Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
1999-02-18
2003-07-22
Font, Frank G. (Department: 2877)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S412000, C313S413000, C315S368110
Reexamination Certificate
active
06597096
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inline three-beam system color cathode-ray tube electron gun for use with a color cathode-ray tube comprising a color picture tube, a color display device or the like.
2. Description of the Related Art
At present, as the demand for a high-resolution color cathode-ray tube increases, a problem concerning the spot shape of the electron beam at, in particular, a peripheral surface of the screen becomes significant.
Also, a problem occurs in which a difference occurs in focusing voltages among three electron beams at, in particular, the peripheral surface of the screen so that satisfactory spot shapes of the three electron beams cannot be obtained at the same time.
This causes a phenomenon in which red characters become unclear on the right-had side of the screen and blue characters become unclear on the left-hand side of the screen in a display monitor.
In order to solve such problems, there is proposed a color cathode-ray tube electron gun which houses a so-called quadrupole lens.
FIG. 1
shows a diagram of a conventional color cathode-ray tube electron gun housing a quadrupole lens.
This electron gun
70
includes three cathodes K
R
, K
G
, K
B
which are parallely arrayed in an inline-fashion. From the cathodes K (K
R
, K
G
, K
B
) to the anode side, there are coaxially disposed a first electrode
11
, a second electrode
12
, a third electrode
13
, a fourth electrode
14
, a fifth electrode
51
,
52
, a sixth electrode
16
and a shield cap
17
, in that order. Then, the fifth electrode is divided by half to provide a first sub-electrode
51
and a second sub-electrode
52
. Also, the second electrode
12
and the fourth electrode
14
are connected electrically.
In this color cathode-ray tube electron gun
70
, a constant first focusing voltage Ef
1
is applied through a stem portion to the third electrode
13
and the sub-electrode
51
.
On the other hand, a second focusing voltage Ef
2
in which a waveform voltage of a parabolic waveform synchronized with a horizontal deflection is superimposed upon the first focusing voltage Ef
1
, is applied to the other sub-electrode
52
.
Thus, a quadrupole lens (not shows) is formed between the first sub-electrode
51
and the second sub-electrode
52
. In addition, this quadrupole lens cases a change of intensity to occur in a focusing lens formed between the sub-electrode
52
and the sixth electrode
16
.
As a result, shapes of electron beams at the left and right peripheral portions of the fluorescent screen may be made satisfactory.
Also,
FIG. 1
shows the electron gun of a QPF (Quadra Potential Focus) type. The following is also true in bipotential type electron gun without the fourth electrode
14
and a unipotential type electron gun.
Subsequently,
FIG. 2
shows a schematic diagram of a color cathode-ray tube.
As shown in
FIG. 2
, three electron beams R, G, B are emitted from an electron gun
1
and impinge upon the left-hand side of the screen
4
and the right-hand side of the screen at peripheral portions of the fluorescent screen
4
. Because these three beams are respectively placed at different positions in a magnetic field of a deflection yoke
2
, the directions and intensities of the magnetic field applied to the three electron beams are different.
Accordingly, the distorted states of electron beam spots at the left and right peripheral portions of the fluorescent screen
4
become different in the three electron beams R, G, B. Incidentally, reference number
3
in the figure denotes a glass bulb. Also, “right-hand side of screen” and “left-hand side of screen” mean the right-hand side and the left-hand side obtained when the fluorescent screen
4
of the color cathode-ray tube is observed from the outside, respectively.
In general, the focusing voltage or the like is set in such a manner that the spot shape of the center electron beam G of the three electron beams R, G, B becomes optimum.
In this case, when the three electron beams R, G, B impinge upon the right-hand side of the fluorescent screen
4
, the red electron beam R passes a relatively outer side of a deflection magnetic field formed by the deflection yoke
2
as compared with the electron beams G and B, and is strongly affected 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 that of the other electron beams G, B.
On the other hand, when the three electron beams R, G, B impinge upon the left-hand side of the fluorescent screen
4
, the blue electron beam B passes a relatively outer side of the deflection magnetic field formed by the deflection yoke
2
as compared with the electron beams G and R, and is strongly affected 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 that of the other electron beams R, G.
Accordingly, in a display monitor, in particular, a large color display monitor having a high resolution, phenomenon, red characters become unclear on the right-hand side screen and blue characters become unclear on the left-hand side screen as mentioned before.
This phenomenon may be expresses such that the respective focusing voltages of the three electron beams R, G, B differ from each other on the peripheral portions of the screen.
For this reason, as a means for solving this problem, there was previously proposed a color cathode-ray tube electron gun for applying lens effects of different intensities to a red electron beam R and a blue electron beam B (see Japanese patent application No. 9-228268, Japanese patent application No. 9-313940, etc.).
FIG. 3
shows an example of an electrode layout of the previously-proposed color cathode-ray tube electron gun mentioned above.
This electron gun
50
includes three cathodes K
R
, K
G
, K
B
that are parallelly arrayed in an inline-fashion. From the cathodes K (K
R
, K
G
, K
B
) to the anode side, there are coaxially disposed a first electrode
11
, a second electrode
12
, a third electrode
13
, a fourth electrode
14
, a fifth electrode
51
,
52
, a sixth electrode
16
and a shield cap
17
, in that order. The second electrode
12
and the fourth electrode
14
are electrically connected.
The fifth electrode corresponding to a focusing electrode is halved to provide a first sub-electrode
51
and a second sub-electrode
52
. Further, the first sub-electrode
51
is trisected to provide a
5
-
1
Ath electrode
51
A, a
5
-
1
Bth electrode
51
B and a
5
-
1
Cth electrode
51
C.
The
5
-
1
Ath electrode
51
A, the
5
-
1
Bth electrode
51
B and the
5
-
1
Cth electrode
51
C constitute a first quadrupole lens. Also, the
5
-
1
Cth electrode
51
C and the
5
-
2
th electrode
52
constitute a second quadrupole lens. Then, the quadrupole lens action of the second quadrupole lens is controlled by the first quadrupole lens.
A fixed focusing voltage Ef
1
is applied to the third electrode
13
and the
5
-
1
Ath electrode
51
A and the
5
-
1
Cth electrode
51
C disposed outside the trisected electrode
51
. A third focusing voltage Ef
3
, in which a waveform voltage (see
FIG. 4
) of a shape similar to a sawtooth synchronized with a horizontal deflection and the fixed focusing voltage Ef
1
are superimposed upon each other, is applied to the
5
-
1
Bth electrode
51
B. Also, a second focusing voltage Ef
2
, in which a waveform voltage (see
FIG. 4
) of a parabolic shape synchronized with the horizontal deflection and the fixed focusing voltage Ef
1
are superimposed upon each other, is applied to the electrode
52
.
These three focusing voltages EF
1
, Ef
2
, Ef
3
are generally applied from a stem portion of the tip end of the electron gun
50
.
Incidentally, the waveform of the third focusing voltage Ef
3
may be a waveform which linearly changes in the form similar to a sawtooth shown in
FIG. 5A
or a waveform of a sine wave shape which intermittently occurs once per period of a horizontal deflection period
Amano Yasunobu
Kikuchi Norifumi
Natori Makoto
Font Frank G.
Kananen, Esq. Ronald P.
Punnoose Roy M.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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