Moving image correcting circuit for display device

Details Moving image correcting circuit for display device Moving image correcting circuit for display device

1999-08-27

2002-09-24

Kostak, Victor R. (Department: 2614)

Television

Image signal processing circuitry specific to television

Motion dependent key signal generation or scene change...

C348S792000, C348S793000, C348S615000

Reexamination Certificate

active

06456337

ABSTRACT:

TECHNICAL FIELD
The invention relates to a moving image correcting circuit of a display device that displays a multitonal image by time-sharing one frame into plural subfields (or subframes) and emitting the subfields corresponding to the luminance level of an input image signal.
BACKGROUND TECHNOLOGY
Display devices using a PDP (Plasma Display Panel) and a LCD (Liquid Crystal Panel) have been attracting public attention as thin, light-weight display units. Completely different from the conventional CRT driving method, the driving method of this PDP is a direct drive by a digitalized image input signal. The luminance tone as emitted from the panel face depends therefore on the number of bits of the signal to be processed.
The PDP may roughly be divided into AC and DC types whose fundamental characteristics differ from each other. In any AC type PDP, sufficient characteristics have been obtained with respect to its luminance and service life. As for the tonal display, however, a 64-tone display was the maximum reported from the trial manufacture level. Recently, a future 256-tone method by Address/Display Separation type drive method (ADS subfield method) has been proposed.
FIGS.
1
(
a
) and (
b
) show the exemplary drive sequence and drive waveform of the PDP used in this ADS subfield method with 8 bits and 256 tones.
In FIG.
1
(
a
). one frame is composed of eight subfileds SF
1
, SF
2
, SF
3
, SF
4
, SF
5
, SF
6
, SF
7
, and SF
8
whose relative ratios of luminance are 1, 2, 4, 8, 16, 32, 64, and 128 respectively. Combination of this luminance of eight screens enables a display in 256 tones.
In FIG.
1
(
b
), the respective subfields are composed of the address duration that writes one screen of refreshed data and the sustaining duration that defines the luminance level of these subfields. In the address duration, a wall charge is formed initially at each pixel simultaneously over all the screens, and then the sustaining pulses are given to all the screens for display. The brightness of the subfield is proportional to the number of sustaining pulses to be set to the predetermined luminance. A two hundred and fifty-six tone display is thus actualized.
The foregoing display unit of address/display separation type drive method was conventionally provided with such a moving image correcting circuit as shown in
FIG. 2
in order to reduce the visual display deviation resulting from the display of a moving image. The moving image correcting circuit shown in
FIG. 2
comprised the moving image correcting portion
11
and the motion vector detecting portion
10
, which in turn consisted, as shown in
FIG. 3
, of the frame memory
12
, correlation value operation part
13
and motion vector generating portion
14
.
In the motion vector detecting portion
10
, the respective components act as follows. Based on the image signal as input into the input terminal
15
, the frame memory
12
makes an image signal by one frame before the current frame picture (referred to as “preceding frame picture”). The correlation value operation part
13
sequentially seeks after the correlation values (differential values) of the image signal for all the blocks in the detection area of the motion vectors in the preceding frame, referring to the block forming the subject of the current frame picture (the block consisting of a single or plural pixels, 2×2 pixels, for example). The motion vector generating portion
14
generates a displacement vector (a signal representing displacement direction and displacement amount) whose starting point and end point are the block position of the preceding frame picture where the correlation value is minimal and the origin of the motion vector (the block position of the preceding frame picture at a position corresponding to the block of current frame picture) respectively. The motion vector generating portion
14
generates this displacement vector as a motion vector of the block forming the subject.
In the moving image correcting portion
11
, the image signal as input into the input terminal
15
was corrected on the basis of the detected value of the motion vector detecting portion
10
(namely, the motion vector). The image signal thus corrected was output to the PDP (not shown) through the intermediary of the output terminal
16
. The moving image was thus corrected by correcting the display position of each subfield for the pixels in the subject block.
We will now describe in detail how the correlation value operation part
13
in the motion vector detecting portion
10
operates the correlation values. For purpose of discussion, we assume here that, as shown in FIGS.
4
(
a
) and (
b
), the detection area KR of the motion vector of the preceding frame picture has 25 blocks (5×5 blocks) and that the image (pictorial image) that was at the position of the block ZB
51
in this detection area KR has now displaced to the position of the block GB
33
in the current frame picture. Further, it is assumed that the blocks ZB
11
to ZB
65
of the preceding frame picture and the blocks GB
11
to GB
55
of the current frame picture are formed respectively with 2×2 pixels (or as many dots).
If the subject block of the current frame picture is GB
33
, the correlation value operation part
13
will sequentially compute, by the following expression,
S=|A
1
−
A
2
|+|
B
1
−
B
2
|+|
C
1
−
C
2
|+|
D
1
−
D
2
|
the correlation values of an image signal for all the blocks ZB
11
to ZB
55
in the detection area KR of the preceding frame picture referring, as datum, to this block GB
33
, all along the direction shown by the alternate long and two short dashed line arrow in FIG.
4
(
a
).
In the formula, A
1
, B
1
, C
1
, and D
1
represent the luminance levels of the pixels forming the respective blocks of preceding frame picture ZB
11
to ZB
55
as shown in FIG.
5
(
a
), while A
2
, B
2
, C
2
, and D
2
indicate the luminance levels of the pixels forming the subject block of current frame picture GB
33
as shown in FIG.
5
(
b
).
The motion vector generating portion
14
compares the plural correlation values as obtained in the correlation value operation part
13
with each other, and generates, as shown by the thick lines in FIG.
4
(
b
), the displacement vector MV whose starting and end points are respectively the position of the block B
51
of the preceding frame picture where the correlation value is minimal and the origin of the motion vector (block ZB
33
position of preceding frame picture corresponding to the block GB
33
in the current frame picture). The motion vector generating portion
14
then outputs this vector MV as the motion picture of the subject block GB
33
.
The motion vectors can be obtained in a similar fashion also for other blocks (for instance, GB
11
or GB
55
) of the current frame picture, when the motion vector detection area KR of the preceding frame picture embraces 25 peripheral blocks (5×5 blocks) centered around the corresponding origin (for example, positions of the blocks of preceding frame picture ZB
11
or ZB
55
corresponding to the block GB
11
or GB
55
).
Since, however, the block position corresponding to the least correlation value does not always coincide with the starting point (or end point) of the displacement vector if any dispersion appears in the correlation value as obtained from the correlation value operation part
13
due, for example, to the noise in the input image signal or to the fluctuation of the input image signal, there were some cases where erroneous motion vectors were detected that differed from the intrinsic motion vectors representing the motion as viewed by humans.
For simplicity, we may assume that the detection area KR of a preceding frame picture is 9×9=81 blocks and that the correlation values obtained from the correlation value operation part
13
for the blocks ZB
11
to ZB
99
in this detection area KR is as shown in FIG.
6
. Let us also assume that a correlation valu

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