Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-07-07
2003-05-06
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
Reexamination Certificate
active
06559814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method and a device for driving a display, and particularly relates to a method and a device which are suitable for driving a plasma display panel (hereinafter referred to simply as PDP).
2. Description of the Related Art
There is a PDP which performs surface discharge. In such a PDP, all the pixels of the display screen simultaneously glow in accordance with data to be displayed. A PDP that performs surface discharge includes a pair of electrodes inside a front glass panel, and contains rare gas inside the sealed space. As a voltage is applied between the electrodes, surface discharge is observed between the surfaces of the electrodes having a dielectric layer and a protection layer formed thereon. This discharge generates ultraviolet light. An inner surface of a rear glass panel is provided with fluorescent materials corresponding to three primary colors, i.e., red (R), green (G), and blue (B). The ultraviolet light excites the fluorescent materials such that these materials emit light to achieve color display. Here, fluorescent materials for R, G, and B are provided for each pixel of the display screen.
Since the PDP is a light emitting device, it provides a visually better display quality. Also, the PDP can provide a large display screen with a thin bulk. All of these factors make the PDP an attractive display device of the next generation to replace the CRT device. A PDP of a surface AC (alternating current) discharge type is especially suitable for a large display screen, and is expected to be a main display device to be used along with high-definition digital television technology. In an information age which is further advancing as can be seen in development of the Internet, a display device is expected to be an integrated part of the multi-media technology, which combines video media such as television with information media such as personal computers.
In such application, HDTV broadcasting utilizing more than 1,000 scan lines or DVD media may serve as a video source. As far as displaying of information is concerned, an effort to attain finer display details has got to a point where we have an SXGA of 1280-x-1024 dots, and a display format is ever more diversified. Against this background, a display device which can cope with various formats and has more than 1000 scan lines is necessary.
FIGS. 1 and 2
are a plan view and a cross-sectional view, respectively, of a PDP disclosed in Japanese Laid-Open Patent Application No. 9-160525 by the applicant of the present application. This PDP is driven based on an ALIS (alternate lighting of surface) method. In
FIGS. 1 and 2
, a PDP
1
includes a front glass panel
3
, discharge sustaining electrodes X
1
, Y
1
, X
2
, Y
2
, X
3
, and Y
3
provided in parallel on the front glass panel
3
, a rear glass panel
4
, address electrodes A
1
through A
4
provided on the rear glass panel
4
in perpendicular to the discharge sustaining electrodes, barrier ribs
2
which shield discharge spaces from each other by extending in parallel to the address electrodes, fluorescent material
5
applied on the rear glass panel
4
, and a gas contained between the front glass panel
3
and the rear glass panel
4
for facilitating discharge.
As shown in
FIG. 2
, a single discharge cell is defined by two discharge sustaining electrodes (e.g, X
1
and Y
1
) and an address electrode (e.g., A
1
). A discharge sustaining electrode can maintain discharge with adjacent discharge sustaining electrodes on either side thereof, so that all the gaps between the discharge sustaining electrodes shown in
FIG. 1
, i.e., lines L
1
through L
5
, serve as display lines. For example, the discharge sustaining electrodes X
1
and Y
1
together create the display line L
1
, and the discharge sustaining electrodes Y
1
and X
2
together create the display line L
2
.
In
FIG. 2
, a voltage is applied between the discharge sustaining electrodes X
1
and Y
1
to generate discharge in a discharge area D
1
, and a voltage is applied between the discharge sustaining electrodes Y
1
and X
2
to generate discharge in a discharge area D
2
. By the same token, a voltage is applied between the discharge sustaining electrodes X
2
and Y
2
to generate discharge in a discharge area D
3
. In this manner, a single discharge sustaining electrode is used for generating display lines on either side thereof. This configuration makes it possible to reduce the number of discharge sustaining electrodes, thereby achieving a finer display pitch and reducing the number of driver circuits for driving the discharge sustaining electrodes.
FIG. 3
is an illustrative drawing showing a configuration of a frame which the PDP displays.
One frame is comprised of a first field and a second field. A field frequency is 60 Hz, so that the field cycle is 16.6 msec. The first field displays odd-number display lines L
1
, L
3
, L
5
, and so on, and the second field displays even-number display lines L
2
, L
4
, L
6
, and so on, thereby displaying all the display lines. Namely, the display scheme is similar to interlace scanning of a CRT device. Each field is comprised of first through eighth sub-field, each of which has a different luminance ratio, i.e., a different discharge period (the number of discharges). The sub-fields are selectively lighted up in accordance with display data so as to represent a different luminance level of each pixel. Each sub-filed includes a reset period for making uniform the conditions of discharge cells as the conditions of discharge cells depend on the way the immediately preceding sub-field was displayed. Each sub-field further includes an address period for writing new display data and a discharge sustaining period for displaying the display data via discharge sustaining operations.
FIGS. 4A through 4E
are illustrative drawings showing signal forms of a given sub-field of the first field in a PDP device. As shown in
FIGS. 4B and 4D
, a reset pulse having a peak voltage Vw, which is greater than a voltage to generate discharge, is applied to all the X-series discharge electrodes during the reset period. This generates first discharge at all the lines L
1
through L
5
. As a result, each discharge cell has a wall voltage developed based on positive ions or electrons.
After the reset pulse, the wall voltage generates a second discharge. Since there is no voltage differential between the discharge electrodes at this time, positive ions and electrons generated by the discharge end up being connected to each other in the discharge space, resulting in disappearance of the wall voltage. This discharge works to make the conditions of all the discharge cells uniform.
During the address period, as shown in
FIGS. 4C and 4E
, the discharge sustaining electrodes Y
1
and Y
2
in this order receive a scan pulse, which changes from a voltage −Vc to a voltage −Vy. At the same time, scan pulses having a peak voltage Va are supplied to the address electrodes in accordance with the display data, thereby effecting discharge. When this happens, the discharge sustaining electrode X
1
forming a pair with the discharge sustaining electrode Y
1
for display in the first field receives a pulse having a voltage Vx, so that the discharge generated between the address electrodes and the discharge sustaining electrode Y
1
is shifted to a space between the discharge sustaining electrodes X
1
and Y
1
.
This generates wall charge necessary for maintaining the discharge in the space between the discharge sustaining electrodes X
1
and Y
1
. Since the discharge sustaining electrode X
2
forming a line which does not display at the same timing with the discharge sustaining electrode X
1
receives 0 V as shown in
FIG. 4D
, spreading of the discharge area toward the discharge sustaining electrode X
2
is prevented.
When the scan pulse having the voltage −Vy is applied to the discharge sustaining electrode Y
2
, the discharge sustaining electrode X
2
forming a display pair with the dis
Kanazawa Yoshikazu
Kariya Kyoji
Hjerpe Richard
Laneau Ronald
Staas & Halsey , LLP
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