Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
2001-06-12
2004-01-06
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S409000
Reexamination Certificate
active
06674227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron gun for a cathode-ray tube and, more particularly, to the structure of control and accelerating electrodes corresponding to a triode of an electron gun, which is for reducing the spot size of an electron beam in a high current region of a cathode-ray tube with high picture quality that requires high resolution.
2. Description of the Related Art
As shown in
FIG. 1
, a general color cathode-ray tube includes a panel
10
having a fluorescent film
11
formed on the inner side thereof, a funnel
12
formed at the rear of the panel, being combined with it, a neck
20
connected to the funnel at the back of the funnel, having an electron gun
30
placed thereinside, a deflection yoke
18
located on the outer surface of the funnel to deflect electron beams upward, downward, left and right, a shadow mask
14
placed inside the panel to perform sorting of colors, and a frame
16
supporting the shadow mask to fix it to the panel.
In the cathode-ray tube constructed as above, hot electrons are emitted from cathodes of the electron gun
30
when a video signal is applied to the electron gun
30
. The emitted electrons are accelerated and focused toward the panel
10
according to a voltage applied thereto from electrodes of the electron gun. Here, the traveling path of the electron beams is adjusted by the magnetic field of a magnet set at the neck
20
, and the electron beams whose traveling path was controlled scan the fluorescent film
11
formed on the inner surface of the panel
10
according to the deflection yoke
18
. The deflected electron beams are subjected to color sorting while passing through lots of holes of the shadow mask
14
. The color-sorted electron beams collide with the fluorescent film
11
to emit lights, presenting the video signal.
The in-line electron gun
30
placed inside the neck
20
includes control, accelerating and focusing electrodes which are located perpendicular to the traveling path of the electron beams, having a predetermined distance between neighboring electrodes, such that the electron beams generated from the cathodes can be controlled by a voltage with a predetermined level applied by the electrodes to arrive at the screen. Referring to
FIG. 2
, the conventional electron gun
30
for the cathode-ray tube has a tri-electrodes part
33
, a front focusing lens part
34
, and a main lens part
35
. The tri-electrodes part
33
consists of three R, G, B cathodes
31
, the control electrode G
1
serving as a common grating of the three cathodes, being placed having a predetermined distance from the cathodes, and the accelerating electrode G
2
located having a predetermined distance from the control electrode.
The front focusing lens part
34
is constructed of a front focusing electrode G
3
placed a predetermined interval from the accelerating electrode G
2
, and a second accelerating electrode G
4
arranged a predetermined distance from the front focusing electrode G
3
. The main lens part
35
includes a focusing electrode
05
located a predetermined distance from the second accelerating electrode and an anode
06
placed a predetermined distance from the accelerating electrode. The upper and lower portions of the aforementioned electrodes are inserted into a support called bead glass
39
, being fixed having a predetermined interval. A shield cup
37
as a shield electrode for shielding and weakening leakage magnetism of the deflection yoke
18
is formed at the end of the anode G
6
.
The electron gun
30
having the above-described structure generates hot electrons when a heater
32
included in the cathode
31
is heated, and these generated electrons form electron beams (R, G, B). After the amount of emission of the electron beams is determined by the control electrode G
1
, the electron beams emitted are accelerated by the accelerating electrode G
2
and subjected to repeated focusing and accelerating processes while passing through the front focusing lens part
34
and the main lens part
35
, to be finally deflected by the deflection yoke
18
horizontally or vertically to scan the fluorescent plane
11
.
The control electrode G
1
of the tri-electrodes part
33
is grounded and the accelerating electrode G
2
is provided with a voltage of 500-1000V The anode G
6
of the main lens part
35
accepts a high voltage of 25-35 kV and the focusing electrode G
5
is provided with an intermediate voltage of 20-30% of the voltage applied to the anode G
6
. Furthermore, the accelerating electrode G
2
and the second accelerating electrode G
4
are supplied with the same voltage and the front focusing electrode G
3
and the focusing electrode GS are provided with the same voltage.
In general, the size of the spot at which the electron beam is focused depends on a spherical aberration generated when the electron beam passes through a passage hole of each electrode. The spot size of electron beam increases due to large spherical aberration, so that the sharpness of the electron beam is reduced, to result in deteriorate the resolution.
In the general cathode-ray tube using the in-line electron gun, three electron beams of red, green and blue are horizontally arranged in parallel. This requires a magnetism-concentrating type deflection yoke using a non-uniform magnetic field in order to converge the three electron beams on one point of the fluorescent plane
11
. The distribution of the magnetic field generated by the magnetism-concentrating deflection yoke
18
has a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field, to prevent misconvergence on the fluorescent plane
This magnetic field has a two-pole component and a four-pole component. The two-pole component deflects the electron beams in a horizontal or vertical direction and the four-pole component performs not only the horizontal or vertical deflection but also prevention of misconvergence. However, these components focus the electron beams in a direction of deteriorating the resolution, that is, vertical direction, diverge the electron beams in the horizontal direction, to result in generation of astigmatism, distorting the spot of the electron beam. This distorted electron beam generates haze called phenomenon spreading of beam phase at its core and the top and bottom thereof, bringing about deterioration in the resolution at the marginal area of the screen. To solve this problem, a horizontally long groove (A) is formed at the accelerating electrode G
2
, as shown in FIG.
3
B.
The electrodes of the electron gun have the electron beam (R, G, B) passage holes formed having a predetermined eccentric distance SI as shown in
FIGS. 3A and 3B
. The electron beams travel having a predetermined eccentric distance among them, and focus on one point of the fluorescent plane
11
when they proceed to the panel from the main lens part
34
. In case of the conventional electron gun, the diameter of the beam passage hole of the control electrode G
1
generally corresponds to 0.5-0.6 mm and that of the accelerating electrode G
2
is similar to that of the control electrode G
1
or increased by about 10% of thereof. Recently, the holes of the control electrode G
1
and the accelerating electrode G
2
have a square shape not the circular one to improve the resolution.
According to a tendency of enlargement of cathode-ray tube size and high resolution of the cathode-ray tube, a high-precision shadow mask is adopted in order to accomplish high resolution required for HDTV, for example, to realize high quality broadcasting and monitoring. The achievement of high resolution also needs a decrease in the spot size corresponding to the pixel size. To reduce the spot size of the electron beam, the effective aperture of the main lens is increased or the diameter of the beam passage hole of the control electrode G
1
is reduced. However, the reduction in the diameter of the beam passage hole of the control electrode G
1
shortens the distance between the catho
Kim Hyun-Cheol
Kim Tae-Kyu
Fleshner & Kim LLP
LG Electronics Inc.
Patel Ashok
Zimmerman Glenn D.
LandOfFree
Electron gun for cathode-ray tube does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electron gun for cathode-ray tube, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electron gun for cathode-ray tube will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3265114