Television – Flutter or jitter correction
Reexamination Certificate
2001-03-08
2004-04-13
Kostak, Victor R. (Department: 2611)
Television
Flutter or jitter correction
C348S607000, C348S625000, C348S626000
Reexamination Certificate
active
06721016
ABSTRACT:
TECHNICAL FIELD
This invention relates to image quality correction devices that carry out a variety of processes on an image signal to correct quality of an image reproduced based on the image signal and, more specifically, to an image quality correction device that corrects the image quality with an appropriate amount of correction according to an amount of jitter in a video signal that greatly affects the image quality.
BACKGROUND ART
FIG. 22
is a conventional image correction device used for an analog video signal Sv, based on which an image is displayed on an image display device used in a television set typified by an LCD or CRT. As shown in the drawing, a signal processing system SPc in the television set carries out a variety of processes on the video signal Sv, and generates signals required for displaying images on an image display device
9
(in the present example, CRT), that is, a scan speed modulation signal VSCc, an image signal Si, and a horizontal synchronization signal Hsync, and a vertical synchronization signal Vsync, each carrying information according to the characteristics of the image display device
9
.
Based on the scan speed modulation signal VSCc, a scan speed modulation driver
6
carries out scanning at a predetermined speed, and generates an image quality correction scan drive signal Sscd to correct the quality of the image displayed on the image display device
9
. Based on the image signal Si, a CRT driver
7
generates a CRT drive signal Scrtd for making the image display device
9
display an image. Based on synchronization signals Ssync, the deflector
8
generates a deflection drive signal Sdfd for making the image display device
9
operate with a predetermined amount of deflection and carry out raster scanning. The image display device
9
is driven by these drive signals Sscd, Scrtd, and Sdfd to display the image carried by the video signal Sv.
The signal processing system SPc includes a sync separator
4
, an image quality correction device IQCc, and a signal processor
5
. The sync separator
4
extracts the horizontal synchronization signal Hsync and the vertical synchronization signal Vsync from the video signal Sv.
Based on the horizontal synchronization signal Hsync and the vertical synchronization signal Vsync, the image quality correction device IQCc performs image quality correction processing on the video signal Sv, and generates an image-quality-corrected video signal SIQc, and also generates the scan speed modulation signal VSCc. Based on the image-quality corrected video signal SIQc, the signal processor
5
generates the image signal Si. Note that the operation of the signal processing system SPc is controlled by a controller
100
c.
The image quality correction device IQCc includes a scan speed modulation signal generator
11
for defining a scan speed for the image display device
9
, a horizontal edge enhancer
12
for defining an amount of horizontal edge enhancement for the image signal Si, a noise reducer (NR)
13
for reducing noise components included in the image signal Si, a multiplexer
14
, a bus interface
15
, and ROM
16
.
Based on the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, and the video signal Sv, the scan speed modulation signal generator
11
determines a raster scan speed VSC (not shown) that corresponds to the image signal Si. Similarly, based on the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, and the video signal Sv, the horizontal edge enhancer
12
determines an amount of horizontal edge enhancement OE (not shown) of the video signal Sv.
Even if the video signal Sv is uniform in quality, the video carried by the video signal Sv and displayed on the image display device
9
is affected by physical characteristics of the television set including the image display device
9
; a drive circuit system such as the scan speed modulation driver
6
, the CRT driver
7
, and the deflector
8
; and a signal processing system. Therefore, the above-stated scan speed VSC and amount of horizontal edge enhancement OE cannot be uniquely determined based on the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, and the video signal Sv. For this reason, depending on the physical characteristics of the television set where the image quality correction device IQCc is used, each predetermined amount of correction is calculated in advance for a correcting operation of each of the scan speed modulation signal generator
11
, the horizontal edge enhancer
12
and the NR
13
.
Then, predetermined amounts of correction SCAc are stored in the ROM
16
. When the quality of the image carried by the video signal Sv is corrected by the image quality correction device IQCc, the predetermined amounts of correction SCAc are read from the ROM
16
thorough a bus interface
15
, and supplied to the scan speed modulation signal generator
11
, the horizontal edge enhancer
12
, and the NR
13
for correcting each operation.
Specifically, the predetermined amounts of correction SCAc include a correction amount of scan speed SVMc that is predetermined for the scan speed VSC defined by the scan speed modulation signal generator
11
; a correction amount of horizontal edge enhancement SOEc that is predetermined for the amount of horizontal edge enhancement OE defined by the horizontal edge enhancer
12
; and a correction amount of noise reduction SNRc that is predetermined for the amount of noise reduction by the NR
13
.
As such, the horizontal edge enhancer
12
determines the amount of horizontal edge enhancement OE of the video signal SV based on the correction amount of horizontal edge enhancement SOEc supplied by the ROM
16
via the bus interface
15
, and generates a horizontal-edge-enhancement-corrected signal OEc. The multiplexer
14
multiplexes the video signal Sv with the horizontal-edge-enhancement-corrected signal OEc, and generates a horizontal-edge-enhanced-corrected signal VOEc, which is the video signal Sv enhanced in horizontal edge by the amount of horizontal edge enhancement OE.
In a similar manner to that of the horizontal edge enhancer
12
, the NR
13
reduces noise of the horizontal-edge-enhanced video signal VOEc, and generates the image-quality-corrected video signal SIQc, based on noise reduction characteristics corrected with the correction amount of noise reduction SNRc supplied by the ROM
16
through the bus interface
15
.
The image processor
5
generates the image signal Si based on the image-quality-corrected video signal SIQc.
As described above, in the conventional image quality correction device IQCc, the video signal Sv is corrected in scan speed modulation, horizontal edge amount, and noise reduction for each predetermined amount, considering effects of the physical characteristics of the television set and other factors. In other words, the amount corrected by the image quality correction device IQCc is always constant irrespectively of change in quality of the video signal Sv.
However, the quality of the video signal Sv changes with time. If the video signal Sv jitters, the image-quality-corrected video signal SIQC and scan speed modulation signal VSCc outputted from the image quality correction device IQCc also jitter. Therefore, based on these jittering image-quality-corrected video signal SIQc and the scan speed modulation signal VSCc, the amount of jitter in video reproduced by the video display device
9
is increased, thereby deteriorating the reproduced video in quality.
For example, if the video signal Sv having jitter is subjected to horizontal edge enhancement for greatly enhancing the edge, glare at an edge part is enhanced by jitter in the horizontal edge enhancement signal itself. Thus, the jitter in the reproduced image is enhanced by the image quality correction processing. To prevent this, the amount of image quality correction for edge enhancement is reduced, while the one for noise reduction is increased.
In other words, to prevent video image quality deterioration
Kostak Victor R.
Matsushita Electric - Industrial Co., Ltd.
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