JP3005102B2 - Spatial light modulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial light modulator having a function of modulating read light into a spatial light pattern in accordance with spatial light writing (image) information.

[0002]

2. Description of the Related Art In recent years, various types of spatial light modulators have been developed as key devices for image projection apparatuses, image display apparatuses, and optical information processing apparatuses. These spatial light modulators
It is used for intermediate recording media of optical printers, image display devices, optical shutters, image processing devices, hologram elements, optical information processing systems, and the like.

[0003] Among them, the optical writing type spatial light modulator has a feature of relatively high resolution. Hereinafter, this optical writing type spatial light modulator will be described with reference to FIGS.
This will be described with reference to FIG.

FIG. 10 is a sectional view of a conventional spatial light modulator. A substrate having a transparent electrode 81 formed on a glass substrate 80, and a transparent electrode 84, a photoconductive film 85,
A liquid crystal alignment process is performed on the substrate on which the light absorbing film 86 and the metal reflection film 87 are formed, and liquid crystal is sealed between these substrates to form a liquid crystal layer 89. The transparent electrodes 81 and 84
TO (Indium Tin Oxide) or tin oxide film (SnO ₂ )
The photoconductive film 85 is made of cadmium sulfide (CdS) or amorphous silicon (a-S
i) and the like. The metal reflection film 87
This is a metal thin film of 1, Ni, Cr or the like, and a pixel pattern is formed in a mosaic shape by photoetching. The metal reflection pixels formed in a mosaic shape are electrically separated from each other.

This element operates by applying a voltage to the liquid crystal layer 89 by utilizing a change in internal resistance of the photoconductive film 85 due to light irradiation. That is, the resistance value of the photoconductive film 85 changes according to the amount of light applied to the photoconductive film 85, and the transparent electrode 8
Since a constant voltage is applied between 1 and the transparent electrode 84, the voltage applied to the liquid crystal layer 89 changes in proportion to the irradiation light amount. Therefore, by converting optical information due to a change in the writing light amount into a voltage change applied to the liquid crystal, and irradiating linearly polarized readout light using the birefringence effect of the liquid crystal due to the voltage change, the reflected light becomes elliptically polarized light, It is converted into optical information. Furthermore, by arranging a polarizer on the output side,
A spatial light intensity distribution can be obtained.

In this method, the output of the reading light is increased by using a metal reflection film instead of the dielectric mirror as the reflection film. However, since the metal reflective film has an extremely small internal resistance in the plane, the metal reflective film is cut in a mosaic shape to prevent drift of charges in the in-plane direction.

FIG. 11 is a sectional view of another type of conventional spatial light modulator, which is a light writing type spatial light modulator for a projection apparatus. In this device, an n-π diode matrix 94 is formed by ion-implanting phosphorus P in a high-resistance π-type silicon (π-Si) layer 93 in a lattice shape.
Is composed. On top of that, the SiO ₂ gate insulating film 95
Is formed, and a dichroic mirror 96 of Si / SiO ₂ is formed between the mirror and the liquid crystal layer. On the opposite side of the π-type silicon (π-Si) layer 93, a transparent electrode 97 and a SiO ₂ film 101 for surface treatment are formed. When operating the element, the π-type silicon (π-Si) layer 93 is used.
AC voltage is applied between the transparent electrode 97 formed on the outside of the substrate and the transparent electrode 91 on the liquid crystal layer 99 side. In this way, the silicon in the π region forming a highly depleted layer is formed. When light is incident on the (π-Si) layer 93, an electron-hole pair is generated, which is attracted to the electric field and collected by the diode 94. If π-type silicon (π-S
i) If the light incident on the layer 93 is spatially modulated in advance by image information or the like, an electric field of a different value is locally applied to the corresponding portion of the liquid crystal layer 99 according to the spatial modulation, and the direction of the liquid crystal molecules is changed. Changes. Therefore, when reading light enters from the liquid crystal layer 99 side, the reflected light is spatially modulated by the written information.

In this system, the resolution of the spatial modulation (image) is determined by the pitch of the diodes 94 arranged in a matrix. As described above, when the structure is subdivided by the diode, the drift of the horizontal charge in the π-type silicon (π-Si) layer 93 is collected by the diode, so that a screen with less blur is obtained.

