JPH07128651A - Image display device - Google Patents

Abstract

PURPOSE:To provide an image display device capable of displaying a uniform image without color slippage and with high contrast. CONSTITUTION:The image display device 1 is constituted of a read light source 2, a polarizing beam splitter 3 converting a beam of light from the read light source 2 to a linearly polarized light beam, a dichroic mirror 4 as a color separation means, a rotation means 5 rotating a polarization direction defined as the vibration direction of the electric field vector of the beam of light of the linearly polarized light beam, a reflection type liquid crystal spatial optical modulation element 6, a writing transmission type liquid crystal spatial optical modulation element 7, a write light source 8, an image forming lens 9, a projection lens 10 and a screen 11. By the rotation meams 5, at least either one side polarization direction of an incident beam on the reflection type liquid crystal spatial optical modulation element 6 and an outgoing beam from the reflection type liquid crystal spatial optical modulation element 6 is rotated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device used in a large screen television or the like.

[0002]

2. Description of the Related Art High-definition televisions having large screens and high-density pixels have been developed and put into practical use in various systems. Above all,
Development of a projection-type image display device using liquid crystal technology instead of the conventional cathode ray tube (CRT) system is active.

In recent years, in order to improve the aperture ratio and obtain a bright image, a projection type image display device using a reflection type liquid crystal spatial light modulator has been attracting attention. As a liquid crystal driving method, a transistor driving method and a light driving method have been developed.
In both cases, the projection optical system is slightly complicated as compared with the projection type image display device using the transmissive spatial light modulator, but the light amplification degree is large and a bright image can be obtained. In the transistor driving method, a transistor is formed on the back surface of a reflective layer that also serves as an electrode, and the liquid crystal of each pixel is controlled by an electric signal to modulate the reading light. On the other hand, in a light-driving reflective liquid crystal spatial light modulator that combines a liquid crystal with a photoconductive layer, an image is written from the photoconductive layer side, and the state of the liquid crystal is changed according to the spatial intensity distribution of the writing light. The read light is modulated and reflected. In addition, as a writing means to the reflection type liquid crystal spatial light modulator of the light driving system,
A transmissive liquid crystal spatial light modulator or CRT is used. Further, as a liquid crystal material, a ferroelectric liquid crystal having an excellent viewing angle characteristic has been attracting attention.

The idea of an optically driven reflective liquid crystal spatial light modulator was first proposed by Hughes as using ZnS (photoconductive layer) + twisted nematic (TN) liquid crystal [Applied Physics Letter, 1
Volume 7 (1970) 51 pages (Appl. Phys.
Lett. 17 (1970) 51)]. Next, CdS
(Photoconductive layer) + TN liquid crystal (light modulation layer)
Applied Physics Letters, Volume 22 (1973)
Year) 90 pages (Appl. Phys. Lett. 22)
(1973) 90). After that, the one using single crystal silicon + TN liquid crystal is disclosed in US Pat.
31, No. 31, JP-A-3-192332, Journal of Applied Physics, 5 volumes (198
5 years) 1356 pages (J. Appl. Phys. 5)
(1985) 1356).

In recent years, a spatial light modulator using a highly sensitive amorphous silicon light-receiving layer as a photoconductive layer has been developed to 100
It has become possible to display moving images on a large screen of inches or more. A spatial light modulator (S) including amorphous silicon (a-Si) and TN liquid crystal in order to improve resolution.
It was the first time I showed how to use LM.
U.S. Pat. No. 4,693,561 to Applied Optics, Vol. 26 (1987), page 241 (Appl. Opt. 26 (1987) 241) and U.S. Pat. No. 4,538,884. Also, a
A spatial light modulator using a photoconductive layer composed of a double layer of Si and CdTe is disclosed in US Pat. No. 4,799,773 and SID International Symposium 1990 Digest of Technical Papers 17A. 2 p327 (SID'90 17
A. 2 p327).

Further, by using a ferroelectric liquid crystal (FLC) capable of high-speed response as a liquid crystal material, higher speed
It has become possible to realize a high-resolution spatial light modulator. The liquid crystal light valve of diode structure a-Si + FLC is applied physics letter, 51 volumes (1
987) page 1232 (Appl. Phys. Le.
tt. 51 (1987) 1232), the idea itself was SPIE 754 (19).
87) 207. Also, Applied Physics Letter, Volume 55 (1989), page 537 (Appl. Phys. Lett. 55 (1989).
537) and U.S. Pat. No. 4,941,735.
Television image writing and projection system is based on SID International Symposium 1991 Digest of Technical Papers 13.3
p254 (SID'91 13.3, p254).

Here, a typical structure of the reflection type liquid crystal spatial light modulator of the optical driving system is shown in FIGS. The reflective liquid crystal spatial light modulator shown in FIG. 5 has transparent conductive electrodes 13, 1
The configuration is such that the photoconductive layer 14, the reflective layer 24, and the liquid crystal layer 25 are sandwiched by the glass substrates 12 and 12 ′ having 3 ′. A dielectric reflecting film is used as the reflecting layer 24 and does not have a pixel structure. Therefore, although limited by the resolution of the element, the written image itself is displayed. Therefore, when a transmissive liquid crystal spatial light modulator having a low aperture ratio is used as the image input means, there is a drawback that the image becomes dark.

