Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-07-27
2002-10-08
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S060000, C345S693000, C315S169400
Reexamination Certificate
active
06462721
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a display apparatus and more particularly, to a display apparatus of a plasma display panel (PDP), and digital micromirror device (DMD).
BACKGROUND ART
A display apparatus of a PDP and DMD makes use of a subfield method, which has binary memory, and which displays dynamic image possessing half tones by temporally superimposing a plurality of binary images that have each been weighted. The following explanation deals with PDP, but applies equally to DMD as well.
The PDP subfield method is explained using
FIGS. 1
,
2
,
3
.
Now, consider a PDP with pixels lined up 10 horizontally and 4 vertically, as shown in FIG.
3
. Assume that the respective R,G,B of each pixel is 8 bits, the brightness thereof is rendered, and that a brightness rendering of 256 gradations (256 gray scales) is possible. The following explanation, unless otherwise stated, deals with a G signal, but the explanation applies equally to R, B as well.
The portion indicated by A in
FIG. 3
has a brightness signal level of 128. If this is represented in binary, a (1000 0000) signal level is added to each pixel in the portion indicated by A. Similarly the portion indicated by B has a brightness of 127 and a (0111 1111) signal level is added to each pixel. The portion indicated by C has a brightness of 126, and a (0111 1110) signal level is added to each pixel. The portion indicated by D has a brightness of 125, and a (0111 1101) signal level is added to each pixel. The portion indicated by E has a brightness of 0, and a (0000 0000) signal level is added to each pixel. Lining up an 8-bit signal for each pixel perpendicularly in each pixel location, and horizontally slicing it bit-by-bit produces a subfield. That is, in an image display method which utilizes the so-called subfield method, by which 1 field is divided into a plurality of differently weighted binary images, and displayed by temporally superimposing these binary images, a subfield is 1 of the divided binary images.
Since each pixel is represented by 8 bits, as shown in
FIG. 2
, 8 subfields can be achieved. Collect the least significant bit of the 8-bit signal of each pixel, line them up in a 10×4 matrix, and let that be subfield SF
1
(FIG.
2
). Collect the second bit from the least significant bit, line them up similarly into a matrix, and let this be subfield SF
2
. Doing this creates subfields SF
1
, SF
2
, SF
3
, SF
4
, SF
5
, SF
6
, SF
7
, SF
8
. Needless to say, subfield SF
8
is formed by collecting and lining up the most significant bits.
FIG. 4
shows the standard form of 1 field of a PDP driving signal. As shown in
FIG. 4
, there are 8 subfields SF
1
, SF
2
, SF
3
, SF
4
, SF
5
, SF
6
, SF
7
, SF
8
in the standard form of a PDP driving signal, and subfields SF
1
through SF
8
are processed in order, and all processing, is performed within 1 field time. The processing of each subfield is explained using FIG.
4
. The processing of each subfield is comprised of setup period P
1
, write period P
2
, sustain period P
3
, and erase period P
4
. At setup period P
1
, a single pulse is applied to a holding electrode E
0
, and a single pulse is also applied to each scanning electrode E
1
, E
2
, E
4
(There are only up to 4 scanning electrodes indicated in
FIG. 4
because there are only 4 scanning lines shown in the example in
FIG. 3
, but in reality, there are a plurality of scanning electrodes, 480, for example.). In accordance with this, preliminary discharge is performed.
At write period P
2
, a horizontal-direction scanning electrode scans sequentially, and a prescribed write is performed only to a pixel that received a pulse from a data electrode E
5
. For example, when processing subfield SF
1
, a write is performed for a pixel represented by “1” in subfield SF
1
depicted in
FIG. 2
, and a write is not performed for a pixel represented by “0.”
At sustain period P
3
, a sustaining electrode (drive pulse) is outputted in accordance with the weighted value of each subfield. For a written pixel represented by “1,” a plasma discharge is performed for each sustaining electrode, and the brightness of a predetermined pixel is achieved with one plasma discharge. In subfield SF
1
, since weighting is “1,” a brightness level of “1” is achieved. In subfield SF
2
since weighting is “2,” a brightness level of “2” is achieved. That is, write period P
2
is the time when a pixel which is to emit light is selected, and sustain period P
3
is the time when light is emitted a number of times that accords with the weighting quantity.