Note that an n-doped diode guard ring 100 is provided around the π-type silicon (π-Si) layer 93.
To prevent the photocurrent from entering the active region at the center from the periphery.

In general, the photoconductive film is not formed in a fine grid, but is formed uniformly in a plane and thinned to increase the resolution. This is intended to reduce in-plane charge drift by increasing the in-plane internal resistance of a photoconductive film such as amorphous silicon and reducing the film thickness.

[0011]

In the conventional optical writing type spatial light modulator, a metal thin film formed in a mosaic shape is used as the reflection film 87, so that the reflection surface must be formed in a uniform plane. However, there is a disadvantage that it is difficult to reduce the size and the resolution cannot be increased.

In another conventional optical writing type spatial light modulator, the resolution is improved by forming the diodes 94 in a lattice shape in the optical writing layer, but there is a drawback that it is difficult to manufacture. is there. Further, when a diode is formed as the optical writing layer, it is difficult to reduce the thickness of the optical writing layer, and the amount of drift of the charge in the in-plane direction is large, so that the resolution cannot be increased.

Further, even when a photoconductive film is used as the optical writing layer, there is a limit to thinning the photoconductive film in order to obtain a necessary change in internal resistance. There is a disadvantage that the resolution cannot be increased.

Accordingly, the present invention provides a high resolution optical writing type spatial light modulator.

[0015]

SUMMARY OF THE INVENTION A spatial light modulator according to the present invention .
It includes a first substrate, a first electrode formed on the first substrate, is formed on the first electrode, for writing information to the optical writing layer, the second A substrate, a second electrode formed on the second substrate , and spatial light formed spatially on the second electrode according to information written on the optical writing layer. modulation layer for modulating, when a voltage is applied between the first electrode and the second electrode, and a plurality of projections to focus localized electric field to a portion of the modulation layer
A spatial light modulator, wherein the protrusions are located above the interface.
Materials that have electrically different physical properties from the materials laminated
It is characterized by being formed with a material .

Further , the spatial light modulator of the present invention has a first
A plate, a first electrode formed on the first substrate,
Optical writing for writing information, formed on one electrode
Embedded layer, a second substrate, and a second substrate formed on the second substrate.
A second electrode, formed on the second electrode;
The light is spatially changed according to the information written in the optical writing layer.
A modulation layer to be modulated, and dispersed in the optical writing layer;
Applying a voltage between the first electrode and the second electrode
The electric field is locally concentrated in a part of the modulation layer.
A spatial light modulator comprising a plurality of microparticles,
The fine particles are about 約 of the thickness of the optical writing layer.
Characterized by having a particle size of

Further, the spatial light modulator of the present invention has a first
A substrate; a first electrode formed on the first substrate;
Light for writing information formed on the first electrode
A writing layer, a second substrate, and a second substrate formed on the second substrate.
A second electrode formed on the second electrode;
According to the information written in the light writing layer, light is spatially
A modulation layer for modulating, dispersed in said modulation layer,
A voltage was applied between the first electrode and the second electrode.
In this case, an electric field is locally concentrated on a part of the modulation layer.
A spatial light modulator comprising a plurality of microparticles, wherein the
The fine particles have a particle size of about 1/3 of the thickness of the modulation layer.
It is characterized by being formed by .

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

In the above arrangement, when a voltage is applied between the first electrode and the second electrode, a plurality of projections or fine particles provided to locally concentrate the electric field cause > Then, an electric field concentration portion is generated in a part of the modulation layer. Therefore,
Light incident on the modulation layer is locally modulated along the electric field concentration portion.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the spatial light modulator according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an optical writing type spatial light modulator according to the present invention. The glass substrate 10 on the optical readout layer side of the glass substrate for holding the liquid crystal molecules has an ITO transparent electrode layer 11 (conductor) on its surface and an incident angle of about 82 ° from the normal direction of the transparent electrode. Silicon monoxide (Si
An oriented thin film 12 (insulator) is formed by obliquely depositing O). A transparent electrode 14 (conductor) and a photoconductive film 15 (semiconductor) are stacked on the glass substrate 13 on the optical writing side. For the photoconductive film 15, an amorphous silicon ( a- Si) layer having a thickness of about 1.5 μm can be used. Further, on the photoconductive film 15, the reading light is not to enter the photoconductive film 15 is formed and layered MgF ₂ and TiO ₂ and the dielectric mirror 16 for 3-layer laminated alternately.
Further, on the dielectric mirror 16, a large number of metal projections 17 are provided.
(Conductor) formed at a pitch of about 2 μm and a height of about 0.5 μm
It is. These metal projections 17 can be manufactured by photoetching a metal thin film deposited by electron beam. This metal includes Al, Ni, C
r or the like may be used. Further, silicon monoxide (SiO) is formed at an incident angle of, for example, about 82 ° from the normal direction of the metal projection 17.
Are formed obliquely to form an oriented thin film 18 (insulator) . However, the dielectric mirror 16 is not an essential element of the present embodiment, and the metal protrusion 17 may be formed directly on the photoconductive film 15 without forming the dielectric mirror 16.

