Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-09-16
2002-08-06
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000
Reexamination Certificate
active
06429833
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for displaying gray scales of a plasma display panel to prevent pseudo-contour from being generated when a moving picture is expressed on the plasma display panel in gray scales.
2. Description of the Related Art
Plasma display panels are display devices which arrange a plurality of discharge cells in a matrix and selectively make the arranged discharge cells emit light, thereby restoring video data input as an electrical signal. The plasma display panel can be driven by a DC driving method or an AC driving method according to whether the polarity of a voltage applied to maintain discharge is changed or not according to time. The plasma display panel can be classified into an opposite discharge type and a surface discharge type according to the method of arranging electrodes for generating discharge. Each type is also classified into a two-electrode structure, a three-electrode structure, or the like according to the number of electrodes installed.
FIG. 1A
is a cross-sectional view of a discharge cell in a DC-type opposite discharge plasma display panel, and
FIG. 1B
is a cross-sectional view of a discharge cell in an AC-type surface discharge plasma display panel. As shown in
FIGS. 1A
(
1
B), the plasma display panel essentially includes discharge spaces
3
(
13
) between a front glass substrate
1
(
11
) and a rear glass substrate
2
(
12
). The DC-type opposite discharge display panel, as shown in
FIG. 1A
, fundamentally has two orthogonal electrodes
4
and
5
which are installed on the front and rear glass substrates
1
and
2
, respectively. The two electrodes
4
and
5
are directly exposed to the discharge space
3
, such that a discharge is sustained due to flow of electrons provided by a cathode. The AC-type surface plasma display panel, as shown in
FIG. 1B
, includes an address (metal) electrode
14
installed on the glass substrate
11
, and a pair of discharge sustaining electrodes
15
installed on the glass substrate
12
to be orthogonal to the address electrode
14
. The discharge sustaining electrodes
15
are covered by a dielectric layer
16
, such that they are electrically isolated from the discharge space
13
. In this case, a sustaining discharge occurs between the two discharge sustaining electrodes
15
installed within the dielectric layer
16
, and is sustained by an effect (wall charge effect) due to a charge being accumulated on the surface of the dielectric layer. That is, even when a voltage lower than a discharge start voltage is applied, discharge occurs where a wall charge exists, since the discharge start voltage is the sum of the applied voltage and a wall voltage generated by the wall charges. The discharge also accumulates a negative-polarity wall charge, so that discharge is repeated and sustained where discharge occurs once.
FIG. 2
is an exploded perspective view of the three-electrode surface discharge plasma display panel shown in
FIG. 1B
, which is already in common use. This structure includes two discharge sustaining electrodes
15
formed parallel to each other within a discharge space formed by barrier ribs, and an address electrode
14
facing the discharge sustaining electrodes
15
to be orthogonal thereto. A fluorescent body
18
that emits red, green and blue lights by ultraviolet rays emitted during discharge, is coated within discharge spaces separated by the barrier ribs
17
.
FIG. 3
is a connection diagram of electrodes of the AC-type surface discharge plasma display panel of FIG.
2
. As shown in
FIG. 2
, several pairs of electrodes
15
are horizontally installed on a rear glass substrate, and two electrodes in each pair face each other in parallel. The electrodes
14
in strips are installed on a front glass substrate in a direction orthogonal to the electrodes
15
. Here, electrodes connected commonly to each other, among the pairs of horizontal electrodes
15
, are common electrodes (X electrodes), and the other electrodes separated from each other are scanning electrodes (Y electrodes). Also, electrodes perpendicular to these X and Y electrodes are address electrodes
14
. In this structure, a discharge for generating wall charge to select a pixel occurs between an address electrode
14
and a scanning electrode, and thereafter, a discharge for displaying pictures repeatedly occurs for a certain time between the scanning electrode and the common electrode. The barrier ribs
17
form discharge spaces and also prevent crosstalk between adjacent pixels by blocking light generated during discharge. A plurality of unit structures are formed on one substrate in a matrix, and ultraviolet rays emitted from the respective unit structures selectively discharge a fluorescent material coated on spaces between adjacent barrier ribs, thereby accomplishing color. These unit structures act as pixels, and these pixels are collected and become a plasma display panel.
The plasma display panel having such a structure must be able to display gray scales in order to provide the performance of a color display device. Display of gray scales is accomplished using a gray scale expressing method of dividing one field into a plurality of sub-fields and time-division controlling them.
FIG. 4
shows a method of displaying a gray scale of an AC-type surface discharge plasma display panel. Here, the horizontal axis denotes time, and the vertical axis denotes the number of horizontal scan lines. In the gray scale display method of
FIG.4
which is an 8-bit gray scale expression method, one field is divided into eight sub-fields, and each sub-field is comprised of an address period and a charge sustaining period. The addressing period forms a wall charge on a pair of display electrodes at a selected place on the entire screen of a plasma display panel due to selective discharge by a writing pulse, to thus write electrical-signalized information (that is, to form wall charges) between the address electrode and the scanning electrode which cross each other. The discharge sustaining period is a light emitting period which realizes image information on a real screen by discharging continuous discharge sustaining pulse between the display electrodes. The discharge sustaining period has a light emitting period ratio of 1:2:4:8:16:32:64:128. According to the principle in which a gray scale of a PDP is realized, the sub-fields are selectively driven, and at this time, emitted light is perceived for a predetermined time by the eyes of a user, so that the user perceives a gray scale as an averaged luminance. For example, in order to accomplish a gray scale of 3, an auxiliary field having a period of 1T and an auxiliary field having a period of 2T are driven, and the sum of the periods is made 3T, so that a gray scale 3 is perceived which is expressed as the amount of exposure light during a period of 3T. In the same way, a gray scale of 127 as a luminance of 127 is obtained by the amount of light exposed during a total of 127T periods by sequentially driving sub-fields having periods of 1T, 2T, 4T, 8T, 16T, 32T and 64T. When 8 sub-fields are used in this way, a total of 256 gray scales (2
8
=256) can be displayed.
Meanwhile,
FIGS. 5A through 5C
are graphs for explaining a principle in which the human eye perceives a gray scale of a still picture. It is assumed that pixel A has a brightness of 127 and pixel B has a brightness of 128. In the pixel A, all sub-fields in the first half except for an auxiliary field having a period of 128T, among 8 sub-fields, emit light, and in the pixel B, only the auxiliary field in the second half having a period of 128T emits light, as shown in FIG.
5
A. When these pixels are temporally at pause, the human eye senses light during a predetermined period at a certain position on the retina as shown in
FIG. 5B
, and thus can properly perceive the correct stimulated values, that is, brightnesses of 127 and 128, as shown in FIG.
5
C.
FIG. 6
is a graph explaining a principle in which the human
Kim Se-woong
Ryeom Jeong-duk
Leydig , Voit & Mayer, Ltd.
Maier Chris
Samsung Display Devices Co. Ltd.
Saras Steven
LandOfFree
Method and apparatus for displaying gray scale of plasma... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for displaying gray scale of plasma..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for displaying gray scale of plasma... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2885187