PDP display drive pulse controller

Details PDP display drive pulse controller PDP display drive pulse controller

2001-07-20

2004-02-10

Luu, Matthew (Department: 2672)

Computer graphics processing and selective visual display system

Display driving control circuitry

Intensity or color driving control

C345S691000, C345S692000, C345S693000, C345S039000, C345S041000, C345S060000

Reexamination Certificate

active

06690388

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a display apparatus, and more specifically, to a plasma display panel (PDP) and digital micromirror device (DMD) display drive pulse controller.
BACKGROUND ART
A display apparatus of a PDP and a DMD makes use of a subfield method, which has binary memory, and which displays a 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.
A PDP subfield method is explained using
FIGS. 1
,
2
, and
3
.
Now, consider a PDP with pixels lined up 10 across and 4 vertically, as shown in FIG.
3
. Let the respective R,G,B of each pixel be 8 bits, assume that 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 signal level of brightness of 128. If this is displayed 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 the location of each pixel, 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 displayed using 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 a 1 field 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 constitutes setup period P
1
, write period P
2
and sustain period P
3
. At setup period P
1
, a single pulse is applied to a sustaining electrode, and a single pulse is also applied to each scanning electrode (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 electrodes scans sequentially, and a predetermined write is performed only to a pixel that received a pulse from a data electrode. 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 pulse (driving pulse) is outputted in accordance with the weighting value of each subfield. For a written pixel represented by “1,” a plasma discharge is performed for each sustaining pulse, 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.
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.
For a screen with overall bright luminance, it is possible to create a bright picture even using as-is a drive pulse acquired from a picture signal, but if an image becomes dark overall, when a drive pulse acquired from a picture signal is used as-is, it results in an extremely dark screen, and a weak picture rendition. The structure of the human eye is such that in bright places the pupil becomes smaller, reducing the amount of light that enters, but when it becomes dark, the pupil continuously enlarges so as to take in more light. To achieve the same effect thereas, there is a well-known method, by which, when a screen darkens overall, a drive pulse number is increased at the same ratio over the entire screen, making an entire screen bright, and rendering a robust picture while maintaining a dark atmosphere.
With regard to the brightness of an overall screen, there is a well-known method, which divides the transition from a bright situation to a dark situation into a plurality of stages, for example, 3 stages, bright, rather bright, dark, and for a bright situation utilizes a 1-times mode (FIG.
4
), which uses a drive pulse as-is, for a rather bright situation, utilizes a 2-times mode (FIG.
6
), which doubles a drive pulse, and for a dark situation, utilizes a 3-times mode (FIG.
7
), which triples a drive pulse This is disclosed, for example, in the Japanese Patent specification of Kokai No. (1996)-286636 (corresponding to the specification of U.S. Pat. No. 5,757,343).
Thus, since a drive pulse is changed in stages, when a screen changes from a certain stage to another stage, for example, from rather bright to dark, an abrupt change is displayed on a screen, occasioning a sense of incongruousness.
A well-known approach is to adjust a fixed multiplication factor of gain with an object of doing away with the abrupt change of this screen, and performing continuous luminance adjustment (For example, the specification of Kokai No. (1996)-286636 (corresponding to the specification of U.S. Pat. No. 5,757,343)). The problem has been that even if a fixed multiplication factor of gain is changed, since a drive pulse is changed in stages to 2-times, 3-times, the sense of incongruousness of the screen at the point in time when the change occurs cannot be fully eliminated.
The present invention is designed to solve this problem, and has as a first object the provision of a PDP display pulse drive controller, which is capable of performing adjustments by changing a drive pulse using not only an integer multiplier, but also a multiplier of a value comprising a fraction, and of performing more continuous luminance adjustment.
An average level, peak level of brightness, PDP power consumption, panel temperature, contrast and such are used as parameters for rendering image brightness.
Performing adjustments by c

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