These transparent substrates produced as described above have their alignment film layers facing each other, and the gap is controlled and formed via a spacer made of an adhesive containing glass fibers having a diameter of 1.5 μm. A liquid crystal layer 19 sandwiching liquid crystal is formed. As the nematic liquid crystal to be enclosed,
For example, E44 manufactured by Merck can be used. Further, instead of a nematic liquid crystal, a ferroelectric liquid crystal may be used as the liquid crystal layer. Further, as the liquid crystal layer, a liquid crystal and a liquid crystal alignment film which are horizontally aligned with the substrate are used, but a liquid crystal and a liquid crystal alignment film which is vertically aligned with the substrate may be used. That is, in order to uniformly align the liquid crystal on the uneven surface, vertically aligned liquid crystal may be more desirable. In this embodiment, the means for locally concentrating the electric field in the modulation layer, that is, the liquid crystal layer 19 corresponds to the metal projection 17.

Here, the manufacturing process of the metal projection 17 will be described with reference to FIGS. FIG. 2 is a perspective view schematically showing a large number of metal protrusions 17 formed on the dielectric mirror. As shown in the figure, a large number of metal projections 17 are formed on the dielectric mirror in a matrix in a matrix.

FIGS. 3A to 3D are explanatory views showing a process of forming one projection of the metal projection 17 by the etching method. First, as shown in FIG.
On the dielectric mirror 16 laminated thereon, a metal thin film 17a is further formed. Next, a cylindrical resist mask 20a as shown in FIG. 3B is formed by photoetching. If the metal thin film 17b is processed by the reactive ion etching (RIE) method as shown in FIG. 3C and the resist mask is removed, the metal protrusion 17 as shown in FIG. 3D can be formed. . Here, the metal projections are electrically separated from each other.

The method of manufacturing the metal projection 17 is as follows.
The method is not necessarily limited to the above-described method, and it suffices if a protrusion that can concentrate the electric field can be formed as a result.

FIG. 4 shows a metal projection in the case where a voltage is applied between the transparent electrode 11 and the transparent electrode 14 of the spatial light modulator having the above-described configuration and writing light is locally incident from the direction of arrow A. The electric field line B of the electric field reaching the transparent electrode 11 from 17 is shown. The bleeding of the electric field caused by the drift of the charge in the lateral direction of the photoconductive film 15 is prevented by the photoconductive film 15.
And the liquid crystal layer 19 can concentrate again on the tip of the metal projection 17 interposed between the metal projection 19 and the liquid crystal layer 19. Therefore, it is possible to modulate the liquid crystal in the minute portion, and it is possible to improve the resolution. In this embodiment, a resolution of about 500 lp / mm was able to be achieved.

Next, another embodiment of the spatial light modulator according to the present invention will be described with reference to the drawings.

FIG. 5 is a sectional view of a second embodiment of the optical writing type spatial light modulator according to the present invention. In the spatial light modulator shown in FIG. 5, a large number of minute projections 35a are formed on a photoconductive film 35 as a means for locally concentrating an electric field. These projections 35a can also be formed by etching the photoconductive film 35 by the same manufacturing procedure as that of the metal projection of the first embodiment. In this case, since the resistance in the in-plane direction of the photoconductive film is very large, the projections need not be separated from each other.

