Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
1998-08-18
2001-01-09
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S412000, C313S426000
Reexamination Certificate
active
06172450
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an inline 3-beam color cathode-ray tube electron gun for use as a color image receiving tube or a color cathode-ray tube comprising a color display device and so on.
At present, there is an increasing demand of improving a resolution of a color cathode-ray tube. In particular, a problem concerning a shape of an electron beam spot at the periphery of a picture screen receives a remarkable attention.
In general, a resolution characteristic of a color cathode-ray tube considerably depends upon the size and shape of an electron beam on the fluorescent screen serving as a screen. That is, if the diameter of this electron beam spot were not small and were not close to a real circle, a satisfactory resolution characteristic could not be obtained.
As a deflection angle of an electron beam increases, an electron beam passage ranging from a cathode-ray tube electron gun to a fluorescent screen is extended. Therefore, if a focusing voltage is maintained in order to obtain an electron beam spot of a small diameter and of a real circle at the central portion of the fluorescent screen, the electron beam at the peripheral portion of the fluorescent screen is placed in the so-called over-focusing state. As a consequence, an electron beam spot of a small diameter and of a real circle cannot be obtained at the peripheral portion of the fluorescent screen so that a satisfactory resolution cannot be obtained.
To solve the above-mentioned problem, there is recently proposed a dynamic focusing system cathode-ray tube electron gun in which a main lens action is weakened by increasing a focusing voltage relative to electron beams bombarded on the peripheral portion of the fluorescent screen as the deflection angle of the electron beam increases.
This dynamic focusing system, however, is not so suitable for the inline 3-beam system cathode-ray tube electron gun without modification. That is, in the prior-art inline 3-beam system cathode-ray tube electron gun in which three cathodes are aligned on one linear line in the horizontal direction, when deflection magnetic fields of a deflection yoke are equal, a vertically-arcuate convergence error (i.e. over-convergence) occurs in the upper, lower, right and left peripheral portions of the fluorescent screen.
Accordingly, a dynamic convergence is executed under the condition that a horizontal deflection magnetic field distribution obtained by the deflection yoke is presented as a pin-cushion-like distribution and that a vertical deflection magnetic field distribution is presented as a barrel-like distribution.
However, when the deflection yoke thus arranged is in use, electron beams deflected toward the peripheral portions of the fluorescent screen after they had passed the deflection yoke are subjected to a convergence action (convex lens effect) in the vertical direction (longitudinal direction) thereof and also subjected to a divergence action (concave lens effect) in the horizontal direction (lateral direction) thereof.
As a result, an electron beam spot at the peripheral portions of the fluorescent screen does not become a real circle but becomes oblong. There is then the problem that the electron beam spot is distorted in the left and right peripheral portions of the fluorescent screen and that the focusing characteristic is deteriorated.
In order to solve the aforementioned problems, Japanese laid-open patent publications Nos. 61-99249, 62-237642 or Japanese laid-open patent publication No. 3-93135, etc. proposed cathode-ray tube electron guns having a so-called electrostatic quadruple lens (hereinafter simply referred to as “quadruple lens”) incorporated therein.
FIG. 1
is a schematic diagram showing an arrangement of a color cathode-ray tube electron gun incorporating a quadruple lens used widely.
As shown in
FIG. 1
, an electron gun
70
includes three cathodes KR, KG, KB parallelly arrayed in an inline fashion. A first electrode
11
, a second electrode
12
, a third electrode
13
, a fourth electrode
14
, a fifth electrode, a sixth electrode
16
and a shield cup
17
are coaxially disposed from this cathode K (KR, KG, KB) to the anode side, in that order. Then, the fifth electrode is halved to provide a 5-1th electrode
51
and a 5-2th electrode
52
. The second electrode
12
and the fourth electrode
14
are connected with each other electrically.
In this color cathode-ray tube electron gun
70
, a constant focusing voltage V
F
is applied to the 5-1th electrode
51
. On the other hand, a voltage (V
F
+V
DF
) in which a parabolic waveform dynamic focusing voltage VDF (see
FIG. 4
) synchronized with the horizontal deflection of the focusing voltage V
F
and the focusing voltage VF are superimposed upon each other is applied to the third electrode
14
and the 5-2th electrode
52
.
Thus, a quadruple lens (not shown) is formed between the 5-1th electrode
51
and the 5-2th electrode
52
, and this quadruple lens causes an intensity change of a focusing lens formed between the 5-2th electrode
52
and the sixth electrode
16
. As a result, it is possible to obtain satisfactory shapes of electron beams on the left and right peripheral portions of the fluorescent screen.
On the surface of the 5-1th electrode
51
opposing the 5-2th electrode
52
is disposed a plate
151
in which there are defined vertically-oblong electron beam passing apertures
151
A,
151
B,
151
C shown in FIG.
3
A. On the other hand, on the surface of the 5-2th electrode
52
opposing the 5-1th electrode
51
is disposed a plate
152
in which there are defined horizontally-oblong electron beam passing apertures
152
A,
152
B,
152
C shown in FIG.
3
B.
FIG. 2
is a schematic diagram showing an arrangement of a color cathode-ray tube electron gun incorporating a quadruple lens used widely.
While the fifth electrode is halved to provide the 5-1th electrode
51
and the 5-2th electrode
52
in the electron gun
70
shown in
FIG. 1
, in an electron gun
80
shown in
FIG. 2
, the fifth electrode
5
is divided by three to provide the 5-1th electrode
51
, the 5-2th electrode
52
and a 5-3th electrode
53
as shown in
FIG. 2. A
rest of the arrangement of the electron gun
80
is similar to that of the electron gun
70
shown in FIG.
1
. Therefore, in
FIG. 2
, elements and parts identical to those of
FIG. 1
are marked with the same reference numerals and need not be described in detail.
In this color cathode-ray tube electron gun
80
, as shown in
FIG. 2
, the constant focusing voltage VF is applied through a stem portion to the central 5-2th electrode
52
of the fifth electrode thus divided by three. On the other hand, the voltage (V
F
+V
DF
) in which the dynamic focusing voltage VDF (see
FIG. 4
) synchronized with the horizontal deflection of the focusing voltage VF and the focusing voltage VF are superimposed upon each other is applied to the third electrode
13
and the 5-1th electrode
51
and the 5-3th electrode
53
located in the outside of the fifth electrode thus divided by three.
Thus, two quadruple lenses (not shown) which are adapted to act in the opposite directions, respectively, are formed between the 5-1th electrode
51
and the 5-2th electrode
52
and between the 5-2th electrode
52
and the 5-3th electrode
53
. The two quadruple lenses causes an intensity change of a focusing lens (not shown) formed between the 5-3th electrode
53
and the sixth electrode
16
. As a result, shapes of electron beams in the left and right peripheral portions of the fluorescent screen may become more satisfactory, i.e. may become substantially close to the shape of the electron beam in the central portion of the fluorescent screen.
On the surface of the 5-1th electrode
51
opposing the 5-2th electrode
52
and the surface of the 5-2th electrode
52
opposing the 5-3th electrode
53
is disposed the plate
151
on which there are defined the vertically-oblong electron beam passing apertures
151
A,
151
B,
151
C as shown in FIG.
3
A.
On the other hand, on the surface of the 5-2th electrod
Amano Yasunobu
Natori Makoto
Kananen Ronald P.
Patel Vip
Rader Fishman & Grauer
Sony Corporation
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