Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-07-15
2001-02-27
Patel, Nimeshkumar D. (Department: 2879)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S061000, C345S065000, C345S067000, C345S071000, C345S060000
Reexamination Certificate
active
06195075
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
1. Field of the Invention
The present invention relates to a plasma display device used for image display on TV, advertisement display boards, etc., and a method of driving the same.
2. Description of the Related Art
FIG. 20
is a perspective view showing a conventional plasma display device. A similar configuration is described in Japanese unexamined patent publication (TOKKAI) Hei6-162934, for example. In
FIG. 20
, an insulating substrate
1
has arranged thereon a plurality of anodes
4
in the form of stripe each having a plurality of resistors
2
and electrode members
3
. A plurality of auxiliary anodes
5
having a shape of stripe are arranged in parallel to the anodes
4
. The anodes
4
are covered with an insulating layer
6
.
A reset cathode
8
and a plurality of cathodes
9
, which are arranged in parallel to the reset cathode
8
, are formed on a lower face of a transparent glass substrate
7
. The cathodes
9
and the reset cathode
8
are disposed above and crossed with the anodes
4
and the auxiliary anodes
5
. A plurality of discharge cells
11
are formed in spaces defined by a partition wall
10
between the anodes
4
and the cathodes
9
facing each other. Also, an auxiliary discharge cell
13
is formed in a space defined by crossing alignment of the auxiliary anodes
5
on one hand and the reset cathode
8
and the cathodes
9
on the other hand. The auxiliary discharge cell
13
communicates with the discharge cells
11
through communication holes
12
. At least a part of the electrode members
3
of the anodes
4
in the discharge cells
11
faces discharge holes
14
formed in the insulating layer
6
and is thus exposed toward the cathodes
9
.
To perform a monochromatic display by this plasma display device, a rare gas such as neon or argon is sealed in the discharge cells
11
and the auxiliary discharge cell
13
. Display is performed using a color generated by discharge illumination of the gas. For multicolor display, on the other hand, a phosphor layer
15
is formed on faces of the insulating layer
6
and the partition wall
10
in each of discharge cells
11
, and a rare gas such as helium, neon or argon containing at least xenon is sealed in the discharge cells
11
and the auxiliary discharge cell
13
. The phosphor layer
15
is excited by the ultraviolet rays generated by the discharge in the gas, and display performed by the illumination color generated from the phosphor layer
15
.
The above-mentioned plasma discharge device is what is called pulse-memory-type device, and it has a matrix circuit as shown in FIG.
21
. In
FIG. 21
, a row of reset cathode R and N (=integer) rows of cathodes K
1
to K
N
are arranged along the rows. Along the column length, on the other hand, there are arranged M (=integer) columns of anodes A
1
to A
M
and L (=integer) columns of auxiliary anodes H
1
to H
L
.
FIG. 22
is a time chart showing driving voltages supplied to respective parts described above. Operation of image display is hereafter described with reference to these figures.
First, during the first period t
1
, the auxiliary anodes H
1
to H
L
and the reset cathode R are impressed with pulse voltages of opposite phases to each other, thereby to cause a reset discharge between the auxiliary anodes H
1
to H
L
and the reset cathode R. Since a stable reset discharge hardly generates by only one application of pulse voltage, the pulse voltage is repeatedly applied to during the period t
1
to trigger a stable reset discharge.
Next, during the scanning period t
3
, a pulse voltage is applied to the auxiliary anodes H
1
to H
L
and the cathode K
1
, and a writing pulse voltage is applied to the anodes A
1
to A
M
corresponding to the display discharge cells respectively. As a result, the residual charged particles due to the reset discharge trigger a stable auxiliary discharge between the auxiliary anodes H
1
to H
L
and the cathode K
1
. Further, this auxiliary discharge induces a stable main discharge in the display discharge cells.
The operation for sustaining the main discharge of the display discharge cells is performed by applying a sustaining pulse voltage to the cathode K
1
again during the period t
6
when sufficient residual charge particles remain due to the main discharge occurred during the period t
3
. Similarly, as far as the sustaining pulse voltage continues to be applied to the cathode K
1
during the periods t
8
, t
10
, . . . , the main discharge of the display discharge cells is performed intermittently and thus sustained.
During the next scanning period t
5
, a pulse voltage is applied to the auxiliary anodes H
1
to H
L
and the cathode K
2
, and a writing pulse voltage is applied to the anodes A
1
to A
M
which respectively correspond to the display discharge cells. Consequently, the residual charged particles generated by the auxiliary discharge between the auxiliary anodes H
1
to H
L
and the cathode K
1
trigger a stable auxiliary discharge between the auxiliary anodes H
1
to H
L
and the cathode K
2
. Further, the thus occurred auxiliary discharge induces a stable main discharge of the display discharge cells.
For sustaining the main discharge of the display discharge cells, a sustaining pulse voltage is applied to the cathode K
2
again during the period t
8
when a sufficient amount of residual charged particles remain due to the main discharge which has been generated during the period t
5
. The main discharge is thus triggered again in the display discharge cells. In the similar manner, as far as a sustaining pulse voltage continues to be applied to the cathode K
2
during the period t
10
, t
12
, . . . , the main discharge of the display discharge cells is performed intermittently and thus sustained.
Further, the above-mentioned operation is performed by sequentially scanning the cathodes K
3
, K
4
, . . . which are successively arranged along the rows, thereby forming a screen of image. In this scanning process, the auxiliary discharge during the period t
5
, t
7
, . . . following the period t
3
is succeeded with the aid of the charged particles due to the just preceding auxiliary discharge.
FIG. 23
is a diagram for explaining operation of the conventional plasma display device shown in
FIG. 20
when a grayscale TV picture is displayed thereon. In
FIG. 23
, an image display has 500 TV lines (i.e., 500 scanning lines), 256 gradations and a field period t
f
of {fraction (1/60)} second. One field can be divided into eight subfields having time periods equal to each other. The writing pulse and the sustaining pulse are alternately applied to the device for each scanning time of one field scanning. The writing period in one scanning cycle is t
s1
, and a sustaining period in each scanning cycle is t
s2
.
Writing and sustaining pulse periods are obtained from a relation expressed as ({fraction (1/60)} [second])/(500[TV lines])/(8 [subfields]), which is equal to about 4 &mgr; seconds. Also, the maximum number of times each subfield contains 2
8
(=128) pulses is obtained from a relation given as 500≧128×N (N: integer), and this leads to a result of N=3. To apply the writing pulse and the sustaining pulse so as not to overlap each other, the maximum time &Sgr;m made available for sustaining discharge is given as
1[&mgr;second]×(128+64+32+16+8+4+2+1)×3 (N: number of times)=765 [&mgr;seconds].
Therefore, the maximum time &Sgr;m to the field period t
f
is about {fraction (1/20)} from a relation (765 [&mgr;seconds])/({fraction (1/60)} [second]) for each field period.
As shown in graph (a) of
FIG. 23
, the conventional subfield arrangement makes it necessary to perform the auxiliary discharge continuously according to the scanning sequence of the cathodes over the entire subfield period. For this reason, a field period t
f
is divided into eight equal subfields, and an idle time is provided a
Hirao Kazunori
Ito Yukiharu
Kosugi Naoki
Mae Hajime
Shino Taichi
Akin Gump Strauss Hauer & Feld L.L.P.
Haynes Mack
Matsushita Electronics Corporation
Patel Nimeshkumar D.
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