Also in this embodiment, the bleeding of the electric field caused by the drift of the electric field in the photoconductive film 35 in the horizontal direction can be concentrated on the tip of the projection 35a formed on the photoconductive film 35. Therefore, the liquid crystal in the minute portion of the liquid crystal layer 37 can be modulated, and the resolution can be improved.

FIG. 6 is a sectional view of a third embodiment of the optical writing type spatial light modulator according to the present invention. In the spatial light modulator shown in FIG. 6, a large number of minute projections 44a are formed on a transparent electrode 44 as means for locally concentrating an electric field. These projections 44a can also be formed by etching the transparent electrode 44 by the same manufacturing procedure as that of the metal projection of the first embodiment. Further, these protrusions 44a may be formed by directly etching the substrate 43. Further, a number of minute metal projections may be formed on the transparent electrode 44.

Also in this embodiment, by concentrating the electric field on the tip of the protrusion 44a formed on the transparent electrode 44, the drift of the charge in the lateral direction of the photoconductive film 45 can be reduced. Therefore, the liquid crystal in a minute portion of the liquid crystal layer 48 can be modulated, and the resolution can be improved.

FIG. 7 is a sectional view of a fourth embodiment of the optical writing type spatial light modulator according to the present invention. The spatial light modulator shown in FIG. 7 is one in which a number of minute projections 51a are formed on a transparent electrode 51 as a means for locally concentrating an electric field. These projections 51a can also be formed by etching the transparent electrode 51 by the same manufacturing procedure as that of the metal projection of the first embodiment. Further, these protrusions 51a may be formed by directly etching the substrate 50. Further, a number of minute metal projections may be formed on the transparent electrode 51.

Also in the present embodiment, the bleeding of the electric field caused by the drift of the electric charge in the lateral direction of the transparent electrode 51 can be concentrated on the tip of the projection 51a formed on the transparent electrode 51. Therefore, the liquid crystal can be modulated in the minute portion of the liquid crystal layer 58, and the resolution can be improved.

FIG. 8 is a sectional view of a fifth embodiment of the optical writing type spatial light modulator according to the present invention. The spatial light modulator shown in FIG. 8 is obtained by dispersing a large number of metal fine particles 66 in a photoconductive film 65 as a means for locally concentrating an electric field. The size of these metal microparticles 66 is, for example, about 0.5 μm. In addition, semiconductors or dielectrics (ferroelectrics) other than metals may be used as these fine particles.

Also in the present embodiment, the bleeding of the electric field caused by the drift of the electric charge in the lateral direction of the transparent electrode 64 can be concentrated on the metal fine particles 66 dispersed in the photoconductive film 65. Therefore, the liquid crystal in the minute portion of the liquid crystal layer 69 can be modulated, and the resolution can be improved.

FIG. 9 is a sectional view of a sixth embodiment of the optical writing type spatial light modulator according to the present invention. In the spatial light modulator shown in FIG. 9, a large number of metal fine particles 79 are dispersed in a liquid crystal layer 78 as means for locally concentrating an electric field.
The size of these metal microparticles 79 is, for example, about 0.5 μm.
m. In addition, semiconductors or dielectrics (ferroelectrics) other than metals may be used as these fine particles.

Also in the present embodiment, the bleeding of the electric field caused by the drift of the electric charge in the horizontal direction of the transparent electrode 75 can be concentrated on the metal fine particles 79 dispersed in the liquid crystal layer 78. Therefore, the liquid crystal in the minute portion of the liquid crystal layer 78 can be modulated, and the resolution can be improved.

In the above embodiment, 35a, 4a
Although the projections of 4a and 51a are conical and the tip is point-shaped, a saddle-shaped linear tip like a triangular prism may be used.

The material for forming the minute projections does not need to be a metal, but may be a material which can concentrate the electric field and is easily processed finely.

Furthermore, by using the above embodiments in combination, it is possible to effectively improve the resolution of the spatial light modulator.

[0047]

As described in detail above, the spatial light modulator according to the present invention has a voltage between the first electrode and the second electrode.
When pressure is applied, multiple protrusions or fine particles
Therefore, an electric field concentration portion can be generated in a part of the modulation layer.
As a result , the electric field can be concentrated more efficiently and local modulation can be performed at the electric field concentration part, so that the resolution of the spatial light modulator can be improved and it can be easily manufactured. It is.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of an optical writing type spatial light modulator according to the present invention.
It is sectional drawing of the Example of FIG.

