Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-01-14
2002-01-08
Saras, Steven (Department: 2775)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000, C315S169400
Reexamination Certificate
active
06337674
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a display panel device, and in particular, to a method for driving a display device such as an alternating-current plasma display panel (AC PDP) device.
2. Background of the Related Art
A flat display device has small size and capacity, and requires a small amount of electric power. A plasma display panel (PDP) device can be used in a television of a considerable size.
The principle that light is emitted from glow discharge generated during the recombination of ionized gas is adopted to the plasma display panel device.
FIG. 1
illustrates a related art three-electrode plasma display panel device for implementing the above-described principle.
FIG. 1
illustrates a cross-sectional view of a pixel. Millions of pixels are formed and used in a display operation of a PDP device.
The alternating-current plasma display panel device includes first and second glass substrates
1
,
2
that are configured in parallel with each other with a space between for plasma to be generated and discharged. Addressing electrodes
4
are deposited on the first glass substrate
1
, and a plurality of X electrodes
6
and a plurality of Y electrodes
7
, which are alternately deposited in parallel with each other, are formed on the second glass substrate
2
. A MgO thin film
5
that is generally used as a dielectric layer is coated over the respective electrodes
4
,
6
,
7
. The MgO thin film
5
serves to cause a second electron generation during bombardment, protect the electrodes and provide the pixels with a memory function. The plasma is generated by applying a proper voltage to the electrodes. The light that is emitted from the plasma is utilized for the display operation. That is, the light stimulates a phosphor, which is provided in close proximity to the electrodes, to display color images.
Related art methods of driving plasma display panels will now be described.
FIG. 2
illustrates an organic connection of a panel
8
having a matrix including multiple plasma display cells, an X electrode driving device
9
coupled to the X electrodes in the panel
8
, a Y electrode driving device or a scan driving device
10
coupled to the Y electrodes in the panel
8
, and an addressing electrode driving device
11
coupled to the addressing electrodes. The X and Y electrodes are also referred to as sustain electrodes.
FIG. 3
a
to
3
d
are waveform diagrams according to a first related art driving method for displaying images on the panel. A pulse is applied to the X electrodes and an Ys electrode that is a selected display line as shown in “a” and “b” time periods of FIGS.
3
b
and
3
c.
Yus electrodes that are not selected are set to a level of Vs as shown in
FIG. 3
d.
Wall charges including positive or negative charges are generated over the sustain electrodes. A data writing operation is performed on the addressing electrodes in “c” time period as shown in
FIG. 3
a.
Thus, a discharge resulting from plasma generation is performed on the cells, and light is emitted therefrom. To maintain such a condition or have a so-called memory function, it is necessary to alternately apply an oppositely-polarized voltage to the X and Y electrodes as illustrated in “d” and “e” time periods. The oppositely polarized voltage maintains a discharge maintenance condition and enables the displayed cell to constantly emit light. Cells where the plasma is not generated are in a dischargeable condition, but light is not emitted therefrom.
FIGS. 4
a
to
4
d
are waveform diagrams of a second related art method of driving the plasma display panel device. In this method, a negative voltage (−Vs) and a ground potential GND are applied to the X and Y electrodes. A narrow erase pulse is used for the Y electrodes like a pulse
30
as shown in
FIG. 4
c
to complete a write operation and leave the wall charges. Thus, the second related art method operates differently from the method illustrated in
FIGS. 3
a
to
3
d.
When the Y electrodes Yus that are not selected maintain a potential level of GND, a voltage pulse
31
of −Vs is applied to the selected Y electrodes with the address data pulse
32
to excite the cells. In order to maintain this condition, pulses
33
,
34
are repeatedly applied to the respective X and Y electrodes. A maintenance pulse
35
is also used for the unselected Y electrodes Yus to prepare for selection.
However, the first and second related art methods have a disadvantage in that a display does not have a plurality of intensity levels. This disadvantage can be overcome in accordance with a third related art method illustrated in
FIGS. 5
a
to
5
f.
In the third related art driving method, a frame is divided and driven in a total write period I, a data write period II as an addressing period, and a maintenance discharge period III. In the total write period I, Y
1
to Y
100
electrodes are set to the potential level of GND, and a write pulse
24
of Vw that is sufficiently large to cause a discharge is applied to the X electrodes. Then, a voltage of Vs is applied to the Y
1
to Y
100
electrodes to have the potential level of Vs, and a pulse
25
is applied to the X electrodes to be in a discharge maintenance condition. Accordingly, the X and Y electrodes enter the addressing period II having the wall charges.
In the addressing period II, the data
27
, which will be displayed, is applied to the addressing electrodes as shown in
FIG. 5
a,
and the selected Y electrode is correspondingly set to the potential level of GND as shown in
FIG. 5
c.
Thereby, the wall charges of a selected cell are erased, and a cell that will be displayed is selected. In this case, an image of a frame is displayed by the discharge maintenance period III, and the intensity levels are determined by the length of the discharge maintenance period III.
FIG. 6
is a timing chart for displaying a plurality of intensity levels determined by the length of the discharge maintenance period. As shown in
FIG. 6
, a frame includes four sub-frames SF
1
, SF
2
, SF
3
, SF
4
. The discharge maintenance periods Td1, Td2, Td3, Td4 have a ratio of 1:2:4:8 and display 16 different intensity levels.
In the above-described related art methods, the plasma display panel device is not in a glowing condition, and thus the light intensity is reduced. U.S. Pat. No. 5,420,602 uses a fourth related art driving method as illustrated in
FIGS. 7
a
to
7
f
to overcome such a disadvantage. This method is similar to the method illustrated in FIG.
5
. However, in the fourth driving method, a write pulse is used more in the total write period, and a glowing amount is increased by lessening the length of the addressing period, differently from the method in FIG.
5
. Moreover, the fourth related art method also has various disadvantages. In the fourth related art method flickering occurs in specific colors, and images that are relatively dark are provided because light is not emitted in the addressing period.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of operating a display device that substantially obviates at least one of the problems caused by disadvantages or limitations of the related art.
Another object of the present invention to provide an alternating-current plasma display panel device that prevents a flickering from occurring in specific colors.
Another object of the present invention is to provide a method for driving a plasma display that divides a frame displaying an image into odd sub-frames and even sub-frames to carry out maintenance discharge on each other in respective addressing periods.
Another object of the present invention is to provide a method of operating a display panel that subdivides the Y-electrode so that concurrent addressing and maintenance discharge occurs.
Another object of the present inventi
Fleshner & Kim LLP
Hyundai Electronics Industries Co,. Ltd.
Spencer William C.
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