Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-06-17
2004-03-16
Hjerpe, Richard (Department: 2778)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S204000
Reexamination Certificate
active
06707436
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for driving a plasma display panel (PDP).
The PDP is a self-luminous type display device with a characteristic good discernment (i.e., high resolution) and with a thin and large display screen. The PDP is attracting attention as a display device with which CRTs will be replaced in the near future. In particular, a surface discharge AC type PDP is highly expected to be a display device compatible with high-quality digital broadcasting, because it can be designed to have a large display screen. The surface discharge AC type PDP will be required to provide a higher quality than a CRT.
A high-quality display may be construed as a high-definition display, a display with a large number of gray-scale levels, a high-luminance display, or a high-contrast display. A high-definition display is accomplished by setting the pitch between pixels to a small value. A display with a large number of gray-scale levels is accomplished by increasing the number of sub-fields within a frame. Moreover, a high-luminance display is accomplished by increasing the amount of visible light permitted by certain power or increasing the number of times of sustain discharge. Furthermore, a high-contrast display is accomplished by minimizing the reflectance of extraneous light from the surface of a display panel or minimizing an amount of glow that occurs during black display which does not contribute to the display.
2. Description of the Related Art
The structure of a conventional plasma display panel and a conventional method for driving a plasma display panel will be described with reference to
FIG. 1
to
FIG. 4
to be described later in “BRIEF DESCRIPTION OF THE DRAWINGS”. This is intended to facilitate an understanding of problems underlying the conventional method for driving a plasma display panel.
FIG. 1
schematically shows the structure of a surface discharge type PDP in which a method, filed for a patent by the present applicant, is implemented. According to the method, lines defined by all sustain discharge electrodes are involved in display. The structure of the PDP has been disclosed in, for example, the specification and drawings of Japanese Unexamined Patent Publication No. 9-160525 published on Jun. 20, 1997.
A PDP
1
consists of sustain discharge electrodes X
1
to X
3
(hereinafter abbreviated to X
1
to X
3
electrodes) and Y
1
to Y
3
(hereinafter abbreviated to Y
1
to Y
3
electrodes), addressing electrodes A
1
to A
4
, and barriers
2
. The above sustain discharge electrodes are juxtaposed in parallel with each other on one substrate. The addressing electrodes are formed to cross the sustain discharge electrodes on the other substrate. The barriers
2
are arranged in parallel with the addressing electrodes, thus separating discharge spaces from each other. A discharge cell is formed in areas defined by the mutually adjoining sustain discharge electrodes and the addressing electrodes crossing the sustain discharge electrodes. Phosphors used to produce visible light are placed in the discharge cells. A gas for bringing about discharge is sealed in a space between the substrates. In this drawing, for brevity's sake, the sustain discharge electrodes are arranged parallel to each other in threes, and the addressing electrodes number four.
In the PDP having the foregoing structure, sustain discharge is induced in lines defined by each sustain discharge electrode and sustain discharge electrodes on both sides thereof. Interspaces or lines (L
1
to L
5
) defined by all the electrodes therefore can work as display lines. For example, the X
1
electrode and Y
1
electrode define a display line L
1
, and the Y
1
electrode and X
2
electrode define a display line L
2
.
FIG. 2
shows a sectional view of the PDP shown in
FIG. 1
along an addressing electrode. There are shown a front substrate
3
, a back substrate
4
, and discharges D
1
to D
3
induced in lines defined by electrodes. In practice, a voltage is applied to the Y
1
electrode and X
1
electrode. This induces the discharge D
1
. When a voltage is applied to the Y
1
electrode and X
2
electrode, the discharge D
2
is induced. The discharge D
3
is induced by applying a voltage to the X
2
electrode and Y
2
electrode. Thus, one electrode is utilized for providing display lines on both sides thereof. Consequently, a high-definition display can be achieved owing to a decreased number of electrodes. Besides, the number of drive circuits for driving the electrodes can be reduced accordingly.
FIG. 3
shows a frame configuration employed in the PDP shown in FIG.
1
. One frame is composed of two fields of a first field and second field. During the first field, odd-numbered lines (L
1
, L
3
and L
5
) are used as display lines to be involved in the display. During the second field, even-numbered lines (L
2
, L
4
) are used as display lines to be involved in the display. Thus, a picture for one screen is displayed during one frame. Each field consists of a plurality of sub-fields for which luminance levels are set in a predetermined ratio. Cells constituting display lines are selectively allowed to glow according to display data during the sub-fields. Thus, gray-scale levels construed as differences in luminance among pixels are expressed. Each sub-field consists of a reset period, an addressing period, and a sustain discharge period. During the reset period, the states of cells that are mutually different depending on the display situation over an immediately preceding sub-field are uniformed. During the addressing period, new display data is written. During the sustain discharge period, sustain discharge is induced in the cells constituting display lines so that the cells are allowed to glow according to display data.
FIG. 4
is a waveform diagram concerning a conventional driving method implemented in the PDP shown in FIG.
1
.
FIG. 4
is concerned with any sub-field within the first field.
During the reset period, a reset pulse of a voltage Vw exceeding a discharge start voltage is applied to all the X electrodes. Discharge is initiated in the lines defined by the X electrodes and adjoining Y electrodes. As a result, first discharge (reset discharge) is induced in all the lines (L
1
to L
5
). Wall charges including positively-charged ions and electrons are produced in the discharge cells. Thereafter, the reset pulse is removed and the electrodes are retained at the same potential. Second discharge (self-erase discharge) is then induced due to the potential difference generated by the wall charges produced on the electrodes. At this time, since the electrodes are retained at the same potential, positively-charged ions and electrons stemming from discharge are recombined with each other within the discharge spaces. Consequently, the wall charges disappear. The magnitude of wall charges in all the display cells can be uniformed with the discharge (the distribution of wall charges is uniformed).
During the next addressing period, a scanning pulse of a voltage −Vy is applied successively to the electrodes starting with the Y
1
electrode. An addressing pulse of a voltage Va is applied to the addressing electrodes according to display data. Consequently, addressing discharge is initiated. At this time, a pulse of a voltage Vx is applied to the X
1
electrode to be paired with the Y
1
electrode to participate in the display within the first field. Discharge having been induced in the spaces defined by the addressing electrodes and the Y
1
electrode shifts to the line between the X
1
electrode and Y
1
electrode. Consequently, wall charges needed to initiate sustain discharge are produced near the X
1
electrode and Y
1
electrode. The potential at the X
2
electrode to be paired with the Y
1
electrode to define a line not involved in the display is retained at 0 V. It is therefore prevented that discharge is induced in the line defined by the X
2
electrode. Likewise, addressing discharge is induced successively in the odd-number
Asao Shigeharu
Kanazawa Yoshikazu
Setoguchi Noriaki
Eisen Alexander
Fujitsu Limited
Hjerpe Richard
Staas & Halsey , LLP
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