Electric lamp and discharge devices: systems – Cathode ray tube circuits – Plural concentrating – accelerating – and/or de-accelerating...
Reexamination Certificate
2003-05-02
2004-02-24
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Plural concentrating, accelerating, and/or de-accelerating...
C315S368150, C315S382000, C313S414000, C313S419000
Reexamination Certificate
active
06696789
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a color picture tube device configured to obtain a high resolution across a whole screen of a picture tube. More specifically, the present invention relates to an electron gun used in the color picture tube device.
FIELD OF THE INVENTION
A color picture tube is required to have a high resolution.
FIG. 8
shows an example of a conventional electron gun providing a high resolution color picture tube with a reliable and simple configuration, which is disclosed in JP 07(1995) 6706. As shown in
FIG. 8
, an electron gun
100
has cathodes
101
, a control electrode
102
, an accelerating electrode
103
, a G
3
electrode
104
, a first focusing electrode
105
, a second focusing electrode
106
, a final accelerating electrode
107
and a shield cup
108
, which are arranged in this order. The accelerating electrode
103
and the G
3
electrode
104
form a prefocus lens, while the second focusing electrode
106
and the final accelerating
107
form a main lens.
A constant voltage Vg
3
(9.0 kV) is applied to the G
3
electrode
104
, while a constant voltage Vfoc
2
(6.5 kV) and a dynamic voltage Vd superimposed thereon are applied to the second focusing electrode
106
, thereby keeping a relationship of Vg
3
>Vfoc
2
.
The dynamic voltage, which is 0V when the deflection angle of an electron beam is 0, will rise gradually with the increase of the deflection angle. This strengthens a quadrupole lens electric field formed by the first focusing electrode
105
and the second focusing electrode
106
.
In this configuration, the voltage Vg
3
at the prefocus lens side can be applied separately from the voltage Vfoc
2
configuring a main lens at the low voltage side. Thereby, the voltage Vfoc
2
can be set lower than Vg
3
while maintaining the level of the voltage Vg
3
. In this manner, the characteristics of the prefocus lens are maintained and a reliable color picture tube device having a high resolution can be provided.
In such a conventional electron gun, a sufficient potential difference is maintained between the voltage Vg
3
(9.0 kV) and a voltage of the accelerating electrode
103
, as the voltage of the accelerating electrode
103
is equal to the voltage Vfoc
1
(600 V) applied to the first focusing electrode
105
. However, a potential difference between the first focusing electrode
105
(600 V) and the second focusing electrode
106
(6.5 kV) is increased, causing the formation of a considerably strong quadrupole lens when an electron beam is not deflected. As a result, the quadrupole lens will have an increased astigmatism, limiting a reduction of the spot diameter of the electron beam on the screen.
Moreover in this configuration, Vfoc
1
is lower than Vfoc
2
under a non-deflection condition, and the dynamic voltage Vd is raised gradually with the increase in the deflection angle so as to change the quadrupole lens, and thus the sensitivity in correcting the deflection astigmatism with respect to the dynamic voltage is inferior.
SUMMARY OF THE INVENTION
In order to solve the above-described problems in conventional techniques, an object of the present invention is to provide a color picture tube device with a small beam spot diameter to provide a high resolution.
For achieving the above-described object, a first color picture tube device according to the present invention has an electron gun including cathodes, a control electrode, an accelerating electrode, a G
3
electrode, a first focusing electrode, a second focusing electrode and a final accelerating electrode that are arranged in this order. A voltage applied to the G
3
electrode is obtained by dividing with a resistor a voltage applied to the final accelerating electrode, and a relationship represented as Va>Vg
3
>Vfoc
2
is satisfied when an electron beam is not deflected, where Va denotes the voltage applied to the final accelerating electrode, Vg
3
denotes the voltage applied to the G
3
electrode, and Vfoc
2
denotes a voltage applied to the second focusing electrode.
A second color picture tube device according to the present invention has an electron gun including cathodes, a control electrode, an accelerating electrode, a G
3
electrode, a first focusing electrode, a second focusing electrode and a final accelerating electrode that are arranged in this order. A voltage applied to the G
3
electrode is obtained by dividing with a resistor a voltage applied to the final accelerating electrode, a relationship represented as Vg
3
>9 kV is satisfied, and a relationship represented as Va>Vg
3
>Vfoc
1
>Vfoc
2
is satisfied when an electron beam is not deflected, where Va denotes the voltage applied to the final accelerating electrode, Vg
3
is a voltage applied to the G
3
electrode, Vfoc
1
denotes a voltage applied to the first focusing electrode and Vfoc
2
denotes a voltage applied to the second focusing electrode.
REFERENCES:
patent: 4935663 (1990-06-01), Shimoma et al.
patent: 7-6706 (1995-01-01), None
Ohta Kazunori
Sukeno Masahiko
Ueda Yasuyuki
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Vu David
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