Contour emphasizing circuit

Details Contour emphasizing circuit Contour emphasizing circuit

1999-09-24

2001-11-20

Hsia, Sherrie (Department: 2614)

Television

Image signal processing circuitry specific to television

Transition or edge sharpeners

C348S630000

Reexamination Certificate

active

06320625

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 digitally driven such as a plasma display (referred only to as PDP) and liquid crystal display (referred only to as LCD).
BACKGROUND ART
In conventional CRT (Cathode Ray Tube) display devices, 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 a 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 the 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 the 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).
In case a video contour-emphasized by the 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, in case a large amplitude signal is input to an input terminal
26
, or in case 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 the 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, in case 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.
This contour emphasizing circuit shown in
FIG. 3
is constituted by A/D conversion circuits
30
r
,
30
g
and
30
b
, a phase adjustment circuit
31
composed of line memories
31
r
,
31
g
and
31
b
, a signal processing circuit
32
, contour adders
34
r
,
34
g
and
34
b
, a Y signal generation circuit
36
, a contour extracting circuit
38
, a gain controller
40
for the contour components and a coefficient multiplication circuit
42
.
The contour extracting circuit
38
is constituted by first and second line memories
48
and
50
, a vertical contour extracting circuit
52
, a contour emphasizing frequency setting circuit
54
, a horizontal contour extracting circuit
56
, a contour synthesis circuit
62
, a core ring circuit
64
and a gain controller
66
.
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
, phase-adjusted by the phase adjustment circuit
31
, signal-processed by the signal processing 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 contour components extracted are input to contour adders
34
r
,
34
g
and
34
b
through the gain controller
40
and the coefficient multiplication circuit
42
, are added to 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 by adding the contour components after converting the analog R, G and B signals to digital signals by A/D conversion circuits
30
r
,
30
g
and
30
b
, contour emphasizing components, unlike conventional examples, do not surpass the dynamic range of A/D conversion circuit. For this reason, when analog color video signals input to input terminals
44
r
,
44
g
and
44
b
of the contour emphasizing circuit 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 digital R, G and B signals from the contour emphasizing circuit in
FIG. 3
to the display device driven by digital video signals and displaying a contour emphasizing video.
However, since the contour extracting circuit
38
requires two line memories of first and second line memories
48
and
50
, the contour emphasizing circuit shown in
FIG. 3
had the following problems as shown in (a), (b) and (c).
(a) Since the line memory requires a number of gates (for example, when the memory capacity is of 1024×8 bits in the line memory, approximately 12,700 more or less), there is a problem that in proportion as the power consumption is made large, the cost comes to be high.
(b) In case it is realized by discrete parts, there is problem that the mounting area comes to be large.
(c) In case it is built in the LSI (Large Scale Integrated Circuit), there are problems that the circuit scale is made large, and the user usage domain comes to be narrow.
The present invention is performed taking into account problems as described above, in case a large amplitude signal is input or even in case a contour emphasizing quantity is “large”, can display a contour emphasizing video without white crushing or black crushing by the display device driven by a digital video signal, as well as realizes a contour emphasizing circuit enabling the limiting of 1 piece of line memory required by the contour extracting circuit.
DISCLOSURE OF THE INVENTION
The contour emphasizing circuit according to the present inventi

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