Optics: image projectors – Color filter
Reexamination Certificate
2003-04-21
2004-12-14
Nguyen, Judy (Department: 2851)
Optics: image projectors
Color filter
C353S037000, C353S098000, C348S743000, C348S759000, C348S790000, C349S025000, C349S106000, C359S891000, C362S551000
Reexamination Certificate
active
06830342
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for displaying a large-sized image, and more particularly, to a display device in which the optical efficiency is enhanced by using a color drum.
2. Description of the Related Art
Recently, a flat panel display that has thin and large-sized screen attainment characteristics attracts public attention, and is anticipated to replace the conventional cathode ray tube (CRT) that has a limitation in the screen size and a large volume. As such a flat panel display, there are a liquid crystal display (LCD), a plasma display panel (PDP), a projector and the like. Among these flat panel displays, the projector that magnifies a small-sized image made by an LCD and projects the magnified image to a large-sized screen through a projection lens stands in the spotlight as a new large-sized screen display.
The projector includes a lamp system for generating light, an optical system for converging the generated light, an image display device for displaying the converged light as colors according to an inputted electric signal, and a projection system for magnifying and projecting the displayed colors. Here, the image display devices are classified into a transmission type image display device for transmitting an incident light according to an inputted electric signal and a reflection type image display device for reflecting the incident light according to the inputted electric signal. The LCD having an advantage of the slimness is mainly used as the image display device.
Recently, as a small-sized image display device is developed, various kinds of projectors are being commercialized. The projectors are generally classified into single panel type using one sheet of image display device, double panel type using two sheets of image display devices and triple panel type using three sheets of image display devices. The single panel type projector that uses one sheet of image display device to display images is currently widely used in aspects of cost and structure.
The single panel type projector can use any one of three ways to express the white color: a first way in which R, G and B color filters are attached to the image display device to express the white color, a second way in which micro lenses are attached to the image display device to split R, G and B color lights in different directions and to express the white color, and a third way in which color wheels are utilized to transmit R, G and B color lights selectively one after another in time order.
FIG. 1
illustrates a conventional projector in which color filters are attached to the image display device and
FIG. 2
illustrates a conventional projector in which a micro lens is attached to the image display device.
Referring to
FIG. 1
, in an image display device
120
, R, G and B pixels
122
are linearly arranged and a filter
124
is attached to each pixel
122
. Light generated by a lamp system
100
is converged by an optical system
110
and incident into the image display device
120
. Here, the image display device
120
expresses the incident light as colors according to inputted electric signals. Accordingly, the converged light is expressed as colors depending on the electric signal inputted to each pixel
122
of the image display device
120
, and transmits the filter
124
or is reflected by the filters
124
. The transmitted colors are magnified and outputted onto a screen
140
by a projection lens
130
.
In such a way, however, since three pixels (R, G, B) express one white light, the total number of pixels on the image display device
120
express the white color of which the resolution is reduced to one third (⅓). Like this, since so large area is required to express one white color, the resolution is lowered. In addition, since the filters
124
attached to the image display device
120
do not have good transmission characteristics, they lower the optical efficiency.
As an alternative proposal, referring to
FIG. 2
, micro lenses
165
each of which corresponds to three pixels
161
,
162
and
163
of R, G and B are arranged on an image display device
160
. Separate R, G and B reflection mirrors
152
,
154
and
156
are provided between the optical system
110
and the image display device
160
in order to split the light and apply the split lights to the pixels
161
,
162
and
163
at specific angles respectively. Accordingly, the light generated by the lamp system
100
passes the optical system
110
, is split into color lights by the reflection mirrors
152
,
154
and
156
, and is then incident into the image display device
160
at different angles depending on the slopes of the reflection mirrors
152
,
154
and
156
. The image display device
160
receives the lights inputted from the reflection mirrors
152
,
154
and
156
through the micro lenses
165
and sends them to corresponding pixels
161
,
162
and
163
to express colors according to the inputted electric signal.
However, even in such a way, since three pixels express one white color like the way in which filters are attached to the image display device (shown in FIG.
1
), the resolution is lowered.
To solve the lowering problem in the resolution appearing in the ways of
FIGS. 1 and 2
, a way shown in
FIG. 3
has been suggested.
FIG. 3
illustrates a conventional projector using a color wheel.
Referring to
FIG. 3
, an image display device
180
includes white pixels
182
,
183
and
184
arranged to express one white color by one pixel and a color wheel
170
between a lamp system
100
and an optical system
110
. The color wheel
170
has R, G and B transmission filters
174
a
,
174
b
and
174
c
arranged on predetermined areas of a rotation disk.
As the light generated by the lamp system
100
is incident into the color wheel
170
, the color wheel
170
is rotated by a motor
172
to split the incident light into color lights sequentially and transmit the split color lights to the optical system
110
. Then, the optical system
110
converges the split color lights to one white pixel of the image display device
180
to express a white color.
Since the above method can express one white color by one white pixel, the resolution is enhanced by three times compared with the related arts shown in
FIGS. 1 and 2
but the brightness is contrary decreased to one third (⅓). This is because the color wheel
170
transmits only the corresponding lights of the respective transmission filter
174
a
,
174
b
and
174
c
and the remaining light is not transmitted but lost to decrease the amount of light so. Accordingly, the light efficiency is decreased.
According to the way described above, the resolution is good but the brightness is bad. To this end, there is being developed a technology which is based on the way shown in FIG.
3
and in which the light reflected from the color wheel and lost is reused to enhance the light efficiency.
FIG. 4
illustrates a conventional projector provided with a road lens.
Referring to
FIG. 4
, a conventional projector includes a lamp system
210
for generating light, a road lens
220
shaped in a rectangular, for receiving the light generated from the lamp system
210
, totally reflecting and outputting the generated light, and totally reflecting and outputting the re-inputted light, a color wheel
230
for selectively transmitting the light outputted from the road lens
220
, a converging lens
240
for converging the transmitted light from the color wheel
230
, an image display device
250
for expressing the converged light in colors, and a projection lens for magnifying and projecting the colors expressed by the projection lens
260
onto a screen
270
.
The lamp system
210
includes a light source
212
for generating the light and an elliptic reflecting mirror
214
for controlling the generated light to be inputted to the road lens
220
. Accordingly, all the light generated by the converging lens
210
is incident into the road lens
220
.
The road lens
220
includes an inside m
Blackman Rochelle
Fleshner & Kim LLP
LG Electronics Inc.
Nguyen Judy
LandOfFree
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