Television – Image signal processing circuitry specific to television – Noise or undesired signal reduction
Reexamination Certificate
1998-02-20
2001-06-19
Eisenzopf, Reinhard J. (Department: 2614)
Television
Image signal processing circuitry specific to television
Noise or undesired signal reduction
C348S624000, C348S617000, C348S612000, C348S607000
Reexamination Certificate
active
06249321
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention is related to device and method for correcting a color distortion on a TV receiver, which can prevent a color distortion generated in reproduction of a color.
2. Description of the Related Art
FIG. 1
illustrates general transmission paths of a broadcasting signal, referring to which a process of a TV broadcasting signal transmission will be explained.
The TV broadcasting signal may be transmitted to a TV receiver
14
at a reception antenna
14
A, taking both a direct path C
1
and indirect path C
2
and C
3
, such as a mountain
12
and a large building
13
. A channel with plural broadcasting signal transmission paths is called a multi-path channel. Since a field intensity of the broadcasting signal received at the TV receiver
14
through the direct path C
1
is high, the broadcasting signal is displayed on a screen bright and clear, while a field intensity of the broadcasting signal received at the TV receiver
14
through the indirect path C
2
or C
3
, i.e., a ghost, is low, the broadcasting signal is displayed on a screen hazy. The ghost in an actual broadcasting channel appears, not only as a difference of brightness simply, but also various forms, such as a color distortion and an orthogonal distortion.
14
B shown on the TV screen is a normal image, and
14
C is a ghost. The ghost can be expressed with three parameters of a delay time, an attenuation constant, and a phase shift. The time delay, a parameter for representing a reception time difference of the broadcasting signal depending on a difference of path distances, is represented in a relative time difference of signal arrival with reference to a signal received through a main path in &mgr;sec units. A ghost with a delay time less than “0” is called a full ghost, and a ghost with a little delay time compared to the main signal is called a near ghost. The near ghost in general is a ghost occurred near the main signal with 1~2 &mgr;sec. and most of the ghosts we see in general ambient are these type of ghosts. The attenuation constant represents a degree of intensity of a signal through an indirect path with respect to a signal through a main path, i.e., an intensity of a signal compared to the main path. Phases of signal carriers through different paths in the multi-oath channel differ from a phase of a main path signal carrier, which is represented as the parameter of phase shift.
As can be known from the ghost parameters, the ghost is dependent on time, broadcasting environment, and broadcasting channel. Conditions of ghost generation vary depending, for example, reflection characteristic changes of reflecting bodies depending on environments, carrier frequencies transmitted from broadcasting stations, and the like, according to which a form of ghost is also changed. Therefore, in order to correct a color distortion coming from the multi-path channel, an adaptive feature is required. The color distortion is caused by a phase shift of a color subcarrier due to a ghost coming from a multi-path channel. As color information is carried on a phase in current TV broadcasting system, the greater the phase difference, the greater the color distortion.
In a study, it is found that the ghosts in general arc mostly distributed as near ghosts with 1~2 &mgr;sec delay times, and almost all within delay times between −2&mgr;sec and 20 &mgr;sec. Therefore, a device for correcting a color distortion should be capable of correcting color distortions caused by ghosts with delay times of such a range. Efforts for improving a color degradation caused by the multi-paths in a TV signal transmission have mostly been concentrated on an apparent particular color of color signals. However, these techniques could not correct color distortions generated by the multi-path perfectly. And, recently researches for canceling ghosts generated by the multi-path channel in a more fundamental fashion are already underway, and some of which are available as commercial products.
However, though ghosts are canceled and colors are restored by compensating the multi-path channel characteristic itself, because such ghost canceling means employs a long transverse filter and an exclusive signal processor, it has a limitation in reducing a hardware cost.
Of color signals, because such background art color distortion correcting means are adapted to correct colors with reference to a particular color apparent to eyes, they can not correct the color distortions generated by a multi-path channel, fundamentally.
And, though ghosts are canceled and colors are restored by compensating the multi-path channel characteristic itself by using a ghost canceling means which can cancel ghosts generated by a multi-path channel recently, because such ghost canceling means employs at long transverse filter and an exclusive signal processor, it has a defect of requiring much hardware cost.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to device and method for correcting a color distortion on a TV receiver that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the method for correcting a color distortion on a TV receiver includes a multi-path channel estimation step wherein a transmission channel existing between a transmitter side in a broadcasting station and a color demodulating circuit in a TV receiver is estimated for obtaining an impulse response using a reference signal transmitted from the broadcasting station for equalizing a multi-path channel, a color subcarrier phase error calculation step wherein a phase error of a color subcarrier between the transmitter side of the broadcasting station and the TV receiver is calculated using the estimated impulse response, and a phase correction of a reproduced color subcarrier step wherein a phase error on the TV receiver in reproduction of a color is corrected as much as the phase error obtained in the color subcarrier phase error calculation step.
In the other aspect of the present invention, there is provided a device for correcting a color distortion on a TV receiver, including a reference signal detecting part for detecting a GCR signal inserted in a video signal received through an antenna, a timing generating part of receiving a synchronizing signal from a synchronization separating part and generating a timing control signal for detecting the GCR signal, a control part for receiving the GCR signal from the reference signal detecting part, calculating a color subcarrier error between a transmitter side in a broadcasting station and a TV receiver caused by multi-paths in a channel, and generating a color signal correcting data as much as the calculated error, and a color signal demodulating part for receiving the correcting data from the control part and correcting a color signal.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
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patent
Bae Kuk Ho
Song Woo Jin
Birch,Stewart, Kolasch & Birch, LLP
Desir Jean W.
Eisenzopf Reinhard J.
LG Electronics Inc.
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