On the other hand, the reflective liquid crystal spatial light modulator shown in FIG. 6 has a high reflectance of Al, Ag, etc., and the read light is reflected by the separated conductive electrode 15. For this reason, even if a transmissive liquid crystal spatial light modulator having a low aperture ratio is used as the image input means, one pixel of the transmissive spatial light modulator and the conductive electrode 15 have the same pitch and have a one-to-one correspondence. As a result, a bright image can be obtained.

Next, FIG. 7 shows an example of an image display device which displays a full-color image by using such a reflection type liquid crystal spatial light modulator of the optical driving system. This image display device
The intensities of the R (red), G (green), and B (blue) three color components of the image to be displayed are input to each reflective liquid crystal spatial light modulation element 6 corresponding to RGB as writing light, and the three RGB colors are displayed. An image written by the separated reading light is read out, and an image is formed on the screen 11 by the projection lens 10 to combine the colors to display a full-color image.

The function of each element will be described in detail below. The read light from the read light source 2 is separated into s-polarized light and p-polarized light by the polarization beam splitter 3, and then only the s-polarized read light is guided to the dichroic mirror 4 to be separated into three colors of RGB. The light is input to the reflective liquid crystal spatial light modulator 6. The reading light is modulated by the light modulation layer according to the intensity of the writing light representing each color component of the image, reflected by the reflection layer, and then passes through the light modulation layer again.
It is guided to the polarization beam splitter 3 via the dichroic mirror 4. In particular, when the peak signal of each color component is written, the read light is modulated by the polarization beam splitter 3 so as to be p-polarized linearly polarized light. Since the polarization beam splitter reflects the light of the s-polarized component and transmits the light of the p-polarized component, the transmittance of the readout light with respect to the polarization beam splitter 3 changes according to the degree of the modulation. By image-forming the read light of each reflective liquid crystal spatial light modulation element 6 corresponding to RGB on the screen 11 by the projection lens 10, color combination can be performed and a full-color image can be displayed. In FIG. 7, 7 is a transmissive liquid crystal spatial light modulator for writing, 8 is a writing light source, and 9 is an imaging lens.

Next, the principle of light modulation of the spatial light modulator will be described as follows.
A spatial light modulation element using a ferroelectric liquid crystal for the light modulation layer will be described as an example. FIG. 8 is a plan view of the reflective liquid crystal spatial light modulator shown in FIG. 6 as viewed from the normal direction (z axis). It is assumed that the x-axis in the figure coincides with the direction of the s-polarized electric field vector. A liquid crystal having a chiral smectic C (Sc ^* ) phase is called a ferroelectric liquid crystal (FLC) because it exhibits ferroelectricity due to its symmetry. The Sc ^* phase has a spiral structure, but when the distance between the substrates sandwiching the liquid crystal layer is shortened, the spiral structure disappears and smectic C (S
c) Become a phase. In the Sc phase, FLC is bistable. That is, when an external electric field is applied in the normal direction of the substrate, all FLC molecules are oriented in one of the two stable states so as to have spontaneous polarization in the electric field direction. The angle formed by the long axes in these two stable states is the tilt angle 2θ.
It is defined as Generally, θ = 22.5 °. For example,
When the orientation treatment is performed in the angle −θ direction from the x axis, all FLC molecules are oriented in either the x axis or −2θ direction in the bistable state depending on the polarity of the external electric field.

The oriented FLC can be regarded as a uniaxial positive optical crystal having the orientation direction as an optical axis. For example, consider a case where s-polarized light propagating in the z-axis direction as represented by the following (Equation 2) enters the FLC oriented in the x-axis direction by an external electric field.

[0013]

[Equation 2]

Here, E is an electric field vector of incident light, λ is a wavelength, and e _x is a unit vector in the x-axis direction. Letting the incident surface be the origin and the optical effective thickness of the FLC is n _ed ,
The electric field vector E ′ of the emitted light is s-polarized light represented by the following (Equation 3).

[0015]

[Equation 3]

That is, the light incident on the s-polarized light is output as the s-polarized light. Since this spatial light modulator is a reflection type, if the thickness of the FLC layer is d ', then d'
= 2d '. Since the polarization beam splitter transmits only the p-polarized component, that is, the E _y component, the emission light intensity I becomes zero.

On the other hand, when the FLC is oriented in the −2θ = −45 ° direction, it can be considered that the optical axis is tilted by −45 °, so that the E _y component E of the electric field vector of the emitted light is obtained.
_y'is expressed by the following (Equation 4).

[0018]

[Equation 4]

Therefore, the output light intensity I passing through the polarization beam splitter becomes maximum when the phase difference δ defined by the following (Equation 5) satisfies the following (Equation 6).

