Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
2000-06-09
2003-11-18
Ramsey, Kenneth J. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S412000, C313S413000
Reexamination Certificate
active
06650039
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cathode ray tube, and more particularly, to an electron gun in a color CRT(Cathode Ray Tube) for enhancing a resolution.
2. Background of the Related Art
In general, as shown in
FIG. 1
, the color CRT is provided with a panel
1
, a funnel
2
of a bulb form welded to an inside surface of the panel, and a neck portion
5
at a rear of the funnel for sealing in the electron gun
4
to emit R. G. B beams
3
of red, green and blue colors. There is a coat
6
of fluorescent material of red, green, and blue colors on an inside surface of the panel, a support frame
8
in the vicinity of the coat of fluorescent material, and a shadow mask
7
fitted to the support frame
8
for selecting a color from the R. G. B beams
3
emitted from the electron gun
4
. There is a deflection yoke
9
on an outer circumference of the funnel for deflecting the R. G. B beams emitted from the electron gun in a vertical or horizontal directions.
Referring to
FIG. 2
, the electron gun has a triode part and a main lens part. The triode part is provided with built-in heaters
4
a
, heat sources, three in-line cathodes
4
b
, a control electrode
4
c
for controlling thermal electrons emitted from the cathodes, and an accelerating electrode
4
d
for accelerating the thermal electrons, arranged in an order with certain gaps starting from the cathodes. The main lens part is provided with a focusing electrode
4
e
for focusing, and finally accelerating the R. G. B beams generated at the triode part, and an anode
4
f
. In the foregoing electron gun, there is a voltage difference occurred between the focusing electrode
4
e
and the anode
4
f
upon application of required voltages to respective electrodes, and the voltage difference forms an electrostatic lens between the electrodes. Accordingly, the R. G. B beams
3
from the triode part is focused in a course passing through the focusing electrode
4
e
and the anode
4
f
onto a center of the flourescent material coat by the electrostatic lens. In this instance, a self convergence deflection yoke
9
is come into operation for deflecting the R. G. B beams focused onto the center of the fluorescent material coat to an entire region of the screen.
A distribution of a magnetic field formed at the deflection yoke is as shown in
FIGS. 3A and 3B
. That is, a horizontal deflection magnetic field is formed in a pin cushion form, and a vertical deflection magnetic field is formed in a barrel form, for correction of mis-convergence in a peripheral region of the fluorescent material coat. As shown in
FIGS. 3C and 3D
, the horizontal deflection magnetic field and the vertical deflection magnetic field may be explained, with the horizontal deflection magnetic field and the vertical deflection magnetic field separated into two polar components and four polar components, respectively. That is, the two polar component deflects an electron beam in horizontal and vertical directions, and the four polar components converges the electron beam in a vertical direction and diverges in a horizontal direction. Therefore, even if a magnetic field is close to be uniform, the R. G. B beams receive substantial astigmatism in the peripheral region of the fluorescent material coat, such that a beam spot is distorted by fine pin cushion and barrel magnetic field components.
FIGS. 4A and 4B
illustrate the electron beam spot distortion on a screen in more detail. That is, as there is no deflective magnetic field applied to the central portion of the screen, the electron beam spot shows no distortion. However, the R. G. B electron beams in the peripheral region are diverged in a horizontal direction and converged excessively in a vertical direction, the electron beams are elongated in horizontal direction substantially, and dispersed in up and down directions, to form a thin haze
11
, that results in deterioration of the resolution in the peripheral region of the screen. This problem becomes the more serious as the CRT becomes the larger, and the deflection angle is the greater.
In order to solve the problem, in most cases of the related art, the astigmatism is corrected synchronous to a deflection signal when the electron beams are deflected toward the peripheral region of the screen, by providing a quadrupole between a first focusing electrode
41
and a second focusing electrode
42
, which is provided by dividing the focusing electrode into two as shown in
FIGS. 5A and 5B
, that forms a quadrupole lens(see
13
in FIG.
6
B). The system shown in
FIGS. 5A and 5B
is disclosed in U.S. Pat. No. 4,772,827, wherein the first focusing electrode
41
on the cathode side has electron beam pass through holes
41
a
, and vertical plate electrodes on both sides and between the electron beam pass through holes
41
a
. And, the second focusing electrode
42
having a high voltage applied thereto has horizontal plate electrodes
42
b
on upper and lower sides, and three electron beam pass through holes
42
a
corresponding to the electron beam pass through holes
41
a
in the first focusing electrode.
The operation of the foregoing electron gun will be explained with reference to FIGS.
5
A~
6
B. The electron beams from the triode part(a beam forming region) pass through a first focusing electrode
41
, a quadrupole part
41
b
on the first focusing electrode side, a quadrupole part
42
b
on the second focusing electrode side, and the second focusing electrode, and are focused at the eletrostatic lens
14
to form an image on the tube screen. Particularly, when the electron beam is deflected toward the peripheral region, though the first focusing electrode
41
is provided with a fixed static voltage, the second focusing electrode
42
is provided with a dynamic voltage varied with a required deflection of the electron beams. That is, as the voltages provided to the first focusing electrode
41
and the second focusing electrode
42
are provided to the quadrupole part
41
b
on the first focusing electrode side and the quadrupole part
42
b
on the second focusing electrode side, the quadrupole lens
13
is formed by the quadrupole, which corrects the astigmatism that affects the electron beams. In general, as a CRT becomes the larger, or the deflection angle becomes the greater, the dynamic voltage to the second focusing electrode is the higher than the static voltage to the first focusing electrode. A voltage difference between the first focusing electrode
41
and the second focusing electrode
42
form the quadrupole lens
13
at the quadrupole, which elongates the electron beams in a vertical direction. Accordingly, the quadrupole lens prevents the haze of the electron beams occurred when the electron beams are deflected to the peripheral region by a non-uniform magnetic field from the main lens
14
and the deflection yoke
9
in advance.
The quadrupole lens will be explained.
Referring to
FIG. 6A
, the electron beams
3
are focused at a central portion of the screen focused onto the central portion of the screen, the electron beams are not focused exactly due to a deflection aberration component when the electron beams are deflected to the peripheral region of the screen. And, portions shown in dashed lines on the drawing are an astigmatism component caused by the deflection yoke
9
when the electron beams are deflected to the peripheral region. A DY lens
12
formed by the deflection yoke
9
diverges the electron beams
3
in a horizontal direction and converges in a vertical direction. According to this, when the electron beams
3
are deflected to the peripheral region, an over-focusing component caused by a distance difference and an under-focusing component caused by the deflection yoke
9
are overlapped in the horizontal direction, to show a serious over-focusing, which results in a great dispersion of an image in the vertical direction, that deteriorates the resolution in the peripheral region.
FIG. 6B
illustrates the quadrupole lens added thereto for improving the above image
Kim Hyun Cheol
Kim Tae Kyu
Fleshner & Kim LLP
LG Electronics Inc.
Perry Anthony
Ramsey Kenneth J.
LandOfFree
Electron gun in color cathode ray tube does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electron gun in color cathode ray tube, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electron gun in color cathode ray tube will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3183723