Television – Image signal processing circuitry specific to television – Transition or edge sharpeners
Reexamination Certificate
1999-09-24
2001-10-02
Hsia, Sherrie (Department: 2614)
Television
Image signal processing circuitry specific to television
Transition or edge sharpeners
C348S630000
Reexamination Certificate
active
06297854
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a contour emphasizing circuit, wherein a digital contour-emphasized video signal on the basis of the input of an analog signal is output, and is employed to indicate contour-emphasized color video signals by a display device (for example, matrix type display device) which is digital driven such as a plasma display (referred only to as PDP) and liquid crystal display (referred only to as LCD).
BACKGROUND ART
In the conventional CRT (Cathode Ray Tube) display device, the contour emphasizing processing is carried out aiming at high picture quality implementation and high-pass characteristic compensation. The contour emphasizing circuit to carry out this contour emphasizing processing is, as shown in
FIG. 1
, composed of an Y/C separation circuit
10
, a color demodulation circuit
12
, a contour extracting circuit, phase adjustment circuits
16
,
18
and
20
, an adder
22
and a matrix circuit
24
.
The Y/C separation circuit
10
separates a Y (luminance) signal and a C (color) signal from the composite video signal (for example, compound color television signal) input to an input terminal
26
, and the color modulation circuit
12
separates a Y signal, an R-Y (color difference) signal and a B-Y (color difference) signal on the basis of a Y signal and a C signal.
The contour extracting circuit
14
extracts a contour component Ye which is a high-pass component of a video signal on the basis of an adder
22
.
The matrix circuit
24
prepares a signal adding the contour component Ye to the R (red), G (green) and B (blue) signals, respectively, on the basis of (Y+Ye) signals added by the adder
22
, an (R-Y) and a (B-Y) signal phase-adjusted by phase adjustment circuits
18
and
20
. That is to say, the matrix circuit
24
prepares R+Ye, G+Ye and B+Ye on the basis of the operations in following equations (1), (2) and (3). By outputting these R+Ye, G+Ye and B+Ye to the CRT display device by means of output terminals
28
r
,
28
g
and
28
b
, videos contour-emphasized by this CRT display device are displayed.
(R-Y)+(Y+Ye)=R+Ye (1)
(G-Y)+(Y+Ye)=G+Ye (2)
(B-Y)+(Y+Ye)=B+Ye (3)
(G-Y) in the above equation (2) is generated by the following equation (4).
When a video contour-emphasized by a matrix type display device driven by digital video signals (for example, R, G and B signals) like PDP and LCD is displayed, each signal of (R+Ye), (G+Ye) and (B+Ye) obtained in output terminals
28
r
,
28
g
and
28
b
in
FIG. 1
is output to the display device after being digitized by the A/D (analog/digital) conversion circuit. However, in such a prior example, when a large amplitude signal is input to an input terminal
26
, or when the contour emphasizing quantity (or contour emphasizing coefficient, the description is omitted, as it is similar afterwards) is “large”, there is a problem that the correct operation cannot be obtained over the dynamic range of A/D conversion circuit.
For example, in case a large amplitude signal is input to the input terminal
26
, by outputting a signal over the dynamic range of the A/D conversion circuit as shown at the left-hand side in FIG.
2
(
a
) from output terminals
28
r
,
28
g
and
28
b
, there are problems that signals exceeding an upper conversion reference voltage value VRT (for example, 5 volts) in the dynamic range as shown at the right-hand in said figure (a) are cut, resulting in producing white crushing or signals under the lower conversion reference voltage value VRT (for example, 3 volts) in the dynamic range are cut, resulting in producing black crushing.
Further, when the contour emphasizing quantity of the contour extracting circuit
14
is “large”, there are problems that signals over the dynamic range of the A/D conversion circuit as shown at the left-hand side in FIG.
2
(
b
) are cut, resulting in producing white crushing or signals under the lower conversion reference voltage value VRB are cut, resulting in producing black crushing.
The present applicant simultaneously proposes a contour emphasizing circuit as shown in
FIG. 3
as a separate application to solve the above mentioned problems.
The contour emphasizing circuit shown in
FIG. 3
consists of A/D conversion circuits
30
r
,
30
g
and
30
b
, a signal processing/phase adjustment circuit
32
, contour adders
34
r
,
34
g
and
34
b
, a Y signal generation circuit, a contour extracting circuit
38
, a gain controller
40
for the contour component and a coefficient multiplication circuit
42
.
Hence, analog R, G and B signals input to input terminals
44
r
,
44
g
and
44
b
are converted to digital signals by A/D conversion circuits
30
r
,
30
g
and
30
b
, signal-processed and phase-adjusted by the signal processing/phase adjustment circuit
32
, and input to contour adders
34
r
,
34
g
and
34
b
. The Y signal generation circuit
36
generates Y signals from digital R, G and B signals, the contour extracting circuit
38
extracts contour components from Y signals, these extracted contour components input to contour adders
34
r
,
34
g
and
34
b
through the gain controller
40
and coefficient multiplication circuit
42
, are added to the original digital R, G and B signals, and supplied to the display device through output terminals
86
r
,
86
g
and
86
b.
As described above, it has been designed that by adding the contour components after the conversion to digital R, G and B signals by A/D conversion circuits
30
r
,
30
g
and
30
b
, the contour emphasizing component as a conventional example does not surpass the dynamic range of the A/D conversion circuit. For this reason, when the analog R, G and B signals input to input terminals
44
r
,
44
g
and
44
b
in
FIG. 3
are large amplitude signals, or even when the contour emphasizing quantity is “large”, neither white crushing nor black crushing is produced when outputting signals from the contour emphasizing circuit in
FIG. 3
to the display device driven by digital R, G and B signals and the contour-emphasized video is expressed.
However, in the contour emphasizing circuit shown in
FIG. 3
, since the contour extracting circuit
38
extracts a vertical contour component on the basis of signals delayed by a specified number of lines (for example, portion of 1 or 2 lines), a Y signal generated by the Y signal generation circuit
36
and this signal, and a horizontal contour component is extracted on the basis of signals delayed by a specified number of dots (for example 2 or 4 dots), a Y signal delayed by a specified number of lines (for example, portion of
1
line) and this Y signal, as shown in FIG.
4
(
a
) and (
b
), there is a problem that a processing error (for example, white edge) is produced in the periphery
11
of the display screen. FIG.
4
(
a
) shows the case when the aspect ratio displays a video of 4:3 in a general purpose television set whose aspect ratio is 4:3, the same figure (
b
) shows the case wherein the aspect ratio displays a video of 4:3 in a wide television set whose aspect ratio is 16:9, and
13
indicates the side color (for example, black) without video display.
That is to say, in FIG.
4
(
a
), the periphery
11
of the display screen corresponds to the blanking portion of the video and the boundary portion of an effective video signal, in the same figure (
b
), the top and bottom of the periphery
11
correspond to the blanking portion of the video and the boundary portion of the effective video signal, the right and left of periphery
11
correspond to the side color
13
and the boundary portion of the effective video signal, and since the contour extracting processing is carried out between lines or between dots without correlation to these boundary portions of effective video signal, thereby a contour emphasizing processing error comes to be produced by the interference between the insignificant signal and the significant signal.
For example, in the boundary portion of t
Kurita Masanori
Suzuki Susumu
Flynn ,Thiel, Boutell & Tanis, P.C.
Fujitsu General Limited
Hsia Sherrie
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