[0020]

[Equation 5]

[0021]

[Equation 6]

However, m is an integer. Therefore, if the thickness d ′ of the FLC is set to satisfy the following (Equation 7), the emitted light can be p-polarized (linearly polarized), and the output light intensity I becomes maximum at this time.

[0023]

[Equation 7]

According to the above principle, the output light intensity I can be changed by the external electric field in the reflection type liquid crystal spatial light modulation element using FLC as the light modulation layer. In the spatial light modulator shown in FIG. 6, the applied voltage of FLC is changed according to the write light quantity to perform light modulation.

In order to obtain a high-contrast image, the spatial light modulation element for displaying black must output the read-out light that is incident as s-polarized linearly polarized light as s-polarized linearly polarized light. For this purpose, one orientation direction of the bistable state of FLC must be exactly matched with the polarization direction of s-polarized light. If the polarization direction of s-polarized light is F,
This is because the output light intensity I does not become zero because the emitted light becomes elliptically polarized light and contains the p-polarized light component when it does not match any of the orientation directions of the LC bistable state. Therefore, the alignment axis of FLC is exactly -22.5 with respect to the x-axis.
It is necessary to perform the alignment treatment so that the angle becomes °. However, under the present circumstances, it is difficult to accurately orient the alignment axis in a desired direction. Therefore, by rotating the spatial light modulator with the substrate normal (z axis) as the rotation axis, the alignment axis of the s-polarized light is changed. The vibration direction of the electric field vector is exactly matched. Since the deviation of the alignment axis from the ideal −22.5 ° differs for each spatial light modulator, the rotation angle of the spatial light modulator also differs for each device.

On the other hand, the projection type image display apparatus using the transmissive liquid crystal spatial light modulator of the transistor driving type has a feature that the aperture ratio does not increase and the image is dark, but the projection optical system is relatively simple. Have. Generally, in a projection type image display device using a transmissive liquid crystal spatial light modulation element, the readout light from a light source is made into linearly polarized light by a polarizer and made incident on the spatial light modulation element. The spatial light modulator is
The incident light is modulated from linearly polarized light to elliptically polarized light according to the voltage applied to the liquid crystal layer, and the light intensity is adjusted by passing through the analyzer.

Generally, TN liquid crystal is used as the liquid crystal material. The TN liquid crystal molecule has optical uniaxial optical anisotropy, and its optical axis coincides with the long axis of the liquid crystal molecule. FIG. 9 schematically shows the TN liquid crystal layer. TN liquid crystal molecule 2
No. 6 is oriented so that it is twisted by 90 ° when no electric field is applied. If the polarization axis of the polarizer 27 coincides with the alignment direction of the TN liquid crystal on the incident side, the light beam emitted from the TN liquid crystal layer becomes linearly polarized light in which the polarization direction is twisted by 90 °.
Therefore, black display can be performed by matching the polarization axis of the analyzer 28 with the direction of the polarization axis of the polarizer 27.

On the other hand, the major axis direction of the TN liquid crystal molecules 26 is oriented in the normal direction of the substrate according to the applied voltage. Therefore, the incident light becomes elliptically polarized light according to the applied voltage and is emitted. Figure 9
When the applied voltage exceeds a certain value as shown in FIG.
Since all the liquid crystal molecules except the liquid crystal molecules in the vicinity are aligned in the normal direction of the substrate, the polarization direction of the emitted light beam does not change, and as a result, white display is performed.

FIG. 10 shows an example of a projection type image device using a conventional transmission type liquid crystal spatial light modulator 30. In order to display a full-color image, the readout light is separated into each color component by a color separation means such as a dichroic mirror, and each color component light is modulated by a spatial light modulation element corresponding to each color, and by a color combining means such as a dichroic prism. Three
The output images of the spatial light modulator elements are combined.

The details will be described below with reference to FIG. The readout light from the readout light source 2 is separated into three colors of RGB by the dichroic mirror 31, and each of the polarizers 27
Incident on. Each of the polarizers 27 converts the readout light into linearly polarized light whose polarization direction matches the alignment direction of the liquid crystal. Thereafter, the read light is incident on the transmissive liquid crystal spatial light modulator 30 and modulated. The polarization axis of the analyzer 28 is adjusted in the same direction as the polarization axis of the polarizer 27. The image that has passed through the analyzer 28 is an image of each color component. The image of each color component is projected onto the projection lens 10 via the dichroic prism 32.
To form a full-color image on the screen 11.

The dichroic prism 32 transmits only the G component light and reflects the B and R component light. In order to realize highly accurate color composition, it is necessary that the G component when displaying white is p-polarized with respect to the B and R reflection surfaces, and the light of the B and R components is s-polarized. Therefore, in the spatial light modulator of the G component, the alignment direction of the liquid crystal of the incident side substrate is made to coincide with the polarization direction of the p-polarized light beam, and in the spatial light modulators of the B and R components, the s-polarized light beam It matches the polarization direction.

