Television – Video display – Cathode-ray tube
Reexamination Certificate
2001-05-17
2004-06-22
Miller, John (Department: 2614)
Television
Video display
Cathode-ray tube
C348S557000, C348S717000, C348S745000, C315S368110
Reexamination Certificate
active
06753932
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image processing apparatus and method as well as a recording medium, and more particularly to an image processing apparatus and method as well as a recording medium suitable for use with an apparatus which has functions for convergence correction, correction of video distortion and correction of non-uniform brightness or chromaticity of a video.
In recent years, a cathode ray tube display apparatus of the raster scanning system has been popularized as a display apparatus for displaying an image. The cathode ray tube display apparatus corrects images of three colors of, for example, red, green and blue against displacement in superposition to display an image. In the following description, such correction against displacement is referred to as “convergence correction”.
In such a cathode ray tube display apparatus as described above, convergence correction is performed with a high degree of accuracy popularly using a method wherein convergence correction current is supplied to a convergence correction coil.
FIG. 1
shows an example of configuration of a convergence correction apparatus that effects such convergence correction. Referring to
FIG. 1
, the convergence correction apparatus
1
shown includes an adjustment apparatus
2
, a storage apparatus
3
, a control apparatus
4
, a corrected waveform outputting apparatus
5
, an output amplifier
6
and a correction coil
7
.
In the convergence correction apparatus
1
shown in
FIG. 1
, convergence adjustment data are produced by the adjustment apparatus
2
in advance and stored into the storage apparatus
3
. The stored convergence adjustment data are read out by the control apparatus
4
and outputted to the corrected waveform outputting apparatus
5
together with synchronization frequency information, raster scan position information and other necessary information determined by the control apparatus
4
. The convergence adjustment data inputted to the corrected waveform outputting apparatus
5
are worked based on the synchronization frequency information, raster scan position information and other information so as to allow optimum convergence correction, and then are converted into a convergence correction waveform and outputted to the output amplifier
6
. The convergence correction waveform inputted to the output amplifier
6
is amplified in voltage and amplitude and supplied to the correction coil
7
attached to the cathode ray tube so that convergence correction is performed.
Conventionally, roughly two correction waveform generation methods are available including a function generation method and a memory mapping method. The function generation method approximates a convergence correction waveform to a finite function based on information such as convergence correction data at a convergence adjustment point and a synchronization frequency to generate a convergence correction waveform in synchronism with raster scanning of the cathode ray tube. According to the function generation method, the memory capacity for storing adjustment data may be smaller than that of the memory mapping method. Therefore, the function generation method is advantageous in that it can be produced at a comparatively low cost, but is disadvantageous in that it is low in degree of freedom in correction.
Meanwhile, according to the correction waveform generation method of the memory mapping method, a display screen is divided into gratings, and regarding each grating point as an adjustment point, a convergence correction amount necessary for the adjustment point is stored into a memory in advance. Then, at each grating point, the corresponding adjustment data stored in the memory is read out, but at any other point, correction data is obtained by interpolation processing using a straight line or a quadratic curve based on the correction data at the grating points, and is used to generate a convergence correction waveform. The memory mapping method exhibits a higher degree of freedom in correction and allows correction of convergence with a higher degree of accuracy than the function generation method. Therefore, particularly a display unit for which a high display quality is required such as, for example, a display unit for a computer frequently uses the memory mapping method.
It is popularly known that a position error of a video displayed on a cathode ray tube can be corrected by adjusting the output timing of video signal data.
FIGS. 2A and 2B
illustrate horizontal linearity correction by adjustment of the output timing of video data in a horizontal period. Particularly,
FIG. 2A
illustrates a displayed video when a position error is not corrected, and
FIG. 2A
illustrates a displayed video when the output timing of video signal data is adjusted to perform horizontal linear correction. Where the horizontal deflecting current is distorted, when no correction is performed, the horizontal linearity is distorted as seen in
FIG. 2A
, but when the video signal is adjusted in a direction of the time base so as to correct the distortion of the horizontal deflecting current, the horizontal linearity can be corrected as seen in FIG.
2
B.
In the example illustrated in
FIGS. 2A and 2B
, the output timing of video signal data is adjusted in a horizontal period. However, if the output timing is adjusted in a vertical period, then correction of image distortion in a vertical period can be performed in a similar manner.
FIG. 3
shows an example of a display apparatus which performs such deflection correction as described above with reference to
FIGS. 2A and 2B
. Referring to
FIG. 3
, the display apparatus
10
shown includes a memory
11
, a digital/analog (D/A) conversion circuit
12
, a correction circuit
13
, a clock (CLK) generation circuit
14
for generating an adjustment clock signal, a video circuit
15
, a deflection circuit
16
, a horizontal deflecting coil
17
, a measuring resistor
18
for detecting horizontal deflecting current, a vertical deflecting coil
19
, and a cathode ray tube
20
.
An input video signal is written into the memory
11
at a timing of a first clock signal clk
1
. Then, the image data written in the memory
11
are read out at another timing of a second clock signal clk
2
and converted into an analog video signal by the D/A conversion circuit
12
, whereafter they are inputted to the video circuit
15
. The image signal inputted to the video circuit
15
is amplified by the video circuit
15
and applied to the cathode of the cathode ray tube
20
.
On the other hand, the correction circuit
13
produces a reference signal for horizontal deflecting current in synchronism with a synchronizing signal. The reference signal produced is written into the memory
11
at a timing of the first clock signal clk
1
similarly to the video signal, and is then read out from the memory
11
at another timing of the second clock signal clk
2
, converted into an analog video signal by the D/A conversion circuit
12
and inputted to the clock generation circuit
14
.
Meanwhile, the synchronizing signal inputted to the deflection circuit
16
to drive the horizontal deflecting coil
17
and the vertical deflecting coil
19
to form a raster on the cathode ray tube
20
. The measuring resistor
18
is a detecting resistor for measuring the horizontal deflecting current, and a voltage which increases in proportion to the horizontal deflecting current is inputted from the measuring resistor
18
to the clock generation circuit
14
. The clock generation circuit
14
compares the detection voltage of the horizontal defection current inputted thereto from the measuring resistor
18
with the reference waveform of the adjusted horizontal deflecting current inputted thereto from the D/A conversion circuit
12
through the memory
11
and supplies an amplified waveform of a difference between the two input waveforms to a voltage-controlled oscillator (VCO). The VCO generates a second clock signal clk
2
adjusted in accordance with the difference between the two input wavefor
Ishii Shinya
Yamazaki Nobuo
Frommer William S.
Frommer & Lawrence & Haug LLP
Miller John
Sony Corporation
Yenke Brian
LandOfFree
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