Optics: image projectors – Temperature control – Blower
Reexamination Certificate
2000-10-13
2002-06-04
Mahoney, Christopher (Department: 2851)
Optics: image projectors
Temperature control
Blower
C353S031000, C353S034000, C353S037000, C353S058000, C353S060000, C353S061000, C353S087000, C353S119000, C359S511000, C359S512000
Reexamination Certificate
active
06398366
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a display apparatus of the projection type wherein an image obtained by irradiating light from a light source upon a light valve is projected on a screen or a like element, and more particularly to a display apparatus of the type which includes a forced air cooling apparatus which includes a cooling fan.
Conventionally, such an apparatus as shown in
FIGS. 9 and 10
is known as a liquid crystal projector apparatus which is an example of a display apparatus of the projection type. Referring to
FIGS. 9 and 10
, the liquid crystal projector apparatus
1
shown includes an outer housing
2
formed in a flattened parallelepiped configuration from a metal sheet or the like. Four stands
3
at which the liquid crystal projector apparatus
1
is placed on a desk or the like are mounted at four corners of the bottom of the outer housing
2
. An optical unit case
4
is mounted horizontally at an intermediate position in the vertical direction of the inside of the outer housing
2
. The optical unit case
4
is formed in a flattened configuration from a metal sheet or the like and is bent such that it has a substantially L-shape in plane. An optical unit
5
for projecting a color image on a screen or the like is accommodated horizontally in the inside of the optical unit case
4
.
The optical unit
5
includes a fly eye lens set
7
serving as illumination optical means and a PS conversion element
8
disposed in series on an optical axis P
1
of a discharge lamp
6
serving as a light source. The optical axis P
1
is bent by 90° into an optical axis P
2
by means of a mirror
9
, and two dichroic mirrors
10
R and
10
G for R (red) and G (green) serving as light decomposition means are disposed in series in a spaced relationship from each other and in an inclined relationship by 45° on the optical axis P
2
bent from the optical axis P
1
. The dichroic mirrors
10
R and
10
G and a reflecting mirror
103
provide three optical axes P
3
, P
4
and P
5
all bent perpendicularly to the optical axis P
2
. Three condenser lenses
11
R,
11
G and
11
B and three spatial optical modulation elements
12
R,
12
B and
12
B for R, G and B (blue) such as transmission type liquid crystal panels or the like serving as optical modulation means are disposed on the optical axes P
3
, P
4
and P
5
, respectively. A cross prism
13
of a square shape serving as optical synthesis means is disposed on an optical axis P
6
of the three spatial optical modulation elements
12
R,
12
G and
12
B. Further, a projection lens
14
is disposed on the outgoing side of the cross prism
13
so that image light outgoing from the three spatial optical modulation elements
12
R,
12
G and
12
B for R, G and B such as transmission type liquid crystal display panels serving as optical modulation means is projected on a screen or the like.
The fly eye lens set
7
decomposes light L
1
from the discharge lamp
6
, which has an intensity distribution, into a large number of light spots. The large number of light spots are superposed on one another by spatial optical modulation elements to make uniform the brightness distribution of the illumination light upon the entire screen of the spatial optical modulation elements
12
R,
12
G and
12
B. The PS conversion element
8
is composed of a plurality of polarizing beam splitters arranged in a rectangular configuration and a plurality of phase difference plates provided intermittently corresponding to the polarizing beam splitters, and converts the polarization direction of the light L
1
from the discharge lamp
6
so that, for example, a P wave component of the light L
1
may be converted into an S wave component. Consequently, the PS conversion element
8
outputs light which includes a comparatively great amount of an S wave component as a whole.
It is to be noted that the three condenser lenses
11
R,
11
G and
11
B and the three spatial optical modulation elements
12
R,
12
G and
12
B are disposed at three directional positions adjacent three faces of the square cross prism
13
. Further, three polarizing plates
17
R,
17
G and
17
B and three polarizing plates
18
R,
18
G and
18
B are disposed on and in parallel to the incoming side and the outgoing side of the three spatial optical modulation elements
12
R,
12
G and
12
B, respectively. In particular, the three polarizing plates
17
R,
17
G and
17
B are adhered to faces on the incoming side of the three condenser lenses
11
R,
11
G and
11
B while the three polarizing plates
18
R,
18
G and
18
B are adhered to three faces on the incoming side of the cross prism
13
.
Light from the discharge lamp
6
is uniformed by the fly eye lens set
7
and is converted into light having an adjusted polarization direction by the PS conversion element
8
. Of the light L
2
having the adjusted polarization direction, light components in the wavelength region of red are reflected by the dichroic mirror
10
R and follow the path P
3
until they are irradiated upon the spatial optical modulation elements
12
R. Then, light components of the light L
2
in the wavelength region of green are reflected by the dichroic mirror
10
G and follow the path P
4
until they are irradiated upon the spatial optical modulation element
12
G. Finally, light components of the light L
2
in the wavelength region of blue which have passed through the dichroic mirrors
10
R and
10
G are reflected by the reflecting mirror
103
and follow the path P
5
until they are irradiated upon the spatial optical modulation element
12
B.
The liquid crystal projector apparatus
1
is constructed in such a manner as described above, and the three spatial optical modulation elements
12
R,
12
G and
12
G therein modulate the three color lights LR
1
, LG
1
and LB
1
with image signals corresponding to the three primary colors of red, green and blue applied thereto. In particular, the polarization planes of lights of predetermined polarization directions which have passed through the polarizing plates
17
R,
17
G and
17
B are rotated by the spatial optical modulation elements
12
R,
12
G and
12
B based on signals applied to the spatial optical modulation elements
12
R,
12
G and
12
B. The predetermined polarization light components whose polarization planes have been rotated in this manner pass through the polarizing plates
18
R,
18
G and
18
B and are introduced as image lights LR
2
, LG
2
and LB
2
into the cross prism
13
. Then, the three image lights LR
2
, LG
2
and LB
2
are synthesized by the cross prism
13
, and the synthesized image light L
2
of R, G and B is emitted along the optical axis P
6
by the projection lens
14
and projected on the screen (not shown) or the like so that a full-color image may be reflected on the screen or the like.
In this instance, the three polarizing plates
17
R,
17
G and
17
B and the three polarizing plates
18
R,
18
G and
18
B disposed in parallel on the incoming side and the outgoing side of the three spatial optical modulation elements
12
R,
12
G and
12
B are incorporated in order to adjust the polarization directions of the three color lights LR
1
, LG
1
and LB
1
and the three image lights LR
2
, LG
2
and LB
2
. Each of the three polarizing plates
17
R,
17
G and
17
B and the three polarizing plates
18
R,
18
G and
18
B is formed from a thin glass plate to which a polarizing film is adhered with a bonding agent. In the polarizing plates
17
R,
17
G and
17
B and
18
R,
18
G and
18
B, a temperature rise is caused by a polarizing action of the same. Therefore, a critical guarantee temperature (normally approximately 70° C.) for long term reliability is set for the polarizing plates
17
R,
17
G and
17
B and
18
R,
18
G and
18
B, and if the polarizing plates
17
R,
17
G and
17
B and
18
R,
18
G and
17
B are subject to a temperature higher than 70° C., then a seizure or a drop in light transmittance occurs with them. Accordingly, it is necessary to normally cool peripheral portions of the polarizing plates
17
R,
17
G a
Hara Nobuyuki
Ohkubo Takuji
Cruz Magda
Frommer William S.
Frommer & Lawrence & Haug LLP
Mahoney Christopher
Sony Corporation
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