[0032]

By the way, a full-color image is displayed by synthesizing the output of the reflection type liquid crystal spatial light modulator of the optical driving system having the pixel structure as shown in FIG. 6 on the screen. In some cases, it is necessary to exactly match the corresponding pixels of each spatial light modulator on the screen. However, when the spatial light modulators are rotated at different optimum angles in order to obtain a high-contrast image, the pixels are not exactly aligned on the screen, resulting in color misregistration. On the contrary, if the pixels are aligned on the screen without rotating each spatial light modulator, a high-contrast image is displayed because the alignment axis of each spatial light modulator is deviated from -22.5 °. I can't. That is, since the alignment direction of the FLC cannot be accurately controlled, it has been impossible to both suppress color misregistration and display a high-contrast image. The above phenomenon is the same in the case of a transistor-driven reflective liquid crystal spatial light modulator.

When a transmissive liquid crystal spatial light modulating element having a small aperture ratio is used as a writing means of the reflective liquid crystal spatial light modulating element of the optical driving system, each pixel of the transmissive liquid crystal spatial light modulating element is a reflective type. Each pixel of liquid crystal spatial light modulator and 1
A bright image can be obtained by making the pair 1 correspond. However, when it is necessary to rotate the reflective liquid crystal spatial light modulator in order to improve the contrast, it is necessary to rotate the transmissive liquid crystal spatial light modulator for writing as well. For this reason, the image is tilted obliquely, so that it is necessary to tilt and install the entire image display device. As a result, the configuration becomes complicated and adjustment is difficult.

In the case of a projection type image display device using a transmissive liquid crystal spatial light modulator, the polarization axis of the polarizer is rotated so that the polarization axis coincides with the alignment direction of the liquid crystal to improve the contrast. You can However, the dichroic prism for color composition is designed so that the composition accuracy is best when the light of G component is p-polarized and the light of B and R components is s-polarized. ing. Therefore, when the alignment direction of the liquid crystal is deviated from the p-polarized light or the s-polarized light, the light emitted from the spatial light modulator is deviated from the p-polarized light or the s-polarized light, and the combining accuracy of the dichroic prism is deteriorated. Display color is not uniform.

In order to solve the above-mentioned problems of the prior art, it is an object of the present invention to provide an image display device capable of displaying a uniform image with high contrast without color shift.

[0036]

In order to solve the above-mentioned problems, a first configuration of an image processing apparatus according to the present invention comprises a light source, a polarizing means for converting a light beam from the light source into a linearly polarized light, and an optical means. An optical element having anisotropy and at least optical rotation means for rotating a polarization direction defined as a vibration direction of an electric field vector of a linearly polarized light beam, wherein the optical rotation means includes incident light to the optical element and the optical element. The polarization direction of at least one of the light emitted from the element is rotated.

In the first configuration, the polarization means is a polarization beam splitter that splits the incident light into linearly polarized light whose polarization directions are orthogonal to each other, and the optical element is a ferroelectric liquid crystal having a plurality of pixels. Is a reflection type liquid crystal spatial light modulator using a light source, a light beam from a light source is incident on the optical rotation means through the polarization beam splitter, and the polarization direction of the read light passing through the optical rotation means is in a bistable state. It is preferably coincident with either of the two stable alignment directions defined as the long axis direction of the ferroelectric liquid crystal molecule.

A second configuration of the image processing apparatus according to the present invention is such that a light source, a polarization beam splitter for separating an incident light into linearly polarized light whose polarization directions are orthogonal to each other, and an incident light into a plurality of color components. Color separation means, a plurality of optical rotation means for rotating the polarization direction, and a plurality of reflective liquid crystal spatial light modulators using a ferroelectric liquid crystal having a plurality of pixels as optical elements having optical anisotropy. At least the read light from the light source is incident on the color separation means via the polarization beam splitter, is separated into a plurality of color components by the color separation means, and then is incident on the optical rotation means for each color component. The oscillation direction of the electric field vector of the readout light that has passed through the optical rotation means is one of two stable orientation directions defined as the major axis direction of the ferroelectric liquid crystal molecules in the bistable state. And wherein the match.

In the above structure, the reflective liquid crystal spatial light modulator has at least a rectifying photoconductive layer and a ferroelectric liquid crystal layer, and a parallel plate translucent substrate having a transparent conductive electrode. It is preferable that a plurality of reflective layers separated in an island shape are provided between the photoconductive layer and the ferroelectric liquid crystal layer.

Further, in the above construction, the optical rotation means is an optically active body, and the thickness l of the optically active body is such that the principal wavelength λ of the incident light beam, the polarization direction of the incident light beam and the ferroelectric liquid crystal are two. one of either the angle Δθ stable direction, the refractive index n with respect to right-handed circularly polarized light of the optical active substance ^+, the refractive index n for the left circularly polarized light of the optically active substance ^- to satisfy the relationship between the equation (1) preferable.

