Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2003-08-27
2004-11-30
Nguyen, Judy (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S084000, C353S099000, C353S102000, C348S742000, C348S760000, C362S293000
Reexamination Certificate
active
06824270
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of Korean Patent Application No. 2002-51523, filed on Aug. 29, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a single-panel color image display apparatus, and more particularly, to a single-panel color image display apparatus having a wide color gamut.
2. Description of the Related Art
Color image display apparatuses of a projection type form an image by controlling the on/off operation of light emitted from a high-output lamp light source on a pixel-by-pixel basis using a micro display (also termed a light valve) such as a liquid crystal display (LCD) or a digital micro device (DMD), and magnify and project the image using a projection optical system, thereby providing a wide screen display. Color image display apparatuses of a projection type are classified into a three-panel type and a single-panel type according to the number of panels of micro display.
In a typical single-panel color image display apparatus, white light irradiated from a white light source is separated into red, green, and blue light beams using a color wheel, and the three colored light beams are sequentially sent to one micro display. The micro display operates according to the sequence of colors received and forms an image.
As described above, the typical single-panel color image display apparatus has a simpler structure and a smaller optical system than a three-panel color image display apparatus which forms color images on three micro displays using an optical separation/combination system. However, the typical single-panel color image display apparatus has a light efficiency equal to about one-third of that of the three-panel color image display apparatus due to the use of the color wheel. Hence, a single-panel color image display apparatus which includes a colored light separator having three dichroic filters and the same light efficiency as that of a three-panel color image display apparatus has been proposed.
Referring to
FIGS. 1 and 2
, a conventional single-panel color image display apparatus includes a lamp light source
1
for emitting white light, reflecting mirror
2
, three dichroic filters
4
R,
4
G, and
4
B which are disposed aslant with respect to one another, a micro lens array
10
, and a liquid crystal display device
20
.
The lamp light source
1
emits white light in a divergent light form. White light emitted from the lamp light source
1
is converted into parallel light using a condenser lens
3
.
White light emitted from the lamp light source
1
is separated into a red light beam R, a green light beam G, and a blue light beam B by the three dichroic filters
4
R,
4
G, and
4
B. The dichroic filter
4
R reflects a red light beam R from white light emitted from the light source
1
and transmits remaining light beams. The dichroic filter
4
G reflects a green light beam G from the remaining light beams passing through the dichroic filter
4
R and transmits a remaining light beam, that is, a blue light beam B. The dichroic filter
4
B reflects the blue light beam B.
Each of the three dichroic filters
4
R,
4
G and
4
B is disposed aslant at an angle of +&thgr; with respect to one other. In other words, the dichroic filter
4
R is disposed aslant at an angle of −&thgr; with respect to the dichroic filter
4
G, and the dichroic filter
4
B is disposed aslant at an angle of +&thgr; with respect to the dichroic filter
4
G. As used herein, “+” indicates the counterclockwise direction, and “−” indicates the clockwise direction.
Accordingly, a primary ray of the red light beam R is incident on the micro lens array
10
at an angle of −&thgr; with respect to a primary ray of the green light beam G, and a primary ray of the blue light beam B is incident on the micro lens array
10
at an angle of +&thgr; with respect to a primary ray of the green light beam G.
The micro lens array
10
is formed by arranging a plurality of cylindrical lenses forming a unit micro lenses
10
a
in a horizontal direction. The micro lens array
10
condenses the R, G, and B colored light beams, which are incident at different angles, on signal electrodes
21
R,
21
G, and
21
B, respectively, of the liquid crystal display device
20
in a striped pattern.
The liquid crystal display device
20
has a structure in which a liquid crystal layer
23
is sandwiched between two transparent glass substrates
24
and
25
. Transparent conductive films
22
and the signal electrodes
21
R,
21
G, and
21
B are formed on both sides of the liquid crystal layer
23
in a matrix structure.
In the conventional single-panel color image display apparatus having the above structure, R, G, and B stripes, which are obtained by separating white light into three primary colors using the three dichroic filters
4
R,
4
G, and
4
B and condensed on the signal electrodes
21
R,
21
G, and
21
B of the liquid crystal display device
20
, are arranged at constant intervals in a horizontal direction due to differences in the incident angles of the chief rays of the R, G, and B colored light beams corresponding to the signal electrodes
21
R,
21
G, and
21
B for the R, G, and B colored light beams. The R, G, and B signal electrodes
21
R,
21
G, and
21
B are subpixels and constitute a single image pixel.
When three subpixels corresponding to three primary colors, that is, R, G, and B colors correspond to the unit micro lenses
10
a
, and the three subpixels form an image on a screen
7
, by a field lens
5
and a projection lens
6
, a set of the three subpixels appears as a single image pixel.
Since the three dichroic filters
4
R,
4
G, and
4
B separate white light emitted from the light source
1
into R, G, and B colored light beams and the R, G, and B colored light beams are reflected in an R, G, and B order in the conventional single-panel color image display apparatus having the above structure, a color gamut is narrow.
Referring to the spectroscopic feature of the light source
1
, the intensity of the green light beam G is the strongest and the intensity of the blue light beam B also is strong, but the intensity of the red light beam R is relatively weak.
However, in a case where the dichroic filter
4
R for reflecting the red light beam R is the first disposed among the three dichroic filters, as in the conventional single-panel color image display apparatus, a considerable amount of the green light beam G, for example, together with the red light beam R are reflected by the dichroic filter
4
R so that the green light beam G is mixed in the red light beam R.
Since the human eye is very sensitive to the green light beam G, the mixture of the green light beam G and the red light beam R makes an accurate color realization difficult, and a color gamut that can be expressed by the color image display apparatus narrows. A color gamut indicates a range of reproducible chromaticity. Thus, a narrow color gamut refers to a small number of reproducible colors.
Further, since three subpixels constitute a single image pixel in the conventional single-panel color image display apparatus, the resolution of the liquid crystal display device
20
is reduced by about one-third. Accordingly, in order to realize the same resolution as single-panel color image display apparatuses using a color wheel, the physical resolution of the liquid crystal display device
20
would need to be increased three times.
As described above, the light efficiency of a single-panel image display apparatus using a color wheel is reduced to one-third of that of a three-panel color image display apparatus. A single-panel image display apparatus using a color scrolling technique has been proposed to solve this problem, as shown in FIG.
3
.
When the color scrolling technique is used, a single-panel color image display apparatus has the same light efficiency as that of a three-panel color image display
Cho Kun-ho
Hwang Ju-seong
Kim Dae-sik
Kim Sung-ha
Lee Hee-joong
Koval Melissa J
Nguyen Judy
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