Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
2000-07-11
2003-08-19
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S413000, C313S440000
Reexamination Certificate
active
06608435
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-197203, filed Jul. 12, 1999; and No. 2000-126072, filed Apr. 26, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a cathode ray tube apparatus. In particular, the present invention relates to a cathode ray tube apparatus incorporating an electron gun assembly capable of compensating for dynamic astigmatism.
In general, a color picture tube
11
, as shown in
FIG. 1
, has an envelope consisting of a panel
10
and a funnel
14
coupled integrally with this panel. On an interior face of this panel
14
, there is formed a phosphor screen consisting of a stripe or dot shaped three-color phosphor layer that emits blue, green, and red lights, that is, a target
12
. A shadow mask
13
having a number of apertures at its inside is mounted in opposite to this phosphor screen
12
. On the other hand, an electron gun assembly
17
for emitting three electron beams
16
B,
16
G, and
16
R is arranged in a neck
15
of the funnel
14
. Then, the three electron beams
16
B,
16
G, and
16
R emitted from this electron gun assembly
17
are deflected by horizontal and vertical deflecting magnetic fields generated from a deflection yoke
19
mounted on the funnel
14
, and are directed to the shadow mask
13
. The phosphor screen
12
is scanned horizontally and vertically with the electron beams
16
B,
16
G, and
16
R passing through the shadow mask
13
so that a color image is displayed.
In such a color picture tube, in particular, an electron gun assembly
17
has an inline type structure for emitting three electron beams
16
B,
16
G, and
16
R in line, consisting of a center beam
16
G and a pair of side beams
16
B and
16
R on both sides thereof. In addition, a side beam through hole of a grid located at a relatively low voltage side and a side beam through hole of a grid located at a high voltage side grid, both forming a main lens portion of the electron gun assembly are not aligned and are eccentrically arranged. As a result, there is widely used practically a self convergence system inline type color picture tube in which three electron beams are converged at a screen center, a pin cushion shaped horizontal deflection magnetic field and a barrel shaped vertical deflection magnetic field are generated by a deflection yoke
19
, and the three electron beams
16
B,
16
G, and
16
R emitted in line are self converged on a screen area.
In such a self-convergent inline type color cathode ray tube, the electron beams passing through the non-uniform magnetic field is subject to the astigmatism. For example, as shown in
FIG. 2A
, the electron beams
16
B,
16
G, and
16
R are subjected to forces indicated by arrows
3
H and
3
V by the pin cushion shaped magnetic field
1
. As a result, as shown in
FIG. 2B
, a beam spot
4
of an electron beam is distorted on the periphery of the phosphor screen. The deflection aberration to which these electron beams are subjected occurs because the electron beams enter an excessively focused state in the vertical direction, and a halo
5
(blurring) is generated in the vertical direction. The deflection aberration to which the electron beams are subject becomes greater as the tube becomes larger, and the deflection becomes wider. Then, the resolution of the phosphor screen periphery is significantly degraded.
Means for solving degradation of the resolution due to such deflection aberration is disclosed in Japanese Patent Application Laid-open Nos. 61-99249, 61-250934, and 2-72546. These electron gun assemblies each, as shown in
FIG. 3
, consist of a first grid G
1
to a fifth grid G
5
. An electron beam generating section GE, a quadruple lens QL, and a final focusing lens EL are formed along the traveling direction of the electron beam. As shown in FIG.
4
A and
FIG. 4B
, two trios of asymmetrical electron beam through holes
7
B,
7
G,
7
R,
8
B,
8
G,
8
R each are provided on an opposite face of the respective grids G
3
and G
4
, and the quadruple lens QL of each electron gun assembly is formed.
The lens powers of these quadruple lens QL and final focusing lens EL are changed in synchronism with the magnetic field of the deflection yoke, whereby the deflection aberration applied to the electron beams deflected at the periphery of the screen due to the deflection magnetic field is corrected. In this manner, a beam spot having a good spot shape in the screen can be obtained.
However, even if such correcting means is provided, the deflection aberration due to the deflection yoke is strong. Even if a halo portion of the electron spot can be eliminated, but the horizontal elongated phenomenon in which the electron beam spot is deformed in a horizontal direction cannot be corrected. In order to correct this horizontal elongation phenomenon, it is required not only to correct the deflection aberration due to the quadruple lens QL, but also to correct the beam shape at an electron beam generating section in synchronism with the deflection magnetic field.
Such color picture tube apparatuses are disclosed in U.S. Pat. No. 4,319,163 and Japanese Patent Application Laid-open No. 8-87967. In these color picture tube apparatuses disclosed in these publications, a second grid is divided into two sections. A grid on the first grid side of the second grid has a circular electron beam through hole, and a grid on a third grid side of the second grid has an horizontally elongated electron beam through hole. In an electron gun assembly of this tube apparatus, a focusing power of a main lens portion is changed, and a dynamic voltage synchronized with a deflection current of a deflection device is applied to the grid on the third grid side. According to such color picture tube apparatus, at a triode portion for generating electron beams, electron beams are dynamically controlled in synchronism with the deflection current of the deflection device, and the focused states of the main lens and the quadruple lens arranged at the main lens are changed. Therefore, according to such structured electron gun assembly, a horizontal deformed phenomenon can be eliminated more significantly, and electron beams can be focused at the periphery of the screen more properly than a conventional dynamic focus electron gun assembly in which the focused states of the main lens and the quadruple lens disposed in the vicinity of the main lens are changed.
However, in the color picture tube device disclosed in the aforementioned publication, from the outside of the color picture tube apparatus, it is required to apply a focus voltage having an intermediate level; a dynamic focus voltage which increases in synchronism with the deflection current of the deflection device with the focus voltage having the intermediate level being a reference; a acceleration voltage having low level applied to the grip on the first grid side of the second grid; and a dynamic focus voltage that increases in synchronism with the deflection current of the deflection device applied to the third grid side of the second grid with this low level acceleration voltage being a reference.
In such electron gun assembly, in comparison with an electron gun assembly for a color picture tube device it is required to newly apply a dynamic focus that performs general dynamic focus, voltage that increases in synchronism with the deflection current of the deflection device with the acceleration voltage having the low level being a reference. In addition, it is required to newly provide a lead wire for supplying a voltage to a stem portion. For this reason, there is a possibility of lowering withstanding voltage characteristics due to an addition of this lead wire, and there is a problem in reliability. In addition, in the color picture tube apparatus provided with this lead wire, re-designing of the stem portion is required. Further, in a driving device for supplying a voltage also, it is requi
Kimiya Junichi
Ookubo Syunji
Patel Ashok
Zimmerman Glenn
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