Further, in the above structure, the optical rotation means is a half-wave plate, and the optical axis of the half-wave plate is an acute angle formed by the polarization direction of the incident light beam and either of the two stable alignment directions of the ferroelectric liquid crystal. Is preferably divided into 2 minutes.

Further, the third structure of the image display device according to the present invention comprises at least a light source, a color separation means, a plurality of transmissive liquid crystal spatial light modulators, a plurality of optical rotation means, and a color synthesizing means. A light beam from the light source is separated into a plurality of color components by the color separation means, enters the corresponding transmissive liquid crystal spatial light modulation element for each color component, and is transmitted from the transmissive liquid crystal spatial light modulation element. The emitted light is incident on the color combining means after the polarization direction is rotated by the corresponding optical rotation means.

[0043]

The substance having optical activity can rotate the polarization direction of linearly polarized light (the vibration direction of the electric field vector). Now, it is assumed that the polarization direction of the linearly polarized light rotates by Φ toward the traveling direction of the light ray by passing through the optical rotatory substance. As described above, the polarization direction of s-polarized light and F
In order to exactly match one stable orientation direction in the bistable state of LC, it is necessary to precisely control the orientation axis of FLC to be tilted by −22.5 ° with respect to the x axis. However, in reality, the alignment axis of the FLC always deviates from the desired angle by Δθ. Therefore, if Φ is set so as to satisfy the following (Equation 8), the polarization direction of the readout light can be made to coincide with one stable orientation direction in the bistable state of FLC.

[0044]

[Equation 8]

Therefore, according to the structure of the present invention, an optical element having optical anisotropy (for example, a spatial light modulator).
A high-contrast output image can be obtained without rotating, and as a result, the corresponding pixels of the three spatial light modulation elements can be accurately matched on the screen at the same time, so that the color shift can be prevented. It can display a clear image.

According to the third aspect of the present invention,
The Φ of the optically active substance is adjusted so that the light emitted from the transmissive liquid crystal spatial light modulator matches the polarization direction of p-polarized light or s-polarized light.
By setting, it is possible to convert light rays to the color synthesizing means into polarized light with high color synthesizing accuracy, so that it is possible to realize an image display device capable of uniform color display without color unevenness.

[0047]

EXAMPLES The present invention will be described in more detail below with reference to examples. (Embodiment 1) FIG. 1 is a block diagram showing an embodiment of an image display device according to the present invention. Image display device 1 of the first embodiment
Is a reading light source 2, a polarization beam splitter 3, a dichroic mirror 4 as a color separation means, an optical rotation means 5, a reflective liquid crystal spatial light modulation element 6, a writing transmissive liquid crystal spatial light modulation element 7, a writing light source 8, an image formation. It includes a lens 9, a projection lens 10, and a screen 11.

Next, the operation principle of the image display device 1 having the above-mentioned structure will be described. The readout light from the readout light source 2 is input to the polarization beam splitter 3,
Only linearly polarized light of the s-polarized component is guided to the dichroic mirror 4. The read light is separated into three colors of RGB by the dichroic mirror 4, and is input to each reflective liquid crystal spatial light modulator 6 via the optical rotation means 5. Each color component of the image to be displayed is displayed on the transmissive liquid crystal spatial light modulator for writing 7, and modulates the writing light from the writing light source 8.
The imaging lens 9 forms an image of each color component on the photoconductive layer of the reflective liquid crystal spatial light modulation element 6. Each reflective liquid crystal spatial light modulator 6 modulates the read light by driving the ferroelectric liquid crystal according to the spatial light intensity distribution of the write light, and reflects the read light by the conductive electrode. The reflected light is again the optical rotation means 5
After passing through, the beam is guided to the polarization beam splitter 3 via the dichroic mirror 4, and only the p-polarized component passes through the polarization beam splitter 3 and is imaged on the screen 11 by the projection lens 10. Then, if the corresponding pixels of the reflective liquid crystal spatial light modulators 6 are made to coincide with each other, color combination is performed and an image is displayed.

Next, the reflective liquid crystal spatial light modulator will be described in detail. FIG. 6 shows the reflective liquid crystal spatial light modulator used in the first embodiment. As shown in FIG. 6, on the transparent insulating substrate 12 (for example, glass), the transparent conductive electrode 13 (for example, ITO (indium-tin oxide), Z) is formed.
nO, SnO _2, etc.) and a photoconductive layer 14 having a rectifying property.
(Amorphous silicon layer having diode structure; p layer 1
8, i layer 19, and n layer 20) are sequentially stacked. Further, on the n-layer 20, a separated minute metal reflection film 15 (for example, Al, Ti, Cr, Ag) corresponding to a pixel is formed.
Such as metal, or a stack of two or more metals)
And an alignment film 16 (for example, a polymer thin film such as polyimide) that aligns the liquid crystal layer 17 are sequentially arranged. Also,
An output light shielding film 21 for reading light is provided between the pixels. In addition, the transparent conductive electrode 13 'on the opposite side
An alignment film 16 ′ (for example, a polymer thin film such as polyimide) is uniformly formed on (for example, ITO, ZnO, SnO ₂ etc.). In FIG. 6, reference numeral 12 'is a transparent insulating substrate (eg, glass).

