Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-03-20
2003-10-14
Chang, Kent (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S208000, C345S210000
Reexamination Certificate
active
06633268
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to AC-type plasma display apparatuses, and more particularly to an AC-type plasma display apparatus suitable for a display device carrying out an address discharge drive at high speed.
In the AC-type plasma display apparatus, a TV device to replace a conventional CRT as a display device having a large screen, being a thin flat type, and in light weight, has already been commercially produced.
Up to the present time, a Video Graphic Array TV having the number of lines of 480 pieces and belonging to a class of 40 inches in duration and a HDTV (abbreviation of High definition Tele-Vision) performing interlace scanning has been realized.
The AC-type plasma display apparatus, though already commercially finished in production, having a considerable number of subjects in terms of its performance, and has not yet excelled CRT in view of a quality of a picture.
As to the performance of a plasma display apparatus, in addition to basic performance required generally as a display apparatus such as display brightness, a contrast, resolution, a gray scale number, and consumption power, a problem in a quality of a picture of a dynamic picture has, in recent years, been encountered.
In a display method of gray scale of a plasma display apparatus, since time duration modulation by a light emit time duration is utilized with respect to amplitude modulation of brightness such as a CRT, an intrinsic deterioration in a quality of a picture relative to a dynamic picture is generated. In order to improve the performance of these plasma display apparatus, it is necessary to drive a plasma display panel at high speed and to enlarge values of various parameters determining a quality of a picture.
In an AC-type plasma display panel of this sort, as everybody knows, three electrodes of display electrodes composed of a paired X electrode-Y electrode in parallel to each other and of an address electrode (A electrode) intersecting these display electrodes are formed, and a surface discharge type panel is constituted. Further, cells are being pixels are constituted at points of intersection of these display electrodes and the address electrodes arranged in rows in a shape of stripes, a considerable number of cells form a two dimensional matrix inside the panel. In a matrix panel such as a plasma display, common electrodes are formed in the cells in every respective lines.
In a display method of gray scale of the plasma display apparatus, a sub-field method is used. A gray scale is expressed by a light emitting time duration of total of one field by dividing time of one field into a plurality of sub-fields, by varying a light emitting time duration in respective sub-fields, and by combining the light emitting time duration of several sub-fields while controlling a light emission of respective sub-field.
For example, when one field is divided into eight sub-fields and ratios of light emitting time durations of respective sub-fields are constituted in such a manner as 1:2:4:8:16:32:64:128, the gray scale of 256 steps from starting 0 ending at 255 can be displayed by controlling whether these sub-fields are emitted light or not and combining the light emitting time duration of respective sub-fields.
The number of gray scales of a plasma display apparatus is determined by the number of the sub-fields. When fine scaling a display of brightness by increasing the number of sub-fields, a quality of a picture having smooth display can be displayed even for a picture image gradually changing the brightness.
In the plasma display apparatus at present, the number of gray scales of brightness is in a degree of 100 gray scales, it occurred such a phenomenon as that delicate changing of brightness smashed into black color when a dark picture image is displayed. In order to display a further fine gray scale even for a dark picture image, the number of 1024 gray scales is necessitated, even constituting it of 2 to the n-th power having the least number of the sub-fields, n is 10, that is, 10 sub-fields are necessitated.
Further, in a sub-field method like this, it is well known that a dynamic false contour noise which deteriorates the quality of picture in the dynamic picture, is generated. In order to reduce this, a method to make inconspicuous the dynamic false contour noise is employed by setting a code of weight of a sub-field as a code different from 2 to the number of power, by being held a redundant property to the code, and by changing a combination of the light emission in a sub-field of display lines or the cells.
For that purpose, the number of sub-fields much more numerous is required and the number of the sub-fields in a degree of 15 is ideal. Since one field of a TV signal is approximately 16.7 ms, it means that an increase in the number of sub-fields is a decrease in time assigned to one sub-field.
A driving method separated into three, such as a reset period, an address period, and a display sustain period is generally used for one sub-field. These periods are common periods in an entire lines of the display panel, this driving method is referred to as an ADS (address display separate method). One example of this driving waveform is shown in FIG.
4
and FIG.
5
and necessity of acceleration of a drive will be explained.
In
FIG. 4
, the entire X electrodes are commonly connected to one another, in the Y electrode, an IC circuit for the purpose of applying a scanning pulse to individual electrodes during an address period is connected to the Y electrode, sustain pulses in a display sustain period are simultaneously applied to entire Y electrodes.
During a reset period of a sub-field, a high voltage pulse (rectangular reset pulse)
100
equal to or more than 300 V is applied to the X electrodes as a reset voltage VR. Thereby, a strong discharge is generated during this period in the entire cells and electrons and ions, constituted as wall charges to respectively in the X electrodes and the Y electrodes, forming an electric field by wall charges themselves accumulated on the X electrode and the Y electrode.
When waveform of the rectangular reset pulse
100
are fallen down, a discharge (self erase discharge/reset discharge) is generated by this electric field, the wall charges are floated in a space and disappears through neutralization. According to this reset discharge, the wall charges of entire cells are reset. During a neutralizing period, voltages of the X electrode, the Y electrode, and the A electrode (address electrode) are set as altogether a GND level, and this neutralizing period is approximately 100 &mgr;s.
Next, during an address period, scanning pulses
106
of a voltage Vy are sequentially applied to the Y electrodes, address pulses
108
of a voltage Va are applied to the A electrodes. In the cells at which the scanning pulses
106
and the address pulses
108
are overlapped with each other, discharges between the electrodes A-Y are generated, the discharges between the electrodes X-Y are generated by being triggered by the discharges between the electrodes A-Y, the wall charges are formed on the X electrodes and the Y electrodes.
During a next display sustain period, sustain pulses
102
and
104
of a voltage Vs are alternately applied to the X electrodes and Y electrode and only for the cells formed the wall charges during an address period, the discharges are selectively generated, and display light is emitted.
This much is a light emitting mechanism of one sub-field, during the address periods, as illustrated in
FIG. 5
, the scanning pulses
106
are sequentially applied from a Y
1
electrode to a Y
480
electrode (VGA is estimated). Accordingly, the display apparatus in which the number of lines being numerous (for example, in HDTV, equal to or more than 1000 pieces) the scanning pulses
106
equal to the number of lines must be applied.
However, in the address discharge generated by the scanning pulses
106
, there is a time delay or there is dispersion depending on the cell, a time duration of a certai
Kajiyama Hiroshi
Kougami Akihiko
Suzuki Keizo
Antonelli Terry Stout & Kraus LLP
Chang Kent
Hitachi , Ltd.
Sheng Tom
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