Optical waveguides – Miscellaneous
Reexamination Certificate
1999-06-03
2001-05-22
Healy, Brian (Department: 2874)
Optical waveguides
Miscellaneous
C385S040000, C385S130000, C385S131000, C385S901000
Reexamination Certificate
active
06236799
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat-panel display device, and more particularly, to a flat-panel display device using an optical waveguide having high resolution of a reproduced image and high efficiency of light.
2. Description of the Related Art
Currently, cathode ray tubes (CRTs) are widely used as display devices for monitors or television sets. However, due to the drawbacks of the CRT being heavy and bulky, light flat-panel display devices such as liquid crystal display devices (LCDs) or plasma display devices are gradually being put into practical use. However, the LCDs are expensive and there are limits on the screen size. Plasma display devices are also expensive and consumes much power.
To overcome these disadvantages, display devices using optical waveguides have been developed. The optical waveguide is suitable for a display device having a large-sized screen because it can transmit bright light to a distant area with little attenuation of light.
FIG. 1
shows a conventional flat-panel display device using an optical waveguide.
The conventional flat-panel display device shown in
FIG. 1
includes a core
15
into which the light output from a light source (not shown) is incident to then be propagated, a cladding
14
positioned on the core
15
and made of a material having a low refractive index so as to totally reflect the light propagated through the core
15
, a light absorption layer
10
positioned on the cladding
14
, for absorbing light, a first electrode
13
positioned on the light absorption layer
10
and to which a predetermined voltage is applied, an electro-optical material layer
16
positioned under the core and whose refractive index changes according to an electric field, a scattering layer
17
for scattering light, and a second electrode
18
which is grounded and made of a transparent material.
In the conventional flat-panel display device constructed as described above, if a predetermined voltage
12
is applied to the first electrode
13
, an electric field
11
is generated between the first and second electrodes
13
and
18
. The refractive index of the electro-optical material layer
16
increases due to the electric field
11
so that the light propagated through the core
15
passes through the electro-optical material layer
16
and collides with scattering particles in the scattering layer
17
to then be scattered. The light scattered in the scattering layer
17
passes through the second electrode
18
made of a transparent material so that light having passed through the second electrode
18
can be observed by a viewer.
However, in the aforementioned conventional flat-panel display device, since the scattering layer
17
has small particles causing scattering in all directions, the light incident into the scattering layer
17
is scattered in all directions and a considerable amount of light flux is reflected at the interface between the electro-optical material layer
16
and the scattering layer
17
. Accordingly, only an extremely small amount of incident light is emitted to the outside. Thus, the light efficiency is very low.
Also, the conventional flat-panel display device cannot reduce the width of a waveguide for outputting light to less than a predetermined width because of its low output efficiency of light, which results in a limited resolution of a reproduced image.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a flat-panel display device having high resolution of a reproduced image, high efficiency of light and a broad viewing angle.
Accordingly, to achieve the above objective, there is provided a flat-panel display device using an optical waveguide including a light source for emitting light, a plurality of optical waveguides into which light emitted from the light source is incident, an optical waveguide arrangement substrate on which the plurality of optical waveguides are arranges and made of a material having a low refractive index so as to totally reflect the light transmitted through the plurality of optical waveguides, a light output controller positioned on the plurality of optical waveguides and made of a material whose refractive index changes according to an electric field, a light output portion positioned on the light output controller, for refracting the light having passed through the light output controller when the light propagated through the plurality of optical waveguides due to the electric field is transmitted through the light output controller and is output therefrom, and outputting the same to the outside, a first electrode positioned on the light output portion, made of a transparent conductive material, and to which a predetermined control voltage is applied, a second electrode positioned under the light output controller, made of a conductive material, and which forms an electric field in conjunction with the first electrode, and a driver for applying the predetermined control voltage to the first and second electrodes.
The first electrode is preferably positioned under the optical waveguide arrangement substrate. Also, the plurality of optical waveguides are preferably cladding-free rectangular-section optical fibers. The light output controller is preferably a liquid crystal layer. Also, the light output portion may be formed of a plurality of cladding-free cylindrical optical fibers.
The flat-panel display device using an optical waveguide according to present invention may further include a transparent protective plate on which the first electrode is formed, wherein the protective plate is adhered to the light output portion by an optical adhesive.
Also, the light source is preferably a light source for emitting light of three primary colors for displaying colors, and each of the plurality of optical waveguides may further include three optical waveguides for propagating the light of three primary colors emitted from the light source.
Alternatively, the light source may be a white light source for displaying colors, each of the plurality of optical waveguides may further include three optical waveguides, and colors filters for three primary colors may be provided in front of the three optical waveguides to propagate the light emitted from the white light source into light of three primary colors.
Also, a gray scale control device for controlling the brightness of the light output from the light source may be further provided between the light source and the plurality of optical waveguides, and the brightness of the light output from the gray scale control device is preferably controlled in accordance with a light brightness control signal output from the driver.
Preferably, the gray scale control device includes a plurality of gray scale control units having a predetermined number of gray scale controllers formed in series, each gray scale controller including an optical waveguide into which the light emitted from the light source is incident, an optical waveguide arrangement substrate on which the optical waveguide is arranged and made of a material having a low refractive index so as to totally reflect the light transmitted through the optical waveguide, a light transmission controller positioned between the optical waveguide and the optical waveguide arrangement substrate and made of a material whose refractive index changes according to an electric field, a light absorption layer positioned under the light transmission controller, for absorbing the light transmitted to the light transmission controller when the light propagated through the optical waveguide is transmitted to the light transmission controller due to the electric field, third and fourth electrodes positioned on the optical waveguide, made of a conductive material and to which the light brightness control signal is applied from the driver, a fifth electrode positioned between the light absorption layer and the optical fiber arrangement substrate and made of a transparent material which produces ele
Han Sang-Yong
Huh Chin-kyu
Lee Si-ken
Yoo Jae-eun
Healy Brian
Iljin Corp.
Nixon & Vanderhye P.C.
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