Computer graphics processing and selective visual display system – Display peripheral interface input device
Utility Patent
1997-04-25
2001-01-02
Luu, Matthew (Department: 2779)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C348S652000
Utility Patent
active
06169536
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color picture quality compensation circuit, and in particular to an improved color compensation circuit in which is a color picture quality is compensated for in reference to a reference color selected by a user.
2. Description of the Conventional Art
Since skin color is most easily retained in human memory, color picture display systems such as television receivers and computer monitors, there have been several approaches for adjusting color picture quality using skin color as a reference color. Referring to
FIG. 1
, one approach is to gather colors within peripheral portions of a “skin color axis” which is positioned at a 123° with respect to the B-Y demodulation axis.
More specifically, in order to produce various skin colors as a reference skin color, the phase of the R-Y demodulation axis is increased to move the R-Y axis toward the skin color axis and the phase of the green color (G-Y axis: not shown) is decreased to move its axis toward the skin color axis whereby the phase of the skin color is within the peripheral portions of the skin color axis.
Yet more specifically, referring to
FIG. 2
, in order to gather a color vector V
1
, which has a positive phase angle with respect to the skin color axis, a R-Y component V
R-Y
of the V
1
is decreased to V
R-Y′
. Because of this decrease, the V
1
now becomes a color vector V
1
, which has a phase closer to the skin color axis, thus producing the color as a reference skin color. Likewise, when a B-Y component V
B-Y
of a color vector V
2
, which has a negative phase angle with respect to the skin color axis, is decreased to a value V
B-Y′
, the color vector V
2
becomes a color vector of V
2′
, which has a phase within the peripheral portions of the skin color axis, thus producing the color as a reference skin color.
An example of such a conventional skin color compensation circuit is shown in FIG.
3
. This conventional compensation circuit includes a burst gate
1
for providing a burst signal derived from a composite color image signal CVBS; a 3.58 MHZ oscillator
2
for providing a reference sub-carrier signal fsc which is in synchronization with the burst signal; a Y/C separation unit
3
for separating Y (Luminance) and C (color) signals from the composit signal CVBS; an amplifier
4
for amplifying the C- signal from the Y/C separation unit; a color demodulator
5
; a delay unit
6
for delaying the Y-signal from the Y/C separation unit
3
for a predetermined time; a matrix amplifier
7
; and a phase detector
8
for detecting the phase of an amplified C-signal provided from the amplifier
4
in conjunction with the reference sub-carrier signal fsc provided from the 3.58 oscillator
2
.
The color demodulator
5
comprises a tint controller “a”, a R-Y demodulator “b”, a 90-degree phase shifter “c”, a B-Y demodulator “d”, and a G-Y demodulator “e”. The matrix amplifier
7
comprises mixers f, g, and h for mixing the output from the delay unit
6
and a color difference signal from the color demodulator
5
, and amplifiers I, j, and k coupled thereto, respectively. The color demodulator
5
demodulates the C- signal into R-Y and B-Y demodulation signals. The user adjusts tint and color saturation in reference to the skin color produced on a display screen (e.g., color picture tube CPT).
Referring to
FIG. 3
, the phase detector
8
detects whether a signal representing skin color is present in the C-signal. If skin color is detected, the tint controller a of the color demodulator
5
is controlled for controlling the positioning of the demodulation axis toward the skin color axis.
However, this conventional approach has drawbacks. For example, if a color vector (e.g., V
1
in
FIG. 2
) is adjusted to move toward the skin color axis, its component value (e.g., V
R-Y
) with respect to the conventional demodulation axis is reduced to another value (e.g., V
R-Y
′) of a smaller magnitude, thus decreasing the overall color density. Further, the color is adjusted in reference to one skin color, incapable of responding to various kinds of skin color individually.
Another conventional approach is now explained in reference to FIG.
4
. In this approach, the angle between the R-Y and the B-Y demodulation axes is fixed at 112° (not at a more conventional 90°), thus increasing the R-Y component. As shown in
FIG. 5
, the phase shifter “c” of the color modulator
5
in this approach is fixed at a 112°, as compared to the phase shifter of the color demodulator of
FIG. 3
being fixed at a 90°. The reference numerals in
FIG. 5
correspond to the same reference numerals in FIG.
3
. Further, the G-Y axis (not shown) is fixed at an angle of 252°. In this approach, since the signal axis is always maintained at a same fixed angle to obtain a stable skin color, when an inputted signal represents no skin color, unnecessary color demodulation would occur.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a color picture quality compensation circuit which overcomes the aforementioned problems encountered in the conventional art.
To achieve the above object, a color picture quality compensation circuit of the present invention, as broadly defined and embodied herein, comprises means for detecting whether a reference color signal is present in a color signal representing a color of a video image; and means for adjusting the color picture quality of the video image in accordance with a preset value corresponding to a detected reference color signal.
According to another aspect of the present invention, a color picture quality compensation circuit comprises means for detecting whether a reference color signal is present in a color signal representing a color of a video image; means for determining a respective one of a plurality of types of reference color corresponding to a detected reference color signal; means for providing preset compensation values, each value corresponding to a respective one of the plurality of types of reference color; and means for adjusting the picture quality of the video image in accordance with one of the compensation values corresponding to the respective type of reference color.
Additional advantages, objects and features of the invention will become more apparent from the description which follows.
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Y. Yoshio, “Skin Color Correcting Circuit” Patent Abstracts of Japan, of JP 04 267 691, vol. 17, No. 61 (1993).
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Ha Yeong-Ho
Hong Kyong-Chul
Lee Kwang-Chun
Blackman Anthony J.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
LG Electronics Inc.
Luu Matthew
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