Television – Image signal processing circuitry specific to television – Brightness control
Reexamination Certificate
1999-05-17
2001-06-12
Eisenzopf, Reinhard J. (Department: 2614)
Television
Image signal processing circuitry specific to television
Brightness control
C348S687000, C348S688000, C348S745000, C348S746000, C348S806000
Reexamination Certificate
active
06246445
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monitor, and more particularly, to a brightness correcting circuit for correcting the brightness of a monitor screen and a brightness correcting method using the same.
2. Description of the Related Art
To produce an image on a monitor screen, a video signal is scanned to the screen via an electron gun. The video signal indicates a “black level” constant direct current (DC) voltage which controls the brightness of the screen. Since different users generally desire different brightnesses of the screen, monitors are constructed so that a user can change the brightness of the screen. As the size of a monitor screen becomes larger, the surface of the screen becomes generally non-spherical, i.e., it approaches a curved surface close to a planar surface.
As an example, a schematic diagram of a picture tube is shown in FIG.
1
. Referring to
FIG. 1
, an electron gun
110
creates an electron beam using a video signal Vout as an input and reproduces an image on a screen
130
by controlling the intensity of the electron beam. When the screen
130
is non-spherical, a distance from the electron gun
110
to the screen
130
is not uniform. Namely, a distance
11
or
13
from the electron gun
110
to the edge of the screen
130
is greater than the distance
12
from the electron gun
110
to the center of the screen
130
.
Accordingly, in a conventional monitor, the brightness at the edge of the screen
130
is generally lower than that at the center. In particular, the brightness is most greatly reduced in the comers of the screen.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a brightness correcting circuit by which it is possible to efficiently correct the brightness at the edge and corners of a monitor screen.
It is another objective of the present invention to provide a parabolic signal generator for generating a parabolic signal, the waveform of which is variable in order to be used for the brightness correcting circuit.
It is still another objective of the present invention to provide a brightness correcting method for efficiently correcting the brightness at the edge and corners of the monitor screen.
Accordingly, to achieve the first and second objectives, there is provided a circuit for correcting the brightness of a monitor screen, comprising a parabolic signal generator for generating a parabolic signal and a corrected video signal generator for controlling the gain of an input video signal in response to the parabolic signal and outputting a corrected video signal.
The parabolic signal generator comprises a horizontal parabolic signal generator, a vertical parabolic signal generator, and an adder. The horizontal parabolic signal generator generates a horizontal parabolic signal, the waveform of which is variable in response to a plurality of control signals, using a horizontal flyback pulse as an input. The vertical parabolic signal generator generates a vertical parabolic signal, the waveform of which is variable in response to other plurality of control signals, using a vertical flyback pulse as an input. The adder adds the horizontal parabolic signal to the vertical parabolic signal and outputs the addition result as the parabolic signal.
According to a preferred embodiment, the horizontal parabolic signal generator comprises a sawtooth generator for generating a first sawtooth signal, using the horizontal flyback pulse as an input. The horizontal parabolic signal generator also includes a multiplier for generating the square signal and the fourth power signal of the first sawtooth, using the first sawtooth as an input. A level controller controls the levels of the first sawtooth, the square signal, and the fourth power signal in response to the plurality of control signals and outputs the signals with controlled levels. An adder adds the level-controlled first sawtooth signal, the level-controlled square signal, and the level-controlled fourth power signal to one another and outputs the addition result as the horizontal parabolic signal.
According to another preferred embodiment, the vertical parabolic signal generator comprises a sawtooth generator for generating a second sawtooth signal, using the vertical flyback pulse as an input. The vertical parabolic signal generator also includes a multiplier for generating the square signal and the fourth power signal of the second sawtooth, using the second sawtooth as an input. A level controller controls the levels of the second sawtooth, the square signal of the second sawtooth, and the fourth power of the second sawtooth in response to the other plurality of control signals and outputs the level-controlled signals. An adder adds the level-controlled second sawtooth signal, the level-controlled square signal, and the level-controlled fourth power signal to one another and outputs the addition result as the vertical parabolic signal.
To achieve the third objective, there is provided a method for correcting the brightness of a monitor screen. The method includes generating a horizontal parabolic signal with a variable waveform and generating a vertical parabolic signal with a variable waveform. The horizontal parabolic signal is added to the vertical parabolic signal and the addition result is output as the parabolic signal. The gain of an input video signal is controlled in response to the parabolic signal and a corrected video signal is output.
According to a preferred embodiment, the step of generating the horizontal parabolic signal comprises the steps of (a) generating a first sawtooth signal using a horizontal flyback pulse as an input, (b) generating the square signal and the fourth power signal of the first sawtooth signal using the first sawtooth signal as an input, (c) controlling the levels of the first sawtooth signal, the square signal of the first sawtooth signal, and the fourth power signal of the first sawtooth signal in response to a plurality of control signals, and (d) adding the first sawtooth signal, the square signal of the first sawtooth signal, and the fourth power signal of the first sawtooth signal, the levels of which are controlled, to each other and outputting the result as a horizontal parabolic signal.
According to another preferred embodiment, the step of generating the vertical parabolic signal comprises the steps of (e) generating a second sawtooth signal using a vertical flyback pulse as an input, (f) generating the square signal and the fourth power signal of the second sawtooth signal using the second sawtooth signal as an input, (g) controlling the levels of the second sawtooth signal, the square signal of the second sawtooth signal, and the fourth power signal of the second sawtooth signal in response to other plurality of control signals, and (h) adding the second sawtooth signal, the square signal of the second sawtooth signal, and the fourth power signal of the second sawtooth signal, the levels of which are controlled, to one another and outputting the addition result as a vertical parabolic signal.
According to the circuit for correcting the brightness of the monitor screen according to the present invention and the brightness correcting method of the present invention, it is possible to efficiently correct the brightness at the edge and the corner of the monitor screen by varying the waveform of the parabolic signal by selectively controlling the control signals of the horizontal parabolic signal generator and the vertical parabolic signal generator.
REFERENCES:
patent: 4701788 (1987-10-01), Desjardins
patent: 4916365 (1990-04-01), Arai
patent: 5298985 (1994-03-01), Tsujihara et al.
patent: 5519447 (1996-05-01), Shima et al.
patent: 5523657 (1996-06-01), Kamei
patent: 5532765 (1996-07-01), Inoue et al.
patent: 5576774 (1996-11-01), Hosoi
patent: 5847777 (1998-12-01), George
patent: 5886750 (1999-03-01), Osuga et al.
Eisenzopf Reinhard J.
Mills & Onello LLP
Natnael Paulos
Samsung Electronics Co,. Ltd.
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