FIG. 2 is a perspective view schematically showing a large number of small metal projections of the optical writing type spatial light modulator shown in FIG.

FIG. 3 is a cross-sectional view showing a step of manufacturing a metal protrusion of the optical writing type spatial light modulator shown in FIG.

FIG. 4 is a schematic diagram illustrating that an electric field concentrates on a tip end of a protrusion in the optical writing type spatial light modulator shown in FIG. 1;

FIG. 5 shows a second embodiment of the optical writing type spatial light modulator according to the present invention.
It is sectional drawing of the Example of FIG.

FIG. 6 shows a third example of the optical writing type spatial light modulator according to the present invention.
It is sectional drawing of the Example of FIG.

FIG. 7 shows a fourth embodiment of the optical writing type spatial light modulator according to the present invention.
It is sectional drawing of the Example of FIG.

FIG. 8 shows a fifth example of the optical writing type spatial light modulator according to the present invention.
It is sectional drawing of the Example of FIG.

FIG. 9 shows a sixth embodiment of the optical writing type spatial light modulator according to the present invention.
It is sectional drawing of the Example of FIG.

FIG. 10 is a sectional view of a conventional optical writing type spatial light modulator.

FIG. 11 is a cross-sectional view of another type of conventional optical writing type spatial light modulator.

[Explanation of symbols]

 10, 13 Glass substrate 11, 14 Transparent electrode 12, 18 Liquid crystal alignment film layer 15 Photoconductive film 16 Dielectric mirror 17 Metal protrusion 19 Liquid crystal layer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukio Tojo 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Terutaka Tokumaru 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp shares In-company (56) References JP-A-2-240192 (JP, A) JP-A-2-93519 (JP, A) JP-T-2-501095 (JP, A) (58) Fields studied (Int. . ^7, DB name) G02F 1/135

Claims (7)

(57) [Claims] A first substrate; a first electrode formed on the first substrate; an optical writing layer formed on the first electrode for writing information; a second substrate, a second electrode formed on the substrate of the second, is formed on the second electrode, according to the written information in the optical writing layer, the light a modulation layer that spatially modulated, when a voltage is applied between the first electrode and the second electrode, a plurality of concentrating localized electric field to a portion of the modulation layer protrusion A spatial light modulator comprising:
A spatial light modulator formed of materials having electrically different physical properties . 2. The device according to claim 1, wherein the protrusion is provided between the optical writing layer and the modulation layer.
3. A spatial light modulator according to claim 1. Wherein the protrusions spatial light modulator according to claim 1, characterized in that it is formed on the optical writing layer. 4. The spatial light modulator according to claim 1, wherein the protrusion is provided between the first substrate and the optical writing layer. 5. The method according to claim 1, wherein the protruding portion is in front of the second substrate.
2. The spatial light modulator according to claim 1, wherein the spatial light modulator is provided between the spatial light modulator and the modulation layer . 6. A first substrate, a first electrode formed on the first substrate, and a first electrode formed on the first electrode for writing information.
An optical writing layer; a second substrate; a second electrode formed on the second substrate; and a second electrode formed on the second electrode.
Modulation layer that spatially modulates light according to the information entered
And dispersed in the optical writing layer, and the first electrode
When a voltage is applied between the second electrode and the second electrode, the modulation
Multiple microparticles that concentrate the electric field locally on a part of the layer
A spatial light modulator comprising: the microparticles having a thickness of about 1 /
Spatial light modulator you characterized in that it is formed by 3 particle size. 7. A first substrate, a first electrode formed on the first substrate, and a first electrode formed on the first electrode for writing information.
An optical writing layer; a second substrate; a second electrode formed on the second substrate; and a second electrode formed on the second electrode.
Modulation layer that spatially modulates light according to the information entered
And dispersed in the modulation layer, the first electrode and the
When a voltage is applied between the modulation layer and the second electrode,
A plurality of fine particles that concentrate the electric field locally on a part of
A spatial light modulator, wherein the fine particles have a thickness of about 1/3 of a thickness of the modulation layer.
Spatial light modulator you characterized in that it is formed by the particle size.