Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1999-09-16
2001-06-19
Ben, Loha (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S290000, C359S295000, C359S227000, C359S230000, C359S320000, C359S323000, C345S085000
Reexamination Certificate
active
06249370
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device for displaying a picture image corresponding to an input signal on a light-shielding plate by selectively intercepting the light to be transmitted through a light-transmitting section provided through the light-shielding plate, depending on the input signal.
2. Description of the Related Art
Those hitherto known as the display device 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 in 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 in 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 to cause an increase in cost.
In order to solve the problems described above, the present applicant has suggested a novel display device (see, for example, Japanese Laid-Open Patent Publication No. 7-287176). As shown in
FIG. 38
, this display device includes actuator elements
400
arranged for respective picture elements. Each of the actuator elements
400
comprises a main actuator element
408
including a piezoelectric/electrostrictive layer
402
and an upper electrode
404
and a lower electrode
406
formed on upper and lower surfaces of the piezoelectric/electrostrictive layer
402
respectively, and an actuator substrate
414
including a vibrating section
410
and a fixed section
412
disposed under the main actuator element
408
. The lower electrode
406
of the main actuator element
408
contacts with the vibrating section
410
. The main actuator element
408
is supported by the vibrating section
410
.
The actuator substrate
414
is composed of ceramics in which the vibrating section
410
and the fixed section
412
are integrated into one unit. A recess
416
is formed in the actuator substrate
414
so that the vibrating section
410
is thin-walled.
A displacement-transmitting section
420
for obtaining a predetermined size of contact area with respect to an optical waveguide plate
418
is connected to the upper electrode
404
of the main actuator element
408
. In the illustrative display device shown in
FIG. 38
, the displacement-transmitting section
420
is arranged such that it is located closely near to the optical waveguide plate
418
in the OFF selection state or the unselection state in which the actuator element
400
stands still, while it contacts with the optical waveguide plate
418
in the ON selection state at a distance of not more than the wavelength of the light.
The light
422
is introduced, for example, from a lateral end of the optical waveguide plate
418
. In this arrangement, all of the light
422
is totally reflected at the inside of the optical waveguide plate
418
without being transmitted through front and back surfaces thereof by controlling the magnitude of the refractive index of the optical waveguide plate
418
. In this state, a voltage signal corresponding to an attribute of an image signal is selectively applied to the actuator element
400
by the aid of the upper electrode
404
and the lower electrode
406
so that the actuator element
400
is allowed to make a variety of displacement actions in conformity with the ON selection, the OFF selection, and the unselection. Thus, the displacement-transmitting section
420
is controlled for its contact and separation with respect to the optical waveguide plate
418
. Accordingly, the scattered light (leakage light)
424
is controlled at a predetermined portion of the optical waveguide plate
418
, and a picture image corresponding to the image signal is displayed on the optical waveguide plate
418
.
When a color picture is displayed by using the display device, the following operation is performed. That is, for example, light sources for the three primary colors are switched to control the light emission time for the three primary colors, while synchronizing the contact time between the optical waveguide plate and the displacement-transmitting plate with the cycle of color development. Alternatively, the contact time between the optical waveguide plate and the displacement-transmitting plate is controlled, while synchronizing the light emission time for the three primary colors with the color development cycle.
Therefore, the illustrative display device suggested by the present applicant is advantageous in that it is unnecessary to increase the number of picture elements as compared with the black-and-white screen, even when the display device is applied to a color display system.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a display device which makes it possible to improve the contrast and improve the image quality of the displayed image, by improving the arrangement of the illustrative display device suggested by the present applicant.
According to the present invention, there is provided a display device comprising a light-shielding plate; light-transmitting sections formed on the light-shielding plate corresponding to a large number of picture elements, for transmitting light toward a first principal surface of the light-shielding plate; and a shutter means provided opposingly to a second principal surface of the light-shielding plate, for selectively intercepting the light to be transmitted through the light-transmitting section, in response to an input signal.
Accordingly, at first, when the light-intercepting operation is not performed by the shutter means, the light is radiated from the first principal surface of the light-shielding plate through the large number of light-transmitting sections provided through the light-shielding plate. At this stage, when a specified picture element is selected in response to the input signal, the light, which has been transmitted through the light-transmitting section corresponding to the concerning picture element, is intercepted by the shutter means.
On the contrary, when the light-intercepting operation is performed by the shutter means for all of the light-transmitting sections, then the light is intercepted by the shutter means, and the light is not radiated from the first principal surface of the light-shielding plate. That is, the black background is displayed. At this stage, when a specified picture element is selected in response to the input signal, the light-intercepting operation effected by the shutter means is stopped for the light-transmitting section corresponding to the concerning picture element. Accordingly, the light is transmitted through the light-shielding plate through the light-transmitting section. Thus, the light is radiated from the portion of the first principal surface of the light-shielding plate corresponding to the concerning light-transmitting section.
Usually, in the case of the display apparatus such as CRT, the black level differs between the black background display on the screen obtained when the device is not in the operation state (state in which the power source is shut off) and the black background display obtained when the device is in the operation state. This difference is caused by any minute light radiation from portions other than the picture elements
Okada Shigeki
Shimogawa Natsumi
Takahashi Masao
Takeuchi Yukihisa
Ben Loha
Burr & Brown
NGK Insulators Ltd.
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