Television – Image signal processing circuitry specific to television – Hue control
Reexamination Certificate
1999-11-19
2002-06-25
Miller, John W. (Department: 2714)
Television
Image signal processing circuitry specific to television
Hue control
C348S651000, C348S654000, C348S708000, C348S713000, C348S659000, C348S660000
Reexamination Certificate
active
06411340
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video signal processing system, and more particularly to a chrominance signal processing apparatus in a video signal processing system. This application is based on Korean patent application 98-57167, which is hereby incorporated by reference for all purposes.
2. Description of the Related Art
Generally, video signal processing systems include, for example, color televisions, video cassette tape recorders, and video color printers. In such a video signal processing system, a composite video signal is divided into a luminance signal and a chrominance signal. The chrominance signal is then processed by various processes such as a color gain control, a color hue control, and flesh tone control, etc. After being processed by such processes, the resultant chrominance signal is transformed, along with the luminance signal, to an original RGB signal which is, in turn, output. To this end, the video signal processing system should be equipped with not only a circuit for transforming the luminance and chrominance signals to an RGB signal format, but also a variety of chrominance signal control circuits for conducting various controls for the chrominance signal including a color gain control, a color hue control, and flesh tone control, etc. according to the user's intention.
FIG. 1
is a block diagram schematically illustrating a digital color television receiver which is a video signal processing system as mentioned above. Referring to
FIG. 1
, a plurality of channels carrying television video signals are received by tuner
100
via an antenna
118
. The tuner
100
allows a user to select a channel from a plurality of channels, and outputs the television video signals of the selected channel to an intermediate frequency (IF) demodulator
102
. The IF demodulator
102
demodulates the television video signal received therein into an IF signal which is sent to an analog/digital (A/D) converter
104
. In the A/D converter
104
, the video signal outputted from the IF demodulator
102
in the IF-modulated state is converted to a digital signal using binary-sampling in a pulse code modulation (PCM) fashion. A comb filter
106
receives the digital data from the A/D converter
104
and separates a luminance signal Y and a chrominance signal C from the received digital data. The chrominance signal C from the comb filter
106
is applied to a chrominance signal demodulator
108
which demodulates the received chrominance signal C into an R-Y chrominance signal Cr and a B-Y chrominance signal Cb. A color gain controller
110
receives the chrominance signals Cr and Cb from the chrominance signal demodulator
108
, conducts a color gain control for those received signals, and outputs the resultant signals, namely, gain-controlled chrominance signals Cb_g and Cr_g, to a color hue controller
112
. The color hue controller
112
controls the gain-controlled chrominance signals Cb_g and Cr_g in accordance with a color hue control coefficient, and then outputs the resultant signals, namely, hue-controlled chrominance signals Cb_h and Cr_h, to a flesh tone controller
114
. In the flesh tone controller
114
, the hue-controlled chrominance signals Cb_h and Cr_h are controlled in terms of flesh tone in accordance with a flesh tone control coefficient. The resultant signals, namely, flesh tone-controlled chrominance signals Cb_f and Cr_f, are applied to an RGB transform unit
116
. The RGB transform unit
116
processes the flesh tone-controlled chrominance signals Cb_f and Cr_f along with the luminance signal Y, thereby transforming these signals to an original RGB signal which is finally outputted.
FIGS. 2
,
4
, and
6
illustrate detailed circuit configurations of the color gain controller
110
, color hue controller
112
and flesh tone controller
114
, respectively. Now, the operations of these controllers will be described in more detail, in conjunction with
FIGS. 2
,
4
, and
6
.
FIG. 2
is a block diagram illustrating a detailed circuit configuration of the color gain controller
110
. As shown in
FIG. 2
, the color gain controller
110
multiplies the chrominance signals Cb and Cr received from the chrominance signal demodulator
108
of
FIG. 1
by a color gain control coefficient G received from a multiplier
200
, respectively. That is, the color gain controller
110
serves to vary the value of a vector A representing the chrominance signal C in proportion to the gain control coefficient G, as shown in
FIG. 3
illustrating a color vector diagram of the chrominance signal C with the chrominance signal Cb as an abscissa and the chrominance signal Cr as an ordinate. The values of output signals from the color gain controller
110
respectively associated with the luminance signal Y and chrominance signals Cb and Cr can be expressed as follows:
Y=Y
Cb
—
g=Cb×G
Cr
—
g=Cr×G
[Equation 1]
The above Equation 1 may be expressed in the form of a matrix equation as follows:
[
Y
Cb_g
Cr_g
]
=
[
1
0
0
0
G
0
0
0
G
]
×
[
Y
Cb
Cr
]
[Equation 1a]
In the above Equation 1a, “Cb” represents a normalized value of the B-Y chrominance signal, “Cr” represents a normalized value of the R-Y chrominance signal, and “G” represents the color gain control coefficient.
FIG. 4
is a block diagram illustrating a detailed circuit configuration of the color hue controller
112
. As shown in
FIG. 4
, the color hue controller
112
serves to rotate or shift the coordinate axes of the chrominance signals Cb and Cr, as shown in
FIG. 5
, thereby achieving a variation in color. The hue of the chrominance signals Cb and Cr, which is the color represented by the color vector A, as shown in
FIG. 5
, may often be unacceptable to the viewer due to an inadequate chrominance signal phase sampling or a particular visual response of the viewer. In such a case, the viewer adjusts the hue of the chrominance signals Cb and Cr by varying the rotation angle or phase angle of the color vector A, while observing the display state of the television receiver, until a desired hue is obtained. In accordance with a viewer's adjustment of the hue, the coordinate axes of the chrominance signals Cb and Cr are rotated or shifted, thereby controlling the hue of the color vector A.
When the viewer shifts the coordinate axes of the chrominance signals Cb and Cr by an angle of &thgr; in order to obtain a desired hue, the color hue control coefficient is set to “&thgr;”. In this case, a color hue control coefficient value of “cos &thgr;” or “−sin &thgr;” is input to the color hue controller
112
via a first switch
402
which is coupled to the values “cos &thgr;” and “−sin &thgr;,” associated with the chrominance signals Cb and Cr, respectively. Another color hue control coefficient value of “sin &thgr;” or “cos &thgr;” is input to the color hue controller
112
via a second switch
408
which is coupled to the values “sin &thgr;” and “cos &thgr;,” associated with the chrominance signals Cb and Cr, respectively. In a first multiplier
400
, the chrominance signal Cb, which is input to the color hue controller
112
, is multiplied by “cos &thgr;” applied to the first multiplier
400
in accordance with a switching operation of the first switch
402
. The resultant value from the first multiplier
400
is stored in a first delay
404
. In a second multiplier
406
, the input chrominance signal Cb is also multiplied by “sin &thgr;” applied to the second multiplier
406
in accordance with a switching operation of the second switch
408
. The resultant value from the second multiplier
406
is stored in a second delay
410
. After completing the multiplication operations for the input chrominance signal Cb, multiplication operations for the input chrominance signal Cr are conducted in the first and second multipliers
400
and
406
using values of “−sin &thgr;” and “cos &thgr;,” respectively. After performing the multiplication operation for the input chrominance signal Cr
Lee Ho-Seong
Park Hong-Ki
Miller John W.
Natnael Paulos
Samsung Electronics Co,. Ltd.
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