Optical: systems and elements – Holographic system or element – Using a hologram as an optical element
Reexamination Certificate
1999-04-13
2001-07-03
Schuberg, Darren (Department: 2872)
Optical: systems and elements
Holographic system or element
Using a hologram as an optical element
C359S025000
Reexamination Certificate
active
06256120
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spatial light modulation device using a hologram lens layer and a color display apparatus using the spatial light modulation device.
2. Description of the Related Art
In a color display apparatus, color filters are necessary constituent elements. A conventional color filter is constituted by a resin layer which uses a pigment or dye as a coloring material and selectively transmit only one of the wavelength bands corresponding to R (red), G (green), and B (blue) which are the three primary colors of light. However, the conventional color filters corresponding RGB are formed in independent regions, respectively. A light ray which can be transmitted through the filter in each region is only one light ray of only one color of RGB in incident white light, and other light rays are absorbed by the filter. When a pixel size decreases, the filters of the color light rays are formed such that the filters partially overlap at boundary portions of the regions. For this reason, black stripes are generally formed on the boundary portions of adjacent regions to avoid color mixture. Therefore, a light transmittance of all the color filters is low, an efficiency of using light cannot be theoretically improved. The absorbed light rays are converted into heat, and the heat may be a factor in degrading display characteristics.
In contrast to this, in recent years, use of color filters (to be referred to as hologram color filters hereinafter) using hologram lenses is studied. According to the hologram color filters, by the diffraction and spectral functions of hologram lenses, white light can be diffracted and dispersed into three light components, i.e., RGB. Since use of such a hologram color filter can obtain a high efficiency of using light, the hologram color filter is effective to a projection type liquid-crystal display apparatus which requires improvement of an efficiency of using light.
FIG. 1
is a device sectional view showing a typical structure of a spatial light modulation device in a projection type color liquid-crystal display apparatus having a reflection scheme disclosed in Publication of Patent Applications (Japanese Unexamined Patent Publication No. 9-189809) filed by the present applicant. In this spatial light modulation device, as a color filter, the hologram color filter described above is used as a color filter. In
FIG. 1
, reference numeral
11
denotes a liquid crystal panel;
12
, a thin-plate glass layer;
13
, a color filter;
14
, a glass substrate; and
15
, a coupling prism.
The liquid-crystal panel
11
has a structure in which a silicon substrate
21
; an active matrix drive circuit
22
formed on the silicon substrate
21
; a pixel electrode layer
23
obtained by regularly arraying pixel electrodes
23
r,
23
g, and
23
b
selectively controlled and driven by the active matrix drive circuit
22
; a dielectric mirror film
24
, an alignment film
25
, a light modulation layer
26
having a liquid crystal sealed by a spacer; an alignment film
27
; and a transparent common electrode layer
28
are sequentially laminated.
The color filter
13
is constituted by a so-called hologram lens array in which unit hologram lenses are regularly arrayed. The color filter
13
has a function of diffracting and dispersing read light (white light) including three primary colors, i.e., R, G, and B in units of color light rays to almost perpendicularly converge the light rays to the positions of the pixel electrodes
23
r
,
23
g
, and
23
b
corresponding to R, G, and B in the liquid-crystal panel
11
. More specifically, main beams of beams are almost perpendicularly incident on the pixel electrodes
23
r
,
23
g
, and
23
b
, and the beams can be converged on the pixel electrodes
23
r
,
23
g
, and
23
b
by the lens functions thereof. Therefore, the projection type color liquid-crystal display apparatus using incident light without waste can be provided. As shown in
FIG. 1
, when the dielectric mirror film
24
is arranged on the pixel electrode layer
23
, the destination of convergence is the dielectric mirror film
24
.
FIG. 2
a diagram showing a color separation theory of read light (white light) of a hologram color filter in the spatial light modulation device shown in FIG.
1
. As shown in
FIG. 2
, the color filter
13
has an arrangement in which a hologram color filter layer
13
r
for R, a hologram color filter layer
13
g
for G, and a hologram color filter layer
13
b
for b which correspond to the three primary colors, i.e., RGB are laminated. Of white light which is admitted on the color filter
13
at a predetermined angle, light rays having corresponding wavelengths are diffracted and dispersed by these layers, respectively.
For example, an R light component is diffracted and dispersed by the first layer
13
r
, a G light component is diffracted and dispersed by the second layer
13
g
, and a B light component is diffracted and dispersed by the third layer
13
b
. The R, G, and B light rays dispersed and diffracted by the layers are substantially converged on the corresponding pixel electrodes
23
b
,
23
g
, and
23
r.
In this manner, a spatial light modulation device using conventional hologram lenses must comprise hologram lens layers corresponding to light colors of the three primary colors, i.e., RGB. More specifically, the hologram lens layers of a three-layer structure. Therefore, in the steps in manufacturing the hologram lens layers, hologram lens layers of three types must be manufactured. In addition, when the three layers are laminated, the positions of the three layers must be aligned with high precision such that light rays diffracted and dispersed by the hologram lens layers are converged on corresponding pixel electrodes, respectively.
For this reason, processes are cumbersome, process costs increase, and a high-definition color liquid-crystal display apparatus cannot be easily manufactured because of a problem in alignment precision.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a spatial light modulation device which can be manufactured by using simpler processes and a color display apparatus using the spatial light modulation device.
It is another object of the present invention to provide a spatial light modulation device which can be manufactured by using the simple processes and has a preferable efficiency of using light and preferable color reproducibility.
To achieve the objects described above, from the first aspect of the present invention, there is provided a spatial light modulation device comprising a single hologram lens layer which diffracts and emits incident light rays in predetermined directions depending on incident angles and wavelength bands, and a light modulation layer for performing light modulation according to video signals of corresponding colors to light rays admitted through the hologram lens layer to emit the light rays.
With this configuration, since the hologram lens layer diffracts and emits incident light rays in the predetermined directions depending on the incident angles and the wavelength bands, although the hologram lens layer is a single hologram lens layer, color light rays, i.e., an R light ray, a G light ray, and a B light ray can be resolved in predetermined directions. Since the hologram lens layer is constituted by a single layer, unlike a conventional hologram lens layer constituted by three layers, an alignment operation of the layers to be laminated is not necessary, manufacturing steps are considerably simplified, and process costs can be reduced.
Preferably, in the spatial light modulation device described above, the light modulation layer may be held between one transparent substrate on which a transparent electrode is formed and the other substrate on which pixel electrodes and a drive circuit layer are formed.
Preferably, in the spatial light modulation device, the pixel electrode may have a planar arrangement in which pixel electrodes for red, pixel electrodes for gr
Nakagaki Shintaro
Shimizu Shigeo
Suzuki Tetsuji
Berkowitz Marvin C.
Nath & Associates PLLC
Novick Harold L.
Schuberg Darren
Victor Company of Japan , Limited
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