Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
1999-12-13
2001-08-14
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S370000
Reexamination Certificate
active
06274990
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device and a method for correcting a landing position of an electron beam in a color cathode ray tube.
FIG. 8
is a diagram showing a plan view of a conventional color cathode ray tube. As shown in
FIG. 8
, a glass bulb
20
forming an envelope of the color cathode ray tube is mainly composed of a glass panel
1
, a funnel
2
, and a neck
21
. Three electron beams emitted from an electron gun
3
incorporated in the neck
21
are deflected up and down and from side to side by a deflection yoke
4
. The three deflected electron beams individually pass a color selection member
5
such as a shadow mask and hit predetermined positions (red, green, and blue phosphor areas) on a fluorescent screen
6
formed on an inner surface of the glass panel
1
. The fluorescent screen
6
is scanned up and down and from side to side with the electron beams to display a color image.
When the electron beams pass the aperture of the color selection member
5
, about 80% of the beams strike the color selection member
5
, resulting in a thermal expansion of the color selection member
5
. The thermal expansion of the color selection member
5
, however, causes the electron beams, which have passed the aperture of the color selection member
5
, to hit positions differing from the predetermined positions on the fluorescent screen
6
, changing the landing positions. A change in an ambient temperature also causes the glass panel
1
to expand or shrink, changing the landing position likewise. While the color cathode ray tube is operating, the temperature of the funnel
2
also varies. This affects heat radiation of the color selection member
5
, changing the amount of thermal expansion of the color selection member
5
.
In the color cathode ray tube, the thermal expansion of the color selection member
5
results in a temperature drift (a positional drift of the landing position resulting from a temperature change of the color selection member
5
), as described above. In addition, a change in the ambient temperature causes the glass panel
1
to expand or shrink, resulting in an environment drift (a positional drift of the landing position resulting from a temperature change of the environment). Conventional methods for correcting the above-mentioned landing position changes (drift) include a method for correcting the courses of electron beams according to changes in the ambient temperature and another method for correcting the courses of electron beams according to the brightness of the image.
The former method, however, cannot correct an extreme landing deviation as large as a single pitch, for instance. The latter method cannot improve correction accuracy because of thermal variation of the color cathode ray tube itself and the like.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device and a method for correcting a landing position in a color cathode ray tube, which enables highly accurate correction and can correct extreme landing deviations.
According to an aspect of the present invention, a device for correcting a landing position of an electron beam in a color cathode ray tube, comprises: a funnel temperature sensor for detecting a temperature of a funnel of the color cathode ray tube; an ambient temperature sensor for detecting an ambient temperature around the color cathode ray tube; a landing correction coil disposed on or around a corner of an outer surface of the color cathode ray tube; and a controlling section for calculating a first temperature difference between the temperature of the funnel and the ambient temperature and a second temperature difference between a predetermined design temperature and the ambient temperature, calculating a current value for the landing correction coil according to the first and second temperature differences, and supplying a current of the obtained current value to the landing correction coil.
According to another aspect of the present invention, a device for correcting a landing position of an electron beam in a color cathode ray tube, comprises: first to fourth funnel temperature sensors for detecting first to fourth temperatures of first to fourth corners of an outer surface of the color cathode ray tube, respectively; an ambient temperature sensor for detecting an ambient temperature around the color cathode ray tube; first to fourth landing correction coils disposed on or around the first to fourth corners of the outer surface of the color cathode ray tube, respectively; a controlling section for calculating first to fourth temperature differences between the first to fourth temperatures and the ambient temperature, calculating a fifth temperature difference between a predetermined design temperature and the ambient temperature, calculating a first current value for the first landing correction coil according to the first and fifth temperature differences, calculating a second current value for the second landing correction coil according to the second and fifth temperature differences, calculating a third current value for the third landing correction coil according to the third and fifth temperature differences, calculating a fourth current value for the fourth landing correction coil according to the fourth and fifth temperature differences, and supplying first to fourth currents of the obtained first to fourth current values to the first to fourth landing correction coils, respectively.
According to a further aspect of the present invention, a method for correcting a landing position of an electron beam in a color cathode ray tube, comprises the steps of: detecting a temperature of a funnel of the color cathode ray tube; detecting an ambient temperature around the color cathode ray tube; calculating a first temperature difference between the temperature of the funnel and the ambient temperature; calculating a second temperature difference between a predetermined design temperature and the ambient temperature; calculating a current value for a landing correction coil disposed on or around a corner of an outer surface of the color cathode ray tube according to the first and second temperature differences; and supplying a current of the obtained current value to the landing correction coil.
According to a further aspect of the present invention, a method for correcting a landing position of an electron beam in a color cathode ray tube, comprises the steps of: detecting a temperature of a funnel of the color cathode ray tube; detecting an ambient temperature around the color cathode ray tube; calculating a first temperature difference between the temperature of the funnel and the ambient temperature; calculating a second temperature difference between a predetermined design temperature and the ambient temperature; calculating four current values for four landing correction coils each disposed on or around corners of an outer surface of the color cathode ray tube according to the first and second temperature differences; and supplying currents of the obtained current values to the four landing correction coils, respectively.
According to a further aspect of the present invention, a method for correcting a landing position of an electron beam in a color cathode ray tube, comprises the steps of: detecting first to fourth temperatures of first to fourth corners of an outer surface of the color cathode ray tube; detecting an ambient temperature around the color cathode ray tube; calculating first to fourth temperature differences between the first to fourth temperatures and the ambient temperature; calculating a fifth temperature difference between a predetermined design temperature and the ambient temperature; calculating a first current value for a first landing correction coil disposed on or around the first corner according to the first and fifth temperature differences, a second current value for a second landing correction coil disposed on or around the second corner according to the second and fifth temperature differences, a third current valu
Hojo Minoru
Kawaguchi Takeo
Clinger James
Mitsubishi Denki & Kabushiki Kaisha
Wong Don
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