Optics: image projectors – Temperature control – Blower
Reexamination Certificate
1999-06-07
2001-07-03
Dowling, William (Department: 2851)
Optics: image projectors
Temperature control
Blower
Reexamination Certificate
active
06254238
ABSTRACT:
FIELD OF THE INVENTION
1. Background of the Invention
The present invention relates to a cooling system for a video projector.
2. Description of Related Art
Heretofore, a video projector for projecting and displaying a video signal delivered from the outside in the form of a video image, as the video image onto a projection screen has been well-known. In this video projector, there is generally used, as an optical source, a projecting lamp having high light intensity, for projecting the video image in the form of an optical image onto the projection screen. Accordingly, there is incorporated a cooling system for cooling the projecting lamp and, as well, an optical system.
As to the cooling system, there has been generally used a forced type air-cooling system in which cooling air streams are induced through the video projector by using of a cooling fan so as to dissipate heat accumulated in the projection lamp and the optical system within the video projector.
FIG. 5
is a partial-broken perspective view showing a cooling system for a video projector according to a first related art. The video projector is composed of a projecting lamp
104
, a polarizing beam splitter
105
, LCD panels
106
, polarizing plates
107
, analizers
108
, a base
109
, a cross dichroic prism
110
, an air filter
111
, a cover plate
112
, intakes
115
,
117
, a case
118
, an outlet axial fan
119
, a projecting lens
120
and an intake axial fan
123
.
In this arrangement, when the intake axial fan
123
and the outlet axial fan
119
are rotated, a cooling stream S is introduced into the case
118
from the outside of the case
118
through the air filter
111
. The cooling air stream S being led through the intake axial fan
123
and then blown through a space between the LCD panels
106
and the cross dichroic prism
110
so as to cool the LCD panels
106
and the cross dichroic prism
110
. The air stream S having passed through the space between the LCD panels
106
and the cross dichroic prism
110
is circulated through the interior of the case
118
. Then, the air stream S is sucked into the intakes
115
,
117
by means of the outlet axial fan
119
so as to cool the projecting lamp
104
. Then, the cooling stream S is led through the cover plate
112
. Finally, the cooling stream S is discharged outside of the case
118
through the outlet axial fan
119
.
Further, Japanese Laid-Open Patent Publication No. Hei 4-271334 (published on Sep. 28, 1992 in Japan) discloses a cooling structure for a liquid crystal projector having two cooling fans for cooling components to be cooled in a case of the projector. The technology will be described as a second related art.
FIG. 6
is a perspective plan view showing a cooling system for the video projector according to the second related art. The video projector includes a plurality of cooling fans
232
,
235
. The first cooling fan
232
is incorporated in a case
201
. The second cooling fan
235
is located between an optical source chamber
203
and a LCD panel chamber
204
. A cooling duct
241
is provided on the exhaust side of the second cooling fan
235
, for leading air fed from the second cooling fan
235
, around a power supply
215
and an optical source
214
in the optical source chamber
203
.
In this arrangement, air which has been sucked into the LCD panel chamber
204
by driving the second cooling fan
235
, passes around optical components
211
to
226
. Thereafter, the air is led from the second cooling fan
235
into the cooling duct
241
. Then, this air is sucked into the optical source chamber
203
by driving the second cooling fan
235
so as to cool the power supply
215
and the optical source
214
. Thereafter, the air is exhausted from an outlet
231
.
Further, Japanese Laid-Open Patent Publication No. Hei 4-191726 (published on Jul. 10, 1992 in Japan) discloses a liquid crystal projector including a single cooling fan for cooling components to be cooled in the case of the projector. The technology will be described as a third related art.
FIG. 7
is a perspective plan view showing a cooling system for the video projector according to the third related art. The video projector is composed of a lamp system box
310
, an optical system box
312
, dichroic mirrors
313
to
315
, polarizing plates
316
to
318
, LCD panels
319
to
321
, projecting lenses
323
to
325
, an intake
326
, a ballast choke
327
, and a heat radiation plate
328
and a cooling fan
330
. In this arrangement, an air stream is sucked through the intake
326
, passing by way of the polarizing plates
316
to
318
, the LCD panels
319
to
321
, the heat radiation plate
328
and the lamp system box
310
, successively. Then, the air stream is sucked into the cooling fan
330
so as to be discharged outside of a case.
However, the cooling system for the video projector in the first related art suffers from the following disadvantages inherent thereto.
As to the first disadvantage, the outlet axial fan
119
is provided with an opposite side
118
b
, which is on the side remote from the projecting lens
120
, on the case
118
. That is, on an operator's side or a viewer's side. Accordingly, the operator or the viewer is exposed to hot exhaust air so as to feel discomfort.
This is because the outlet axial fan
119
has to be located in proximity with the projecting lamp
104
since the projecting lamp
104
which exhibits a highest temperature should be effectively cooled. An optical system composed of several optical components
105
to
109
and having a large occupying area is present between the projecting lamp
104
and the projecting lens
120
. Accordingly, the projecting lamp
104
has to be located on the opposite side
118
b
remote from the projecting lens
120
, that is on the side where the operator or the viewer is existing. Thus, hot air is inevitably discharged to the side where the operator or the viewer is present.
Even though the outlet axial fan
119
is provided with the opposite side
118
b
of the case
118
to a lens side
118
a
so as to discharge the hot air to the opposite side
118
b
of the case
118
, the passage of the cooling air stream S in the case
118
would become extremely long so as to increase ventilation resistance. This causes that the cooling efficiency would becomes greatly low since the axial flow fan has a structure having a low static pressure. Thus, this arrangement is not useful.
Further, even though the projecting lamp
104
is located on the lens side
118
a
in the case
118
, the position of the optical system cannot be changed. Accordingly, the projecting lamp
104
has to be attached in a narrow space with an inclined posture. However, the inclined posture of the projecting lamp
104
causes the temperature distributions inside and around the projecting lamp
104
to be not uniform. Accordingly, a locally high temperature part is produced so that a filament in the projecting lamp
104
is possibly broken, thereby the use life of the projecting lamp
104
becomes shorter. Thus, this arrangement is also not useful.
As to the second disadvantage, a projected image is not uniform.
The reason is that an axial fan whose discharging direction is along the rotary shaft thereof is used as the intake axial fan
123
. This causes that the cooling air stream S flows, being inclined in a diagonal direction of surfaces of the LCD panels
106
while the inclination of the cooling air stream S depends upon a rotating direction of the intake axial fan
123
. Accordingly, the flowing velocity of the cooling air stream S is not uniform over the entire surface of the LCD panels
106
. Thus, the temperature distribution over the entire surface of the LCD panels
106
is locally not uniform. Further, since the cooling air stream S is forced to flow through a narrow gap between the LCD panels
106
and the cross dichroic prism
110
, the cooling air stream S likely to be disturbed by components for supporting the LCD panels
106
and the like. Accordingly, the cooling air stream S can hardly flow in
Dowling William
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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