Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
2001-12-21
2004-03-23
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S412000, C313S409000, C313S448000, C313S449000, C313S439000, C313S432000
Reexamination Certificate
active
06710532
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an electron gun in cathode ray tube. More particularly, the invention relates to a focus electrode and an anode in an electron gun of a cathode ray tube (CRT).
2. Background of the Related Art
FIG. 1
illustrates a schematic side view section of a CRT. The CRT of
FIG. 1
includes a panel
1
and a funnel
2
forming a front and rear of the CRT. An electron gun
3
is provided in a neck part
2
a
at one end of the funnel
2
for emitting electron beams
3
a
. A deflection yoke
4
is disposed around an outer surface of the funnel
2
for deflecting the electron beams
3
a
. A shadow mask
5
is positioned between the electron gun
3
and the panel
1
for passing the deflected electron beams
3
a
therethrough. A fluorescent surface
7
coated on an inside surface of the panel
1
.
FIG. 2
illustrates a side view of the electron gun
3
built into the neck part
2
a
of the color CRT. Referring to
FIG. 2
, the electron gun
3
includes cathodes
8
, a control electrode
9
, acceleration electrode
10
, first and second pre-focus electrode
11
a
and
11
b
, a focus electrode
12
, and an anode
13
, each having a preset voltage applied thereto. The control electrode
9
and the acceleration electrode
10
are planar. The pre-focus electrodes
11
a
and
11
b
, the focus electrode
12
, and the anode
13
are non-circular cylindrical. Each have electron beam pass-through holes for passing electron beams
3
a
therethrough.
When the foregoing CRT is put into operation, the electron beams
3
a
are emitted from the cathodes
8
, and accelerated toward the anode
13
by a potential difference. Since preset voltages are applied to respective electrodes, the electron beams are controlled, accelerated, and pre-focused, respectively, by the control electrode
9
, the acceleration electrode
10
, the pre-focus electrode
11
a
and
11
b
. The main focusing of the electron beams is performed by a main focus electrostatic lens formed by a potential difference between the focus electrode
12
and the anode
13
. The electron beams
3
a
are, then, deflected in the up, down, left, and or right direction by the deflection yoke
4
, selectively passed through the shadow mask
5
, and land on the fluorescent surface
7
to form a picture on the panel
1
.
In the case of electron guns in recent large-sized color CRTs where a heavy current is essential, the heavy current makes the electron beam flux thicker, and leads it to pass through a protaxis of the main focus electrostatic lens. The electron beam passing through the protaxis has more spherical aberration than one passing through a paraxis. The spherical aberration causes blooming, a phenomena in which a spot size of the electron beam is formed greater at a central part of the screen. It is known that a horizontal spot size caused by blooming can be reduced by a VM (velocity Modulation) coil fitted to an outer circumference of the neck. However, since there has been no proper device external to the CRT for reducing a spot enlarged in a vertical direction due to spherical aberration, vertical blooming still remains on the screen, and deteriorates a vertical focus characteristic of the screen.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
SUMMARY OF THE INVENTION
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Accordingly, the invention is directed to an electron gun in a CRT that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the invention is to provide an electron gun in a CRT, in which a vertical diameter dv of a main focus electrostatic lens is configured to be greater in proportion to increased thickness of the electron beam flux where heavy current is used for the electron gun, preventing occurrence of spherical aberration, and improving a vertical resolution of a picture.
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 invention, as embodied and broadly described, an electron gun in a CRT includes three cathodes for emitting electron beams, a plurality of acceleration electrodes, and a focus electrode and an anode, each including an opposite rim having a single electron beam pass-through hole with a vertical width V and a horizontal width H, and an electrostatic field control body at a distance D from the rim, with a bridge width ‘t’, and a vertical width v and a horizontal width h of a central electron beam pass-through hole, wherein the electrostatic field control body and the focus electrode and the anode can be related by the following equation (1):
(
VxvxD
)/29≧
H−
(2×
S
), (1)
where, S denotes a sum of the horizontal width h and the bridge width t of the electrostatic field control body.
To further achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, an electron gun in a CRT includes at least one cathode for emitting electron beams, at least one acceleration electrode, and a focus electrode and an anode each including an opposite rim having an electron beam pass-through hole with a vertical width V and a horizontal width H, and an electrostatic field control body positioned at a distance D from the rim, with a bridge width ‘t’, and a vertical width v and a horizontal width h of a central electron beam pass-through hole, wherein the electrostatic field control body and the focus electrode and the anode are configured to satisfy the following equation (1):
(
VxvxD
)/29≧
H
−(2×
S
), (1)
where, S denotes a sum of the horizontal width h and the bridge width t of the electrostatic field control body.
To further achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, a method of optimizing the performance of an electrostatic field control body of an electron gun for a CRT includes (1) determining parameters influencing a vertical width dv of the electrostatic field control body, (2) determining parameters influencing a horizontal width dh of the electrostatic field control body; and (3) optimizing the electrostatic field control body based on the parameters determined in steps (1) and (2).
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.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
REFERENCES:
patent: 4877998 (1989-10-01), Maninger et al.
patent: 5066887 (1991-11-01), New
patent: 5430349 (1995-07-01), New et al.
patent: 6222310 (2001-04-01), Mera et al.
patent: 6255767 (2001-07-01), Lee et al.
Fleshner & Kim LLP
Harper Holly
Patel Nimeshkumar D.
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