At erase period P
4
, residual charge is all erased.
As shown in
FIG. 4
, subfields SF
1
, SF
2
SF
3
, SF
4
, SF
5
, SF
6
, SF
7
, SF
8
are weighted at 1, 2, 4, 8, 16, 32, 64, 128, respectively. Therefore, the brightness level of each pixel can be adjusted using 256 gradations, from 0 to 255.
In the B region of
FIG. 3
, light is emitted in subfields SF
1
, SF
2
SF
3
, SF
4
, SF
5
, SF
6
, SF
7
, but light is not emitted in subfield SF
8
. Therefore, a brightness level of “127” (=1+2+4+8+16+32+64) is achieved.
And in the A region of
FIG. 3
, light is not emitted in subfields SF
1
, SF
2
, SF
3
, SF
4
, SF
5
, SF
6
, SF
7
, but light is emitted in subfield SF
8
. Therefore, a brightness level of “128” is achieved.
There are a number-of variations of PDP driving signals relative to the standard form of PDP driving signal shown in
FIG. 4
, and such variations are explained.
FIG. 5
shows a 2-times mode PDP driving signal. Furthermore, the PDP driving signal shown in
FIG. 4
is a 1-times mode. For the 1-times mode of
FIG. 4
, the number of sustaining electrodes comprising sustain period P
3
in subfields SF
1
through SF
8
, that is, the weighting values, were 1, 2, 4, 8, 16, 32, 64, 128, respectively, but for the 2-times mode of
FIG. 5
, the number of sustaining electrodes comprising sustain period P
3
in subfields SF
1
through SF
8
become 2, 4, 8, 16, 32, 64, 128, 256, respectively, with all subfields being doubled. In accordance with this, compared to a standard form PDP driving signal that is a 1-times mode, a 2-times mode PDP driving signal can display an image with 2 times the brightness.
FIG. 6
shows a 3-times mode PDP driving signal. Therefore, the number of sustaining electrodes comprising sustain period P
3
in subfields SF
1
through SF
8
becomes 3, 6, 12, 24, 48, 96, 192, 384, respectively, with all subfields being tripled.
By so doing, although dependent on the degree of margin in 1 field, it is possible to create a maximum 6-times mode PDP driving signal. In accordance with this, it becomes possible to display an image with 6 times the brightness.
Here, a mode multiplier is generally expressed as N times. Furthermore, this N can also be expressed as a weighting multiplier N.
FIG.
7
(A) shows a standard form PDP driving signal, and FIG.
7
(B) shows a variation of a PDP driving- signal, which, by adding 1 subfield, comprises subfields SF
1
through SF
9
. For the standard form, the final subfield SF
8
is weighted by a sustaining electrode of
128
, and for the variation in FIG.
7
(B), each of the last 2 subfields SF
8
, SF
9
is weighted by a sustaining electrode of
64
. For example, when a brightness level of 130 is represented, with the standard form of FIG.
7
(A), this can be achieved using both subfield SF
2
(weighted 2) and subfield SF
8
(weighted 128), whereas with the variation of FIG.
7
(B), this brightness level can be achieved using 3 subfields, subfield SF
2
(weighted 2), subfield SF
8
(weighted 64), and subfield SF
9
(weighted 64). By increasing the number of subfields in this way, it is possible to decrease the weight of the subfield with the greatest weight. Decreasing the weight like this enables pseudo-contour noise to be decreased, giving the display of an image greater clarity.
Here, the number of subfields is generally expressed as Z. For the standard form of FIG.
7
(A), the subfield number Z is 8, and 1 pixel is represented by 8 bits. As for FIG.
7
(B), the subfield number Z is
Ishikawa Yuichi
Kasahara Mitsuhiro
Morita Tomoko
Eisen Alexander
Greenblum & Bernstein P.L.C.
Hjerpe Richard
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