Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
1999-08-17
2001-02-06
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169200, C315S387000, C345S048000, C313S496000
Reexamination Certificate
active
06184627
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an image display device used in color television receivers and terminal displays for computers, etc.
BACKGROUND ART
FIG. 6
is a schematic exploded perspective view of a conventional image display device. In this conventional image display device, a rear electrode
1
, a group of linear cathodes
2
serving as a beam source, a beam extraction electrode
3
, a control electrode
4
, a focusing electrode
5
, a horizontal deflection electrode
6
, a vertical deflection electrode
7
, and a screen
8
are arranged in this order from the rear towards the anode, and are stored inside a vacuum container (not shown in the drawings).
The group of linear cathodes
2
serving as a beam source is made by extending a plurality of linear cathodes horizontally, so as to generate electron beams that are distributed linearly in a horizontal direction. A plurality of these cathodes is arranged at predetermined intervals in a vertical direction. In this conventional image display device, the intervals between the linear cathodes in the vertical direction are 5.5 mm, with a number of
19
cathodes denoted
2
a
to
2
s
. However, in order to avoid making
FIG. 6
too complicated, only four linear cathodes from
2
a
to
2
d
are shown. The linear cathode
2
a
to
2
s
are made by applying an oxide cathode material to the surface of a tungsten wire with a diameter of 10-30 &mgr;m, for example. These linear cathodes are then operated for a constant time in sequence from the upper linear cathode
2
a
to the lower linear cathode
2
s
, so that each cathode emits an electron beam every
18
horizontal scanning periods.
In addition to prevent the generation of electron beams from linear cathodes other than predetermined linear cathodes, the rear electrode
1
also has the function to ensure that electron beams are emitted only in the direction of the anode. The vacuum container is not shown in
FIG. 6
, but depending on the circumstances, the rear electrode
1
can be taken and formed in one piece with the vacuum container.
The beam extraction electrode
3
is made of a conductive board
11
provided with a plurality of through holes
10
and has the function to divide and select a plurality of electron beams emitted from the group
2
of linear cathodes horizontally via the through holes
10
. On the beam extraction electrode
3
, the through holes
10
are arranged on the conductive board
11
with constant horizontal pitch, in opposition to the linear cathodes
2
a
to
2
s
. In this conventional image display device, the horizontal pitch of the through holes
10
is 1.28 mm and there are 107 through holes
10
in the horizontal direction.
The control electrode
4
is made of 107 long vertical conductive boards
15
, which have through holes
14
that are positioned in opposition to the through holes
10
of the beam extraction electrode
3
. However, in order to avoid making
FIG. 6
too complicated, only nine conductive boards
15
are shown. Furthermore, based on the image signal for each section, the control electrode
4
simultaneously modulates the throughput of the electron beams that are divided into
107
horizontal sections.
Each section is divided into two pixels, and as each pixel has three primary colors (phosphors) of R (red), G (green), and B (blue), the six signals of 2 (pixels)×3 (primary colors) that correspond to each section are synchronized with the horizontal deflection, described later, and are then added one after another in time division (within one horizontal scanning period).
The focusing electrode
5
is made of a conductive board
17
that has a plurality of through holes
16
, which have the function to focus the electron beam. The through holes
16
in this conductive board
17
are formed in positions opposing the through holes
14
formed in the control electrode
4
.
The horizontal deflection electrode
6
is made of a pair of a comb-shaped conductive boards
18
and
18
′ arranged vertically along both horizontal sides of the through holes
16
formed in the focusing electrode
5
, and its function is to simultaneously deflect the electron beam that is divided into
107
sections in a horizontal direction, so that the two groups of the primary color phosphor stripes R, G, and B on the screen
8
, which will be described later, are irradiated successively in six stages and emit light.
The vertical deflection electrode
7
is made of a pair of comb-shaped conductive boards
19
and
19
′ arranged horizontally, in the space between vertically neighboring through holes
16
formed on the focusing electrode
5
. With these two conductive boards
19
and
19
′, the voltage for vertical deflection is applied, and the vertical deflection electrode
7
deflects the electron beam vertically. Here, the vertical deflection electrode
7
deflects the electron beam which is emitted by the
19
linear cathodes
2
a
to
2
s
in
12
stages each, or in other words,
12
horizontal scanning line segments each, and
228
horizontal scanning lines are drawn in a vertical direction on the screen
8
.
In this conventional image display device as described above, the horizontal deflection electrode
6
and the vertical deflection electrode
7
are both comb-shaped and spread out. Since the distance to the screen
8
is longer than the distance between the horizontal and vertical deflection electrodes, the electron beam can be irradiated onto arbitrary positions of the screen
8
with small amounts of deflection. Therefore, with this configuration, it is possible to decrease the distortion for both horizontal and vertical deflection.
The screen
8
is made of a glass pane, and the R,G and B primary color phosphors which emit light due to irradiation with the electron beam are applied in a stripe-like shape separated by black guard bands (black matrix) onto the rear side of this glass pane, with a metal backing arranged on top (not shown in the drawings). In
FIG. 6
, the broken lines drawn on the screen
8
show the vertical sections, displayed in correspondence to the plurality of linear cathodes
2
a
to
2
s
. Further, the alternate-long-and-two-short dash lines indicate the horizontal sections displayed in correspondence to the plurality of conductive boards
15
, which make up the control electrode
4
.
In one section, partitioned by both (the broken lines and the alternate long and two short dash lines), as shown enlarged in
FIG. 7
, two groups of primary color phosphor stripes
20
R,
20
G and
20
B of R, G and B are applied vertically in stripe-like shapes, separated by black guard bands
22
in the horizontal direction. The horizontal lines are formed for 12 lines in the vertical direction. The size of one section (1 unit) in this conventional example is 1.0 mm horizontally, and 4.4 mm vertically, but for illustrative reasons, the lengthwise and crosswise proportions in
FIG. 7
are different from the image that appears on the actual screen.
However, in this conventional image display device above, due to thermal expansion of the structural elements when operating the image display device, misalignments between the screen and a group of flat electrodes occur, and due to environmental magnetic fields (for example the earth's magnetism at that position) deviations of the beam track between the group of flat electrodes and the screen occur, causing misalignments between the beam spot and the phosphor stripes on the screen, resulting in a deterioration of the image quality, such as color misalignments, etc.
DISCLOSURE OF INVENTION
It is an object of this invention to solve the above-mentioned problems, and to provide an image display device, wherein misalignments of the beam spot position with respect to the phosphor stripes on the screen, which are caused for various reasons, are eliminated, and image deterioration, such as color misalignments, does not occur, which is achieved by detecting the relative position of the beam spot with respect to the phosphor stripes, and performing a correction bas
Hamada Kiyoshi
Ohsugi Michio
Taniguchi Hironari
Alemu Ephrem
Matsushita Electronics Corporation
Merchant & Gould P.C.
Wong Don
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