Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2001-12-21
2003-07-08
Dowling, William (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C349S005000, C348S742000
Reexamination Certificate
active
06588906
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 2001-45221, filed Jul. 26, 2001, in the Korean Industrial 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 color image display apparatus, and more particularly, to a single-panel color image display apparatus using a single display device to display an image according to an electrical video signal and which achieves the same optical efficiency and resolution as a three-panel color image display apparatus using three display devices.
2. Description of the Related Art
FIG. 1
is a diagram showing an example of a conventional single-panel color image display apparatus
200
,
FIG. 2
is a diagram showing a light path in a micro lens array and a liquid crystal display device of the single-panel color image display apparatus
200
of FIG.
1
. Referring to
FIGS. 1 and 2
, the conventional single-panel color image display apparatus includes a light unit
202
, three dichroic mirrors
4
R,
4
G, and
4
B which are obliquely provided, a micro lens array
10
, and a liquid crystal display device
20
.
The light unit
202
includes a white light source, i.e., a lamp
1
, a spherical mirror
2
installed to surround one side of the lamp
1
, and a condenser lens
3
condensing and converting diverging light directly incident from the lamp
1
and diverging light incident after being reflected from the spherical mirror
2
into parallel light.
White light emitted from the light unit
202
is divided into red light R, green light G, and blue light B by the three dichroic mirrors
4
R,
4
G, and
4
B. The dichroic mirror
4
R reflects red light R of the white light incident from the light unit and transmits light of the other colors, that is, green light G and blue light B. The dichroic mirror
4
G reflects green light G of the color light transmitted by the dichroic mirror
4
R and transmits light of the last color, that is, blue light B. The dichroic mirror
4
B reflects the blue light B.
Each of the three dichroic mirrors
4
R,
4
G and
4
B is disposed at an angle &thgr; with respect to the dichroic mirror(s) adjacent to it, thus having the shape of the ribs of a fan. In other words, the dichroic mirror
4
R is askew at an angle of −&thgr; with respect to the dichroic mirror
4
G, and the dichroic mirror
4
B is askew at an angle of +&thgr; with respect to the dichroic mirror
4
G. Here, “+” indicates the counterclockwise direction, and “−” indicates the clockwise direction.
Accordingly, a chief ray of red light R is incident on the micro lens array
10
at an angle of −&thgr; with respect to a chief ray of green light G, and a chief ray of blue light B is incident on the micro lens array
10
at an angle of +&thgr; with respect to a chief ray of green light G.
The micro lens array
10
is the horizontal arrangement of a plurality of cylindrical lenses which form a unit micro lens
10
a
. The micro lens array
10
condenses red light R, green light G, and blue light B, which are incident on the micro lens array
10
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 signal electrodes
21
R,
21
G, and
21
B are formed on both sides of the liquid crystal layer
23
in a matrix pattern.
In a conventional single-panel color image display apparatus having the above structure, R, G and B stripes obtained by dividing white light into three primary color rays using the three dichroic mirrors
4
R,
4
G, and
4
B and condensing the rays on signal electrodes of the liquid crystal display device
20
are arranged at regular intervals in a horizontal direction due to differences among incident angles of the chief rays of red light R, green light G, and blue light B. These R, G, and B stripes correspond to the R, G, and B video signal electrodes
21
R,
21
G, and
21
B. The R, G, and B signal electrodes
21
R,
21
G, and
21
B are subpixels and constitute a single image pixel.
Three subpixels corresponding to red, green, and blue correspond to a unit micro lens
10
a
. When the three subpixels form an image on a screen
7
through a field lens
5
and a projection lens
6
, a set of the three subpixels appears as a single image pixel. Accordingly, a viewer can see a color image composed of image pixels.
However, since three subpixels constitute a single image pixel in such a conventional single-panel color image display apparatus, the resolution of a liquid crystal display device is reduced to ⅓. Accordingly, in order to realize the same resolution as projection type single-panel image display apparatuses using a color wheel, which are disclosed in U.S. Pat. Nos. 5,633,755 and 5,159,485, the physical resolution of the liquid crystal display device
20
should be increased by three times.
When the physical resolution of the liquid crystal display device
20
is increased by three times, an aperture ratio is deteriorated, thus decreasing light efficiency. In addition, yield decreases, thus increasing manufacturing costs. Moreover, when the liquid crystal display device
20
is manufactured to have three times higher resolution, the size of the liquid crystal display device
20
may increase. As the liquid crystal display device
20
becomes larger, the condenser lens
3
, the field lens
5
, or the projection lens
6
should also be larger, which increases manufacturing costs.
SUMMARY OF THE INVENTION
To solve the above problems, it is an aspect of the present invention to provide a single-panel color image display apparatus having an improved structure of a color light beam splitting unit. The color light beam splitting unit of the present invention splits a white light beam emitted from a light unit into a plurality of color light beams, thus having physically the same resolution as a conventional projection type single-panel image display apparatus using a color wheel and having substantially the same light efficiency and resolution as a conventional three-panel color image display apparatus using three display devices.
To achieve the above aspect of the invention, the present invention comprises a single-panel color image display apparatus including a light unit, a color light beam splitting unit, an image generator, and a projection lens unit. The light unit emits white light. The color light beam splitting unit comprises a plurality of switchable color filters which selectively transmit and/or reflect a plurality of color light beams. The color light beam splitting unit splits the white light incident from the light unit into a plurality of color light beams and reflects the plurality of color light beams. The image generator generates a plurality of color images using the plurality of color light beams from the color light beam splitting unit. The projection lens unit projects the plurality of color images generated by the image generator onto a screen.
The color light beam splitting unit includes as many switchable color filters as color light beams generated by splitting. That is, in the color light beam splitting unit of the present invention, the number of switchable color filters corresponds to the number of color light beams generated by splitting.
The switchable color filters alternately select and reflect the plurality of color light beams in response to electrical signals during each period of a subframe, which is one of as many subframes as color light beams generated by splitting. That is, the number of subframes corresponds to the number of color light beams generated by splitting.
In other words, each of the switchable color filters includes as many electronically switchable selective reflection/transmitting layers as color light beams
Dowling William
Samsung Electronics Co,. Ltd.
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