Computer graphics processing and selective visual display system – Computer graphics processing – Graphic manipulation
Reexamination Certificate
1999-04-06
2001-12-18
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Graphic manipulation
C345S671000, C348S445000, C348S458000, C348S459000, C348S913000
Reexamination Certificate
active
06331862
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image display device, and more particularly, to an image display device capable of displaying an expanded image signal when an image signal input to the device has a smaller number of pixels than the number of pixels of a display panel.
The present invention also relates to a driver circuit for use in a display device with a high-resolution display panel in which the resolution is switched during an operation.
2. Description of the Related Art
In image display devices for use in personal computers or the like, the number of pixels of a display panel is defined in various standards. Widely used standards include VGA, SGVA, XGA, SXGA, and UXGA. In these standards, the number of pixels per frame is defined as follows.
VGA: 640 pixels in the horizontal direction and 480 pixels in the vertical direction;
SVGA: 800 pixels in the horizontal direction and 600 pixels in the vertical direction;
XGA: 1024 pixels in the horizontal direction and 768 pixels in the vertical direction;
SXGA: 1280 pixels in the horizontal direction and 1024 pixels in the vertical direction; and
UXGA: 1600 pixels in the horizontal direction and 1200 pixels in the vertical direction.
(In the above description, VGA, SVGA, XGA, SXGA, and UXGA are all registered trademarks of IBM Corp.)
In some cases, it is required to display an image signal on a display device according to a standard which is different from that of the image signal such as when a VGA image signal is displayed on an XGA display panel. In such a case, it is required to expand a VGA image signal to a size corresponding to the size of the XGA high-resolution display panel.
Two conventional signal expansion techniques are known in the art of the image display device as described below.
A first technique is, as shown in
FIG. 8
, to switch the sampling frequency at which an analog-to-digital converter
101
converts an analog signal to a digital signal.
For example, when an analog signal such as that shown on the top of
FIG. 9
is given, if the analog signal is sampled in response to a clock signal
1
at a fixed frequency, then digital data
1
is obtained as denoted by A, B, C, D, E, F, G, . . . If the same analog signal is sampled in response to a clock signal
2
at a higher frequency, then different digital data
2
is obtained as denoted by h, i, j, k, l, m, n, o, p, q, r, . . . The latter digital data
2
includes an increased number of data compared to the digital data
1
obtained using the clock
1
. This means that the image signal is expanded.
The second technique is to detect the resolution of a given image signal and to set the expansion ratio to a value corresponding to the ratio of the resolution of the display panel to that of the given image. Each frame of image signal is expanded according to the above expansion ratio by means of interpolation using an arithmetic circuit.
For example, when a VGA image signal is converted to an XGA image signal, the required expansion ratio is 1.6. This expansion ratio may be achieved for example by converting five data to eight data. More specifically, eight data h, i, j, k,
1
, m, n, and o are produced by means of calculation from five original data A, B, C, D, and E as shown ion FIG.
10
. The calculation may be performed using the following equations:
h=A×
1.0 for data
h,
i=A×
0.3+
B×
0.2 for data
i,
j=B×
1.0 for data
j,
k=B×
0.1+
C×
0.4 for data
k,
l=C×
0.4+
D×
0.1 for data
l,
m=D×
1.0 for data
m
for data
m,
n=D×
0.2+
E×
0.3 for data
n
,
and
o=E×
1.0 for data
o.
In the standards described above, each pixel usually consists of three dots representing red (R), blue (B), and green (G), respectively.
When images according to various standards are modified so as to fit them to the display panel, it is required to expand or reduce the image including characters or the like such that the expanded or reduced image is displayed over the fixed display area of the screen.
The following signal expansion techniques are known in the art of the display device.
In one technique, the resolution of given image data is detected using a detection circuit and an expansion ratio is set depending on the ratio of the resolution of the display panel to the detected resolution of the image data. One frame of image data is stored in a frame memory and two consecutive lines of image data are read at a time from the frame memory. The two lines of image are expanded according to the above expansion ratio by means of interpolation using an arithmetic circuit, and resultant image is displayed on the display panel.
In the structure in which pixels each consisting of three dots are arranged in a matrix fashion, original luminance data to be displayed on three dots in each line are expanded using the arithmetic circuit wherein luminance is weighted by predetermined factors. The resultant expanded luminance data is applied to dots of respective pixels so that an image expanded in the direction along the line is displayed on the display panel.
In the above-described techniques, data calculation and re-sampling are required. Besides, an additional memory is required. As a result, the circuit becomes greater in scale and thus it becomes difficult to achieve a small-sized display device and higher cost is required.
One technique of displaying an expanded image without using an additional memory is to employ a display device constructed as shown in
FIG. 26
, which will be further improved according to the present invention as will be described later.
The display device shown in
FIG. 26
includes a thin-film transistor liquid crystal display panel
201
including source interconnection lines and gate interconnection lines extending in a matrix fashion, first horizontal driver
202
and a second horizontal driver
203
connected to the source interconnection lines of the display panel
201
, a vertical driver
204
connected to the gate interconnection lines of the display panel
201
, and a signal processing circuit
205
for controlling the drivers
202
,
203
, and
204
.
The signal processing circuit
205
includes a sampling circuit
207
to which an image signal or an original data is input, a frequency divider
208
and a signal selection circuit
209
both connected to the sampling circuit
207
, a horizontal control circuit
210
for controlling the horizontal drivers
202
and
203
, and a vertical control circuit
211
for controlling the vertical driver
204
. A clock generator
212
is connected to the signal processing circuit
205
. The liquid crystal display panel
201
employed herein is assumed to be of the XGA type including 1024 pixels in the horizontal direction and 768 pixels in the vertical direction.
In the display device shown in
FIG. 26
, if original data or an image signal according to the VGA standard (at a clock frequency of 27.175 MHz) such as a signal H (ABCDE . . . ) shown in
FIG. 27
is input to the signal processing circuit
205
, the signal is input to the sampling circuit
207
. In synchronization with a sampling clock signal at 40.28 MHz, the sampling circuit
207
produces converted data I (AABCCDEE . . . ) as shown in FIG.
27
. The resultant converted data I is sent to the frequency divider
208
. In the above operation, in order to convert the VGA image signal with 1H=640 data to an XGA signal with 1H=1024 data, it is required to increase the number of data by a factor of 1.6 and thus the sampling is performed at a sampling clock frequency of 40.28 MHz which is 1.6 times the original clock frequency of 27.175 MHz.
After that, the converted data is divided by the frequency divider
208
into odd-numbered signals and even-numbered signals. The odd-numbered signals ABCE, . . . , which are represented by J in
FIG. 27
, are supplied via the signal selection circuit
209
to the first horizontal drier
202
. Similarly, the even-numb
Fujiyoshi Tatsumi
Hebiguchi Hiroyuki
Kawahata Ken
Saito Junichi
Yamada Yukimitsu
Brinks Hofer Gilson & Lione
LG Philips LCD Co., Ltd.
Luu Matthew
Sajous Wesner
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