Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-11-23
2001-05-22
Mengistu, Amare (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C315S169300, C313S495000, C313S422000, C345S075200
Reexamination Certificate
active
06236381
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image display apparatus, and more particularly relates to a thin image display apparatus used for a video camera and the like.
BACKGROUND OF THE INVENTION
Conventionally, cathode ray tubes have been used mainly as image display apparatuses for color televisions, personal computers and the like. However, in recent years, image display apparatuses have been required to be miniaturized, and made lighter and thinner. In order to satisfy these demands, various types of thin image display apparatus have been developed and commercialized.
Under these circumstances, various types of thin image display apparatus have been researched and developed recently. In particular, liquid crystal displays and plasma displays have been developed actively. The liquid crystal displays have been applied to various types of products such as portable personal computers, portable televisions, video cameras, carnavigation systems and the like. In addition to that, the plasma displays have been applied to products such as large-scale displays, for example, 20 inch-displays or 40-inch displays.
However, problems of such a liquid crystal display include a narrow visual angle and a slow response. Regarding a plasma display, high brightness can't be obtained and the consumed electricity is large. A thin image display apparatus called a field emission image display apparatus has attracted considerable attention to solve these problems. The field emission image display apparatus uses field emission, or a phenomenon in which electrons are emitted in a vacuum at room temperature. The field emission image display apparatus is a spontaneous luminescent type, and therefore it is possible to obtain a wide visual angle and high brightness. Further, the basic principle (to illuminate a fluorescent substance with electron beams) is same as that of a conventional cathode ray tube, and therefore a picture with natural color and high reproduction can be displayed.
The above-mentioned type of a field emission image display apparatus is disclosed in Unexamined Published Japanese Patent Application (Tokkai-Hei) No. 1-100842. Another image display apparatus disclosed in Tokkai-Hei No. 2-33839 is known as a spontaneous light emission type image display apparatus with high-quality images, which is different from the above-mentioned field emission image display apparatus in the structure but uses a linear hot cathode.
FIG. 7
is a perspective exploded view showing a first conventional image display apparatus (refer to Tokkai-Hei No. 2-33839). As shown in
FIG. 7
, the conventional image display apparatus comprises a back electrode
100
, a linear cathode
101
, an electron beam-attracting electrode
102
, a control electrode
103
, a first focusing electrode
104
, a second focusing electrode
105
, a horizontal deflecting electrode
106
, a vertical deflecting electrode
107
, a front glass container
109
a
having a fluorescent layer
108
on the inner surface, and a rear glass container
109
b
. The back electrode
100
, the linear cathode
101
, the electron beam-attracting electrode
102
, the control electrode
103
, the first focusing electrode
104
, the second focusing electrode
105
, the horizontal deflecting electrode
106
and the vertical deflecting electrode
107
are contained between the rear glass container
109
b
and the front glass container
109
a
(the fluorescent layer
108
side), and the space where those components are contained between the glass containers (
109
a
,
109
b
) is maintained under vacuum.
In the image display apparatus, electron beams are formed in a matrix by the linear cathode
101
and the electron beam-attracting electrode
102
, and focused by using the first focusing electrode
104
and the second focusing electrode
105
. The electron beams are further deflected by the horizontal deflecting electrode
106
and the vertical deflecting electrode
107
before being landed on predetermined positions of the fluorescent layer
108
. The control electrode
103
controls the electron beams over time, and adjusts each electron beam independently according to picture signals for displaying pixels.
FIG. 8
is a cross-sectional view showing the schematic structure of a second conventional image display apparatus (refer to Tokkai-Hei No. 1-100842). As shown in
FIG. 8
, the conventional image display apparatus comprises an electron emission source
210
, fluorescent layers
208
a
and
208
b
, a faceplate
209
and a transparent electrode
207
. The fluorescent layers
208
a
and
208
b
are provided on the faceplate
209
via the transparent electrode
207
and the fluorescent layers
208
a
and
208
b
face the electron emission source
210
in parallel. The electron emission source
210
comprises a substrate
204
, a thin film
202
formed on the substrate
204
and electrodes
201
a
and
201
b
, which are provided for applying a voltage to the thin film
202
. An electron emission part
203
is provided by processing the thin film
202
.
According to the above-mentioned image display apparatus, the deflection of electron beams emitted from the electron emission part
203
is adjusted by controlling a voltage applied to the electrodes
201
a
and
201
b
, and the deflected electron beams are landed on predetermined positions of the fluorescent layers
208
a
and
208
b
to illuminate these fluorescent layers. The conventional image display apparatus is also provided with a flat electrode (not shown in
FIG. 8
) between the electron emission source
210
and the fluorescent layers (
208
a
,
208
b
). In the disclosed technique, the voltage applied to the flat electrode is lower than that of the transparent electrode
207
in order to focus the electron beams on the fluorescent layers by utilizing the lens effect. Since the flat electrode is designed only to adjust the deflection degree for the inherently-deflected electron beams, it does not function to deflect the electron beams actively.
The respective components for the image display apparatuses in the conventional technique are thin and flat. Therefore, a combination of these components can form a thin image display apparatus having a flat screen.
In the image display apparatus according to the conventional technique, however, errors will occur during manufacturing or assembling the respective components. Such errors will affect directly the deviation of the landing position of an electron beam. For example, in an image display apparatus where one pitch of an electron source corresponds to one stripe pitch of the fluorescent layer, 10 &mgr;m deviation of the electron source results in 10 &mgr;m deviation of the position that the electron beam is landed on the fluorescent layer. Accuracy variations such as deviation of the deflection electrode and differences in level will also result in direct influences on the deviation of the landing positions for the electron beams. Therefore, in such an image display apparatus, landing an electron beam on a predetermined position of a fluorescent layer is difficult when the positions of the components comprising the electron sources and the deflection electrode are deviated. As a result, more inconveniences such as overlap irradiation may occur, and thus, the image quality of the image display apparatus will deteriorate, and an image display apparatus with high resolution cannot be easily obtained.
In order to improve the resolution of an image display apparatus, electron beams should be further focused (i.e., a spot diameter of an electron beam should be reduced), and the electron beam should be landed on a fluorescent layer with higher accuracy. In a conventional image display apparatus, however, a remarkable improvement cannot be obtained because of the structural limitations, even by using regular actions including deflecting actions. For example, the spot diameter should be decreased to ⅕ and also the landing accuracy, to ⅕ or less in order to improve the solution by 5 times, which is considerably difficult in the co
Imai Kanji
Kurata Takatsugu
Matsuo Koji
Ohsugi Michio
Taniguchi Hironari
Matsushita Electronics Corporation
Mengistu Amare
Merchant & Gould P.C.
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