Optics: image projectors – Temperature control – Blower
Reexamination Certificate
2000-01-31
2001-05-29
Dowling, William (Department: 2851)
Optics: image projectors
Temperature control
Blower
C353S061000
Reexamination Certificate
active
06238050
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal projector using a transmission liquid crystal panel, or more in particular to (1) a liquid crystal projector for projecting the illumination light from a light source on a liquid crystal panel, and projecting an image of the liquid crystal panel on a screen through a projection lens. The invention also relates to (2) a liquid crystal projector in which the illumination light from a light source is split into three colors of R, G and B by a dichroic mirror and irradiated on three liquid crystal panels, images on the three liquid crystal panels are synthesized in color through a dichroic prism and a synthesized image is projected on a screen through a projection lens. Further, the invention relates to (3) a liquid crystal projector in which the illumination light from a light source is irradiated on a liquid crystal panel through a reflector, a first lens array and a second lens array so that the light emitted from the liquid crystal panel is projected on a screen by a projection lens.
A conventional liquid crystal projector using a transmission liquid crystal of this type is known, as described in JP-A-63-216026, for example, which comprises a light source (corresponding to 21), a first reflection mirror (corresponding to 23), a first dichroic mirror (corresponding to 26), a second reflection mirror (corresponding to 30), a second dichroic mirror (corresponding to 27), a third reflection mirror (corresponding to 28), a fourth reflection mirror (corresponding to 29), a first transmission liquid crystal panel (corresponding to 33), a second transmission liquid crystal panel (corresponding to 39), a third transmission liquid crystal panel (corresponding to 45), a dichroic prism (corresponding to 49) and a projection lens (corresponding to 50), wherein the illumination light from the light source is irradiated on the first dichroic mirror through the first reflection mirror, the first emitted light split in color by the first dichroic mirror is irradiated on the first liquid crystal panel through the second reflection mirror, the second emitted light split in color by the first dichroic mirror is irradiated on the second dichroic mirror, the first emitted light split in color by the second dichroic mirror is irradiated on the second liquid crystal panel, the second emitted light split in color by the second dichroic mirror is irradiated on the third liquid crystal panel through the third reflection mirror and the fourth reflection mirror, the transmitted light from the first liquid crystal panel, the transmitted light from the second liquid crystal panel and the transmitted light from the third liquid crystal panel are synthesized in color by the dichroic prism, and the emitted light thus synthesized in color is projected on the screen by the projection lens.
Another conventional liquid crystal projector is known, as disclosed in JP-A-3-10218, comprising an exhaust fan (corresponding to 15, 27) for cooling a light source.
As disclosed in “High-Efficiency Illumination Optical System for Liquid Crystal Projector Using Deformed Open Lens Array”, 22Fa06 of Optical Federation Symposium, Hamamatsu '94, pp.135-136, JAPAN OPTICS '94, sponsored by the Japan Optical Society (Application Physics Association), for example, a liquid crystal projector is known, comprising a light source including a metal halide lamp and a parabolic mirror, a UV-IR cut filter, a first lens array and a second lens array.
A liquid crystal projector configured of a combination of the above-mentioned three conventional liquid crystal projectors already finds applications. The prior art will be described below with reference to the drawings.
FIG. 9
is a diagram showing an optical system of a liquid crystal projector comprising a combination of the above-mentioned configurations of the conventional liquid crystal projectors.
The illumination light
51
from a metal halide lamp
50
constituting a light source enters a lamp reflector
52
of a parabolic mirror, a UV-IR cut filter
53
, a first lens array
54
, a cold mirror
55
constituting a first reflection mirror, a second lens array
56
, and a first dichroic mirror
57
for transmitting the R color light and reflecting the G and B color light, so that the R color light
58
is transmitted and the G and R color light
59
are reflected. The R color light
58
is reflected on an increased reflection aluminum mirror
60
constituting a second reflection mirror, and enters a R color light liquid crystal panel
63
constituting a first transmission liquid crystal panel through a condenser lens
61
and a polarizing plate
62
. The G and B color light
59
enter a second dichroic mirror
64
which reflects the G color light and transmits the B color light, so that the G color light
65
is reflected and the B color light
66
is transmitted. The G color light
65
enters a G color light liquid crystal panel
69
making up a second transmission liquid crystal panel through a condenser lens
67
and a polarizing plate
68
. The B color light
66
, on the other hand, enters a B color light liquid crystal panel
76
making up a third transmission liquid crystal panel through a relay lens
70
, an increased reflection aluminum mirror
71
making up a third reflection mirror, a relay lens
72
, an increased reflection aluminum mirror
73
making up a fourth reflection mirror, a condenser lens
74
and a polarizing plate
75
.
The R transmitted light
77
from the liquid crystal panel
63
, the G transmitted light
78
from the liquid crystal panel
69
and the B transmitted light
79
from the liquid crystal panel
76
are synthesized in color by a dichroic prism
80
. The emitted light
81
thus synthesized in color is projected on a screen (not shown) by a projection lens
82
.
In order to prevent the heat generated by the high-temperature light source from having an effect on the component parts other than the light source, an exhaust fan
83
for cooling the light source is arranged in the neighborhood of the metal halide lamp
50
and the lamp reflector
52
thereby to exhaust the hot air
84
out of the housing (not shown) of the liquid crystal projector.
The liquid crystal projector having this configuration can produce a bright, large image on the screen while cooling the high-temperature light source. Also, the first lens array
54
and the second lens array
56
configured as an optical integrator can irradiate a uniform illumination light on the liquid crystal panels
63
,
69
,
76
, thus producing a bright, large image on the screen with a uniform peripheral illuminance. In the conventional liquid crystal projector of this configuration, however, has the problem that the hot air
84
exhausted by the exhaust fan
83
often flows toward the viewers located in the neighborhood of the liquid crystal projector and thus gives the feeling of discomfort to the viewers. Also, the liquid crystal projector is sometimes used in the vicinity of the video equipment such as the personal computer liable to succumb to heat easily. In such a case, such video equipment is required to be located at a position not exposed to the hot air. Further, in order to efficiently exhaust the heat generated from the light source, care must be exercised not to place any object constituting a stumbling block to the exhaustion in a path of the hot air, thereby posing the problem of operating inconveniences.
On the other hand, JP-A-5-59424 (UM) proposes a configuration in which an exhaust fan for cooling a light source is arranged in the same plane as the front cylinder section of a projection lens so that the light is projected in the same direction as the hot air is exhausted. In this configuration, the hot air exhausted from the exhaust fan is prevented from flowing toward the viewers located in the neighborhood of the liquid crystal projector. The viewers thus feel no inconvenience, nor is it necessary to take care not to arrange the equipment easily affected by heat in the neighborhood of the liquid crys
Deguchi Masaharu
Inage Hisao
Kakuda Takashi
Konuma Nobuhiro
Matsuda Yutaka
Dowling William
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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