The material used for the photoconductive layer 14 is, for example, CdS, CdTe, CdSe, ZnS, ZnS.
e, GaAs, GaN, GaP, GaAlAs, InP
Compound semiconductors such as Si, SeTe, amorphous semiconductors such as AsSe, Si, Ge, Si _{1- x} C _X , Si _1-x G
polycrystalline or amorphous semiconductors such as e _x , Ge _1-x C _x (0 <x <1), and (1) phthalocyanine pigment (abbreviated as Pc), for example, metal-free Pc, XPc (X = Cu , Ni,
Co, TiO, Mg, Si (OH) _2, etc.), AlCl
PcCl, TiOClPcCl, InClPcCl, I
nClPc, InBrPcBr, etc., (2) azo dyes such as monoazo dyes and disazo dyes, (3) penylene pigments such as penylene anhydride and penylene acid imide,
(4) indigoid dye, (5) quinacridone pigment,
(6) Polycyclic quinones such as anthraquinones and pyrenequinones, (7) cyanine dyes, (8) xanthene dyes,
(9) Charge transfer complexes such as PVK / TNF, (10) eutectic complexes formed from pyrylium salt dye and polycarbonate resin, (11) azurenium salt compounds and other organic semiconductors.

Amorphous Si, Ge, Si
_1-xC_x, Si_1-xGe_x, Ge_1-xC_x(Hereinafter, a-
Si, a-Ge, a-Si_1-xC_x, A-Si_1-xGe
_x, A-Ge _1-xC_xAbbreviated as) to the photoconductive layer 14
If used, it may contain hydrogen or halogen elements.
Acid to reduce the dielectric constant and increase the resistivity.
Elemental or nitrogen may be included. It also controls the resistivity.
For this purpose, elements such as p-type impurities such as B, Al and Ga, or
Is an n-type impurity such as P, As or Sb.
May be. In this way, the amorphous material doped with impurities is
P / n type, p / i type, i / n type, p / i / n type
Which junction to form and the depletion layer to form in the photoconductive layer 14
It is also possible to control the dielectric constant and dark resistance or operating voltage polarity.
Wear. In addition to such amorphous materials,
Two or more of the above materials are stacked to form a heterojunction,
A depletion layer may be formed in the electric layer 14. The photoconductive layer 1
The film thickness of 4 is preferably in the range of 0.1 to 10 μm.
Yes.

Next, a method for manufacturing the reflective liquid crystal spatial light modulator having the above structure will be described. First, 50 mm
A transparent electrode material such as ITO is formed into a film having a thickness of 1000 Å on a glass substrate 12 having a size of 50 mm × 1.0 mm by a sputter deposition method to form a transparent conductive electrode 13. Then, p / i /
Hydrogenated amorphous silicon of n structure (hereinafter a-S
i: abbreviated as H) film having a film thickness of 2 μm, and the photoconductive layer 1
4 is formed. Here, B (boron) is 4 in the p-layer 18.
The n layer 20 is P-doped with only 00 ppm.
(Phosphorus) is doped by 40 ppm. Also,
The p-layer 18 has a film thickness of 1000 angstroms, and the i-layer 19 has
Has a film thickness of 17,000 angstroms, and the n layer 20 has a film thickness of 2000 angstroms. Then, a Cr film is formed on the surface of the photoconductive layer 14 by a vacuum vapor deposition method and divided into fine shapes by photolithography to form a metal of 1000 × 1000 pixels with a size of 28 μm × 28 μm and a pitch of 2 μm. The reflective film 15 is formed. Then, the photoconductive layer 14 between the adjacent metal reflection films 15 is formed.
All of the n layer 20 and part of the i layer 19 are removed by etching to form a groove. As a result, the metal reflection films 15 and 15 adjacent to each other are not connected by the n layer having a low resistance, and are electrically separated from each other to improve the resolution. further,
An output light shielding film 21 made of a metal such as Al, Cr, Ti, or Ag is formed on the bottom of the groove. As a result, the malfunction of switching due to the read output light sneaking into the photoconductive layer 14 is eliminated, and the read light intensity can be increased. Then, the organic output light-shielding film 22 is filled in the groove portion. As a result, the degree of blocking the read light can be further improved.

Then, a polyamic acid is applied from above by spin coating and heat curing is performed to form a polyimide alignment film 16. Polyimide alignment film 1 at this time
The film thickness of 6 is 100 angstrom. The orientation treatment (rubbing treatment) is performed by rubbing the surface in a certain direction with a nylon cloth.

Similarly, a transparent conductive electrode 13 'made of ITO and a polyimide alignment film 16' are sequentially formed on the other glass substrate 12 ', and an alignment treatment is performed. Then, beads having a diameter of 1 μm are distributed on the other glass substrate 12 ′, and one glass substrate 12 is bonded to form a gap of 1 μm between the two substrates. Then, by injecting a ferroelectric liquid crystal into this gap and performing a heat treatment, a liquid crystal layer 17 having a thickness of 1 μm is formed between both substrates.

