Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2000-06-21
2003-01-07
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S368180, C315S368210
Reexamination Certificate
active
06504324
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an in-line-three-beam-system color-cathode-ray-tube electron gun used for a color cathode-ray tube constituting a color picture tube or a color display unit and a color cathode-ray tube provided with the electron gun.
2. Description of the Related Art
A request for better resolution of a color cathode-ray tube is increasingly raised at present. Particularly, a problem of a spot shape of an electron beam around a screen is greatly focused on.
Moreover, a problem that preferable shapes of three electron beams cannot be obtained at the same time because a focus-voltage difference occurs between the three electron beams around a screen is particularly noticed.
This causes a generally observed phenomenon that a red character becomes unclear on the right side of a screen of a display monitor and a blue character becomes unclear at the left side of the screen.
To solve the above problem, a color-cathode-ray-tube electron gun having so-called built-in quadrupole lens is proposed.
FIG. 1
shows a schematic block diagram of a generally-widely-used, color-cathode-ray-tube electron gun having a built-in quadrupole lens.
The electron gun
70
has three cathodes K
R
, K
G
, and K
B
in-line-arranged in parallel, and 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 arranged in order from the cathodes (K
R
, K
G
, and K
B
) toward an anode. Moreover, the fifth electrode is divided into a (
5
-
1
)th electrode
51
and a (
5
-
2
)th electrode
52
. Furthermore, the second electrode
12
and the fourth electrode
14
are electrically connected to each other.
In the case of the color-cathode-ray-tube electron gun
70
, a fixed-focus voltage (first focus voltage) Ef
1
is applied to the third electrode
13
and the (
5
-
1
)th electrode
51
through a stem portion.
Moreover, a second focus voltage Ef
2
, on which a parabolic(so-called parabola-shaped)-waveform voltage horizontally-deflectively synchronizing with the first focus voltage Ef
1
is superimposed, is applied to the (
5
-
2
)th electrode
52
.
Thereby, a quadrupole lens (not illustrated) is formed between the (
5
-
1
)th electrode
51
and the (
5
-
2
)th electrode
52
and, moreover, the quadruole lens causes an intensity change in a focus lens (not illustrated) formed between the (
5
-
2
)th electrode
52
and the sixth electrode
16
.
As a result, it is possible to form electron beams in the peripheral portions in the right and left directions of a fluorescent screen into preferable shapes.
FIG. 2
shows a schematic view of a color cathode-ray tube.
As shown in
FIG. 2
, three electron beams R, G, and B emitted from an electron gun
1
and colliding with circumferential portions of a fluorescent screen on the right and left sides are located away from each other in a magnetic field of a deflection yoke. Therefore, the directions and intensities of a magnetic field received by three electron beams are different from each other.
Therefore, the distortion states of electron beam spots at the right and left circumferential portions of the fluorescent screen
4
are different from each other among three electron beams R, G, and B. In
FIG. 2
, symbol
3
denotes a glass bulb. Moreover, “Right Side of Screen” and “Left Side of Screen” denote the right side and the left side of the fluorescent screen
4
of the color cathode-ray tube when observing the screen
4
from the outside.
The focus voltage is usually set so that the shape of the spot of the central electron beam G among three electron beams R, G, and B becomes optimum.
In this case, when the three electron beams R, G, and B collide with the right side of the fluorescent screen
4
, the red electron beam R passes through further outside of a deflection magnetic field formed by the deflection yoke
2
than the electron beams G and B and is greatly influenced by the deflection magnetic field. As a result, the distortion of the beam spot of the electron beam R on the fluorescent screen
4
becomes larger than those of the electron beams G and B.
Moreover, when the three electron beams R, G, and B collide with the left side of the fluorescent screen
4
, the blue electron beam B passes through further outside of a deflection magnetic field formed by the deflection yoke
2
than the electron beams G and R and is greatly influenced by the deflection magnetic field. As a result, the distortion of the beam spot of the electron beam B on the fluorescent screen
4
becomes larger than those of the electron beams R and G.
Therefore, in the case of a display monitor, particularly a recent, large, color-display monitor having a high resolution, a phenomenon occurs that a red character becomes unclear at the right side of a screen and a blue character becomes unclear at the left side of the screen, as described above.
It can be said that the phenomenon occurs because a difference is produced around a screen among focus voltages of three electron beams R, G, and B.
Therefore, as one of the means for solving the problems, a color-cathode-ray-tube electron gun his been previously proposed which provides lens effects different in intensity for a red electron beam R and a blue electron beam B (refer to Japanese Patent Laid-Open Nos. Hei 11-067120 and Hei 11-149885).
FIG. 3
shows an electrode arrangement of a configuration of the above previously-proposed, color-cathode-ray-tube electron gun.
The electron gun
50
has three cathodes K
R
, K
G
, and K
B
in-line-arranged in parallel, and a first electrode
11
, a second electrode
12
, a third electrode
13
, a fourth electrode
14
, a fifth electrode (to be described later), a sixth electrode
16
, and a shield cup
17
are coaxially arranged in order from the cathodes (K
R
, K
G
, and K
B
) toward an anode. Moreover, the second electrode
12
and the fourth electrode
14
are electrically connected to each other.
The fifth electrode corresponding to a focus electrode is divided into a (
5
-
1
)th electrode
51
and a (
5
-
2
)th electrode
52
. Moreover, the (
5
-
1
)th electrode
51
is divided into a (
5
-
1
A)th electrode
51
A, (
5
-
1
B)th electrode
51
B, and a (
5
-
1
C)th electrode
51
C.
A first quadrupole lens is constituted by the (
5
-
1
A)th electrode
51
A, the (
5
-B)th electrode
51
B, and the (
5
-
1
C)th electrode
51
C, and a second quadrupole lens is constituted by the (
5
-
1
C)th electrode
51
C and the (
5
-
2
)th electrode
52
. Moreover, the quadruple-electrode action of the second quadrupole lens is controlled by the first quadrupole lens.
A fixed focus voltage (first focus voltage) Ef
1
is applied to the third electrode
13
and the (
5
-
1
A)th electrode
51
A and the (
5
-
1
C)th electrode
51
C outside of the three-divided (
5
-
1
)th electrode
51
. A third focus voltage Ef
3
on which a voltage having a waveform voltage having a shape similar to serration synchronizing with horizontal deflection (refer to
FIG. 4
) and the fixed focus voltage Ef
1
are superimposed is applied to the (
5
-
1
B)th electrode
51
B. Moreover, a second focus voltage Ef
2
on which a parabolic-waveform voltage synchronizing with horizontal deflection (refer to
FIG. 4
) and the fixed focus voltage Ef
1
are superimposed is applied to the (
5
-
2
)th electrode
52
.
These three focus voltages Ef
1
, Ef
2
, and Ef
3
are normally supplied from a system portion at the front end of the electron gun
50
.
A waveform of the third focus voltage Ef
3
can be a waveform having a shape similar to the serration shown and linearly changing, as shown in
FIG. 5A
, or a sinusoidal waveform intermittently generated every horizontal deflection cycle, as shown in FIG.
5
B.
The (
5
-
1
A)th electrode
51
A, the (
5
-
1
)th electrode
51
B, and the (
5
-
1
C)th electrode
51
C are respectively provided with three electron-beam passing bores.
In the case of the above previously-proposed, color-cathode-ray-tube electron gun, it is possible to indep
Amano Yasunobu
Natori Makoto
Kananen, Esq. Ronald P.
Philogene Haissa
Rader & Fishman & Grauer, PLLC
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