discharge fan
32
and the internal cooling fans
39
were driven, the noise value amounted to 46.1 dB. Accordingly, the projector
10
of the related art has a drawback that a large noise is produced.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a projector which can obviate the drawbacks described above.
It is another and more specific object of the present invention to provide a projector which can positively implement the cooling process while reducing the noise propagating out therefrom.
In order to achieve the above objects according to the present invention, a projector includes:
a first housing provided with first heat-generating elements used for generating an image, first fans producing cooling airflows towards each one of the first heat-generating elements and vents via which the coo
Gotoh Takeshi
Hamada Tetsuya
Hayashi Keiji
Ishiwa Masaru
Kobayashi Tetsuya
Adams Russell
Cruz Magda
Greer Burns & Crain Ltd.
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