Optical waveguides – Planar optical waveguide
Reexamination Certificate
1998-03-23
2001-09-25
Lee, John D. (Department: 2874)
Optical waveguides
Planar optical waveguide
C385S128000, C385S901000
Reexamination Certificate
active
06295403
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical waveguide plate to be used for a display which consumes less electric power, and which has large screen brightness. In particular, the present invention relates to a structure of the optical waveguide plate to be used for the display for displaying, on the optical waveguide plate, a picture image corresponding to an image signal by controlling leakage light at a predetermined position on the optical waveguide plate by controlling the displacement action of an actuator element in a direction to make contact or separation with respect to the optical waveguide plate in accordance with an attribute of the image signal to be inputted.
2. Description of the Related Art
Those hitherto known as the display include, for example, cathode ray tubes (CRT) and liquid crystal display devices.
Those known as the cathode ray tube include, for example, ordinary television receivers and monitor units for computers. Although the cathode ray tube has a bright screen, it consumes a large amount of electric power. Further, the cathode ray tube involves a problem that the depth of the entire display device is large as compared with the size of the screen.
On the other hand, the liquid crystal display device is advantageous in that the entire device can be miniaturized, and the display device consumes a small amount of electric power. However, the liquid crystal display device involves problems that it is inferior in brightness of the screen, and the field angle of the screen is narrow.
In the case of the cathode ray tube and the liquid crystal display device, it is necessary for a color screen to use a number of picture elements (image pixels) which is three times a number of picture elements used in a black-and-white screen. For this reason, other problems occur in that the device itself is complicated, a great deal of electric power is consumed, and it is inevitable that cost is increased.
In order to solve the problems described above, the present applicant has suggested a novel display (see, for example, Japanese Laid-Open Patent Publication No. 7-287176). As shown in
FIG. 14
, this display includes actuator elements
100
arranged for respective picture elements. Each of the actuator elements
100
comprises a main actuator element
108
including a piezoelectric/electrostrictive layer
102
and an upper electrode
104
and a lower electrode
106
formed on upper and lower surfaces of the piezoelectric/electrostrictive layer
102
respectively, and a substrate
114
including a vibrating section
110
and a fixed section
112
disposed under the main actuator element
108
. The lower electrode
106
of the main actuator element
108
contacts with the vibrating section
110
. The main actuator element
108
is supported by the vibrating section
110
.
The substrate
114
is composed of a ceramic in which the vibrating section
110
and the fixed section
112
are integrated into one unit. A recess
116
is formed in the substrate
114
so that the vibrating section
110
is thin-walled.
A displacement-transmitting section
120
for obtaining a predetermined size of contact area with an optical waveguide plate
118
is connected with the upper electrode
104
of the main actuator element
108
. In the illustrative display shown in
FIG. 14
, the displacement-transmitting section
120
is arranged such that it is located closely near to the optical waveguide plate
118
in the ordinary state in which the actuator element
100
stands still, while it contacts with the optical waveguide plate
118
in the excited state at a distance of not more than the wavelength of the light.
The light
122
is introduced, for example, from a lateral end of the optical waveguide plate
118
. In this arrangement, all of the light
122
is totally reflected at the inside of the optical waveguide plate
118
without being transmitted through front and back surfaces thereof by controlling the magnitude of the refractive index of the optical waveguide plate
118
. In this state, a voltage signal corresponding to an attribute of an image signal is selectively applied to the actuator element
100
by the aid of the upper electrode
104
and the lower electrode
106
so that the actuator element
100
is allowed to make displacement in conformity with the ordinary state and the excited state. Thus, the displacement-transmitting section
120
is controlled for its contact and separation with respect to the optical waveguide plate
118
. Accordingly, the scattered light (leakage light)
124
is controlled at a predetermined portion of the optical waveguide plate
118
, and a picture image corresponding to the image signal is displayed on the optical waveguide plate
118
.
The display described above is advantageous, for example, in that (1) it is possible to decrease the electric power consumption, (2) it is possible to increase the screen brightness, and (3) it is unnecessary to increase the number of picture elements as compared with the black-and-white screen when the display is allowed to have a color screen.
By the way, as shown in
FIGS. 15 and 16
, the optical waveguide plate
118
is composed of a transparent material such as glass and acrylic resin, because it is necessary that the light
122
introduced from a light source
126
is totally reflected. However, it is feared that light emission (false light emission) occurs due to, for example, plane roughness, scratches, and dirt on the surface of the transparent material even at portions which should not be subjected to light emission, and the contrast of the display (ratio between the brightness of the display portion and the brightness of the non-display portion) is lowered.
FIG. 15
shows an example of occurrence of the false light emission due to the scratch “a” formed on the surface of the optical waveguide plate
118
.
FIG. 16
shows an example of occurrence of the false light emission due to the dirt “b” adhered to the surface of the optical waveguide plate
118
.
Further, the light emission occurs at portions (non-display portions) which are not intended to effect light emission, and hence the incident light is decreased at portions (display portions) which are intended to effect light emission. Therefore, it is feared that the decrease in brightness would be caused.
SUMMARY OF THE INVENTION
The present invention has been made taking the foregoing problems into consideration, an object of which is to provide an optical waveguide plate for a display which makes it possible to decrease the plane roughness on the surface of a main optical waveguide plate body, substantially eliminate scratches, dirt and the like, and improve the contrast and the brightness of the display.
At first, it is premised that an optical waveguide plate for a display according to the present invention is used for the display comprising a driving section including a number of actuator elements arranged corresponding to a large number of picture elements, in particular the display for displaying, on the optical waveguide plate, a picture image corresponding to an image signal by controlling leakage light at a predetermined portion of the optical waveguide plate by controlling displacement action of each of the actuator elements in a direction to make contact or separation with respect to the optical waveguide plate in accordance with an attribute of the image signal to be inputted.
The optical waveguide plate according to the present invention is constructed such that a surface-smoothing material, which has substantially the same optical refractive index as that of a main optical waveguide plate body, is formed on at least one surface of the main optical waveguide plate body into which the light from a light source is introduced.
Accordingly, even when the main optical waveguide plate body involves a great deal of plane roughness on the surface, or even when the scratch or the dirt exists on the surface, the surface of the main optical waveguide plate body is optically smooth owing to t
Nanataki Tsutomu
Takeuchi Yukihisa
Burr & Brown
Lee John D.
NGK Insulators Ltd.
Song Sarah N.
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