As described above, the reflective liquid crystal spatial light modulator having the structure of FIG. 5B is obtained. The alignment treatment of the ferroelectric liquid crystal was performed in a direction tilted by −22.5 ° from the x axis. However, in reality, the alignment direction of each reflective liquid crystal spatial light modulator 6 was tilted from -22.5 ° by Δθ as shown in FIG. Therefore, in the image processing apparatus 1 according to the first embodiment, the optical rotation means 5 made of an optically active substance such as α crystal is provided in order to rotate the polarization direction of the readout light by Δθ. The thickness 1 of the optical rotation means 5 is the same as the above (Equation 1).
Determined by Here, n ⁻ and n ⁺ are the optical rotation means 5
Is the refractive index for left-handed circularly polarized light and right-handed circularly polarized light. That is, by optimizing the thickness of the optical rotation means 5 according to Δθ of each reflective liquid crystal spatial light modulation element 6, the polarization direction of the read light incident on the reflective liquid crystal spatial light modulation element 6 is changed to the ferroelectric liquid crystal. Can be aligned with one of the orientation directions in the bistable state of. Therefore, in the image display device 1 of the first embodiment, it is possible to obtain a high-contrast output image of 300: 1 or more without rotating the reflective liquid crystal spatial light modulation element 6, and as a result, three simultaneous output images are obtained. Since the corresponding pixels of the reflective liquid crystal spatial light modulation element 6 can be accurately matched on the screen 11, a clear image without color shift can be displayed.

(Embodiment 2) FIG. 3 is a block diagram showing another embodiment of the image display apparatus according to the present invention. The basic structure is the same as that of the image display device 1 shown in FIG. 1, but a CRT 23 is used as an image input means. In the second embodiment, as in the first embodiment, the alignment direction of the reflective liquid crystal spatial light modulator 6 is deviated from the desired −22.5 ° by ± 1 °. Therefore, the polarization direction of the readout light is made to coincide with one of the orientation directions in the bistable state of the ferroelectric liquid crystal by the optical rotation means 5.

In the second embodiment, a half-wave plate is used as the optical rotation means 5. The half-wave plate is made of a uniaxial optical crystal, and the angle formed by the optical axis with the polarization direction of the incident light is Φ.
Then, the polarization direction of the light beam emitted from the half-wave plate is −Φ. Therefore, by rotating the half-wave plate so that the optical axis bisects an acute angle formed by the polarization direction of the incident light beam and one orientation direction in the bistable state of the ferroelectric liquid crystal, It is possible to match the polarization direction of the light beam incident on the type liquid crystal spatial light modulation element 6 with the stable alignment direction of the ferroelectric liquid crystal. As a result, also in the image display device 1'of the second embodiment, a high-contrast output image of 300: 1 or more can be obtained without rotating the reflective liquid crystal spatial light modulation element 6.

(Embodiment 3) FIG. 4 is a constitutional view showing still another embodiment of the image display device according to the present invention. In the third embodiment, the transmissive liquid crystal spatial light modulator 30 is used instead of the reflective liquid crystal spatial light modulator 6. The basic operation is the same as that of the conventional example, but a half-wave plate is arranged as the optical rotation means 5 between the analyzer 28 and the dichroic prism 32. The color combination characteristics of the dichroic prism 32 are designed so that the accuracy is best for p-polarized light for G component light and for s-polarized light for B component light and R component light. However, the alignment direction of the liquid crystal of each transmissive liquid crystal spatial light modulator 30 is deviated from the polarization direction of p-polarized light or s-polarized light. In addition, the deviation was different for each spatial light modulator. Incidentally, this Example 3
In the transmissive liquid crystal spatial light modulator 30 used in
The components were deviated from the polarization directions of p-polarized light and s-polarized light by -1 °, B component by 0.5 °, and R component by 1.2 °, respectively.

In order to improve the contrast of the image,
When the polarization axes of the polarizer 27 and the analyzer 28 were aligned with the alignment direction of the liquid crystal, the outgoing light from the transmissive liquid crystal spatial light modulator 30 was deviated by the above angle from the polarization direction of p-polarized light or s-polarized light. . Therefore, the optical axis of the half-wave plate as the optical rotation means 5 is -0.5 ° for the G component, 0.25 ° for the B component, and 0.6 ° for the R component. It was deviated from the polarization directions of p-polarized light and s-polarized light. As a result, the light beam to the dichroic prism 32 can be converted into the polarized light with the highest color combining accuracy, and an image display device capable of uniform color display without color unevenness can be configured.

[0060]

As described above, according to the image display device of the present invention, a high-contrast output image can be obtained without rotating an optical element having optical anisotropy (for example, a spatial light modulator). As a result, the corresponding pixels of the three spatial light modulators can be accurately matched on the screen at the same time, so that a clear image without color shift can be displayed.

