Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2003-01-31
2004-06-01
Clinger, James (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S060000
Reexamination Certificate
active
06744215
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control method and system for improving the color temperature of an alternating current (AC) plasma display panel (PDP), and more particularly, to a method and apparatus for controlling the color temperature of an AC PDP, which is capable of maintaining high luminance and luminous efficiency even in an XGA class discharge cell as well as a VGA class discharge cell because a discharge space is dispersed from a sustain electrode to the direction of a writing electrode, to thus obtain strong sustain discharge having a large discharge space when a pulse is simultaneously applied to the writing electrode while a sustain pulse waveform is applied during a sustain period of the AC PDP, of improving only the bright of a blue cell whose luminance is relatively low regardless of a cell structure because different pulses can be independently applied to the writing electrodes of red, blue, and green cells during the application of the sustain pulse, and of controlling a color temperature by increasing the luminance of the blue and green cells. As a result, it is possible to improve the color temperature of a white cell in a state of high luminance.
BACKGROUND ART
FIG. 1A
is a perspective view illustrating upper and lower substrates of a common alternating current (AC) surface discharge PDP, which are separated from each other.
FIG. 1B
is a plane view illustrating the upper and lower substrates of an AC PDP, which are separated from each other. The AC surface discharge PDP includes a front substrate
1
for displaying information and a back substrate
2
having the same width as that of the front substrate
1
and positioned to be parallel to the front substrate
1
.
The front substrate
1
includes a plurality of sustain electrode lines X and Y including transparent electrodes
6
and bus electrodes
7
having low resistivity, the sustain electrode lines X and Y for applying a voltage waveform, a dielectric layer
8
formed between sustain electrode lines, the dielectric layer
8
for restricting discharge current, and a protective layer
9
formed on the dielectric layer
8
, the protective layer
9
for protecting the sustain electrode lines. The back substrate
2
includes a plurality of partitions
3
forming a discharge space, a plurality of writing electrode lines
4
formed to be perpendicular to the sustain electrode lines between the partitions
3
, and a fluorescent film
5
whose discharge spaces are formed to wrap the corresponding writing electrode lines
4
on both partition surfaces and a back substrate, the fluorescent film
5
for receiving vacuum ultraviolet (VUV) generated during discharge and emitting a visible ray.
FIG. 2A
is an entire driving waveform chart illustrating waveforms applied to the respective electrodes X, Y and Z during a sub field in a conventional AC PDP.
FIG. 2B
is an enlarged waveform chart for a sustain pulse.
FIG. 2A
illustrates an example of voltage waveforms applied to the sustain electrode lines X and Y formed of the transparent electrodes
6
and the bus electrodes
7
of
FIG. 1
in order to display information on the AC PDP and the writing electrode lines
4
. A time can be divided into an erase period T
1
, a write period T
2
, and a sustain period T
3
. During the erase period T
1
, a wall charge that becomes uneven while the AC PDP displays previous information becomes even over an entire panel by alternately applying a low lamp type pulse and a high pulse to the sustain electrode lines X and Y as illustrated in FIG.
2
A. During the write period T
2
, information is written by accumulating a wall charge after writing discharge only on a cell to be displayed by a voltage difference between the sustain electrode line X and the writing electrode line Z. During the sustain period T
3
, information is displayed by alternately applying a voltage to both sustain electrode lines X and Y and making a visible ray emitted only from the cell, into which information is written during the write period T
2
.
In a common AC PDP, the waveforms of the X and Y pulses that are both sustain electrode lines are square waves in the sustain period T
3
. A voltage is not applied to the writing electrode.
FIG. 2B
illustrates enlarged waveforms applied to the respective electrodes for a time, for which a sustain pulse is applied. T
4
denotes a rest period, during which no voltage is applied to all of the electrodes. In T
5
, the moment a voltage of a square wave is applied to the sustain electrode X and discharge starts, a visible ray is emitted for a short time. After a rest period T
6
, when a square wave is applied to the sustain electrode Y, discharge occurs and a visible ray is emitted. At this time, no voltage is applied to a writing electrode Z.
Among three primary colors of red R, green G, and blue B used by the common AC PDP in order to express an image, blue is emitted so that the intensity of light is weaker than the intensity of those of green and red due to the characteristic of a discharge gas such as Ne. Accordingly, the AC PDP has a low color temperature. Therefore, in order to use the AC PDP as a commonly used display device, the color temperature must be raised. Accordingly, various methods for raising the color temperature of the AC PDP are provided.
FIGS. 3A
to
3
C illustrate one of conventional methods for raising the color temperature of the AC PDP by gamma-correcting an analog video signal. Generally, an analog video signal input from the AC PDP is digitalized in 256 luminance steps from 0 to 255 in each color in order to realize gray scales and is expressed by the number of sustain pulses. The analog video signal input to the AC PDP is not corrected in consideration of the characteristic of the AC PDP but is a signal, in which red, green, and blue have the same peak value. In a conventional technology, in order to raise the color temperature of the PDP, as shown in
FIGS. 3A
to
3
C, red (
FIG. 3A
) and green (
FIG. 3B
) analog video signals excluding a blue (
FIG. 3C
) analog video signal having relatively low luminance are inverse gamma corrected so that a peak value of each color is lowered before a digitalizing step and are digitalized. After such a step, the number of sustain pulses having the maximum luminance of red and green is smaller than the number of sustain pulses having the maximum luminance of blue. Accordingly, the color temperature can be raised. For example, if 255 sustain pulses are used for expressing the maximum luminance of blue, the maximum luminance is expressed by about 200 sustain pulses in the case of green and by about 180 sustain pulses in the case of red.
In the conventional method of raising the color temperature, because all of the 255 sustain pulses required for expressing the maximum luminance of green and red are not used, it is disadvantageous to realizing gray scales. As a result, a step phenomenon occurs in red and green in expressing an image that becomes gradually bright or dark.
FIGS. 4A and 4B
are views for explaining another method among conventional technologies used for raising the color temperature of the AC PDP. A method of raising the color temperature using uneven partitions is shown. Distance between partitions of a common AC PDP is uniform so that red, green, and blue have discharge spaces of the same width as shown in FIG.
4
A. The red, green, and blue cells are combined with each other, to thus form a pixel. When the distance between partitions in a part for displaying a specific color is widened, a discharge space is widened and thus, strong discharge is obtained. Accordingly, it is possible to obtain higher luminance than other colors. A method of raising the color temperature of the AC PDP using the above phenomenon is the method using the uneven partitions shown in FIG.
4
B. That is, as illustrated in
FIG. 4B
, the distance between the partitions of blue having relatively lower luminance than red and green is widened. In order to sustain the size of a pixel to be uniform, the distance between the partitions of red an
Chien Sung Il
Cho Ki Duck
Tae Heung Sik
Clinger James
Volpe and Koenig P.C.
Yeint Co., Ltd.
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