Further, in particular, according to the third structure of the image display device of the present invention, the optical rotatory power is adjusted so that the light emitted from the transmissive liquid crystal spatial light modulator matches the polarization direction of p-polarized light or s-polarized light. By setting Φ of the substance, the light beam to the color synthesizing means can be converted into polarized light with high color synthesizing accuracy, so that it is possible to realize an image display device capable of uniform color display without uneven color orientation. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an image display device according to the present invention.

FIG. 2 is a plan view illustrating the principle of optical rotation means in an embodiment of the image display device according to the present invention.

FIG. 3 is a configuration diagram showing another embodiment of the image display device according to the present invention.

FIG. 4 is a configuration diagram showing still another embodiment of the image display device according to the present invention.

FIG. 5 is a cross-sectional view of a reflective liquid crystal spatial light modulator that does not have a pixel structure.

FIG. 6 is a cross-sectional view of a reflective liquid crystal spatial light modulator having a pixel structure.

FIG. 7 is a configuration diagram showing a conventional image display device.

FIG. 8 is a plan view for explaining the alignment of the ferroelectric liquid crystal.

FIG. 9 is a schematic view of a TN liquid crystal layer.

FIG. 10 is a configuration diagram showing a conventional image display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image display device 2 Reading light source 3 Polarization beam splitter 4 Dichroic mirror 5 Optical rotation means 6 Reflective liquid crystal spatial light modulator 7 Transmissive liquid crystal spatial light modulator 8 Writing light source 9 Imaging lens 10 Projection lens 11 Screen

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunihito Ogawa 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A light source, a polarizing means for converting a light beam from the light source into linearly polarized light, an optical element having optical anisotropy, and a polarization direction defined as a vibration direction of an electric field vector of the linearly polarized light beam. An image display device, comprising at least an optical rotation means for rotating the optical element, wherein the optical rotation means rotates the polarization direction of at least one of the light incident on the optical element and the light emitted from the optical element. 2. The polarizing means is a polarizing beam splitter for separating an incident light into linearly polarized light whose polarization directions are orthogonal to each other, and the optical element is a reflection type liquid crystal spatial light using a ferroelectric liquid crystal having a plurality of pixels. A light beam from a light source, which is a modulator, is incident on the optical rotation means via the polarization beam splitter, and the polarization direction of the readout light passing through the optical rotation means is the long axis of the ferroelectric liquid crystal molecule in a bistable state. The image display device according to claim 1, which coincides with one of two stable orientation directions defined as a direction. 3. A light source, a polarization beam splitter for separating an incident light into linearly polarized light whose polarization directions are orthogonal to each other, a color separation means for separating the incident light into a plurality of color components, and a plurality of optical rotations for rotating the polarization directions. Means and a plurality of reflective liquid crystal spatial light modulators using a ferroelectric liquid crystal having a plurality of pixels as optical elements having optical anisotropy, and the reading light from the light source is the polarization beam splitter. After being incident on the color separation means through the color separation means and separated into a plurality of color components by the color separation means, each color component enters the optical rotation means and vibrates the electric field vector of the read light passing through the optical rotation means. An image display device characterized in that the direction thereof coincides with one of two stable alignment directions defined as the long axis direction of ferroelectric liquid crystal molecules in a bistable state. 4. A reflective liquid crystal spatial light modulator comprising at least a rectifying photoconductive layer and a ferroelectric liquid crystal layer.
3. A structure sandwiched by parallel plate translucent substrates having transparent conductive electrodes, wherein a plurality of island-shaped reflective layers are provided between the photoconductive layer and the ferroelectric liquid crystal layer. Or the image display device according to item 3. 5. The optical rotatory means is an optically active substance, and the thickness l of the optically active substance is one of a dominant wavelength λ of an incident light beam, a polarization direction of the incident light beam, and two stable directions of the ferroelectric liquid crystal. angle Δθ either forms, the refractive index n ⁺ for the right circularly polarized light of the optical active substance, the refractive index n for the left circularly polarized light of the optical active substance ^- and claims 1, 2 or 3 satisfies the following equation (1)
The image processing device according to item 1. [Equation 1] 6. The optical rotation means is a half-wave plate, and the optical axis of the half-wave plate bisects an acute angle between the polarization direction of the incident light beam and one of two stable alignment directions of the ferroelectric liquid crystal. The image processing device according to item 2 or 3. 7. A light source, a color separation means, a plurality of transmissive liquid crystal spatial light modulators, a plurality of optical rotation means, and a color synthesizing means are provided at least, and a light beam from the light source is generated by the color separation means. The polarized light is separated into a plurality of color components, enters the transmissive liquid crystal spatial light modulation element corresponding to each color component, and the outgoing light from the transmissive liquid crystal spatial light modulation element rotates the polarization direction by the corresponding optical rotation means. The image display device is characterized in that the light is incident on the color synthesizing means after being processed.